FFmpeg Documentation: 1. Introduction

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# 1. Introduction

FFmpeg is a very fast video and audio converter. It can also grab from a live audio/video source.

The command line interface is designed to be intuitive, in the sense that FFmpeg tries to figure out all parameters that can possibly be derived automatically. You usually only have to specify the target bitrate you want.

FFmpeg can also convert from any sample rate to any other, and resize video on the fly with a high quality polyphase filter.

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# 2. Quick Start

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## 2.1 Video and Audio grabbing

FFmpeg can grab video and audio from devices given that you specify the input format and device.

    ffmpeg -f oss -i /dev/dsp -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 (http://bytesex.org/xawtv/) by Gerd Knorr. You also have to set the audio recording levels correctly with a standard mixer.

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## 2.2 X11 grabbing

FFmpeg can grab the X11 display.

    ffmpeg -f x11grab -s cif -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 -s cif -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.

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## 2.3 Video and Audio file format conversion

* FFmpeg can use any supported file format and protocol as input:

Examples:

* 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 22050Hz 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 -ab 64k /tmp/a.mp2 -ab 128k /tmp/b.mp2 -map 0:0 -map 0:0

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 -vcodec mpeg4 -b 800k -g 300 -bf 2 -acodec libmp3lame -ab 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 -formats`.

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# 3. Invocation

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## 3.1 Syntax

The generic syntax is:

    ffmpeg [[infile options][`-i' infile]]... {[outfile options] outfile}...

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.

* To set the video bitrate of the output file to 64kbit/s:

    ffmpeg -i input.avi -b 64k output.avi

* To force the frame rate of the input and output file to 24 fps:

    ffmpeg -r 24 -i input.avi 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 input file to 1 fps and the output file to 24 fps:

    ffmpeg -r 1 -i input.avi -r 24 output.avi

The format option may be needed for raw input files.

By default, FFmpeg tries to convert as losslessly as possible: It uses the same audio and video parameters for the outputs as the one specified for the inputs.

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## 3.2 Main options

``-L'`

  Show license.

``-h'`

  Show help.

``-version'`

  Show version.

``-formats'`

  Show available formats, codecs, protocols, ...

``-f fmt'`

  Force format.

``-i filename'`

  input filename

``-y'`

  Overwrite output files.

``-t duration'`

  Restrict the transcoded/captured video sequence to the duration specified in seconds. `hh:mm:ss[.xxx]` syntax is also supported.

``-fs limit_size'`

  Set the file size limit.

``-ss position'`

  Seek to given time position in seconds. `hh:mm:ss[.xxx]` syntax is also supported.

``-itsoffset offset'`

  Set the input time offset in seconds. `[-]hh:mm:ss[.xxx]` syntax is also supported. This option affects all the input files that follow it. The offset is added to the timestamps of the input files. Specifying a positive offset means that the corresponding streams are delayed by 'offset' seconds.

``-title string'`

  Set the title.

``-timestamp time'`

  Set the timestamp.

``-author string'`

  Set the author.

``-copyright string'`

  Set the copyright.

``-comment string'`

  Set the comment.

``-album string'`

  Set the album.

``-track number'`

  Set the track.

``-year number'`

  Set the year.

``-v verbose'`

  Control amount of logging.

``-target type'`

  Specify target file type ("vcd", "svcd", "dvd", "dv", "dv50", "pal-vcd", "ntsc-svcd", ... ). 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

``-dframes number'`

  Set the number of data frames to record.

``-scodec codec'`

  Force subtitle codec ('copy' to copy stream).

``-newsubtitle'`

  Add a new subtitle stream to the current output stream.

``-slang code'`

  Set the ISO 639 language code (3 letters) of the current subtitle stream.

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## 3.3 Video Options

``-b bitrate'`

  Set the video bitrate in bit/s (default = 200 kb/s).

``-vframes number'`

  Set the number of video frames to record.

``-r fps'`

  Set frame rate (Hz value, fraction or abbreviation), (default = 25).

``-s size'`

  Set frame size. The format is ``wxh'` (ffserver default = 160x128, ffmpeg default = same as source). The following abbreviations are recognized:

  ``sqcif'`

    128x96

  ``qcif'`

    176x144

  ``cif'`

    352x288

  ``4cif'`

    704x576

  ``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

``-aspect aspect'`

  Set aspect ratio (4:3, 16:9 or 1.3333, 1.7777).

``-croptop size'`

  Set top crop band size (in pixels).

``-cropbottom size'`

  Set bottom crop band size (in pixels).

``-cropleft size'`

  Set left crop band size (in pixels).

``-cropright size'`

  Set right crop band size (in pixels).

``-padtop size'`

  Set top pad band size (in pixels).

``-padbottom size'`

  Set bottom pad band size (in pixels).

``-padleft size'`

  Set left pad band size (in pixels).

``-padright size'`

  Set right pad band size (in pixels).

``-padcolor (hex color)'`

  Set color of padded bands. The value for padcolor is expressed as a six digit hexadecimal number where the first two digits represent red, the middle two digits green and last two digits blue (default = 000000 (black)).

``-vn'`

  Disable video recording.

``-bt tolerance'`

  Set video bitrate tolerance (in bit/s).

``-maxrate bitrate'`

  Set max video bitrate (in bit/s).

``-minrate bitrate'`

  Set min video bitrate (in bit/s).

``-bufsize size'`

  Set video buffer verifier buffer size (in bits).

``-vcodec codec'`

  Force video codec to codec. Use the `copy` special value to tell that the raw codec data must be copied as is.

``-sameq'`

  Use same video quality as source (implies VBR).

``-pass n'`

  Select the pass number (1 or 2). It is useful to do two pass encoding. The statistics of the video are recorded in the first pass and the video is generated at the exact requested bitrate in the second pass.

``-passlogfile file'`

  Set two pass logfile name to file.

``-newvideo'`

  Add a new video stream to the current output stream.

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## 3.4 Advanced Video Options

``-pix_fmt format'`

  Set pixel format. Use 'list' as parameter to show all the supported pixel formats.

``-sws_flags flags'`

  Set SwScaler flags (only available when compiled with SwScaler support).

``-g gop_size'`

  Set the group of pictures size.

``-intra'`

  Use only intra frames.

``-vdt n'`

  Discard threshold.

``-qscale q'`

  Use fixed video quantizer scale (VBR).

``-qmin q'`

  minimum video quantizer scale (VBR)

``-qmax q'`

  maximum video quantizer scale (VBR)

``-qdiff q'`

  maximum difference between the quantizer scales (VBR)

``-qblur blur'`

  video quantizer scale blur (VBR)

``-qcomp compression'`

  video quantizer scale compression (VBR)

``-lmin lambda'`

  minimum video lagrange factor (VBR)

``-lmax lambda'`

  max video lagrange factor (VBR)

``-mblmin lambda'`

  minimum macroblock quantizer scale (VBR)

``-mblmax lambda'`

  maximum macroblock quantizer scale (VBR)

  These four options (lmin, lmax, mblmin, 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

``-rc_init_cplx complexity'`

  initial complexity for single pass encoding

``-b_qfactor factor'`

  qp factor between P- and B-frames

``-i_qfactor factor'`

  qp factor between P- and I-frames

``-b_qoffset offset'`

  qp offset between P- and B-frames

``-i_qoffset offset'`

  qp offset between P- and I-frames

``-rc_eq equation'`

  Set rate control equation (see section FFmpeg formula evaluator) (default = `tex^qComp`).

``-rc_override override'`

  rate control override for specific intervals

``-me_method method'`

  Set motion estimation method to method. Available methods are (from lowest to best quality):

  ``zero'`

    Try just the (0, 0) vector.

  ``phods'`
  ``log'`
  ``x1'`
  ``hex'`
  ``umh'`
  ``epzs'`

    (default method)

  ``full'`

    exhaustive search (slow and marginally better than epzs)

``-dct_algo algo'`

  Set DCT algorithm to algo. Available values are:

  ``0'`

    FF_DCT_AUTO (default)

  ``1'`

    FF_DCT_FASTINT

  ``2'`

    FF_DCT_INT

  ``3'`

    FF_DCT_MMX

  ``4'`

    FF_DCT_MLIB

  ``5'`

    FF_DCT_ALTIVEC

``-idct_algo algo'`

  Set IDCT algorithm to algo. Available values are:

  ``0'`

    FF_IDCT_AUTO (default)

  ``1'`

    FF_IDCT_INT

  ``2'`

    FF_IDCT_SIMPLE

  ``3'`

    FF_IDCT_SIMPLEMMX

  ``4'`

    FF_IDCT_LIBMPEG2MMX

  ``5'`

    FF_IDCT_PS2

  ``6'`

    FF_IDCT_MLIB

  ``7'`

    FF_IDCT_ARM

  ``8'`

    FF_IDCT_ALTIVEC

  ``9'`

    FF_IDCT_SH4

  ``10'`

    FF_IDCT_SIMPLEARM

``-er n'`

  Set error resilience to n.

  ``1'`

    FF_ER_CAREFUL (default)

  ``2'`

    FF_ER_COMPLIANT

  ``3'`

    FF_ER_AGGRESSIVE

  ``4'`

    FF_ER_VERY_AGGRESSIVE

``-ec bit_mask'`

  Set error concealment to bit_mask. bit_mask is a bit mask of the following values:

  ``1'`

    FF_EC_GUESS_MVS (default = enabled)

  ``2'`

    FF_EC_DEBLOCK (default = enabled)

``-bf frames'`

  Use 'frames' B-frames (supported for MPEG-1, MPEG-2 and MPEG-4).

``-mbd mode'`

  macroblock decision

  ``0'`

    FF_MB_DECISION_SIMPLE: Use mb_cmp (cannot change it yet in FFmpeg).

  ``1'`

    FF_MB_DECISION_BITS: Choose the one which needs the fewest bits.

  ``2'`

    FF_MB_DECISION_RD: rate distortion

``-4mv'`

  Use four motion vector by macroblock (MPEG-4 only).

``-part'`

  Use data partitioning (MPEG-4 only).

``-bug param'`

  Work around encoder bugs that are not auto-detected.

``-strict strictness'`

  How strictly to follow the standards.

``-aic'`

  Enable Advanced intra coding (h263+).

``-umv'`

  Enable Unlimited Motion Vector (h263+)

``-deinterlace'`

  Deinterlace pictures.

``-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.

``-vhook module'`

  Insert video processing module. module contains the module name and its parameters separated by spaces.

``-top n'`

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

``-dc precision'`

  Intra_dc_precision.

``-vtag fourcc/tag'`

  Force video tag/fourcc.

``-qphist'`

  Show QP histogram.

``-vbsf bitstream filter'`

  Bitstream filters available are "dump_extra", "remove_extra", "noise".

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## 3.5 Audio Options

``-aframes number'`

  Set the number of audio frames to record.

``-ar freq'`

  Set the audio sampling frequency (default = 44100 Hz).

``-ab bitrate'`

  Set the audio bitrate in bit/s (default = 64k).

``-ac channels'`

  Set the number of audio channels (default = 1).

``-an'`

  Disable audio recording.

``-acodec codec'`

  Force audio codec to codec. Use the `copy` special value to specify that the raw codec data must be copied as is.

``-newaudio'`

  Add a new audio track to the output file. If you want to specify parameters, do so before `-newaudio` (`-acodec`, `-ab`, etc..).

  Mapping will be done automatically, if the number of output streams is equal to the number of input streams, else it will pick the first one that matches. You can override the mapping using `-map` as usual.

  Example:

      ffmpeg -i file.mpg -vcodec copy -acodec ac3 -ab 384k test.mpg -acodec mp2 -ab 192k -newaudio

``-alang code'`

  Set the ISO 639 language code (3 letters) of the current audio stream.

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## 3.6 Advanced Audio options:

``-atag fourcc/tag'`

  Force audio tag/fourcc.

``-absf bitstream filter'`

  Bitstream filters available are "dump_extra", "remove_extra", "noise", "mp3comp", "mp3decomp".

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## 3.7 Subtitle options:

``-scodec codec'`

  Force subtitle codec ('copy' to copy stream).

``-newsubtitle'`

  Add a new subtitle stream to the current output stream.

``-slang code'`

  Set the ISO 639 language code (3 letters) of the current subtitle stream.

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## 3.8 Audio/Video grab options

``-vc channel'`

  Set video grab channel (DV1394 only).

``-tvstd standard'`

  Set television standard (NTSC, PAL (SECAM)).

``-isync'`

  Synchronize read on input.

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## 3.9 Advanced options

``-map input stream id[:input stream id]'`

  Set stream mapping from input streams to output streams. Just enumerate the input streams in the order you want them in the output. [input stream id] sets the (input) stream to sync against.

``-map_meta_data outfile:infile'`

  Set meta data information of outfile from infile.

``-debug'`

  Print specific debug info.

``-benchmark'`

  Add timings for benchmarking.

``-dump'`

  Dump each input packet.

``-hex'`

  When dumping packets, also dump the payload.

``-bitexact'`

  Only use bit exact algorithms (for codec testing).

``-ps size'`

  Set packet size in bits.

``-re'`

  Read input at native frame rate. Mainly used to simulate a grab device.

``-loop_input'`

  Loop over the input stream. Currently it works only for image streams. This option is used for automatic FFserver testing.

``-loop_output number_of_times'`

  Repeatedly loop output for formats that support looping such as animated GIF (0 will loop the output infinitely).

``-threads count'`

  Thread count.

``-vsync parameter'`

  Video sync method. Video will be stretched/squeezed to match the timestamps, it is done by duplicating and dropping frames. 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.

``-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.

``-copyts'`

  Copy timestamps from input to output.

``-shortest'`

  Finish encoding when the shortest input stream ends.

``-dts_delta_threshold'`

  Timestamp discontinuity delta threshold.

``-muxdelay seconds'`

  Set the maximum demux-decode delay.

``-muxpreload seconds'`

  Set the initial demux-decode delay.

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## 3.10 FFmpeg formula evaluator

When evaluating a rate control string, FFmpeg uses an internal formula evaluator.

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

The following unary operators are available: `+`, `-`, `(...)`.

The following functions are available:

sinh(x)
cosh(x)
tanh(x)
sin(x)
cos(x)
tan(x)
exp(x)
log(x)
squish(x)
gauss(x)
abs(x)
max(x, y)
min(x, y)
gt(x, y)
lt(x, y)
eq(x, y)
bits2qp(bits)
qp2bits(qp)

The following constants are available:

PI
E
iTex
pTex
tex
mv
fCode
iCount
mcVar
var
isI
isP
isB
avgQP
qComp
avgIITex
avgPITex
avgPPTex
avgBPTex
avgTex

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## 3.11 Protocols

The filename can be ``-'` to read from standard input or to write to standard output.

FFmpeg also handles many protocols specified with an URL syntax.

Use 'ffmpeg -formats' to see a list of the supported protocols.

The protocol `http:` is currently used only to communicate with FFserver (see the FFserver documentation). When FFmpeg will be a video player it will also be used for streaming :-)

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# 4. Tips

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# About This Document

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