This works around ffmpeg bug https://trac.ffmpeg.org/ticket/10755
where for specific files that are:
- Ogg container format, with supported audio stream (e.g. Vorbis),
- But the video stream is not Ogg-compatible (e.g. Theora), but rather
it is an embedded "album art" (AV_DISPOSITION_ATTACHED_PIC) in
MJPEG, PNG or some other non-Ogg format.
Calling any sort of ffmpeg "seek" function on that video stream just
aborts from innards of ffmpeg.
So to work around this:
- Detect such files (ogg container, non-theora video, attached picture
disposition) and for those:
- Never seek within them, and only ever decode one frame. Return that
frame for any & all "give me a frame" requests.
- Additionally, calculating "how many frames this video has" for such
files also returns nonsense ("millions of frames") since their frame
rate is set to like 90000 or similar. So pretend they have a "sane"
frame rate. Do all this frame rate calculation just once when opening
the video, and use that result in all other places.
- Never build proxies for such video files, since e.g. "timecode"
for them does not make sense.
All of this could be removed once/if ffmpeg fixes their issue.
Pull Request: https://projects.blender.org/blender/blender/pulls/132920
4515713db7