#9883: FFmpeg AVIF decoder does not seem to handle transparency when decoding
YUV420P
-------------------------------------+-------------------------------------
Reporter: btdmaster | Type: defect
Status: new | Priority: normal
Component: ffmpeg | Version:
| unspecified
Keywords: transparent | Blocked By:
Blocking: #7621 | Reproduced by developer: 0
Analyzed by developer: 0 |
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FFmpeg seems to ignore transparency when decoding YUV420P. For example,
compare the following:
{{{
% ffmpeg -i transparency-present.avif transparency-missing.png
% convert transparency-present.avif transparency-present.png
Arch Linux FFmpeg 2:5.1-1
}}}
This can also be reproduced when printing the file with ffplay and mpv
(which, from what I understand, also used FFmpeg) but not with firefox or
chafa, hence suggesting FFmpeg is the culprit.
I also found a similar limitation in libavif, though only for converting
to yuv4mpeg2
(https://github.com/AOMediaCodec/libavif/blob/98a453fdbb0340eaf8bd6f794359483048e72305/apps/shared/y4m.c#L435):
{{{
% avifdec -i transparency-present.avif -o transparency-also-missing.y4m
Arch Linux libavif 0.10.1-2
}}}
FFmpeg does not seem to use libavif, but I thought that may provide some
insight into the problem.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/9883>
FFmpeg <https://ffmpeg.org>
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