WSL2を使ってffmpegをソースからビルドする

sudo apt-get update
sudo apt-get upgrade

git clone https://github.com/rdp/ffmpeg-windows-build-helpers.git
cd ffmpeg-windows-build-helpers

time ./cross_compile_ffmpeg.sh --disable-nonfree=n

$ ./cross_compile_ffmpeg.sh -h

available option=default_value:
      --build-ffmpeg-static=y  (ffmpeg.exe, ffplay.exe and ffprobe.exe)
      --build-ffmpeg-shared=n  (ffmpeg.exe (with libavformat-x.dll, etc., ffplay.exe, ffprobe.exe and dll-files)
      --ffmpeg-git-checkout-version=[master] if you want to build a particular version of FFmpeg, ex: n3.1.1 or a specific git hash
      --ffmpeg-git-checkout=[https://github.com/FFmpeg/FFmpeg.git] if you want to clone FFmpeg from other repositories
      --ffmpeg-source-dir=[default empty] specifiy the directory of ffmpeg source code. When specified, git will not be used.
      --x265-git-checkout-version=[master] if you want to build a particular version of x265, ex: --x265-git-checkout-version=Release_3.2 or a specific git hash
      --fdk-aac-git-checkout-version= if you want to build a particular version of fdk-aac, ex: --fdk-aac-git-checkout-version=v2.0.1 or another tag
      --gcc-cpu-count=[number of cpu cores set it higher than 1 if you have multiple cores and > 1GB RAM, this speeds up initial cross compiler build. FFmpeg build uses number of cores no matter what]
      --disable-nonfree=y (set to n to include nonfree like libfdk-aac,decklink)
      --build-intel-qsv=y (set to y to include the [non windows xp compat.] qsv library and ffmpeg module. NB this not not hevc_qsv...
      --sandbox-ok=n [skip sandbox prompt if y]
      -d [meaning "defaults" skip all prompts, just build ffmpeg static with some reasonable defaults like no git updates]
      --build-libmxf=n [builds libMXF, libMXF++, writeavidmxfi.exe and writeaviddv50.exe from the BBC-Ingex project]
      --build-mp4box=n [builds MP4Box.exe from the gpac project]
      --build-mplayer=n [builds mplayer.exe and mencoder.exe]
      --build-vlc=n [builds a [rather bloated] vlc.exe]
      --build-lsw=n [builds L-Smash Works VapourSynth and AviUtl plugins]
      --build-ismindex=n [builds ffmpeg utility ismindex.exe]
      -a 'build all' builds ffmpeg, mplayer, vlc, etc. with all fixings turned on [many disabled from disuse these days]
      --build-svt-hevc=n [builds libsvt-hevc modules within ffmpeg etc.]
      --build-dvbtee=n [build dvbtee.exe a DVB profiler]
      --compiler-flavors=[multi,win32,win64,native] [default prompt, or skip if you already have one built, multi is both win32 and win64]
      --cflags=[default is -mtune=generic -O3, which works on any cpu, see README for options]
      --git-get-latest=y [do a git pull for latest code from repositories like FFmpeg--can force a rebuild if changes are detected]
      --build-x264-with-libav=n build x264.exe with bundled/included libav ffmpeg libraries within it
      --prefer-stable=y build a few libraries from releases instead of git master
      --debug Make this script  print out each line as it executes
      --enable-gpl=[y] set to n to do an lgpl build
      --build-dependencies=y [builds the ffmpeg dependencies. Disable it when the dependencies was built once and can greatly reduce build time. ]

Could not find the following execs (svn is actually package subversion, makeinfo is actually package texinfo if you're missing them): libtoolize cmake python clang meson bzip2 autogen gperf nasm unzip pax g++ makeinfo bison flex cvs yasm automake autoconf gcc svn make pkg-config ragel
Install the missing packages before running this script.
for ubuntu:
$ sudo apt-get update
$ sudo apt-get install subversion ragel curl texinfo g++ ed bison flex cvs yasm automake libtool autoconf gcc cmake git make pkg-config zlib1g-dev unzip pax nasm gperf autogen bzip2 autoconf-archive p7zip-full meson clang python3-distutils python-is-python3 -y
NB if you use WSL Ubuntu 20.04 you need to do an extra step: https://github.com/rdp/ffmpeg-windows-build-helpers/issues/452

sudo apt-get install subversion ragel curl texinfo g++ ed bison flex cvs yasm automake libtool autoconf gcc cmake git make pkg-config zlib1g-dev unzip pax nasm gperf autogen bzip2 autoconf-archive p7zip-full meson clang python3-distutils python-is-python3

time ./cross_compile_ffmpeg.sh --disable-nonfree=n

windows WSL detected: you must first disable 'binfmt' by running this
      sudo bash -c 'echo 0 > /proc/sys/fs/binfmt_misc/WSLInterop'
      then try again

cat /proc/sys/fs/binfmt_misc/WSLInterop

enabled
interpreter /init
flags: PF
offset 0
magic 4d5a

sudo bash -c 'echo 0 > /proc/sys/fs/binfmt_misc/WSLInterop'
cat /proc/sys/fs/binfmt_misc/WSLInterop

disabled
interpreter /init
flags: PF
offset 0
magic 4d5a

time ./cross_compile_ffmpeg.sh --disable-nonfree=n

What version of MinGW-w64 would you like to build or update?
  1. Both Win32 and Win64
  2. Win32 (32-bit only)
  3. Win64 (64-bit only)
  4. Local native
  5. Exit
Input your choice [1-5]: 3