Notes on FFmpeg (1)
source link: https://jdhao.github.io/2021/04/16/ffmpeg_notes_1/
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Install ffmpeg
If we have root rights, we can install ffmpeg via package manager. On Centos 7, run the following command:
yum install epel-release
yum localinstall --nogpgcheck https://download1.rpmfusion.org/free/el/rpmfusion-free-release-7.noarch.rpm
yum install ffmpeg ffmpeg-devel
If you want to download binary releases, this site can help you. It has binary release for ffmpeg, ffprobe for different systems. It seems that the provided ffmpeg is statically linked, so all you need is that one file to get to work.
This site alao provides binary release for ffmpeg.
Run command ffmpeg -version to verify that ffmpeg has been correctly
installed. You will see the following output:
ffmpeg version 3.4.8 Copyright (c) 2000-2020 the FFmpeg developers
built with gcc 4.8.5 (GCC) 20150623 (Red Hat 4.8.5-39)
configuration: --prefix=/usr --bindir=/usr/bin --datadir=/usr/share/ffmpeg
--docdir=/usr/share/doc/ffmpeg --incdir=/usr/include/ffmpeg --libdir=/usr/lib64
--mandir=/usr/share/man --arch=x86_64 --optflags='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2
-fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64
-mtune=generic' --extra-ldflags='-Wl,-z,relro ' --extra-cflags=' ' --enable-libopencore-amrnb
--enable-libopencore-amrwb --enable-libvo-amrwbenc --enable-version3 --enable-bzlib --disable-crystalhd
--enable-fontconfig --enable-gcrypt --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray
--enable-libcdio --enable-libdrm --enable-indev=jack --enable-libfreetype --enable-libfribidi --enable-libgsm
--enable-libmp3lame --enable-nvenc --enable-openal --enable-opencl --enable-opengl --enable-libopenjpeg
--enable-libopus --disable-encoder=libopus --enable-libpulse --enable-librsvg --enable-libsoxr --enable-libspeex
--enable-libtheora --enable-libvorbis --enable-libv4l2 --enable-libvidstab --enable-libvpx --enable-libx264
--enable-libx265 --enable-libxvid --enable-libzvbi --enable-avfilter --enable-avresample --enable-libmodplug
--enable-postproc --enable-pthreads --disable-static --enable-shared --enable-gpl --disable-debug
--disable-stripping --shlibdir=/usr/lib64 --enable-libmfx --enable-runtime-cpudetect
libavutil 55. 78.100 / 55. 78.100
libavcodec 57.107.100 / 57.107.100
libavformat 57. 83.100 / 57. 83.100
libavdevice 57. 10.100 / 57. 10.100
libavfilter 6.107.100 / 6.107.100
libavresample 3. 7. 0 / 3. 7. 0
libswscale 4. 8.100 / 4. 8.100
libswresample 2. 9.100 / 2. 9.100
libpostproc 54. 7.100 / 54. 7.100
suppress excessive logging
Every time I run ffmpeg command, its version, compilation configuration and
libary info is printed on the command line. This can be disabled using
-hide_banner option:
ffmpeg -hide_banner ...
We can also use -loglevel option to specify the verbosity of logging.
ffmpeg -loglevel warning ...
ffmpeg -loglevel info
The log level quite will silence any logging. In case you use -loglevel, it
is useful to specify -stats to print some running stats for ffmpeg.
Extract a frame every N seconds
How do we extract a frame from a video every N seconds?
ffmpeg -i input.mp4 -vf "fps=1/5" output_%3d.jpg
ffmpeg -i input.mp4 -r 0.2 output_%3d.jpg
Extract audio from video file
Run the following command to extract audio from a video file:
ffmpeg -i input.mp4 -vn -acodec copy output.aac
If we use this command, we need to know the audio format (i.e., acc, or other
formats). Use ffprobe to get the audio format. The output contains something
like the following:
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s (default)
Other option to use to extract audio from video:
ffmpeg -i input.mp4 -map a output.mp3
ffmpeg -i input.mp4 -map a output.aac
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