# Minimal LGPL FFmpeg for Audio Converter

`build-ffmpeg.sh` builds a small, statically linked, LGPL-2.1-or-later
`ffmpeg.exe` + `ffprobe.exe` (Windows x64) from source and puts them in
`tools/bin/ffmpeg/` (gitignored), the single place the app copies them from.
Full verification results: `docs/ffmpeg-build.md`.

## Run it

1. Install MSYS2 once: `winget install --id MSYS2.MSYS2 -e --silent --accept-package-agreements --accept-source-agreements`,
   then in an MSYS2 shell run `pacman -Syu` (twice if it restarts).
2. From an **MSYS2 MINGW64** shell (or `set MSYSTEM=MINGW64` then
   `C:\msys64\usr\bin\bash.exe -l <script>`):

   ```sh
   bash tools/ffmpeg/build-ffmpeg.sh        # installs packages, clones, builds (~5 min)
   bash tools/ffmpeg/test-ffmpeg.sh         # round-trip tests -> out/ffmpeg-tests/results.txt
   ```

   `SKIP_PACMAN=1` skips the `pacman -S` step; `JOBS=n` sets make parallelism.
   The script is re-runnable: it reuses `out/ffmpeg-src/`, checks the pinned
   commit SHA, wipes and rebuilds `out/ffmpeg-build/`, and prints the exact
   configure line. It fails if the licence is not LGPL-2.1-or-later or if an
   exe imports a non-system DLL.

Output in `tools/bin/ffmpeg/`: `ffmpeg.exe`, `ffprobe.exe`, `LICENSE.txt`
(FFmpeg `COPYING.LGPLv2.1`), `buildconf.txt` (`ffmpeg -buildconf`),
`SOURCE.txt` (tag, commit, URLs, dependency versions, configure line).

## Pinned versions

| Component | Version | Source | Licence |
|---|---|---|---|
| FFmpeg | tag `n9.0.2`, commit `946fcce07b6dcd0331c8cc609192aeff5e1924f8` | https://github.com/FFmpeg/FFmpeg/tree/n9.0.2 (tarball https://ffmpeg.org/releases/ffmpeg-9.0.2.tar.xz) | LGPL-2.1-or-later |
| LAME | `mingw-w64-x86_64-lame 3.100-3` | https://lame.sourceforge.io/ | LGPL-2.0-or-later |
| libogg | `mingw-w64-x86_64-libogg 1.3.6-1` | https://xiph.org/downloads/ | BSD-3-Clause |
| libvorbis | `mingw-w64-x86_64-libvorbis 1.3.7-3` | https://xiph.org/downloads/ | BSD-3-Clause |
| libopus | `mingw-w64-x86_64-opus 1.6.1-1` | https://opus-codec.org/ | BSD-3-Clause |
| zlib (PNG decoder) | `mingw-w64-x86_64-zlib 1.3.2-2` | https://zlib.net/ | zlib |
| GCC | `mingw-w64-x86_64-gcc 16.2.0-5` | MSYS2 | GPL with runtime exception (libgcc) |
| MinGW-w64 CRT / winpthreads | `14.0.0.r426.g4564ee4b5-1` | MSYS2 | ZPL / MIT / BSD |

MSYS2 package recipes: https://github.com/msys2/MINGW-packages. The libraries
are linked from their static `.a` files (`-static`).

## Configure line

```
./configure --arch=x86_64 --target-os=mingw32 --pkg-config-flags=--static --extra-cflags=-static --extra-ldflags=-static --disable-shared --enable-static --disable-autodetect --disable-everything --disable-programs --enable-ffmpeg --enable-ffprobe --disable-doc --disable-debug --disable-network --disable-devices --disable-hwaccels --enable-indev=lavfi --enable-small --enable-zlib --enable-libmp3lame --enable-libopus --enable-libvorbis --enable-protocol=file,pipe --enable-decoder=mp3float,mp3,aac,aac_fixed,aac_latm,alac,flac,vorbis,opus,wmav1,wmav2,wmapro,wmalossless,amrnb,amrwb,ac3,ac3_fixed,eac3,gsm,adpcm_ima_wav,adpcm_ms,pcm_s8,pcm_u8,pcm_s16le,pcm_s16be,pcm_u16le,pcm_u16be,pcm_s24le,pcm_s24be,pcm_u24le,pcm_u24be,pcm_s32le,pcm_s32be,pcm_u32le,pcm_u32be,pcm_s64le,pcm_s64be,pcm_f16le,pcm_f24le,pcm_f32le,pcm_f32be,pcm_f64le,pcm_f64be,pcm_s16le_planar,pcm_s24le_planar,pcm_s32le_planar,pcm_s8_planar,pcm_alaw,pcm_mulaw,mjpeg,png,bmp,wrapped_avframe --enable-encoder=libmp3lame,libopus,libvorbis,aac,flac,alac,wmav2,pcm_s16le,pcm_s24le,pcm_s32le,pcm_f32le,pcm_s16be,pcm_s24be,pcm_s32be,pcm_u8,mjpeg --enable-demuxer=mov,matroska,ogg,wav,w64,aiff,flac,mp3,aac,asf,avi,amr,amrnb,amrwb,caf,ac3,eac3,mpegts,image2,image2pipe,image_jpeg_pipe,image_png_pipe,image_bmp_pipe,mjpeg,pcm_s16le,pcm_s16be,pcm_s24le,pcm_f32le,gsm --enable-muxer=mp3,ipod,mp4,mov,wav,w64,flac,ogg,opus,aiff,asf,adts,null,image2,mjpeg,pcm_s16le --enable-parser=mpegaudio,aac,aac_latm,flac,vorbis,opus,ac3,amr,gsm,mjpeg,png,bmp --enable-bsf=aac_adtstoasc,opus_metadata,null --enable-filter=abuffer,abuffersink,buffer,buffersink,aresample,aformat,atrim,asetpts,volume,loudnorm,anull,apad,sine,anullsrc,format,null,trim,setpts,scale,testsrc,testsrc2
```

## LGPL compliance notes

- No `--enable-gpl`, `--enable-nonfree` or `--enable-version3`; configure
  reports `License: LGPL version 2.1 or later`. The script enforces this
  (config.h and `-buildconf` checks).
- Ship `LICENSE.txt` (LGPL-2.1) and `SOURCE.txt` next to the exes, and credit
  FFmpeg, LAME, libogg/libvorbis, libopus and zlib in THIRD-PARTY-NOTICES.
- FFmpeg runs as a separate process (`ffmpeg.exe`), so the app itself is not a
  derivative work; users can replace the exes with their own build.
- Corresponding source: the pinned FFmpeg tag above (unmodified), the MSYS2
  package versions above, and this script. Keep offering the same source
  (link or copy) for as long as the binaries are distributed.
- LAME (LGPL) is statically linked into an LGPL program; the combined work stays
  LGPL and is relinkable from the published source + script.

## Notes

- `lavfi` is an input *device* (libavdevice), not a demuxer: it is enabled with
  `--enable-indev=lavfi`. `wrapped_avframe` is needed for lavfi video sources.
- `libopus` only accepts 48/24/16/12/8 kHz; ffmpeg auto-resamples when no `-ar`
  is given, but `-ar 44100` with `-c:a libopus` fails ("Could not open encoder").
- No AMR encoder (opencore-amr is Apache-2.0 and would need `--enable-version3`);
  AMR-NB/WB decoding works.
- Filters `crop,hflip,vflip,rotate,transpose` are pulled in automatically by
  the ffmpeg CLI (autorotate); they are not requested.