Re: [FFmpeg-devel] [PATCH v12 0/8] [WIP] webp: add support for animated WebP decoding

[James Zern via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

On Tue, May 21, 2024 at 9:50 AM Thilo Borgmann via ffmpeg-devel
<ffmpeg-devel@ffmpeg.org> wrote:
>
> Hi,
>
> [...]
> >>> Tests mostly work for me. There are a few images (that I reported
> >>> earlier) that give:
> >>
> >> thanks for testing!
> >>
> >>
> >>>     Canvas change detected. The output will be damaged. Use -threads 1
> >>> to try decoding with best effort.
> >>> They don't animate without that option and with it render incorrectly.
> >>
> >> That issue yields from the canvas frame being the synchronization object
> >> (ThreadFrame) - doing so prevents the canvas size changed mid-stream.
> >> _Maybe_ this can be fixed switching the whole frame multithreading away
> >> from ThreadFrame to sth else, not sure though and no experience with the
> >> alternatives (AVExecutor?). Maybe Andreas can predict if it's
> >> worth/valid to change that whole part of it? I'm not against putting
> >> more effort into it to get it right.
>
> I could fix 488x488.webp and have an almost identical output to libwebp.
>
> 488x488.webp features an ARGB canvas and has both, ARGB & YUVA420P
> p-frames.
>
> Do you have more files with other variations of canvas & p-frames? If
> they at all exist... e.g. canvas YUV and p-frames RGB?
>

Sent a few created with `gif2webp -mixed` off list. A more exhaustive
set can be created using cwebp and webpmux to assemble them.

> Pinged Meta as well for real-world samples. Will take some more days
> until I get feedback. Will then post the next iteration...
>
> Thanks,
> Thilo
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