Difference between revisions of "FFmpeg"
(→Screen cast: reorganize flags to %video_input %audio_input %video_options %audio_options. the style is an arbitrary way of achieving consistency; rename alsa in to "default", and x11 in to $DISPLAY) |
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=== Screen cast === | === Screen cast === | ||
− | FFmpeg includes the [http://www.ffmpeg.org/ffmpeg-devices.html#x11grab x11grab] and [ | + | FFmpeg includes the [http://www.ffmpeg.org/ffmpeg-devices.html#x11grab x11grab] and [http://www.ffmpeg.org/ffmpeg-devices.html#alsa-1 ALSA] virtual devices that enable capturing the entire user display and audio output. |
First create {{ic|test.mkv}} with lossless encoding: | First create {{ic|test.mkv}} with lossless encoding: | ||
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$ ffmpeg -f x11grab -i $DISPLAY -f alsa -i default -c:v ffvhuff -c:a flac test.mkv | $ ffmpeg -f x11grab -i $DISPLAY -f alsa -i default -c:v ffvhuff -c:a flac test.mkv | ||
− | + | then we process it into a smaller [[Wikipedia:WebM]] file: | |
$ ffmpeg -i test.mkv -c:v libvpx -c:a libvorbis -b:v 2000k -q:a 3 test.webm | $ ffmpeg -i test.mkv -c:v libvpx -c:a libvorbis -b:v 2000k -q:a 3 test.webm |
Revision as of 20:23, 27 November 2013
From the project home page:
- FFmpeg is a complete, cross-platform solution to record, convert and stream audio and video. It includes libavcodec - the leading audio/video codec library.
Contents
- 1 Package installation
- 2 Encoding examples
- 2.1 Screen cast
- 2.2 Recording webcam
- 2.3 VOB to any container
- 2.4 x264 lossless
- 2.5 Single-pass MPEG-2 (near lossless)
- 2.6 x264: constant rate factor
- 2.7 YouTube
- 2.8 Two-pass x264 (very high-quality)
- 2.9 Two-pass MPEG-4 (very high-quality)
- 2.10 Subtitles
- 2.11 Volume gain
- 2.12 Extracting audio
- 2.13 Stripping audio
- 3 Preset files
- 4 Package removal
- 5 See also
Package installation
Various flavors and related projects can be installed from the official repositories and the AUR:
- ffmpeg – official package
Notable variants:
- ffmpeg-gitAUR – development version
- ffmpeg-fullAUR – built with as much optional features enabled as possible
Forks:
- ffmbcAUR – targeted for broadcasting usage
- libav-gitAUR – the binary it provides is called
avconv
instead offfmpeg
Encoding examples
Screen cast
FFmpeg includes the x11grab and ALSA virtual devices that enable capturing the entire user display and audio output.
First create test.mkv
with lossless encoding:
$ ffmpeg -f x11grab -i $DISPLAY -f alsa -i default -c:v ffvhuff -c:a flac test.mkv
then we process it into a smaller Wikipedia:WebM file:
$ ffmpeg -i test.mkv -c:v libvpx -c:a libvorbis -b:v 2000k -q:a 3 test.webm
Recording webcam
FFmpeg supports grabbing input from Video4Linux2 devices. The following command will record a video from the webcam, assuming that the webcam is correctly recognized under /dev/video0
:
$ ffmpeg -f v4l2 -s 640x480 -i /dev/video0 output.mpg
The above produces a silent video. It is also possible to include audio sources from a microphone. The following command will include a stream from the default ALSA recording device into the video:
$ ffmpeg -f alsa -i default -f v4l2 -s 640x480 -i /dev/video0 output.mpg
To use PulseAudio with an ALSA backend:
$ ffmpeg -f alsa -i pulse -f v4l2 -s 640x480 -i /dev/video0 output.mpg
For a higher quality capture, try encoding the output using higher quality codecs:
$ ffmpeg -f alsa -i default -f v4l2 -s 640x480 -i /dev/video0 -acodec flac \ -vcodec libx264 output.mkv
VOB to any container
Concatenate the desired Wikipedia:VOB files into a single stream and mux them to MPEG-2:
$ cat f0.VOB f1.VOB f2.VOB | ffmpeg -i - out.mp2
x264 lossless
The ultrafast preset will provide the fastest encoding and is useful for quick capturing (such as screencasting):
$ ffmpeg -i input -vcodec libx264 -preset ultrafast -qp 0 -acodec copy output.mkv
On the opposite end of the preset spectrum is veryslow and will encode slower than ultrafast but provide a smaller output file size:
$ ffmpeg -i input -vcodec libx264 -preset veryslow -qp 0 -acodec copy output.mkv
Both examples will provide the same quality output.
Single-pass MPEG-2 (near lossless)
Allow FFmpeg to automatically set DVD standardized parameters. Encode to DVD MPEG-2 at ~30 FPS:
$ ffmpeg -i video.VOB -target ntsc-dvd -q:a 0 -q:v 0 output.mpg
Encode to DVD MPEG-2 at ~24 FPS:
$ ffmpeg -i video.VOB -target film-dvd -q:a 0 -q:v 0 output.mpg
x264: constant rate factor
Used when you want a specific quality output. General usage is to use the highest -crf
value that still provides an acceptable quality. Lower values are higher quality; 0 is lossless, 18 is visually lossless, and 23 is the default value. A sane range is between 18 and 28. Use the slowest -preset
you have patience for. See the x264 Encoding Guide for more information.
$ ffmpeg -i video -vcodec libx264 -preset slow -crf 22 -acodec libmp3lame -aq 4 output.mkv
-tune
option can be used to match the type and content of the of media being encoded.
YouTube
FFmpeg is very useful to encode videos and strip their size before you upload them on YouTube. The following single line of code takes an input file and outputs a mkv container.
$ ffmpeg -i video -c:v libx264 -crf 18 -preset slow -pix_fmt yuv420p -c:a copy output.mkv
For more information see the forums. You can also create a custom alias ytconvert
which takes the name of the input file as first argument and the name of the .mkv container as second argument. To do so add the following to your ~/.bashrc
:
youtubeConvert(){ ffmpeg -i $1 -c:v libx264 -crf 18 -preset slow -pix_fmt yuv420p -c:a copy $2.mkv } alias ytconvert=youtubeConvert
See also Arch Linux forum thread.
Two-pass x264 (very high-quality)
Audio deactivated as only video statistics are recorded during the first of multiple pass runs:
$ ffmpeg -i video.VOB -an -vcodec libx264 -pass 1 -preset veryslow \ -threads 0 -b 3000k -x264opts frameref=15:fast_pskip=0 -f rawvideo -y /dev/null
Container format is automatically detected and muxed into from the output file extenstion (.mkv
):
$ ffmpeg -i video.VOB -acodec libvo-aacenc -ab 256k -ar 96000 -vcodec libx264 \ -pass 2 -preset veryslow -threads 0 -b 3000k -x264opts frameref=15:fast_pskip=0 video.mkv
Unknown encoder 'libvo-aacenc'
error (given the fact that your ffmpeg is compiled with libvo-aacenc enabled), you may want to try -acodec libvo_aacenc
, an underscore instead of hyphen.Two-pass MPEG-4 (very high-quality)
Audio deactivated as only video statistics are logged during the first of multiple pass runs:
$ ffmpeg -i video.VOB -an -vcodec mpeg4 -pass 1 -mbd 2 -trellis 2 -flags +cbp+mv0 \ -pre_dia_size 4 -dia_size 4 -precmp 4 -cmp 4 -subcmp 4 -preme 2 -qns 2 -b 3000k \ -f rawvideo -y /dev/null
Container format is automatically detected and muxed into from the output file extenstion (.avi
):
$ ffmpeg -i video.VOB -acodec copy -vcodec mpeg4 -vtag DX50 -pass 2 -mbd 2 -trellis 2 \ -flags +cbp+mv0 -pre_dia_size 4 -dia_size 4 -precmp 4 -cmp 4 -subcmp 4 -preme 2 -qns 2 \ -b 3000k video.avi
- Introducing
threads
=n
>1
for-vcodec mpeg4
may skew the effects of motion estimation and lead to reduced video quality and compression efficiency. - The two-pass MPEG-4 example above also supports output to the MP4 container (replace
.avi
with.mp4
).
Determining bitrates with fixed output file sizes
- (Desired File Size in MB - Audio File Size in MB) x 8192 kb/MB / Length of Media in Seconds (s) = Bitrate in kb/s
- (3900 MB - 275 MB) = 3625 MB x 8192 kb/MB / 8830 s = 3363 kb/s required to achieve an approximate total output file size of 3900 MB
Subtitles
Extracting
Subtitles embedded in container files, such as MPEG-2 and Matroska, can be extracted and converted into SRT, SSA, among other subtitle formats.
- Inspect a file to determine if it contains a subtitle stream:
$ ffprobe foo.mkv
... Stream #0:0(und): Video: h264 (High), yuv420p, 1920x800 [SAR 1:1 DAR 12:5], 23.98 fps, 23.98 tbr, 1k tbn, 47.95 tbc (default) Metadata: CREATION_TIME : 2012-06-05 05:04:15 LANGUAGE : und Stream #0:1(und): Audio: aac, 44100 Hz, stereo, fltp (default) Metadata: CREATION_TIME : 2012-06-05 05:10:34 LANGUAGE : und HANDLER_NAME : GPAC ISO Audio Handler Stream #0:2: Subtitle: ssa (default)
-
foo.mkv
has an embedded SSA subtitle which can be extracted into an independent file:
$ ffmpeg -i foo.mkv foo.ssa
Hardsubbing
(instructions based on an FFmpeg wiki article)
Hardsubbing entails merging subtitles with the video. Hardsubs can't be disabled, nor language switched.
- Overlay
foo.mpg
with the subtitles infoo.ssa
:
$ ffmpeg -i foo.mpg -c copy -vf subtitles=foo.ssa out.mpg
Volume gain
Change the audio volume in multiples of 256 where 256 = 100% (normal) volume. Additional values such as 400 are also valid options.
-vol 256 = 100% -vol 512 = 200% -vol 768 = 300% -vol 1024 = 400% -vol 2048 = 800%
To double the volume (512 = 200%) of an MP3 file:
$ ffmpeg -i file.mp3 -vol 512 louder file.mp3
To quadruple the volume (1024 = 400%) of an Ogg file:
$ ffmpeg -i file.ogg -vol 1024 louder file.ogg
Note that gain metadata is only written to the output file. Unlike mp3gain or ogggain, the source sound file is untouched.
Extracting audio
$ ffmpeg -i video.mpg
... Input #0, avi, from 'video.mpg': Duration: 01:58:28.96, start: 0.000000, bitrate: 3000 kb/s Stream #0.0: Video: mpeg4, yuv420p, 720x480 [PAR 1:1 DAR 16:9], 29.97 tbr, 29.97 tbn, 29.97 tbc Stream #0.1: Audio: ac3, 48000 Hz, stereo, s16, 384 kb/s Stream #0.2: Audio: ac3, 48000 Hz, 5.1, s16, 448 kb/s Stream #0.3: Audio: dts, 48000 Hz, 5.1 768 kb/s ...
Extract the first (-map 0:1
) AC-3 encoded audio stream exactly as it was multiplexed into the file:
$ ffmpeg -i video.mpg -map 0:1 -acodec copy -vn video.ac3
Convert the third (-map 0:3
) DTS audio stream to an AAC file with a bitrate of 192 kb/s and a sampling rate of 96000 Hz:
$ ffmpeg -i video.mpg -map 0:3 -acodec libvo-aacenc -ab 192k -ar 96000 -vn output.aac
-vn
disables the processing of the video stream.
Extract audio stream with certain time interval:
$ ffmpeg -ss 00:01:25 -t 00:00:05 -i video.mpg -map 0:1 -acodec copy -vn output.ac3
-ss
specifies the start point, and -t
specifies the duration.
Stripping audio
- Copy the first video stream (
-map 0:0
) along with the second AC-3 audio stream (-map 0:2
). - Convert the AC-3 audio stream to two-channel MP3 with a bitrate of 128 kb/s and a sampling rate of 48000 Hz.
$ ffmpeg -i video.mpg -map 0:0 -map 0:2 -vcodec copy -acodec libmp3lame \ -ab 128k -ar 48000 -ac 2 video.mkv
$ ffmpeg -i video.mkv
... Input #0, avi, from 'video.mpg': Duration: 01:58:28.96, start: 0.000000, bitrate: 3000 kb/s Stream #0.0: Video: mpeg4, yuv420p, 720x480 [PAR 1:1 DAR 16:9], 29.97 tbr, 29.97 tbn, 29.97 tbc Stream #0.1: Audio: mp3, 48000 Hz, stereo, s16, 128 kb/s
Preset files
Populate ~/.ffmpeg
with the default preset files:
$ cp -iR /usr/share/ffmpeg ~/.ffmpeg
Create new and/or modify the default preset files:
~/.ffmpeg/libavcodec-vhq.ffpreset
vtag=DX50 mbd=2 trellis=2 flags=+cbp+mv0 pre_dia_size=4 dia_size=4 precmp=4 cmp=4 subcmp=4 preme=2 qns=2
Using preset files
Enable the -vpre
option after declaring the desired -vcodec
libavcodec-vhq.ffpreset
-
libavcodec
= Name of the vcodec/acodec -
vhq
= Name of specific preset to be called out -
ffpreset
= FFmpeg preset filetype suffix
Two-pass MPEG-4 (very high quality)
First pass of a multipass (bitrate) ratecontrol transcode:
$ ffmpeg -i video.mpg -an -vcodec mpeg4 -pass 1 -vpre vhq -f rawvideo -y /dev/null
Ratecontrol based on the video statistics logged from the first pass:
$ ffmpeg -i video.mpg -acodec libvorbis -aq 8 -ar 48000 -vcodec mpeg4 \ -pass 2 -vpre vhq -b 3000k output.mp4
- libvorbis quality settings (VBR)
-
-aq 4
= 128 kb/s -
-aq 5
= 160 kb/s -
-aq 6
= 192 kb/s -
-aq 7
= 224 kb/s -
-aq 8
= 256 kb/s
-
- aoTuV is generally preferred over libvorbis provided by Xiph.Org and is provided by libvorbis-aotuv in the AUR.
Package removal
pacman will not remove configuration files outside of the defaults that were created during package installation. This includes user-created preset files.
See also
- x264 Settings - MeWiki documentation
- FFmpeg documentation - official documentation
- Encoding with the x264 codec - MEncoder documentation
- H.264 encoding guide - Avidemux wiki
- Using FFmpeg - Linux how to pages
- List of supported audio and video streams