[FFmpeg-devel] [PATCH] webp: fix transforms after a palette with pixel packing.

[James Zern]

Hi,

On Thu, Aug 26, 2021 at 9:06 AM Maryla Ustarroz
<maryla-at-google.com at ffmpeg.org> wrote:
>

Note top posting is discouraged here [1].

> We've just added a file to libwebp-test-data that covers this case:
> https://chromium.googlesource.com/webm/libwebp-test-data/+/refs/heads/main/dual_transform.webp
> FFmpeg currently fails to decode it, but it works with this patch.
>
> My understanding is that an ffmpeg developer needs to upload the file to
> fate, and then I can add a fate test to the patch?
>

Yes, a link to the file is all that's needed [2][3]. You may include
this as a reply to the initial patch or in the commit message for
visibility.

[1] https://ffmpeg.org/contact.html#MailingLists
[2] https://ffmpeg.org/developer.html#Adding-files-to-the-fate_002dsuite-dataset
[3] https://ffmpeg.org/fate.html#Uploading-new-samples-to-the-fate-suite

>
>
> On Fri, Aug 20, 2021 at 7:07 PM James Zern <jzern-at-google.com at ffmpeg.org>
> wrote:
>
> > On Thu, Aug 19, 2021 at 12:56 AM Maryla <maryla-at-google.com at ffmpeg.org>
> > wrote:
> > >
> > > When a color indexing transform with 16 or fewer colors is used,
> > > WebP uses "pixel packing", i.e. storing several pixels in one byte,
> > > which virtually reduces the width of the image (see WebPContext's
> > > reduced_width field). This reduced_width should always be used when
> > > reading and applying subsequent transforms.
> > >
> > > Fixes: 9368
> >
> > Is there anything in
> > https://chromium.googlesource.com/webm/libwebp-test-data that covers
> > this or can you add the file from the ticket to fate?
> > _______________________________________________
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> >
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> >
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