ffmpeg 文档编制


内容表

1 梗概

ffmpeg [ global_options ] {[ input_file_options ] -i ‘ input_url ’} ... {[ output_file_options ] ‘ output_url ’} ...

2 描述

ffmpeg 是非常快的视频、音频转换器,还可以抓取实时音频/视频源。此外,它可以在任意采样率之间转换,并使用高质量多相滤波器即时调整视频大小。

ffmpeg reads from an arbitrary number of input "files" (which can be regular files, pipes, network streams, grabbing devices, etc.), specified by the -i option, and writes to an arbitrary number of output "files", which are specified by a plain output url. Anything found on the command line which cannot be interpreted as an option is considered to be an output url.

Each input or output url can, in principle, contain any number of streams of different types (video/audio/subtitle/attachment/data). The allowed number and/or types of streams may be limited by the container format. Selecting which streams from which inputs will go into which output is either done automatically or with the -map option (see the Stream selection chapter).

To refer to input files in options, you must use their indices (0-based). E.g. the first input file is 0 , the second is 1 , etc. Similarly, streams within a file are referred to by their indices. E.g. 2:3 refers to the fourth stream in the third input file. Also see the Stream specifiers chapter.

As a general rule, options are applied to the next specified file. Therefore, order is important, and you can have the same option on the command line multiple times. Each occurrence is then applied to the next input or output file. Exceptions from this rule are the global options (e.g. verbosity level), which should be specified first.

Do not mix input and output files – first specify all input files, then all output files. Also do not mix options which belong to different files. All options apply ONLY to the next input or output file and are reset between files.

  • To set the video bitrate of the output file to 64 kbit/s:
    ffmpeg -i input.avi -b:v 64k -bufsize 64k output.avi
                                    
  • To force the frame rate of the output file to 24 fps:
    ffmpeg -i input.avi -r 24 output.avi
                                    
  • To force the frame rate of the input file (valid for raw formats only) to 1 fps and the frame rate of the output file to 24 fps:
    ffmpeg -r 1 -i input.m2v -r 24 output.avi
                                    

The format option may be needed for raw input files.

3 详细描述

The transcoding process in ffmpeg for each output can be described by the following diagram:

 _______              ______________
|       |            |              |
| input |  demuxer   | encoded data |   decoder
| file  | ---------> | packets      | -----+
|_______|            |______________|      |
                                           v
                                       _________
                                      |         |
                                      | decoded |
                                      | frames  |
                                      |_________|
 ________             ______________       |
|        |           |              |      |
| output | <-------- | encoded data | <----+
| file   |   muxer   | packets      |   encoder
|________|           |______________|
                    

ffmpeg calls the libavformat library (containing demuxers) to read input files and get packets containing encoded data from them. When there are multiple input files, ffmpeg tries to keep them synchronized by tracking lowest timestamp on any active input stream.

Encoded packets are then passed to the decoder (unless streamcopy is selected for the stream, see further for a description). The decoder produces uncompressed frames (raw video/PCM audio/...) which can be processed further by filtering (see next section). After filtering, the frames are passed to the encoder, which encodes them and outputs encoded packets. Finally those are passed to the muxer, which writes the encoded packets to the output file.

3.1 Filtering

Before encoding, ffmpeg can process raw audio and video frames using filters from the libavfilter library. Several chained filters form a filter graph. ffmpeg distinguishes between two types of filtergraphs: simple and complex.

3.1.1 Simple filtergraphs

Simple filtergraphs are those that have exactly one input and output, both of the same type. In the above diagram they can be represented by simply inserting an additional step between decoding and encoding:

 _________                        ______________
|         |                      |              |
| decoded |                      | encoded data |
| frames  |\                   _ | packets      |
|_________| \                  /||______________|
             \   __________   /
  simple     _\||          | /  encoder
  filtergraph   | filtered |/
                | frames   |
                |__________|
                    

Simple filtergraphs are configured with the per-stream ‘ -filter ’ option (with ‘ -vf ’ and ‘ -af ’ aliases for video and audio respectively). A simple filtergraph for video can look for example like this:

 _______        _____________        _______        ________
|       |      |             |      |       |      |        |
| input | ---> | deinterlace | ---> | scale | ---> | output |
|_______|      |_____________|      |_______|      |________|
                    

Note that some filters change frame properties but not frame contents. E.g. the fps filter in the example above changes number of frames, but does not touch the frame contents. Another example is the setpts filter, which only sets timestamps and otherwise passes the frames unchanged.

3.1.2 Complex filtergraphs

Complex filtergraphs are those which cannot be described as simply a linear processing chain applied to one stream. This is the case, for example, when the graph has more than one input and/or output, or when output stream type is different from input. They can be represented with the following diagram:

 _________
|         |
| input 0 |\                    __________
|_________| \                  |          |
             \   _________    /| output 0 |
              \ |         |  / |__________|
 _________     \| complex | /
|         |     |         |/
| input 1 |---->| filter  |\
|_________|     |         | \   __________
               /| graph   |  \ |          |
              / |         |   \| output 1 |
 _________   /  |_________|    |__________|
|         | /
| input 2 |/
|_________|
                    

Complex filtergraphs are configured with the ‘ -filter_complex ’ option. Note that this option is global, since a complex filtergraph, by its nature, cannot be unambiguously associated with a single stream or file.

The ‘ -lavfi ’ option is equivalent to ‘ -filter_complex ’.

A trivial example of a complex filtergraph is the overlay filter, which has two video inputs and one video output, containing one video overlaid on top of the other. Its audio counterpart is the amix filter.

3.2 流拷贝

Stream copy is a mode selected by supplying the copy parameter to the ‘ -codec ’ option. It makes ffmpeg omit the decoding and encoding step for the specified stream, so it does only demuxing and muxing. It is useful for changing the container format or modifying container-level metadata. The diagram above will, in this case, simplify to this:

 _______              ______________            ________
|       |            |              |          |        |
| input |  demuxer   | encoded data |  muxer   | output |
| file  | ---------> | packets      | -------> | file   |
|_______|            |______________|          |________|
                    

Since there is no decoding or encoding, it is very fast and there is no quality loss. However, it might not work in some cases because of many factors. Applying filters is obviously also impossible, since filters work on uncompressed data.

4 流选定

ffmpeg provides the -map option for manual control of stream selection in each output file. Users can skip -map and let ffmpeg perform automatic stream selection as described below. The -vn / -an / -sn / -dn options can be used to skip inclusion of video, audio, subtitle and data streams respectively, whether manually mapped or automatically selected, except for those streams which are outputs of complex filtergraphs.

4.1 描述

The sub-sections that follow describe the various rules that are involved in stream selection. The examples that follow next show how these rules are applied in practice.

While every effort is made to accurately reflect the behavior of the program, FFmpeg is under continuous development and the code may have changed since the time of this writing.

4.1.1 Automatic stream selection

In the absence of any map options for a particular output file, ffmpeg inspects the output format to check which type of streams can be included in it, viz. video, audio and/or subtitles. For each acceptable stream type, ffmpeg will pick one stream, when available, from among all the inputs.

It will select that stream based upon the following criteria:

  • for video, it is the stream with the highest resolution,
  • for audio, it is the stream with the most channels,
  • for subtitles, it is the first subtitle stream found but there’s a caveat. The output format’s default subtitle encoder can be either text-based or image-based, and only a subtitle stream of the same type will be chosen.

In the case where several streams of the same type rate equally, the stream with the lowest index is chosen.

Data or attachment streams are not automatically selected and can only be included 使用 -map .

4.1.2 Manual stream selection

When -map is used, only user-mapped streams are included in that output file, with one possible exception for filtergraph outputs described below.

4.1.3 Complex filtergraphs

If there are any complex filtergraph output streams with unlabeled pads, they will be added to the first output file. This will lead to a fatal error if the stream type is not supported by the output format. In the absence of the map option, the inclusion of these streams leads to the automatic stream selection of their types being skipped. If map options are present, these filtergraph streams are included in addition to the mapped streams.

Complex filtergraph output streams with labeled pads must be mapped once and exactly once.

4.1.4 Stream handling

Stream handling is independent of stream selection, with an exception for subtitles described below. Stream handling is set via the -codec option addressed to streams within a specific output file. In particular, codec options are applied by ffmpeg after the stream selection process and thus do not influence the latter. If no -codec option is specified for a stream type, ffmpeg will select the default encoder registered by the output file muxer.

An exception exists for subtitles. If a subtitle encoder is specified for an output file, the first subtitle stream found of any type, text or image, will be included. ffmpeg does not validate if the specified encoder can convert the selected stream or if the converted stream is acceptable within the output format. This applies generally as well: when the user sets an encoder manually, the stream selection process cannot check if the encoded stream can be muxed into the output file. If it cannot, ffmpeg will abort and all output files will fail to be processed.

4.2 范例

The following examples illustrate the behavior, quirks and limitations of ffmpeg’s stream selection methods.

They assume the following three input files.

input file 'A.avi'
      stream 0: video 640x360
      stream 1: audio 2 channels
input file 'B.mp4'
      stream 0: video 1920x1080
      stream 1: audio 2 channels
      stream 2: subtitles (text)
      stream 3: audio 5.1 channels
      stream 4: subtitles (text)
input file 'C.mkv'
      stream 0: video 1280x720
      stream 1: audio 2 channels
      stream 2: subtitles (image)
                    

Example: automatic stream selection

ffmpeg -i A.avi -i B.mp4 out1.mkv out2.wav -map 1:a -c:a copy out3.mov
                        

There are three output files specified, and for the first two, no -map options are set, so ffmpeg will select streams for these two files automatically.

out1.mkv ’ is a Matroska container file and accepts video, audio and subtitle streams, so ffmpeg will try to select one of each type.
For video, it will select stream 0 from ‘ B.mp4 ’, which has the highest resolution among all the input video streams.
For audio, it will select stream 3 from ‘ B.mp4 ’, since it has the greatest number of channels.
For subtitles, it will select stream 2 from ‘ B.mp4 ’, which is the first subtitle stream from among ‘ A.avi ’ and ‘ B.mp4 ’.

out2.wav ’ accepts only audio streams, so only stream 3 from ‘ B.mp4 ’ is selected.

For ‘ out3.mov ’, since a -map option is set, no automatic stream selection will occur. The -map 1:a option will select all audio streams from the second input ‘ B.mp4 ’. No other streams will be included in this output file.

For the first two outputs, all included streams will be transcoded. The encoders chosen will be the default ones registered by each output format, which may not match the codec of the selected input streams.

For the third output, codec option for audio streams has been set to copy , so no decoding-filtering-encoding operations will occur, or can occur. Packets of selected streams shall be conveyed from the input file and muxed within the output file.

Example: automatic subtitles selection

ffmpeg -i C.mkv out1.mkv -c:s dvdsub -an out2.mkv
                        

Although ‘ out1.mkv ’ is a Matroska container file which accepts subtitle streams, only a video and audio stream shall be selected. The subtitle stream of ‘ C.mkv ’ is image-based and the default subtitle encoder of the Matroska muxer is text-based, so a transcode operation for the subtitles is expected to fail and hence the stream isn’t selected. However, in ‘ out2.mkv ’, a subtitle encoder is specified in the command and so, the subtitle stream is selected, in addition to the video stream. The presence of -an disables audio stream selection for ‘ out2.mkv ’.

Example: unlabeled filtergraph outputs

ffmpeg -i A.avi -i C.mkv -i B.mp4 -filter_complex "overlay" out1.mp4 out2.srt
                        

A filtergraph is setup here using the -filter_complex option and consists of a single video filter. The overlay filter requires exactly two video inputs, but none are specified, so the first two available video streams are used, those of ‘ A.avi ’ and ‘ C.mkv ’. The output pad of the filter has no label and so is sent to the first output file ‘ out1.mp4 ’. Due to this, automatic selection of the video stream is skipped, which would have selected the stream in ‘ B.mp4 ’. The audio stream with most channels viz. stream 3 in ‘ B.mp4 ’, is chosen automatically. No subtitle stream is chosen however, since the MP4 format has no default subtitle encoder registered, and the user hasn’t specified a subtitle encoder.

The 2nd output file, ‘ out2.srt ’, only accepts text-based subtitle streams. So, even though the first subtitle stream available belongs to ‘ C.mkv ’, it is image-based and hence skipped. The selected stream, stream 2 in ‘ B.mp4 ’, is the first text-based subtitle stream.

Example: labeled filtergraph outputs

ffmpeg -i A.avi -i B.mp4 -i C.mkv -filter_complex "[1:v]hue=s=0[outv];overlay;aresample" \
       -map '[outv]' -an        out1.mp4 \
                                out2.mkv \
       -map '[outv]' -map 1:a:0 out3.mkv
                        

The above command will fail, as the output pad labelled [outv] has been mapped twice. None of the output files shall be processed.

ffmpeg -i A.avi -i B.mp4 -i C.mkv -filter_complex "[1:v]hue=s=0[outv];overlay;aresample" \
       -an        out1.mp4 \
                  out2.mkv \
       -map 1:a:0 out3.mkv
                        

This command above will also fail as the hue filter output has a label, [outv] , and hasn’t been mapped anywhere.

The command should be modified as follows,

ffmpeg -i A.avi -i B.mp4 -i C.mkv -filter_complex "[1:v]hue=s=0,split=2[outv1][outv2];overlay;aresample" \
        -map '[outv1]' -an        out1.mp4 \
                                  out2.mkv \
        -map '[outv2]' -map 1:a:0 out3.mkv
                        

The video stream from ‘ B.mp4 ’ is sent to the hue filter, whose output is cloned once using the split filter, and both outputs labelled. Then a copy each is mapped to the first and third output files.

The overlay filter, requiring two video inputs, uses the first two unused video streams. Those are the streams from ‘ A.avi ’ and ‘ C.mkv ’. The overlay output isn’t labelled, so it is sent to the first output file ‘ out1.mp4 ’, regardless of the presence of the -map option.

The aresample filter is sent the first unused audio stream, that of ‘ A.avi ’. Since this filter output is also unlabelled, it too is mapped to the first output file. The presence of -an only suppresses automatic or manual stream selection of audio streams, not outputs sent from filtergraphs. Both these mapped streams shall be ordered before the mapped stream in ‘ out1.mp4 ’.

The video, audio and subtitle streams mapped to out2.mkv are entirely determined by automatic stream selection.

out3.mkv ’ consists of the cloned video output from the hue filter and the first audio stream from ‘ B.mp4 ’.

5 选项

All the numerical options, if not specified otherwise, accept a string representing a number as input, which may be followed by one of the SI unit prefixes, for example: ’K’, ’M’, or ’G’.

If ’i’ is appended to the SI unit prefix, the complete prefix will be interpreted as a unit prefix for binary multiples, which are based on powers of 1024 instead of powers of 1000. Appending ’B’ to the SI unit prefix multiplies the value by 8. This allows using, for example: ’KB’, ’MiB’, ’G’ and ’B’ as number suffixes.

Options which do not take arguments are boolean options, and set the corresponding value to true. They can be set to false by prefixing the option name with "no". For example using "-nofoo" will set the boolean option with name "foo" to false.

5.1 Stream specifiers

Some options are applied per-stream, e.g. bitrate or codec. Stream specifiers are used to precisely specify which stream(s) a given option belongs to.

A stream specifier is a string generally appended to the option name and separated from it by a colon. E.g. -codec:a:1 ac3 contains the a:1 stream specifier, which matches the second audio stream. Therefore, it would select the ac3 codec for the second audio stream.

A stream specifier can match several streams, so that the option is applied to all of them. E.g. the stream specifier in -b:a 128k matches all audio streams.

An empty stream specifier matches all streams. For example, -codec copy -codec: copy would copy all the streams without reencoding.

Possible forms of stream specifiers are:

stream_index

Matches the stream with this index. E.g. -threads:1 4 would set the thread count for the second stream to 4. If stream_index is used as an additional stream specifier (see below), then it selects stream number stream_index from the matching streams. Stream numbering is based on the order of the streams as detected by libavformat except when a program ID is also specified. In this case it is based on the ordering of the streams in the program.

stream_type [: additional_stream_specifier ]

stream_type is one of following: ’v’ or ’V’ for video, ’a’ for audio, ’s’ for subtitle, ’d’ for data, and ’t’ for attachments. ’v’ matches all video streams, ’V’ only matches video streams which are not attached pictures, video thumbnails or cover arts. If additional_stream_specifier is used, then it matches streams which both have this type and match the additional_stream_specifier . Otherwise, it matches all streams of the specified type.

p: program_id [: additional_stream_specifier ]

Matches streams which are in the program with the id program_id . If additional_stream_specifier is used, then it matches streams which both are part of the program and match the additional_stream_specifier .

# stream_id or i: stream_id

Match the stream by stream id (e.g. PID in MPEG-TS container).

m: key [: value ]

Matches streams with the metadata tag key having the specified value. If value is not given, matches streams that contain the given tag with any value.

u

Matches streams with usable configuration, the codec must be defined and the essential information such as video dimension or audio sample rate must be present.

Note that in ffmpeg , matching by metadata will only work properly for input files.

5.2 Generic options

These options are shared amongst the ff* tools.

-L

展示许可。

-h, -?, -help, --help [ arg ]

Show help. An optional parameter may be specified to print help about a specific item. If no argument is specified, only basic (non advanced) tool options are shown.

Possible values of arg are:

long

Print advanced tool options in addition to the basic tool options.

full

Print complete list of options, including shared and private options for encoders, decoders, demuxers, muxers, filters, etc.

decoder= decoder_name

Print detailed information about the decoder named decoder_name . Use the ‘ -decoders ’ option to get a list of all decoders.

encoder= encoder_name

Print detailed information about the encoder named encoder_name . Use the ‘ -encoders ’ option to get a list of all encoders.

demuxer= demuxer_name

Print detailed information about the demuxer named demuxer_name . Use the ‘ -formats ’ option to get a list of all demuxers and muxers.

muxer= muxer_name

Print detailed information about the muxer named muxer_name . Use the ‘ -formats ’ option to get a list of all muxers and demuxers.

filter= filter_name

Print detailed information about the filter name filter_name . Use the ‘ -filters ’ option to get a list of all filters.

bsf= bitstream_filter_name

Print detailed information about the bitstream filter name bitstream_filter_name . Use the ‘ -bsfs ’ option to get a list of all bitstream filters.

-version

Show version.

-formats

Show available formats (including devices).

-demuxers

Show available demuxers.

-muxers

Show available muxers.

-devices

Show available devices.

-codecs

Show all codecs known to libavcodec.

Note that the term ’codec’ is used throughout this documentation as a shortcut for what is more correctly called a media bitstream format.

-decoders

Show available decoders.

-encoders

Show all available encoders.

-bsfs

Show available bitstream filters.

-protocols

Show available protocols.

-filters

Show available libavfilter filters.

-pix_fmts

Show available pixel formats.

-sample_fmts

Show available sample formats.

-layouts

Show channel names and standard channel layouts.

-colors

Show recognized color names.

-sources device [, opt1 = val1 [, opt2 = val2 ]...]

Show autodetected sources of the input device. Some devices may provide system-dependent source names that cannot be autodetected. The returned list cannot be assumed to be always complete.

ffmpeg -sources pulse,server=192.168.0.4
                                
-sinks device [, opt1 = val1 [, opt2 = val2 ]...]

Show autodetected sinks of the output device. Some devices may provide system-dependent sink names that cannot be autodetected. The returned list cannot be assumed to be always complete.

ffmpeg -sinks pulse,server=192.168.0.4
                                
-loglevel [ flags +] loglevel | -v [ flags +] loglevel

Set logging level and flags used by the library.

The optional flags prefix can consist of the following values:

repeat

Indicates that repeated log output should not be compressed to the first line and the "Last message repeated n times" line will be omitted.

level

Indicates that log output should add a [level] prefix to each message line. This can be used as an alternative to log coloring, e.g. when dumping the log to file.

Flags can also be used alone by adding a ’+’/’-’ prefix to set/reset a single flag without affecting other flags or changing loglevel . When setting both flags and loglevel , a ’+’ separator is expected between the last flags value and before loglevel .

loglevel is a string or a number containing one of the following values:

quiet, -8

Show nothing at all; be silent.

panic, 0

Only show fatal errors which could lead the process to crash, such as an assertion failure. This is not currently used for anything.

fatal, 8

Only show fatal errors. These are errors after which the process absolutely cannot continue.

error, 16

Show all errors, including ones which can be recovered from.

warning, 24

Show all warnings and errors. Any message related to possibly incorrect or unexpected events will be shown.

info, 32

Show informative messages during processing. This is in addition to warnings and errors. This is the default value.

verbose, 40

如同 info , except more verbose.

debug, 48

Show everything, including debugging information.

trace, 56

For example to enable repeated log output, add the level prefix, and set loglevel to verbose :

ffmpeg -loglevel repeat+level+verbose -i input output
                                

Another example that enables repeated log output without affecting current state of level prefix flag or loglevel :

ffmpeg [...] -loglevel +repeat
                                

By default the program logs to stderr. If coloring is supported by the terminal, colors are used to mark errors and warnings. Log coloring can be disabled setting the environment variable AV_LOG_FORCE_NOCOLOR NO_COLOR , or can be forced setting the environment variable AV_LOG_FORCE_COLOR . The use of the environment variable NO_COLOR is deprecated and will be dropped in a future FFmpeg version.

-report

Dump full command line and console output to a file named program - YYYYMMDD - HHMMSS .log in the current directory. This file can be useful for bug reports. It also implies -loglevel debug .

Setting the environment variable FFREPORT to any value has the same effect. If the value is a ’:’-separated key=value sequence, these options will affect the report; option values must be escaped if they contain special characters or the options delimiter ’:’ (see the “Quoting and escaping” section in the ffmpeg-utils manual).

The following options are recognized:

file

set the file name to use for the report; %p is expanded to the name of the program, %t is expanded to a timestamp, %% is expanded to a plain %

level

set the log verbosity level using a numerical value (see -loglevel ).

For example, to output a report to a file named ‘ ffreport.log ’ using a log level of 32 (alias for log level info ):

FFREPORT=file=ffreport.log:level=32 ffmpeg -i input output
                                

Errors in parsing the environment variable are not fatal, and will not appear in the report.

-hide_banner

抑制打印横幅。

All FFmpeg tools will normally show a copyright notice, build options and library versions. This option can be used to suppress printing this information.

-cpuflags flags ( global )

Allows setting and clearing cpu flags. This option is intended for testing. Do not use it unless you know what you’re doing.

ffmpeg -cpuflags -sse+mmx ...
ffmpeg -cpuflags mmx ...
ffmpeg -cpuflags 0 ...
                                

Possible flags for this option are:

x86
mmx
mmxext
sse
sse2
sse2slow
sse3
sse3slow
ssse3
atom
sse4.1
sse4.2
avx
avx2
xop
fma3
fma4
3dnow
3dnowext
bmi1
bmi2
cmov
ARM
armv5te
armv6
armv6t2
vfp
vfpv3
neon
setend
AArch64
armv8
vfp
neon
PowerPC
altivec
Specific Processors
pentium2
pentium3
pentium4
k6
k62
athlon
athlonxp
k8

5.3 AVOptions

These options are provided directly by the libavformat, libavdevice and libavcodec libraries. To see the list of available AVOptions, use the ‘ -help ’ option. They are separated into two categories:

generic

These options can be set for any container, codec or device. Generic options are listed under AVFormatContext options for containers/devices and under AVCodecContext options for codecs.

private

These options are specific to the given container, device or codec. Private options are listed under their corresponding containers/devices/codecs.

For example to write an ID3v2.3 header instead of a default ID3v2.4 to an MP3 file, use the ‘ id3v2_version ’ private option of the MP3 muxer:

ffmpeg -i input.flac -id3v2_version 3 out.mp3
                        

All codec AVOptions are per-stream, and thus a stream specifier should be attached to them:

ffmpeg -i multichannel.mxf -map 0:v:0 -map 0:a:0 -map 0:a:0 -c:a:0 ac3 -b:a:0 640k -ac:a:1 2 -c:a:1 aac -b:2 128k out.mp4
                        

In the above example, a multichannel audio stream is mapped twice for output. The first instance is encoded with codec ac3 and bitrate 640k. The second instance is downmixed to 2 channels and encoded with codec aac. A bitrate of 128k is specified for it using absolute index of the output stream.

Note: the ‘ -nooption ’ syntax cannot be used for boolean AVOptions, use ‘ -option 0 ’/‘ -option 1 ’.

Note: the old undocumented way of specifying per-stream AVOptions by prepending v/a/s to the options name is now obsolete and will be removed soon.

5.4 主要选项

-f fmt ( input/output )

Force input or output file format. The format is normally auto detected for input files and guessed from the file extension for output files, so this option is not needed in most cases.

-i url ( input )

输入文件 URL

-y ( global )

不询问覆写输出文件。

-n ( global )

Do not overwrite output files, and exit immediately if a specified output file already exists.

-stream_loop number ( input )

Set number of times input stream shall be looped. Loop 0 means no loop, loop -1 means infinite loop.

-c[: stream_specifier ] codec ( input/output,per-stream )
-codec[: stream_specifier ] codec ( input/output,per-stream )

Select an encoder (when used before an output file) or a decoder (when used before an input file) for one or more streams. codec is the name of a decoder/encoder or a special value copy (output only) to indicate that the stream is not to be re-encoded.

例如

ffmpeg -i INPUT -map 0 -c:v libx264 -c:a copy OUTPUT
                                

encodes all video streams with libx264 and copies all audio streams.

For each stream, the last matching c option is applied, so

ffmpeg -i INPUT -map 0 -c copy -c:v:1 libx264 -c:a:137 libvorbis OUTPUT
                                

will copy all the streams except the second video, which will be encoded with libx264, and the 138th audio, which will be encoded with libvorbis.

-t duration ( input/output )

When used as an input option (before -i ), limit the duration of data read from the input file.

When used as an output option (before an output url), stop writing the output after its duration reaches duration .

duration must be a time duration specification, see (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual .

-to and -t are mutually exclusive and -t has priority.

-to position ( input/output )

Stop writing the output or reading the input at position . position must be a time duration specification, see (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual .

-to and -t are mutually exclusive and -t has priority.

-fs limit_size ( output )

Set the file size limit, expressed in bytes. No further chunk of bytes is written after the limit is exceeded. The size of the output file is slightly more than the requested file size.

-ss position ( input/output )

When used as an input option (before -i ), seeks in this input file to position . Note that in most formats it is not possible to seek exactly, so ffmpeg will seek to the closest seek point before position . When transcoding and ‘ -accurate_seek ’ is enabled (the default), this extra segment between the seek point and position will be decoded and discarded. When doing stream copy or when ‘ -noaccurate_seek ’ is used, it will be preserved.

When used as an output option (before an output url), decodes but discards input until the timestamps reach position .

position must be a time duration specification, see (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual .

-sseof position ( input )

Like the -ss option but relative to the "end of file". That is negative values are earlier in the file, 0 is at EOF.

-itsoffset offset ( input )

Set the input time offset.

offset must be a time duration specification, see (ffmpeg-utils)the Time duration section in the ffmpeg-utils(1) manual .

The offset is added to the timestamps of the input files. Specifying a positive offset means that the corresponding streams are delayed by the time duration specified in offset .

-itsscale scale ( input,per-stream )

Rescale input timestamps. scale should be a floating point number.

-timestamp date ( output )

Set the recording timestamp in the container.

date must be a date specification, see (ffmpeg-utils)the Date section in the ffmpeg-utils(1) manual .

-metadata[:metadata_specifier] key = value ( output,per-metadata )

Set a metadata key/value pair.

An optional metadata_specifier may be given to set metadata on streams, chapters or programs. See -map_metadata 文档编制,了解细节。

This option overrides metadata set with -map_metadata . It is also possible to delete metadata by using an empty value.

For example, for setting the title in the output file:

ffmpeg -i in.avi -metadata title="my title" out.flv
                                

To set the language of the first audio stream:

ffmpeg -i INPUT -metadata:s:a:0 language=eng OUTPUT
                                
-disposition[:stream_specifier] value ( output,per-stream )

Sets the disposition for a stream.

This option overrides the disposition copied from the input stream. It is also possible to delete the disposition by setting it to 0.

The following dispositions are recognized:

default
dub
original
comment
lyrics
karaoke
forced
hearing_impaired
visual_impaired
clean_effects
attached_pic
captions
descriptions
dependent
metadata

For example, to make the second audio stream the default stream:

ffmpeg -i in.mkv -c copy -disposition:a:1 default out.mkv
                                

To make the second subtitle stream the default stream and remove the default disposition from the first subtitle stream:

ffmpeg -i in.mkv -c copy -disposition:s:0 0 -disposition:s:1 default out.mkv
                                

To add an embedded cover/thumbnail:

ffmpeg -i in.mp4 -i IMAGE -map 0 -map 1 -c copy -c:v:1 png -disposition:v:1 attached_pic out.mp4
                                

Not all muxers support embedded thumbnails, and those who do, only support a few formats, like JPEG or PNG.

-program [title= title :][program_num= program_num :]st= stream [:st= stream ...] ( output )

Creates a program with the specified title , program_num and adds the specified stream (s) to it.

-target type ( output )

Specify target file type ( vcd , svcd , dvd , dv , dv50 ). type may be prefixed with pal- , ntsc- film- to use the corresponding standard. All the format options (bitrate, codecs, buffer sizes) are then set automatically. You can just type:

ffmpeg -i myfile.avi -target vcd /tmp/vcd.mpg
                                

Nevertheless you can specify additional options as long as you know they do not conflict with the standard, as in:

ffmpeg -i myfile.avi -target vcd -bf 2 /tmp/vcd.mpg
                                
-dn ( input/output )

As an input option, blocks all data streams of a file from being filtered or being automatically selected or mapped for any output. See -discard option to disable streams individually.

As an output option, disables data recording i.e. automatic selection or mapping of any data stream. For full manual control see the -map option.

-dframes number ( output )

Set the number of data frames to output. This is an obsolete alias for -frames:d , which you should use instead.

-frames[: stream_specifier ] framecount ( output,per-stream )

Stop writing to the stream after framecount 帧。

-q[: stream_specifier ] q ( output,per-stream )
-qscale[: stream_specifier ] q ( output,per-stream )

Use fixed quality scale (VBR). The meaning of q / qscale is codec-dependent. 若 qscale is used without a stream_specifier then it applies only to the video stream, this is to maintain compatibility with previous behavior and as specifying the same codec specific value to 2 different codecs that is audio and video generally is not what is intended when no stream_specifier is used.

-filter[: stream_specifier ] filtergraph ( output,per-stream )

Create the filtergraph specified by filtergraph and use it to filter the stream.

filtergraph is a description of the filtergraph to apply to the stream, and must have a single input and a single output of the same type of the stream. In the filtergraph, the input is associated to the label in , and the output to the label out 。请参阅 the ffmpeg-filters manual for more information about the filtergraph syntax.

-filter_complex option if you want to create filtergraphs with multiple inputs and/or outputs.

-filter_script[: stream_specifier ] filename ( output,per-stream )

This option is similar to ‘ -filter ’, the only difference is that its argument is the name of the file from which a filtergraph description is to be read.

-filter_threads nb_threads ( global )

Defines how many threads are used to process a filter pipeline. Each pipeline will produce a thread pool with this many threads available for parallel processing. The default is the number of available CPUs.

-pre[: stream_specifier ] preset_name ( output,per-stream )

Specify the preset for matching stream(s).

-stats ( global )

Print encoding progress/statistics. It is on by default, to explicitly disable it you need to specify -nostats .

-progress url ( global )

Send program-friendly progress information to url .

Progress information is written approximately every second and at the end of the encoding process. It is made of " key = value " lines. key consists of only alphanumeric characters. The last key of a sequence of progress information is always "progress".

-stdin

Enable interaction on standard input. On by default unless standard input is used as an input. To explicitly disable interaction you need to specify -nostdin .

Disabling interaction on standard input is useful, for example, if ffmpeg is in the background process group. Roughly the same result can be achieved with ffmpeg ... < /dev/null but it requires a shell.

-debug_ts ( global )

Print timestamp information. It is off by default. This option is mostly useful for testing and debugging purposes, and the output format may change from one version to another, so it should not be employed by portable scripts.

See also the option -fdebug ts .

-attach filename ( output )

Add an attachment to the output file. This is supported by a few formats like Matroska for e.g. fonts used in rendering subtitles. Attachments are implemented as a specific type of stream, so this option will add a new stream to the file. It is then possible to use per-stream options on this stream in the usual way. Attachment streams created with this option will be created after all the other streams (i.e. those created with -map or automatic mappings).

Note that for Matroska you also have to set the mimetype metadata tag:

ffmpeg -i INPUT -attach DejaVuSans.ttf -metadata:s:2 mimetype=application/x-truetype-font out.mkv
                                

(assuming that the attachment stream will be third in the output file).

-dump_attachment[: stream_specifier ] filename ( input,per-stream )

Extract the matching attachment stream into a file named filename . If filename is empty, then the value of the filename metadata tag will be used.

E.g. to extract the first attachment to a file named ’out.ttf’:

ffmpeg -dump_attachment:t:0 out.ttf -i INPUT
                                

To extract all attachments to files determined by the filename tag:

ffmpeg -dump_attachment:t "" -i INPUT
                                

Technical note – attachments are implemented as codec extradata, so this option can actually be used to extract extradata from any stream, not just attachments.

-noautorotate

Disable automatically rotating video based on file metadata.

5.5 视频选项

-vframes number ( output )

Set the number of video frames to output. This is an obsolete alias for -frames:v , which you should use instead.

-r[: stream_specifier ] fps ( input/output,per-stream )

Set frame rate (Hz value, fraction or abbreviation).

As an input option, ignore any timestamps stored in the file and instead generate timestamps assuming constant frame rate fps . This is not the same as the ‘ -framerate ’ option used for some input formats like image2 or v4l2 (it used to be the same in older versions of FFmpeg). If in doubt use ‘ -framerate ’ instead of the input option ‘ -r ’.

As an output option, duplicate or drop input frames to achieve constant output frame rate fps .

-s[: stream_specifier ] size ( input/output,per-stream )

Set frame size.

As an input option, this is a shortcut for the ‘ video_size ’ private option, recognized by some demuxers for which the frame size is either not stored in the file or is configurable – e.g. raw video or video grabbers.

As an output option, this inserts the scale video filter to the end of the corresponding filtergraph. Please use the scale filter directly to insert it at the beginning or some other place.

The format is ‘ wxh ’ (default - same as source).

-aspect[: stream_specifier ] aspect ( output,per-stream )

Set the video display aspect ratio specified by aspect .

aspect can be a floating point number string, or a string of the form num : den , where num and den are the numerator and denominator of the aspect ratio. For example "4:3", "16:9", "1.3333", and "1.7777" are valid argument values.

If used together with ‘ -vcodec copy ’, it will affect the aspect ratio stored at container level, but not the aspect ratio stored in encoded frames, if it exists.

-vn ( input/output )

As an input option, blocks all video streams of a file from being filtered or being automatically selected or mapped for any output. See -discard option to disable streams individually.

As an output option, disables video recording i.e. automatic selection or mapping of any video stream. For full manual control see the -map option.

-vcodec codec ( output )

Set the video codec. This is an alias for -codec:v .

-pass[: stream_specifier ] n ( output,per-stream )

Select the pass number (1 or 2). It is used to do two-pass video encoding. The statistics of the video are recorded in the first pass into a log file (see also the option -passlogfile), and in the second pass that log file is used to generate the video at the exact requested bitrate. On pass 1, you may just deactivate audio and set output to null, examples for Windows and Unix:

ffmpeg -i foo.mov -c:v libxvid -pass 1 -an -f rawvideo -y NUL
ffmpeg -i foo.mov -c:v libxvid -pass 1 -an -f rawvideo -y /dev/null
                                
-passlogfile[: stream_specifier ] prefix ( output,per-stream )

Set two-pass log file name prefix to prefix , the default file name prefix is “ffmpeg2pass”. The complete file name will be ‘ PREFIX-N.log ’, where N is a number specific to the output stream

-vf filtergraph ( output )

Create the filtergraph specified by filtergraph and use it to filter the stream.

This is an alias for -filter:v ,见 -filter 选项 .

5.6 高级视频选项

-pix_fmt[: stream_specifier ] format ( input/output,per-stream )

Set pixel format. Use -pix_fmts to show all the supported pixel formats. If the selected pixel format can not be selected, ffmpeg will print a warning and select the best pixel format supported by the encoder. 若 pix_fmt is prefixed by a + , ffmpeg will exit with an error if the requested pixel format can not be selected, and automatic conversions inside filtergraphs are disabled. 若 pix_fmt is a single + , ffmpeg selects the same pixel format as the input (or graph output) and automatic conversions are disabled.

-sws_flags flags ( input/output )

设置 SwScaler 标志。

-rc_override[: stream_specifier ] override ( output,per-stream )

Rate control override for specific intervals, formatted as "int,int,int" list separated with slashes. Two first values are the beginning and end frame numbers, last one is quantizer to use if positive, or quality factor if negative.

-ilme

Force interlacing support in encoder (MPEG-2 and MPEG-4 only). Use this option if your input file is interlaced and you want to keep the interlaced format for minimum losses. The alternative is to deinterlace the input stream with ‘ -deinterlace ’, but deinterlacing introduces losses.

-psnr

Calculate PSNR of compressed frames.

-vstats

Dump video coding statistics to ‘ vstats_HHMMSS.log ’.

-vstats_file file

Dump video coding statistics to file .

-vstats_version file

Specifies which version of the vstats format to use. Default is 2.

version = 1 :

frame= %5d q= %2.1f PSNR= %6.2f f_size= %6d s_size= %8.0fkB time= %0.3f br= %7.1fkbits/s avg_br= %7.1fkbits/s

version > 1:

out= %2d st= %2d frame= %5d q= %2.1f PSNR= %6.2f f_size= %6d s_size= %8.0fkB time= %0.3f br= %7.1fkbits/s avg_br= %7.1fkbits/s

-top[: stream_specifier ] n ( output,per-stream )

top=1/bottom=0/auto=-1 field first

-dc precision

Intra_dc_precision.

-vtag fourcc/tag ( output )

Force video tag/fourcc. This is an alias for -tag:v .

-qphist ( global )

Show QP histogram

-vbsf bitstream_filter

Deprecated see -bsf

-force_key_frames[: stream_specifier ] time [, time ...] ( output,per-stream )
-force_key_frames[: stream_specifier ] expr: expr ( output,per-stream )

Force key frames at the specified timestamps, more precisely at the first frames after each specified time.

If the argument is prefixed with expr: , the string expr is interpreted like an expression and is evaluated for each frame. A key frame is forced in case the evaluation is non-zero.

If one of the times is " chapters [ delta ]", it is expanded into the time of the beginning of all chapters in the file, shifted by delta , expressed as a time in seconds. This option can be useful to ensure that a seek point is present at a chapter mark or any other designated place in the output file.

For example, to insert a key frame at 5 minutes, plus key frames 0.1 second before the beginning of every chapter:

-force_key_frames 0:05:00,chapters-0.1
                                

The expression in expr can contain the following constants:

n

the number of current processed frame, starting from 0

n_forced

the number of forced frames

prev_forced_n

the number of the previous forced frame, it is NAN when no keyframe was forced yet

prev_forced_t

the time of the previous forced frame, it is NAN when no keyframe was forced yet

t

the time of the current processed frame

For example to force a key frame every 5 seconds, you can specify:

-force_key_frames expr:gte(t,n_forced*5)
                                

To force a key frame 5 seconds after the time of the last forced one, starting from second 13:

-force_key_frames expr:if(isnan(prev_forced_t),gte(t,13),gte(t,prev_forced_t+5))
                                

Note that forcing too many keyframes is very harmful for the lookahead algorithms of certain encoders: using fixed-GOP options or similar would be more efficient.

-copyinkf[: stream_specifier ] ( output,per-stream )

When doing stream copy, copy also non-key frames found at the beginning.

-init_hw_device type [= name ][: device [, key=value ...]]

Initialise a new hardware device of type type called name , using the given device parameters. If no name is specified it will receive a default name of the form " type %d".

The meaning of device and the following arguments depends on the device type:

cuda

device is the number of the CUDA device.

dxva2

device is the number of the Direct3D 9 display adapter.

vaapi

device is either an X11 display name or a DRM render node. If not specified, it will attempt to open the default X11 display ( $DISPLAY ) and then the first DRM render node ( /dev/dri/renderD128 ).

vdpau

device is an X11 display name. If not specified, it will attempt to open the default X11 display ( $DISPLAY ).

qsv

device selects a value in ‘ MFX_IMPL_* ’. Allowed values are:

auto
sw
hw
auto_any
hw_any
hw2
hw3
hw4

If not specified, ‘ auto_any ’ is used. (Note that it may be easier to achieve the desired result for QSV by creating the platform-appropriate subdevice (‘ dxva2 ’ or ‘ vaapi ’) and then deriving a QSV device from that.)

opencl

device selects the platform and device as platform_index.device_index .

The set of devices can also be filtered using the key-value pairs to find only devices matching particular platform or device strings.

The strings usable as filters are:

platform_profile
platform_version
platform_name
platform_vendor
platform_extensions
device_name
device_vendor
driver_version
device_version
device_profile
device_extensions
device_type

The indices and filters must together uniquely select a device.

范例:

-init_hw_device opencl:0.1

Choose the second device on the first platform.

-init_hw_device opencl:,device_name=Foo9000

Choose the device with a name containing the string Foo9000 .

-init_hw_device opencl:1,device_type=gpu,device_extensions=cl_khr_fp16

Choose the GPU device on the second platform supporting the cl_khr_fp16 extension.

-init_hw_device type [= name ]@ source

Initialise a new hardware device of type type called name , deriving it from the existing device with the name source .

-init_hw_device list

List all hardware device types supported in this build of ffmpeg.

-filter_hw_device name

Pass the hardware device called name to all filters in any filter graph. This can be used to set the device to upload to with the hwupload filter, or the device to map to with the hwmap filter. Other filters may also make use of this parameter when they require a hardware device. Note that this is typically only required when the input is not already in hardware frames - when it is, filters will derive the device they require from the context of the frames they receive as input.

This is a global setting, so all filters will receive the same device.

-hwaccel[: stream_specifier ] hwaccel ( input,per-stream )

Use hardware acceleration to decode the matching stream(s). The allowed values of hwaccel are:

none

Do not use any hardware acceleration (the default).

auto

Automatically select the hardware acceleration method.

vdpau

Use VDPAU (Video Decode and Presentation API for Unix) hardware acceleration.

dxva2

Use DXVA2 (DirectX Video Acceleration) hardware acceleration.

vaapi

Use VAAPI (Video Acceleration API) hardware acceleration.

qsv

Use the Intel QuickSync Video acceleration for video transcoding.

Unlike most other values, this option does not enable accelerated decoding (that is used automatically whenever a qsv decoder is selected), but accelerated transcoding, without copying the frames into the system memory.

For it to work, both the decoder and the encoder must support QSV acceleration and no filters must be used.

This option has no effect if the selected hwaccel is not available or not supported by the chosen decoder.

Note that most acceleration methods are intended for playback and will not be faster than software decoding on modern CPUs. Additionally, ffmpeg will usually need to copy the decoded frames from the GPU memory into the system memory, resulting in further performance loss. This option is thus mainly useful for testing.

-hwaccel_device[: stream_specifier ] hwaccel_device ( input,per-stream )

Select a device to use for hardware acceleration.

This option only makes sense when the ‘ -hwaccel ’ option is also specified. It can either refer to an existing device created with ‘ -init_hw_device ’ by name, or it can create a new device as if ‘ -init_hw_device type : hwaccel_device were called immediately before.

-hwaccels

List all hardware acceleration methods supported in this build of ffmpeg.

5.7 音频选项

-aframes number ( output )

Set the number of audio frames to output. This is an obsolete alias for -frames:a , which you should use instead.

-ar[: stream_specifier ] freq ( input/output,per-stream )

Set the audio sampling frequency. For output streams it is set by default to the frequency of the corresponding input stream. For input streams this option only makes sense for audio grabbing devices and raw demuxers and is mapped to the corresponding demuxer options.

-aq q ( output )

Set the audio quality (codec-specific, VBR). This is an alias for -q:a.

-ac[: stream_specifier ] channels ( input/output,per-stream )

Set the number of audio channels. For output streams it is set by default to the number of input audio channels. For input streams this option only makes sense for audio grabbing devices and raw demuxers and is mapped to the corresponding demuxer options.

-an ( input/output )

As an input option, blocks all audio streams of a file from being filtered or being automatically selected or mapped for any output. See -discard option to disable streams individually.

As an output option, disables audio recording i.e. automatic selection or mapping of any audio stream. For full manual control see the -map option.

-acodec codec ( input/output )

Set the audio codec. This is an alias for -codec:a .

-sample_fmt[: stream_specifier ] sample_fmt ( output,per-stream )

Set the audio sample format. Use -sample_fmts to get a list of supported sample formats.

-af filtergraph ( output )

Create the filtergraph specified by filtergraph and use it to filter the stream.

This is an alias for -filter:a ,见 -filter 选项 .

5.8 高级音频选项

-atag fourcc/tag ( output )

Force audio tag/fourcc. This is an alias for -tag:a .

-absf bitstream_filter

Deprecated, see -bsf

-guess_layout_max channels ( input,per-stream )

If some input channel layout is not known, try to guess only if it corresponds to at most the specified number of channels. For example, 2 tells to ffmpeg to recognize 1 channel as mono and 2 channels as stereo but not 6 channels as 5.1. The default is to always try to guess. Use 0 to disable all guessing.

5.9 字幕选项

-scodec codec ( input/output )

Set the subtitle codec. This is an alias for -codec:s .

-sn ( input/output )

As an input option, blocks all subtitle streams of a file from being filtered or being automatically selected or mapped for any output. See -discard option to disable streams individually.

As an output option, disables subtitle recording i.e. automatic selection or mapping of any subtitle stream. For full manual control see the -map option.

-sbsf bitstream_filter

Deprecated, see -bsf

5.10 高级字幕选项

-fix_sub_duration

Fix subtitles durations. For each subtitle, wait for the next packet in the same stream and adjust the duration of the first to avoid overlap. This is necessary with some subtitles codecs, especially DVB subtitles, because the duration in the original packet is only a rough estimate and the end is actually marked by an empty subtitle frame. Failing to use this option when necessary can result in exaggerated durations or muxing failures due to non-monotonic timestamps.

Note that this option will delay the output of all data until the next subtitle packet is decoded: it may increase memory consumption and latency a lot.

-canvas_size size

Set the size of the canvas used to render subtitles.

5.11 高级选项

-map [-] input_file_id [: stream_specifier ][?][, sync_file_id [: stream_specifier ]] | [linklabel] ( output )

Designate one or more input streams as a source for the output file. Each input stream is identified by the input file index input_file_id and the input stream index input_stream_id within the input file. Both indices start at 0. If specified, sync_file_id : stream_specifier sets which input stream is used as a presentation sync reference.

The first -map option on the command line specifies the source for output stream 0, the second -map option specifies the source for output stream 1, etc.

A - character before the stream identifier creates a "negative" mapping. It disables matching streams from already created mappings.

A trailing ? after the stream index will allow the map to be optional: if the map matches no streams the map will be ignored instead of failing. Note the map will still fail if an invalid input file index is used; such as if the map refers to a non-existent input.

An alternative [linklabel] form will map outputs from complex filter graphs (see the ‘ -filter_complex ’ option) to the output file. linklabel must correspond to a defined output link label in the graph.

For example, to map ALL streams from the first input file to output

ffmpeg -i INPUT -map 0 output
                                

For example, if you have two audio streams in the first input file, these streams are identified by "0:0" and "0:1". You can use -map to select which streams to place in an output file. For example:

ffmpeg -i INPUT -map 0:1 out.wav
                                

will map the input stream in ‘ INPUT ’ identified by "0:1" to the (single) output stream in ‘ out.wav ’.

For example, to select the stream with index 2 from input file ‘ a.mov ’ (specified by the identifier "0:2"), and stream with index 6 from input ‘ b.mov ’ (specified by the identifier "1:6"), and copy them to the output file ‘ out.mov ’:

ffmpeg -i a.mov -i b.mov -c copy -map 0:2 -map 1:6 out.mov
                                

To select all video and the third audio stream from an input file:

ffmpeg -i INPUT -map 0:v -map 0:a:2 OUTPUT
                                

To map all the streams except the second audio, use negative mappings

ffmpeg -i INPUT -map 0 -map -0:a:1 OUTPUT
                                

To map the video and audio streams from the first input, and using the trailing ? , ignore the audio mapping if no audio streams exist in the first input:

ffmpeg -i INPUT -map 0:v -map 0:a? OUTPUT
                                

To pick the English audio stream:

ffmpeg -i INPUT -map 0:m:language:eng OUTPUT
                                

Note that using this option disables the default mappings for this output file.

-ignore_unknown

Ignore input streams with unknown type instead of failing if copying such streams is attempted.

-copy_unknown

Allow input streams with unknown type to be copied instead of failing if copying such streams is attempted.

-map_channel [ input_file_id . stream_specifier . channel_id |-1][?][: output_file_id . stream_specifier ]

Map an audio channel from a given input to an output. If output_file_id . stream_specifier is not set, the audio channel will be mapped on all the audio streams.

Using "-1" instead of input_file_id . stream_specifier . channel_id will map a muted channel.

A trailing ? will allow the map_channel to be optional: if the map_channel matches no channel the map_channel will be ignored instead of failing.

For example, assuming INPUT is a stereo audio file, you can switch the two audio channels with the following command:

ffmpeg -i INPUT -map_channel 0.0.1 -map_channel 0.0.0 OUTPUT
                                

If you want to mute the first channel and keep the second:

ffmpeg -i INPUT -map_channel -1 -map_channel 0.0.1 OUTPUT
                                

The order of the "-map_channel" option specifies the order of the channels in the output stream. The output channel layout is guessed from the number of channels mapped (mono if one "-map_channel", stereo if two, etc.). Using "-ac" in combination of "-map_channel" makes the channel gain levels to be updated if input and output channel layouts don’t match (for instance two "-map_channel" options and "-ac 6").

You can also extract each channel of an input to specific outputs; the following command extracts two channels of the INPUT audio stream (file 0, stream 0) to the respective OUTPUT_CH0 and OUTPUT_CH1 outputs:

ffmpeg -i INPUT -map_channel 0.0.0 OUTPUT_CH0 -map_channel 0.0.1 OUTPUT_CH1
                                

The following example splits the channels of a stereo input into two separate streams, which are put into the same output file:

ffmpeg -i stereo.wav -map 0:0 -map 0:0 -map_channel 0.0.0:0.0 -map_channel 0.0.1:0.1 -y out.ogg
                                

Note that currently each output stream can only contain channels from a single input stream; you can’t for example use "-map_channel" to pick multiple input audio channels contained in different streams (from the same or different files) and merge them into a single output stream. It is therefore not currently possible, for example, to turn two separate mono streams into a single stereo stream. However splitting a stereo stream into two single channel mono streams is possible.

If you need this feature, a possible workaround is to use the amerge filter. For example, if you need to merge a media (here ‘ input.mkv ’) with 2 mono audio streams into one single stereo channel audio stream (and keep the video stream), you can use the following command:

ffmpeg -i input.mkv -filter_complex "[0:1] [0:2] amerge" -c:a pcm_s16le -c:v copy output.mkv
                                

To map the first two audio channels from the first input, and using the trailing ? , ignore the audio channel mapping if the first input is mono instead of stereo:

ffmpeg -i INPUT -map_channel 0.0.0 -map_channel 0.0.1? OUTPUT
                                
-map_metadata[: metadata_spec_out ] infile [: metadata_spec_in ] ( output,per-metadata )

Set metadata information of the next output file from infile 。注意 those are file indices (zero-based), not filenames. Optional metadata_spec_in/out parameters specify, which metadata to copy. A metadata specifier can have the following forms:

g

global metadata, i.e. metadata that applies to the whole file

s [: stream_spec ]

per-stream metadata. stream_spec is a stream specifier as described in the Stream specifiers chapter. In an input metadata specifier, the first matching stream is copied from. In an output metadata specifier, all matching streams are copied to.

c : chapter_index

per-chapter metadata. chapter_index is the zero-based chapter index.

p : program_index

per-program metadata. program_index is the zero-based program index.

If metadata specifier is omitted, it defaults to global.

By default, global metadata is copied from the first input file, per-stream and per-chapter metadata is copied along with streams/chapters. These default mappings are disabled by creating any mapping of the relevant type. A negative file index can be used to create a dummy mapping that just disables automatic copying.

For example to copy metadata from the first stream of the input file to global metadata of the output file:

ffmpeg -i in.ogg -map_metadata 0:s:0 out.mp3
                                

To do the reverse, i.e. copy global metadata to all audio streams:

ffmpeg -i in.mkv -map_metadata:s:a 0:g out.mkv
                                

Note that simple 0 would work as well in this example, since global metadata is assumed by default.

-map_chapters input_file_index ( output )

Copy chapters from input file with index input_file_index to the next output file. If no chapter mapping is specified, then chapters are copied from the first input file with at least one chapter. Use a negative file index to disable any chapter copying.

-benchmark ( global )

Show benchmarking information at the end of an encode. Shows real, system and user time used and maximum memory consumption. Maximum memory consumption is not supported on all systems, it will usually display as 0 if not supported.

-benchmark_all ( global )

Show benchmarking information during the encode. Shows real, system and user time used in various steps (audio/video encode/decode).

-timelimit duration ( global )

Exit after ffmpeg has been running for duration seconds.

-dump ( global )

Dump each input packet to stderr.

-hex ( global )

When dumping packets, also dump the payload.

-re ( input )

Read input at native frame rate. Mainly used to simulate a grab device, or live input stream (e.g. when reading from a file). Should not be used with actual grab devices or live input streams (where it can cause packet loss). By default ffmpeg attempts to read the input(s) as fast as possible. This option will slow down the reading of the input(s) to the native frame rate of the input(s). It is useful for real-time output (e.g. live streaming).

-vsync parameter

Video sync method. For compatibility reasons old values can be specified as numbers. Newly added values will have to be specified as strings always.

0, passthrough

Each frame is passed with its timestamp from the demuxer to the muxer.

1, cfr

Frames will be duplicated and dropped to achieve exactly the requested constant frame rate.

2, vfr

Frames are passed through with their timestamp or dropped so as to prevent 2 frames from having the same timestamp.

drop

As passthrough but destroys all timestamps, making the muxer generate fresh timestamps based on frame-rate.

-1, auto

Chooses between 1 and 2 depending on muxer capabilities. This is the default method.

Note that the timestamps may be further modified by the muxer, after this. For example, in the case that the format option ‘ avoid_negative_ts ’ is enabled.

With -map you can select from which stream the timestamps should be taken. You can leave either video or audio unchanged and sync the remaining stream(s) to the unchanged one.

-frame_drop_threshold parameter

Frame drop threshold, which specifies how much behind video frames can be before they are dropped. In frame rate units, so 1.0 is one frame. The default is -1.1. One possible usecase is to avoid framedrops in case of noisy timestamps or to increase frame drop precision in case of exact timestamps.

-async samples_per_second

Audio sync method. "Stretches/squeezes" the audio stream to match the timestamps, the parameter is the maximum samples per second by which the audio is changed. -async 1 is a special case where only the start of the audio stream is corrected without any later correction.

Note that the timestamps may be further modified by the muxer, after this. For example, in the case that the format option ‘ avoid_negative_ts ’ is enabled.

This option has been deprecated. Use the aresample audio filter instead.

-copyts

Do not process input timestamps, but keep their values without trying to sanitize them. In particular, do not remove the initial start time offset value.

Note that, depending on the ‘ vsync ’ option or on specific muxer processing (e.g. in case the format option ‘ avoid_negative_ts ’ is enabled) the output timestamps may mismatch with the input timestamps even when this option is selected.

-start_at_zero

When used with ‘ copyts ’, shift input timestamps so they start at zero.

This means that using e.g. -ss 50 will make output timestamps start at 50 seconds, regardless of what timestamp the input file started at.

-copytb mode

Specify how to set the encoder timebase when stream copying. mode is an integer numeric value, and can assume one of the following values:

1

Use the demuxer timebase.

The time base is copied to the output encoder from the corresponding input demuxer. This is sometimes required to avoid non monotonically increasing timestamps when copying video streams with variable frame rate.

0

Use the decoder timebase.

The time base is copied to the output encoder from the corresponding input decoder.

-1

Try to make the choice automatically, in order to generate a sane output.

Default value is -1.

-enc_time_base[: stream_specifier ] timebase ( output,per-stream )

Set the encoder timebase. timebase is a floating point number, and can assume one of the following values:

0

Assign a default value according to the media type.

For video - use 1/framerate, for audio - use 1/samplerate.

-1

Use the input stream timebase when possible.

If an input stream is not available, the default timebase will be used.

>0

Use the provided number as the timebase.

This field can be provided as a ratio of two integers (e.g. 1:24, 1:48000) or as a floating point number (e.g. 0.04166, 2.0833e-5)

Default value is 0.

-bitexact ( input/output )

Enable bitexact mode for (de)muxer and (de/en)coder

-shortest ( output )

Finish encoding when the shortest input stream ends.

-dts_delta_threshold

Timestamp discontinuity delta threshold.

-muxdelay seconds ( output )

Set the maximum demux-decode delay.

-muxpreload seconds ( output )

Set the initial demux-decode delay.

-streamid output-stream-index : new-value ( output )

Assign a new stream-id value to an output stream. This option should be specified prior to the output filename to which it applies. For the situation where multiple output files exist, a streamid may be reassigned to a different value.

For example, to set the stream 0 PID to 33 and the stream 1 PID to 36 for an output mpegts file:

ffmpeg -i inurl -streamid 0:33 -streamid 1:36 out.ts
                                
-bsf[: stream_specifier ] bitstream_filters ( output,per-stream )

Set bitstream filters for matching streams. bitstream_filters is a comma-separated list of bitstream filters. Use the -bsfs option to get the list of bitstream filters.

ffmpeg -i h264.mp4 -c:v copy -bsf:v h264_mp4toannexb -an out.h264
                                
ffmpeg -i file.mov -an -vn -bsf:s mov2textsub -c:s copy -f rawvideo sub.txt
                                
-tag[: stream_specifier ] codec_tag ( input/output,per-stream )

Force a tag/fourcc for matching streams.

-timecode hh : mm : ss SEP ff

Specify Timecode for writing. SEP is ’:’ for non drop timecode and ’;’ (or ’.’) for drop.

ffmpeg -i input.mpg -timecode 01:02:03.04 -r 30000/1001 -s ntsc output.mpg
                                

-filter_complex filtergraph ( global )

Define a complex filtergraph, i.e. one with arbitrary number of inputs and/or outputs. For simple graphs – those with one input and one output of the same type – see the ‘ -filter ’ options. filtergraph is a description of the filtergraph, as described in the “Filtergraph syntax” section of the ffmpeg-filters manual.

Input link labels must refer to input streams using the [file_index:stream_specifier] syntax (i.e. the same as ‘ -map ’ uses). If stream_specifier matches multiple streams, the first one will be used. An unlabeled input will be connected to the first unused input stream of the matching type.

Output link labels are referred to with ‘ -map ’. Unlabeled outputs are added to the first output file.

Note that with this option it is possible to use only lavfi sources without normal input files.

For example, to overlay an image over video

ffmpeg -i video.mkv -i image.png -filter_complex '[0:v][1:v]overlay[out]' -map
'[out]' out.mkv
                                

Here [0:v] refers to the first video stream in the first input file, which is linked to the first (main) input of the overlay filter. Similarly the first video stream in the second input is linked to the second (overlay) input of overlay.

Assuming there is only one video stream in each input file, we can omit input labels, so the above is equivalent to

ffmpeg -i video.mkv -i image.png -filter_complex 'overlay[out]' -map
'[out]' out.mkv
                                

Furthermore we can omit the output label and the single output from the filter graph will be added to the output file automatically, so we can simply write

ffmpeg -i video.mkv -i image.png -filter_complex 'overlay' out.mkv
                                

To generate 5 seconds of pure red video using lavfi color source:

ffmpeg -filter_complex 'color=c=red' -t 5 out.mkv
                                
-filter_complex_threads nb_threads ( global )

Defines how many threads are used to process a filter_complex graph. Similar to filter_threads but used for -filter_complex graphs only. The default is the number of available CPUs.

-lavfi filtergraph ( global )

Define a complex filtergraph, i.e. one with arbitrary number of inputs and/or outputs. Equivalent to ‘ -filter_complex ’.

-filter_complex_script filename ( global )

This option is similar to ‘ -filter_complex ’, the only difference is that its argument is the name of the file from which a complex filtergraph description is to be read.

-accurate_seek ( input )

This option enables or disables accurate seeking in input files with the ‘ -ss ’ option. It is enabled by default, so seeking is accurate when transcoding. Use ‘ -noaccurate_seek ’ to disable it, which may be useful e.g. when copying some streams and transcoding the others.

-seek_timestamp ( input )

This option enables or disables seeking by timestamp in input files with the ‘ -ss ’ option. It is disabled by default. If enabled, the argument to the ‘ -ss ’ option is considered an actual timestamp, and is not offset by the start time of the file. This matters only for files which do not start from timestamp 0, such as transport streams.

-thread_queue_size size ( input )

This option sets the maximum number of queued packets when reading from the file or device. With low latency / high rate live streams, packets may be discarded if they are not read in a timely manner; raising this value can avoid it.

-sdp_file file ( global )

Print sdp information for an output stream to file . This allows dumping sdp information when at least one output isn’t an rtp stream. (Requires at least one of the output formats to be rtp).

-discard ( input )

Allows discarding specific streams or frames from streams. Any input stream can be fully discarded, using value all whereas selective discarding of frames from a stream occurs at the demuxer and is not supported by all demuxers.

none

Discard no frame.

default

Default, which discards no frames.

noref

Discard all non-reference frames.

bidir

Discard all bidirectional frames.

nokey

Discard all frames excepts keyframes.

all

Discard all frames.

-abort_on flags ( global )

Stop and abort on various conditions. The following flags are available:

empty_output

No packets were passed to the muxer, the output is empty.

-xerror ( global )

Stop and exit on error

-max_muxing_queue_size packets ( output,per-stream )

When transcoding audio and/or video streams, ffmpeg will not begin writing into the output until it has one packet for each such stream. While waiting for that to happen, packets for other streams are buffered. This option sets the size of this buffer, in packets, for the matching output stream.

The default value of this option should be high enough for most uses, so only touch this option if you are sure that you need it.

As a special exception, you can use a bitmap subtitle stream as input: it will be converted into a video with the same size as the largest video in the file, or 720x576 if no video is present. Note that this is an experimental and temporary solution. It will be removed once libavfilter has proper support for subtitles.

For example, to hardcode subtitles on top of a DVB-T recording stored in MPEG-TS format, delaying the subtitles by 1 second:

ffmpeg -i input.ts -filter_complex \
  '[#0x2ef] setpts=PTS+1/TB [sub] ; [#0x2d0] [sub] overlay' \
  -sn -map '#0x2dc' output.mkv
                        

(0x2d0, 0x2dc and 0x2ef are the MPEG-TS PIDs of respectively the video, audio and subtitles streams; 0:0, 0:3 and 0:7 would have worked too)

5.12 预置文件

A preset file contains a sequence of option = value pairs, one for each line, specifying a sequence of options which would be awkward to specify on the command line. Lines starting with the hash (’#’) character are ignored and are used to provide comments. Check the ‘ presets ’ directory in the FFmpeg source tree for examples.

There are two types of preset files: ffpreset and avpreset files.

5.12.1 ffpreset 文件

指定 ffpreset 文件,采用 vpre , apre , spre ,和 fpre 选项。 fpre option takes the filename of the preset instead of a preset name as input and can be used for any kind of codec. For the vpre , apre ,和 spre options, the options specified in a preset file are applied to the currently selected codec of the same type as the preset option.

The argument passed to the vpre , apre ,和 spre preset options identifies the preset file to use according to the following rules:

First ffmpeg searches for a file named arg .ffpreset in the directories ‘ $FFMPEG_DATADIR ’ (if set), and ‘ $HOME/.ffmpeg ’, and in the datadir defined at configuration time (usually ‘ PREFIX/share/ffmpeg ’) or in a ‘ ffpresets ’ folder along the executable on win32, in that order. For example, if the argument is libvpx-1080p , it will search for the file ‘ libvpx-1080p.ffpreset ’.

If no such file is found, then ffmpeg will search for a file named codec_name - arg .ffpreset in the above-mentioned directories, where codec_name is the name of the codec to which the preset file options will be applied. For example, if you select the video codec with -vcodec libvpx and use -vpre 1080p , then it will search for the file ‘ libvpx-1080p.ffpreset ’.

5.12.2 avpreset 文件

avpreset files are specified with the pre option. They work similar to ffpreset files, but they only allow encoder- specific options. Therefore, an option = value pair specifying an encoder cannot be used.

When the pre option is specified, ffmpeg will look for files with the suffix .avpreset in the directories ‘ $AVCONV_DATADIR ’ (if set), and ‘ $HOME/.avconv ’, and in the datadir defined at configuration time (usually ‘ PREFIX/share/ffmpeg ’), in that order.

First ffmpeg searches for a file named codec_name - arg .avpreset in the above-mentioned directories, where codec_name is the name of the codec to which the preset file options will be applied. For example, if you select the video codec with -vcodec libvpx and use -pre 1080p , then it will search for the file ‘ libvpx-1080p.avpreset ’.

If no such file is found, then ffmpeg will search for a file named arg .avpreset in the same directories.

6 范例

6.1 视频和音频抓取

If you specify the input format and device then ffmpeg can grab video and audio directly.

ffmpeg -f oss -i /dev/dsp -f video4linux2 -i /dev/video0 /tmp/out.mpg
                        

Or with an ALSA audio source (mono input, card id 1) instead of OSS:

ffmpeg -f alsa -ac 1 -i hw:1 -f video4linux2 -i /dev/video0 /tmp/out.mpg
                        

Note that you must activate the right video source and channel before launching ffmpeg with any TV viewer such as xawtv by Gerd Knorr. You also have to set the audio recording levels correctly with a standard mixer.

6.2 X11 抓取

抓取 X11 显示采用 ffmpeg 通过

ffmpeg -f x11grab -video_size cif -framerate 25 -i :0.0 /tmp/out.mpg
                        

0.0 is display.screen number of your X11 server, same as the DISPLAY environment variable.

ffmpeg -f x11grab -video_size cif -framerate 25 -i :0.0+10,20 /tmp/out.mpg
                        

0.0 is display.screen number of your X11 server, same as the DISPLAY environment variable. 10 is the x-offset and 20 the y-offset for the grabbing.

6.3 视频和音频文件格式转换

任何支持文件格式和协议,都可以充当 ffmpeg 输入:

范例:

  • You can use YUV files as input:
    ffmpeg -i /tmp/test%d.Y /tmp/out.mpg
                                    

    It will use the files:

    /tmp/test0.Y, /tmp/test0.U, /tmp/test0.V,
    /tmp/test1.Y, /tmp/test1.U, /tmp/test1.V, etc...
                                    

    The Y files use twice the resolution of the U and V files. They are raw files, without header. They can be generated by all decent video decoders. You must specify the size of the image with the ‘ -s ’ option if ffmpeg cannot guess it.

  • You can input from a raw YUV420P file:
    ffmpeg -i /tmp/test.yuv /tmp/out.avi
                                    

    test.yuv is a file containing raw YUV planar data. Each frame is composed of the Y plane followed by the U and V planes at half vertical and horizontal resolution.

  • You can output to a raw YUV420P file:
    ffmpeg -i mydivx.avi hugefile.yuv
                                    
  • You can set several input files and output files:
    ffmpeg -i /tmp/a.wav -s 640x480 -i /tmp/a.yuv /tmp/a.mpg
                                    

    Converts the audio file a.wav and the raw YUV video file a.yuv to MPEG file a.mpg.

  • You can also do audio and video conversions at the same time:
    ffmpeg -i /tmp/a.wav -ar 22050 /tmp/a.mp2
                                    

    Converts a.wav to MPEG audio at 22050 Hz sample rate.

  • You can encode to several formats at the same time and define a mapping from input stream to output streams:
    ffmpeg -i /tmp/a.wav -map 0:a -b:a 64k /tmp/a.mp2 -map 0:a -b:a 128k /tmp/b.mp2
                                    

    Converts a.wav to a.mp2 at 64 kbits and to b.mp2 at 128 kbits. ’-map file:index’ specifies which input stream is used for each output stream, in the order of the definition of output streams.

  • You can transcode decrypted VOBs:
    ffmpeg -i snatch_1.vob -f avi -c:v mpeg4 -b:v 800k -g 300 -bf 2 -c:a libmp3lame -b:a 128k snatch.avi
                                    

    This is a typical DVD ripping example; the input is a VOB file, the output an AVI file with MPEG-4 video and MP3 audio. Note that in this command we use B-frames so the MPEG-4 stream is DivX5 compatible, and GOP size is 300 which means one intra frame every 10 seconds for 29.97fps input video. Furthermore, the audio stream is MP3-encoded so you need to enable LAME support by passing --enable-libmp3lame to configure. The mapping is particularly useful for DVD transcoding to get the desired audio language.

    NOTE: To see the supported input formats, use ffmpeg -demuxers .

  • You can extract images from a video, or create a video from many images:

    For extracting images from a video:

    ffmpeg -i foo.avi -r 1 -s WxH -f image2 foo-%03d.jpeg
                                    

    This will extract one video frame per second from the video and will output them in files named ‘ foo-001.jpeg ’, ‘ foo-002.jpeg ’, etc. Images will be rescaled to fit the new WxH values.

    If you want to extract just a limited number of frames, you can use the above command in combination with the -frames:v -t option, or in combination with -ss to start extracting from a certain point in time.

    For creating a video from many images:

    ffmpeg -f image2 -framerate 12 -i foo-%03d.jpeg -s WxH foo.avi
                                    

    The syntax foo-%03d.jpeg specifies to use a decimal number composed of three digits padded with zeroes to express the sequence number. It is the same syntax supported by the C printf function, but only formats accepting a normal integer are suitable.

    When importing an image sequence, -i also supports expanding shell-like wildcard patterns (globbing) internally, by selecting the image2-specific -pattern_type glob option.

    For example, for creating a video from filenames matching the glob pattern foo-*.jpeg :

    ffmpeg -f image2 -pattern_type glob -framerate 12 -i 'foo-*.jpeg' -s WxH foo.avi
                                    
  • You can put many streams of the same type in the output:
    ffmpeg -i test1.avi -i test2.avi -map 1:1 -map 1:0 -map 0:1 -map 0:0 -c copy -y test12.nut
                                    

    The resulting output file ‘ test12.nut ’ will contain the first four streams from the input files in reverse order.

  • To force CBR video output:
    ffmpeg -i myfile.avi -b 4000k -minrate 4000k -maxrate 4000k -bufsize 1835k out.m2v
                                    
  • The four options lmin, lmax, mblmin and mblmax use ’lambda’ units, but you may use the QP2LAMBDA constant to easily convert from ’q’ units:
    ffmpeg -i src.ext -lmax 21*QP2LAMBDA dst.ext
                                    

7 Syntax

This section documents the syntax and formats employed by the FFmpeg libraries and tools.

7.1 Quoting and escaping

FFmpeg adopts the following quoting and escaping mechanism, unless explicitly specified. The following rules are applied:

  • ' ’ and ‘ \ ’ are special characters (respectively used for quoting and escaping). In addition to them, there might be other special characters depending on the specific syntax where the escaping and quoting are employed.
  • A special character is escaped by prefixing it with a ‘ \ ’.
  • All characters enclosed between ‘ '' ’ are included literally in the parsed string. The quote character ‘ ' ’ itself cannot be quoted, so you may need to close the quote and escape it.
  • Leading and trailing whitespaces, unless escaped or quoted, are removed from the parsed string.

Note that you may need to add a second level of escaping when using the command line or a script, which depends on the syntax of the adopted shell language.

The function av_get_token defined in ‘ libavutil/avstring.h ’ can be used to parse a token quoted or escaped according to the rules defined above.

The tool ‘ tools/ffescape ’ in the FFmpeg source tree can be used to automatically quote or escape a string in a script.

7.1.1 范例

  • Escape the string Crime d'Amour containing the ' special character:
    Crime d\'Amour
                                    
  • The string above contains a quote, so the ' needs to be escaped when quoting it:
    'Crime d'\''Amour'
                                    
  • Include leading or trailing whitespaces using quoting:
    '  this string starts and ends with whitespaces  '
                                    
  • Escaping and quoting can be mixed together:
    ' The string '\'string\'' is a string '
                                    
  • To include a literal ‘ \ ’ you can use either escaping or quoting:
    'c:\foo' can be written as c:\\foo
                                    

7.2 Date

The accepted syntax is:

[(YYYY-MM-DD|YYYYMMDD)[T|t| ]]((HH:MM:SS[.m...]]])|(HHMMSS[.m...]]]))[Z]
now
                        

If the value is "now" it takes the current time.

Time is local time unless Z is appended, in which case it is interpreted as UTC. If the year-month-day part is not specified it takes the current year-month-day.

7.3 Time duration

There are two accepted syntaxes for expressing time duration.

[-][HH:]MM:SS[.m...]
                        

HH expresses the number of hours, MM the number of minutes for a maximum of 2 digits, and SS the number of seconds for a maximum of 2 digits. The m at the end expresses decimal value for SS .

[-]S+[.m...]
                        

S expresses the number of seconds, with the optional decimal part m .

In both expressions, the optional ‘ - ’ indicates negative duration.

7.3.1 Examples

The following examples are all valid time duration:

55

55 seconds

12:03:45

12 hours, 03 minutes and 45 seconds

23.189

23.189 seconds

7.4 Video size

Specify the size of the sourced video, it may be a string of the form width x height , or the name of a size abbreviation.

The following abbreviations are recognized:

ntsc

720x480

pal

720x576

qntsc

352x240

qpal

352x288

sntsc

640x480

spal

768x576

film

352x240

ntsc-film

352x240

sqcif

128x96

qcif

176x144

cif

352x288

4cif

704x576

16cif

1408x1152

qqvga

160x120

qvga

320x240

vga

640x480

svga

800x600

xga

1024x768

uxga

1600x1200

qxga

2048x1536

sxga

1280x1024

qsxga

2560x2048

hsxga

5120x4096

wvga

852x480

wxga

1366x768

wsxga

1600x1024

wuxga

1920x1200

woxga

2560x1600

wqsxga

3200x2048

wquxga

3840x2400

whsxga

6400x4096

whuxga

7680x4800

cga

320x200

ega

640x350

hd480

852x480

hd720

1280x720

hd1080

1920x1080

2k

2048x1080

2kflat

1998x1080

2kscope

2048x858

4k

4096x2160

4kflat

3996x2160

4kscope

4096x1716

nhd

640x360

hqvga

240x160

wqvga

400x240

fwqvga

432x240

hvga

480x320

qhd

960x540

2kdci

2048x1080

4kdci

4096x2160

uhd2160

3840x2160

uhd4320

7680x4320

7.5 Video rate

Specify the frame rate of a video, expressed as the number of frames generated per second. It has to be a string in the format frame_rate_num / frame_rate_den , an integer number, a float number or a valid video frame rate abbreviation.

The following abbreviations are recognized:

ntsc

30000/1001

pal

25/1

qntsc

30000/1001

qpal

25/1

sntsc

30000/1001

spal

25/1

film

24/1

ntsc-film

24000/1001

7.6 Ratio

A ratio can be expressed as an expression, or in the form numerator : denominator .

Note that a ratio with infinite (1/0) or negative value is considered valid, so you should check on the returned value if you want to exclude those values.

The undefined value can be expressed using the "0:0" string.

7.7 Color

It can be the name of a color as defined below (case insensitive match) or a [0x|#]RRGGBB[AA] sequence, possibly followed by @ and a string representing the alpha component.

The alpha component may be a string composed by "0x" followed by an hexadecimal number or a decimal number between 0.0 and 1.0, which represents the opacity value (‘ 0x00 ’ or ‘ 0.0 ’ means completely transparent, ‘ 0xff ’ or ‘ 1.0 ’ completely opaque). If the alpha component is not specified then ‘ 0xff ’ is assumed.

The string ‘ random ’ will result in a random color.

The following names of colors are recognized:

AliceBlue

0xF0F8FF

AntiqueWhite

0xFAEBD7

Aqua

0x00FFFF

Aquamarine

0x7FFFD4

Azure

0xF0FFFF

Beige

0xF5F5DC

Bisque

0xFFE4C4

Black

0x000000

BlanchedAlmond

0xFFEBCD

Blue

0x0000FF

BlueViolet

0x8A2BE2

Brown

0xA52A2A

BurlyWood

0xDEB887

CadetBlue

0x5F9EA0

Chartreuse

0x7FFF00

Chocolate

0xD2691E

Coral

0xFF7F50

CornflowerBlue

0x6495ED

Cornsilk

0xFFF8DC

Crimson

0xDC143C

Cyan

0x00FFFF

DarkBlue

0x00008B

DarkCyan

0x008B8B

DarkGoldenRod

0xB8860B

DarkGray

0xA9A9A9

DarkGreen

0x006400

DarkKhaki

0xBDB76B

DarkMagenta

0x8B008B

DarkOliveGreen

0x556B2F

Darkorange

0xFF8C00

DarkOrchid

0x9932CC

DarkRed

0x8B0000

DarkSalmon

0xE9967A

DarkSeaGreen

0x8FBC8F

DarkSlateBlue

0x483D8B

DarkSlateGray

0x2F4F4F

DarkTurquoise

0x00CED1

DarkViolet

0x9400D3

DeepPink

0xFF1493

DeepSkyBlue

0x00BFFF

DimGray

0x696969

DodgerBlue

0x1E90FF

FireBrick

0xB22222

FloralWhite

0xFFFAF0

ForestGreen

0x228B22

Fuchsia

0xFF00FF

Gainsboro

0xDCDCDC

GhostWhite

0xF8F8FF

Gold

0xFFD700

GoldenRod

0xDAA520

Gray

0x808080

Green

0x008000

GreenYellow

0xADFF2F

HoneyDew

0xF0FFF0

HotPink

0xFF69B4

IndianRed

0xCD5C5C

Indigo

0x4B0082

Ivory

0xFFFFF0

Khaki

0xF0E68C

Lavender

0xE6E6FA

LavenderBlush

0xFFF0F5

LawnGreen

0x7CFC00

LemonChiffon

0xFFFACD

LightBlue

0xADD8E6

LightCoral

0xF08080

LightCyan

0xE0FFFF

LightGoldenRodYellow

0xFAFAD2

LightGreen

0x90EE90

LightGrey

0xD3D3D3

LightPink

0xFFB6C1

LightSalmon

0xFFA07A

LightSeaGreen

0x20B2AA

LightSkyBlue

0x87CEFA

LightSlateGray

0x778899

LightSteelBlue

0xB0C4DE

LightYellow

0xFFFFE0

Lime

0x00FF00

LimeGreen

0x32CD32

Linen

0xFAF0E6

Magenta

0xFF00FF

Maroon

0x800000

MediumAquaMarine

0x66CDAA

MediumBlue

0x0000CD

MediumOrchid

0xBA55D3

MediumPurple

0x9370D8

MediumSeaGreen

0x3CB371

MediumSlateBlue

0x7B68EE

MediumSpringGreen

0x00FA9A

MediumTurquoise

0x48D1CC

MediumVioletRed

0xC71585

MidnightBlue

0x191970

MintCream

0xF5FFFA

MistyRose

0xFFE4E1

Moccasin

0xFFE4B5

NavajoWhite

0xFFDEAD

Navy

0x000080

OldLace

0xFDF5E6

Olive

0x808000

OliveDrab

0x6B8E23

Orange

0xFFA500

OrangeRed

0xFF4500

Orchid

0xDA70D6

PaleGoldenRod

0xEEE8AA

PaleGreen

0x98FB98

PaleTurquoise

0xAFEEEE

PaleVioletRed

0xD87093

PapayaWhip

0xFFEFD5

PeachPuff

0xFFDAB9

Peru

0xCD853F

Pink

0xFFC0CB

Plum

0xDDA0DD

PowderBlue

0xB0E0E6

Purple

0x800080

Red

0xFF0000

RosyBrown

0xBC8F8F

RoyalBlue

0x4169E1

SaddleBrown

0x8B4513

Salmon

0xFA8072

SandyBrown

0xF4A460

SeaGreen

0x2E8B57

SeaShell

0xFFF5EE

Sienna

0xA0522D

Silver

0xC0C0C0

SkyBlue

0x87CEEB

SlateBlue

0x6A5ACD

SlateGray

0x708090

Snow

0xFFFAFA

SpringGreen

0x00FF7F

SteelBlue

0x4682B4

Tan

0xD2B48C

Teal

0x008080

Thistle

0xD8BFD8

Tomato

0xFF6347

Turquoise

0x40E0D0

Violet

0xEE82EE

Wheat

0xF5DEB3

White

0xFFFFFF

WhiteSmoke

0xF5F5F5

Yellow

0xFFFF00

YellowGreen

0x9ACD32

7.8 Channel Layout

A channel layout specifies the spatial disposition of the channels in a multi-channel audio stream. To specify a channel layout, FFmpeg makes use of a special syntax.

Individual channels are identified by an id, as given by the table below:

FL

front left

FR

front right

FC

front center

LFE

low frequency

BL

back left

BR

back right

FLC

front left-of-center

FRC

front right-of-center

BC

back center

SL

side left

SR

side right

TC

top center

TFL

top front left

TFC

top front center

TFR

top front right

TBL

top back left

TBC

top back center

TBR

top back right

DL

downmix left

DR

downmix right

WL

wide left

WR

wide right

SDL

surround direct left

SDR

surround direct right

LFE2

low frequency 2

Standard channel layout compositions can be specified by using the following identifiers:

mono

FC

stereo

FL+FR

2.1

FL+FR+LFE

3.0

FL+FR+FC

3.0(back)

FL+FR+BC

4.0

FL+FR+FC+BC

quad

FL+FR+BL+BR

quad(side)

FL+FR+SL+SR

3.1

FL+FR+FC+LFE

5.0

FL+FR+FC+BL+BR

5.0(side)

FL+FR+FC+SL+SR

4.1

FL+FR+FC+LFE+BC

5.1

FL+FR+FC+LFE+BL+BR

5.1(side)

FL+FR+FC+LFE+SL+SR

6.0

FL+FR+FC+BC+SL+SR

6.0(front)

FL+FR+FLC+FRC+SL+SR

hexagonal

FL+FR+FC+BL+BR+BC

6.1

FL+FR+FC+LFE+BC+SL+SR

6.1

FL+FR+FC+LFE+BL+BR+BC

6.1(front)

FL+FR+LFE+FLC+FRC+SL+SR

7.0

FL+FR+FC+BL+BR+SL+SR

7.0(front)

FL+FR+FC+FLC+FRC+SL+SR

7.1

FL+FR+FC+LFE+BL+BR+SL+SR

7.1(wide)

FL+FR+FC+LFE+BL+BR+FLC+FRC

7.1(wide-side)

FL+FR+FC+LFE+FLC+FRC+SL+SR

octagonal

FL+FR+FC+BL+BR+BC+SL+SR

downmix

DL+DR

A custom channel layout can be specified as a sequence of terms, separated by ’+’ or ’|’. Each term can be:

  • the name of a standard channel layout (e.g. ‘ mono ’, ‘ stereo ’, ‘ 4.0 ’, ‘ quad ’, ‘ 5.0 ’, etc.)
  • the name of a single channel (e.g. ‘ FL ’, ‘ FR ’, ‘ FC ’, ‘ LFE ’, etc.)
  • a number of channels, in decimal, followed by ’c’, yielding the default channel layout for that number of channels (see the function av_get_default_channel_layout ). Note that not all channel counts have a default layout.
  • a number of channels, in decimal, followed by ’C’, yielding an unknown channel layout with the specified number of channels. Note that not all channel layout specification strings support unknown channel layouts.
  • a channel layout mask, in hexadecimal starting with "0x" (see the AV_CH_* macros in ‘ libavutil/channel_layout.h ’.

Before libavutil version 53 the trailing character "c" to specify a number of channels was optional, but now it is required, while a channel layout mask can also be specified as a decimal number (if and only if not followed by "c" or "C").

See also the function av_get_channel_layout defined in ‘ libavutil/channel_layout.h ’.

8 Expression Evaluation

When evaluating an arithmetic expression, FFmpeg uses an internal formula evaluator, implemented through the ‘ libavutil/eval.h ’ interface.

An expression may contain unary, binary operators, constants, and functions.

Two expressions expr1 and expr2 can be combined to form another expression " expr1 ; expr2 ". expr1 and expr2 are evaluated in turn, and the new expression evaluates to the value of expr2 .

The following binary operators are available: + , - , * , / , ^ .

The following unary operators are available: + , - .

The following functions are available:

abs(x)

Compute absolute value of x .

acos(x)

Compute arccosine of x .

asin(x)

Compute arcsine of x .

atan(x)

Compute arctangent of x .

atan2(x, y)

Compute principal value of the arc tangent of y / x .

between(x, min, max)

Return 1 if x is greater than or equal to min and lesser than or equal to max , 0 otherwise.

bitand(x, y)
bitor(x, y)

Compute bitwise and/or operation on x and y .

The results of the evaluation of x and y are converted to integers before executing the bitwise operation.

Note that both the conversion to integer and the conversion back to floating point can lose precision. Beware of unexpected results for large numbers (usually 2^53 and larger).

ceil(expr)

Round the value of expression expr upwards to the nearest integer. For example, "ceil(1.5)" is "2.0".

clip(x, min, max)

Return the value of x clipped between min and max .

cos(x)

Compute cosine of x .

cosh(x)

Compute hyperbolic cosine of x .

eq(x, y)

Return 1 if x and y are equivalent, 0 otherwise.

exp(x)

Compute exponential of x (with base e , the Euler’s number).

floor(expr)

Round the value of expression expr downwards to the nearest integer. For example, "floor(-1.5)" is "-2.0".

gauss(x)

Compute Gauss function of x , corresponding to exp(-x*x/2) / sqrt(2*PI) .

gcd(x, y)

Return the greatest common divisor of x and y . If both x and y are 0 or either or both are less than zero then behavior is undefined.

gt(x, y)

Return 1 if x is greater than y , 0 otherwise.

gte(x, y)

Return 1 if x is greater than or equal to y , 0 otherwise.

hypot(x, y)

This function is similar to the C function with the same name; it returns "sqrt( x * x + y * y )", the length of the hypotenuse of a right triangle with sides of length x and y , or the distance of the point ( x , y ) from the origin.

if(x, y)

Evaluate x , and if the result is non-zero return the result of the evaluation of y , return 0 otherwise.

if(x, y, z)

Evaluate x , and if the result is non-zero return the evaluation result of y , otherwise the evaluation result of z .

ifnot(x, y)

Evaluate x , and if the result is zero return the result of the evaluation of y , return 0 otherwise.

ifnot(x, y, z)

Evaluate x , and if the result is zero return the evaluation result of y , otherwise the evaluation result of z .

isinf(x)

Return 1.0 if x is +/-INFINITY, 0.0 otherwise.

isnan(x)

Return 1.0 if x is NAN, 0.0 otherwise.

ld(var)

Load the value of the internal variable with number var , which was previously stored with st( var , expr ). The function returns the loaded value.

lerp(x, y, z)

Return linear interpolation between x and y by amount of z .

log(x)

Compute natural logarithm of x .

lt(x, y)

Return 1 if x is lesser than y , 0 otherwise.

lte(x, y)

Return 1 if x is lesser than or equal to y , 0 otherwise.

max(x, y)

Return the maximum between x and y .

min(x, y)

Return the minimum between x and y .

mod(x, y)

Compute the remainder of division of x by y .

not(expr)

Return 1.0 if expr is zero, 0.0 otherwise.

pow(x, y)

Compute the power of x elevated y , it is equivalent to "( x )^( y )".

print(t)
print(t, l)

Print the value of expression t with loglevel l . If l is not specified then a default log level is used. Returns the value of the expression printed.

Prints t with loglevel l

random(x)

Return a pseudo random value between 0.0 and 1.0. x is the index of the internal variable which will be used to save the seed/state.

root(expr, max)

Find an input value for which the function represented by expr with argument ld(0) is 0 in the interval 0.. max .

The expression in expr must denote a continuous function or the result is undefined.

ld(0) is used to represent the function input value, which means that the given expression will be evaluated multiple times with various input values that the expression can access through ld(0) . When the expression evaluates to 0 then the corresponding input value will be returned.

round(expr)

Round the value of expression expr to the nearest integer. For example, "round(1.5)" is "2.0".

sin(x)

Compute sine of x .

sinh(x)

Compute hyperbolic sine of x .

sqrt(expr)

Compute the square root of expr . This is equivalent to "( expr )^.5".

squish(x)

Compute expression 1/(1 + exp(4*x)) .

st(var, expr)

Store the value of the expression expr in an internal variable. var specifies the number of the variable where to store the value, and it is a value ranging from 0 to 9. The function returns the value stored in the internal variable. Note, Variables are currently not shared between expressions.

tan(x)

Compute tangent of x .

tanh(x)

Compute hyperbolic tangent of x .

taylor(expr, x)
taylor(expr, x, id)

Evaluate a Taylor series at x , given an expression representing the ld(id) -th derivative of a function at 0.

When the series does not converge the result is undefined.

ld(id) is used to represent the derivative order in expr , which means that the given expression will be evaluated multiple times with various input values that the expression can access through ld(id) . If id is not specified then 0 is assumed.

Note, when you have the derivatives at y instead of 0, taylor(expr, x-y) can be used.

time(0)

Return the current (wallclock) time in seconds.

trunc(expr)

Round the value of expression expr towards zero to the nearest integer. For example, "trunc(-1.5)" is "-1.0".

while(cond, expr)

Evaluate expression expr while the expression cond is non-zero, and returns the value of the last expr evaluation, or NAN if cond was always false.

The following constants are available:

PI

area of the unit disc, approximately 3.14

E

exp(1) (Euler’s number), approximately 2.718

PHI

golden ratio (1+sqrt(5))/2, approximately 1.618

Assuming that an expression is considered "true" if it has a non-zero value, note that:

* works like AND

+ works like OR

For example the construct:

if (A AND B) then C
                        

is equivalent to:

if(A*B, C)
                        

In your C code, you can extend the list of unary and binary functions, and define recognized constants, so that they are available for your expressions.

The evaluator also recognizes the International System unit prefixes. If ’i’ is appended after the prefix, binary prefixes are used, which are based on powers of 1024 instead of powers of 1000. The ’B’ postfix multiplies the value by 8, and can be appended after a unit prefix or used alone. This allows using for example ’KB’, ’MiB’, ’G’ and ’B’ as number postfix.

The list of available International System prefixes follows, with indication of the corresponding powers of 10 and of 2.

y

10^-24 / 2^-80

z

10^-21 / 2^-70

a

10^-18 / 2^-60

f

10^-15 / 2^-50

p

10^-12 / 2^-40

n

10^-9 / 2^-30

u

10^-6 / 2^-20

m

10^-3 / 2^-10

c

10^-2

d

10^-1

h

10^2

k

10^3 / 2^10

K

10^3 / 2^10

M

10^6 / 2^20

G

10^9 / 2^30

T

10^12 / 2^40

P

10^15 / 2^40

E

10^18 / 2^50

Z

10^21 / 2^60

Y

10^24 / 2^70

9 编解码器选项

libavcodec provides some generic global options, which can be set on all the encoders and decoders. In addition each codec may support so-called private options, which are specific for a given codec.

Sometimes, a global option may only affect a specific kind of codec, and may be nonsensical or ignored by another, so you need to be aware of the meaning of the specified options. Also some options are meant only for decoding or encoding.

Options may be set by specifying - option value in the FFmpeg tools, or by setting the value explicitly in the AVCodecContext options or using the ‘ libavutil/opt.h ’ API for programmatic use.

The list of supported options follow:

b integer ( encoding,audio,video )

Set bitrate in bits/s. Default value is 200K.

ab integer ( encoding,audio )

Set audio bitrate (in bits/s). Default value is 128K.

bt integer ( encoding,video )

Set video bitrate tolerance (in bits/s). In 1-pass mode, bitrate tolerance specifies how far ratecontrol is willing to deviate from the target average bitrate value. This is not related to min/max bitrate. Lowering tolerance too much has an adverse effect on quality.

flags flags ( decoding/encoding,audio,video,subtitles )

Set generic flags.

Possible values:

mv4

Use four motion vector by macroblock (mpeg4).

qpel

Use 1/4 pel motion compensation.

loop

Use loop filter.

qscale

Use fixed qscale.

pass1

Use internal 2pass ratecontrol in first pass mode.

pass2

Use internal 2pass ratecontrol in second pass mode.

gray

Only decode/encode grayscale.

emu_edge

Do not draw edges.

psnr

Set error[?] variables during encoding.

truncated
drop_changed

Don’t output frames whose parameters differ from first decoded frame in stream. Error AVERROR_INPUT_CHANGED is returned when a frame is dropped.

ildct

Use interlaced DCT.

low_delay

Force low delay.

global_header

Place global headers in extradata instead of every keyframe.

bitexact

Only write platform-, build- and time-independent data. (except (I)DCT). This ensures that file and data checksums are reproducible and match between platforms. Its primary use is for regression testing.

aic

Apply H263 advanced intra coding / mpeg4 ac prediction.

cbp

Deprecated, use mpegvideo private options instead.

qprd

Deprecated, use mpegvideo private options instead.

ilme

Apply interlaced motion estimation.

cgop

Use closed gop.

me_method integer ( encoding,video )

Set motion estimation method.

Possible values:

zero

zero motion estimation (fastest)

full

full motion estimation (slowest)

epzs

EPZS motion estimation (default)

esa

esa motion estimation (alias for full)

tesa

tesa motion estimation

dia

dia motion estimation (alias for epzs)

log

log motion estimation

phods

phods motion estimation

x1

X1 motion estimation

hex

hex motion estimation

umh

umh motion estimation

iter

iter motion estimation

extradata_size integer

Set extradata size.

time_base rational number

Set codec time base.

It is the fundamental unit of time (in seconds) in terms of which frame timestamps are represented. For fixed-fps content, timebase should be 1 / frame_rate and timestamp increments should be identically 1.

g integer ( encoding,video )

Set the group of picture (GOP) size. Default value is 12.

ar integer ( decoding/encoding,audio )

Set audio sampling rate (in Hz).

ac integer ( decoding/encoding,audio )

Set number of audio channels.

cutoff integer ( encoding,audio )

Set cutoff bandwidth. (Supported only by selected encoders, see their respective documentation sections.)

frame_size integer ( encoding,audio )

Set audio frame size.

Each submitted frame except the last must contain exactly frame_size samples per channel. May be 0 when the codec has CODEC_CAP_VARIABLE_FRAME_SIZE set, in that case the frame size is not restricted. It is set by some decoders to indicate constant frame size.

frame_number integer

Set the frame number.

delay integer
qcomp float ( encoding,video )

Set video quantizer scale compression (VBR). It is used as a constant in the ratecontrol equation. Recommended range for default rc_eq: 0.0-1.0.

qblur float ( encoding,video )

Set video quantizer scale blur (VBR).

qmin integer ( encoding,video )

Set min video quantizer scale (VBR). Must be included between -1 and 69, default value is 2.

qmax integer ( encoding,video )

Set max video quantizer scale (VBR). Must be included between -1 and 1024, default value is 31.

qdiff integer ( encoding,video )

Set max difference between the quantizer scale (VBR).

bf integer ( encoding,video )

Set max number of B frames between non-B-frames.

Must be an integer between -1 and 16. 0 means that B-frames are disabled. If a value of -1 is used, it will choose an automatic value depending on the encoder.

Default value is 0.

b_qfactor float ( encoding,video )

Set qp factor between P and B frames.

rc_strategy integer ( encoding,video )

Set ratecontrol method.

b_strategy integer ( encoding,video )

Set strategy to choose between I/P/B-frames.

ps integer ( encoding,video )

Set RTP payload size in bytes.

mv_bits integer
header_bits integer
i_tex_bits integer
p_tex_bits integer
i_count integer
p_count integer
skip_count integer
misc_bits integer
frame_bits integer
codec_tag integer
bug flags ( decoding,video )

Workaround not auto detected encoder bugs.

Possible values:

autodetect
old_msmpeg4

some old lavc generated msmpeg4v3 files (no autodetection)

xvid_ilace

Xvid interlacing bug (autodetected if fourcc==XVIX)

ump4

(autodetected if fourcc==UMP4)

no_padding

padding bug (autodetected)

amv
ac_vlc

illegal vlc bug (autodetected per fourcc)

qpel_chroma
std_qpel

old standard qpel (autodetected per fourcc/version)

qpel_chroma2
direct_blocksize

direct-qpel-blocksize bug (autodetected per fourcc/version)

edge

edge padding bug (autodetected per fourcc/version)

hpel_chroma
dc_clip
ms

Workaround various bugs in microsoft broken decoders.

trunc

trancated frames

lelim integer ( encoding,video )

Set single coefficient elimination threshold for luminance (negative values also consider DC coefficient).

celim integer ( encoding,video )

Set single coefficient elimination threshold for chrominance (negative values also consider dc coefficient)

strict integer ( decoding/encoding,audio,video )

Specify how strictly to follow the standards.

Possible values:

very

strictly conform to an older more strict version of the spec or reference software

strict

strictly conform to all the things in the spec no matter what consequences

normal
unofficial

allow unofficial extensions

experimental

allow non standardized experimental things, experimental (unfinished/work in progress/not well tested) decoders and encoders. Note: experimental decoders can pose a security risk, do not use this for decoding untrusted input.

b_qoffset float ( encoding,video )

Set QP offset between P and B frames.

err_detect flags ( decoding,audio,video )

Set error detection flags.

Possible values:

crccheck

verify embedded CRCs

bitstream

detect bitstream specification deviations

buffer

detect improper bitstream length

explode

abort decoding on minor error detection

ignore_err

ignore decoding errors, and continue decoding. This is useful if you want to analyze the content of a video and thus want everything to be decoded no matter what. This option will not result in a video that is pleasing to watch in case of errors.

careful

consider things that violate the spec and have not been seen in the wild as errors

compliant

consider all spec non compliancies as errors

aggressive

consider things that a sane encoder should not do as an error

has_b_frames integer
block_align integer
mpeg_quant integer ( encoding,video )

Use MPEG quantizers instead of H.263.

qsquish float ( encoding,video )

How to keep quantizer between qmin and qmax (0 = clip, 1 = use differentiable function).

rc_qmod_amp float ( encoding,video )

Set experimental quantizer modulation.

rc_qmod_freq integer ( encoding,video )

Set experimental quantizer modulation.

rc_override_count integer
rc_eq string ( encoding,video )

Set rate control equation. When computing the expression, besides the standard functions defined in the section ’Expression Evaluation’, the following functions are available: bits2qp(bits), qp2bits(qp). Also the following constants are available: iTex pTex tex mv fCode iCount mcVar var isI isP isB avgQP qComp avgIITex avgPITex avgPPTex avgBPTex avgTex.

maxrate integer ( encoding,audio,video )

Set max bitrate tolerance (in bits/s). Requires bufsize to be set.

minrate integer ( encoding,audio,video )

Set min bitrate tolerance (in bits/s). Most useful in setting up a CBR encode. It is of little use elsewise.

bufsize integer ( encoding,audio,video )

Set ratecontrol buffer size (in bits).

rc_buf_aggressivity float ( encoding,video )

Currently useless.

i_qfactor float ( encoding,video )

Set QP factor between P and I frames.

i_qoffset float ( encoding,video )

Set QP offset between P and I frames.

rc_init_cplx float ( encoding,video )

Set initial complexity for 1-pass encoding.

dct integer ( encoding,video )

Set DCT algorithm.

Possible values:

auto

autoselect a good one (default)

fastint

fast integer

int

accurate integer

mmx
altivec
faan

floating point AAN DCT

lumi_mask float ( encoding,video )

Compress bright areas stronger than medium ones.

tcplx_mask float ( encoding,video )

Set temporal complexity masking.

scplx_mask float ( encoding,video )

Set spatial complexity masking.

p_mask float ( encoding,video )

Set inter masking.

dark_mask float ( encoding,video )

Compress dark areas stronger than medium ones.

idct integer ( decoding/encoding,video )

Select IDCT implementation.

Possible values:

auto
int
simple
simplemmx
simpleauto

Automatically pick a IDCT compatible with the simple one

arm
altivec
sh4
simplearm
simplearmv5te
simplearmv6
simpleneon
simplealpha
ipp
xvidmmx
faani

floating point AAN IDCT

slice_count integer
ec flags ( decoding,video )

Set error concealment strategy.

Possible values:

guess_mvs

iterative motion vector (MV) search (slow)

deblock

use strong deblock filter for damaged MBs

favor_inter

favor predicting from the previous frame instead of the current

bits_per_coded_sample integer
pred integer ( encoding,video )

Set prediction method.

Possible values:

left
plane
median
aspect rational number ( encoding,video )

Set sample aspect ratio.

sar rational number ( encoding,video )

Set sample aspect ratio. Alias to aspect .

debug flags ( decoding/encoding,audio,video,subtitles )

Print specific debug info.

Possible values:

pict

picture info

rc

rate control

bitstream
mb_type

macroblock (MB) type

qp

per-block quantization parameter (QP)

dct_coeff
green_metadata

display complexity metadata for the upcoming frame, GoP or for a given duration.

skip
startcode
er

error recognition

mmco

memory management control operations (H.264)

bugs
buffers

picture buffer allocations

thread_ops

threading operations

nomc

skip motion compensation

cmp integer ( encoding,video )

Set full pel me compare function.

Possible values:

sad

sum of absolute differences, fast (default)

sse

sum of squared errors

satd

sum of absolute Hadamard transformed differences

dct

sum of absolute DCT transformed differences

psnr

sum of squared quantization errors (avoid, low quality)

bit

number of bits needed for the block

rd

rate distortion optimal, slow

zero

0

vsad

sum of absolute vertical differences

vsse

sum of squared vertical differences

nsse

noise preserving sum of squared differences

w53

5/3 wavelet, only used in snow

w97

9/7 wavelet, only used in snow

dctmax
chroma
subcmp integer ( encoding,video )

Set sub pel me compare function.

Possible values:

sad

sum of absolute differences, fast (default)

sse

sum of squared errors

satd

sum of absolute Hadamard transformed differences

dct

sum of absolute DCT transformed differences

psnr

sum of squared quantization errors (avoid, low quality)

bit

number of bits needed for the block

rd

rate distortion optimal, slow

zero

0

vsad

sum of absolute vertical differences

vsse

sum of squared vertical differences

nsse

noise preserving sum of squared differences

w53

5/3 wavelet, only used in snow

w97

9/7 wavelet, only used in snow

dctmax
chroma
mbcmp integer ( encoding,video )

Set macroblock compare function.

Possible values:

sad

sum of absolute differences, fast (default)

sse

sum of squared errors

satd

sum of absolute Hadamard transformed differences

dct

sum of absolute DCT transformed differences

psnr

sum of squared quantization errors (avoid, low quality)

bit

number of bits needed for the block

rd

rate distortion optimal, slow

zero

0

vsad

sum of absolute vertical differences

vsse

sum of squared vertical differences

nsse

noise preserving sum of squared differences

w53

5/3 wavelet, only used in snow

w97

9/7 wavelet, only used in snow

dctmax
chroma
ildctcmp integer ( encoding,video )

Set interlaced dct compare function.

Possible values:

sad

sum of absolute differences, fast (default)

sse

sum of squared errors

satd

sum of absolute Hadamard transformed differences

dct

sum of absolute DCT transformed differences

psnr

sum of squared quantization errors (avoid, low quality)

bit

number of bits needed for the block

rd

rate distortion optimal, slow

zero

0

vsad

sum of absolute vertical differences

vsse

sum of squared vertical differences

nsse

noise preserving sum of squared differences

w53

5/3 wavelet, only used in snow

w97

9/7 wavelet, only used in snow

dctmax
chroma
dia_size integer ( encoding,video )

Set diamond type & size for motion estimation.

last_pred integer ( encoding,video )

Set amount of motion predictors from the previous frame.

preme integer ( encoding,video )

Set pre motion estimation.

precmp integer ( encoding,video )

Set pre motion estimation compare function.

Possible values:

sad

sum of absolute differences, fast (default)

sse

sum of squared errors

satd

sum of absolute Hadamard transformed differences

dct

sum of absolute DCT transformed differences

psnr

sum of squared quantization errors (avoid, low quality)

bit

number of bits needed for the block

rd

rate distortion optimal, slow

zero

0

vsad

sum of absolute vertical differences

vsse

sum of squared vertical differences

nsse

noise preserving sum of squared differences

w53

5/3 wavelet, only used in snow

w97

9/7 wavelet, only used in snow

dctmax
chroma
pre_dia_size integer ( encoding,video )

Set diamond type & size for motion estimation pre-pass.

subq integer ( encoding,video )

Set sub pel motion estimation quality.

dtg_active_format integer
me_range integer ( encoding,video )

Set limit motion vectors range (1023 for DivX player).

ibias integer ( encoding,video )

Set intra quant bias.

pbias integer ( encoding,video )

Set inter quant bias.

color_table_id integer
global_quality integer ( encoding,audio,video )
coder integer ( encoding,video )

Possible values:

vlc

variable length coder / huffman coder

ac

arithmetic coder

raw

raw (no encoding)

rle

run-length coder

deflate

deflate-based coder

context integer ( encoding,video )

Set context model.

slice_flags integer
mbd integer ( encoding,video )

Set macroblock decision algorithm (high quality mode).

Possible values:

simple

use mbcmp (default)

bits

use fewest bits

rd

use best rate distortion

stream_codec_tag integer
sc_threshold integer ( encoding,video )

Set scene change threshold.

lmin integer ( encoding,video )

Set min lagrange factor (VBR).

lmax integer ( encoding,video )

Set max lagrange factor (VBR).

nr integer ( encoding,video )

Set noise reduction.

rc_init_occupancy integer ( encoding,video )

Set number of bits which should be loaded into the rc buffer before decoding starts.

flags2 flags ( decoding/encoding,audio,video