PyAV and opencv-python each bundle an LGPL FFmpeg build (dynamic link).
Record the installed wheel versions and the FFmpeg version each bundles,
then place the matching FFmpeg source + each project's build recipe here.

Capture commands (run against the shipped runtime):
  python -c "import av; print('PyAV', av.__version__, av.ffmpeg_version_info)"
  python -c "import cv2; print('opencv-python', cv2.__version__); print(cv2.getBuildInformation())"

Source:
  PyAV bindings + build recipe: https://github.com/PyAV-Org/PyAV
  opencv-python FFmpeg build:   https://github.com/opencv/opencv-python
  Upstream FFmpeg source:       https://github.com/FFmpeg/FFmpeg

If a wheel's bundled FFmpeg cannot be confirmed LGPL, swap it for a build
you control before shipping.
