[FFmpeg-devel] [PATCH] avcodec[/format]/webpenc: use WebPAnimEncoder API to generate animated WebP

Urvang Joshi urvang at google.com
Thu Apr 23 23:21:01 CEST 2015

On Thu, Apr 16, 2015 at 3:40 PM Urvang Joshi <urvang at google.com> wrote:

> On Thu, Apr 16, 2015 at 3:09 PM James Almer <jamrial at gmail.com> wrote:
>> On 16/04/15 4:18 PM, Urvang Joshi wrote:
>> > Hi,
>> > Here's the patch without whitespace changes.
>> >
>> > Thanks,
>> > Urvang
>> This patch doesn't apply cleanly. Looks like something weird with the
>> indentation still.
>> Was this patch handmade? It says the hash for libwebpenc.c is 95d56ac
>> (same as git head),
>> but the contents of the patch don't match.
> Sorry, I should have mentioned that it was created with
> "--ignore-all-space" option, so using the same option when applying the
> patch would have worked.
> But to avoid any confusion, here's the re-created patch, that should apply
> cleanly with just 'git am'.
>> After fixing the conflicts and compiling the patch seems to work, but the
>> resulting
>> animated webp files are smaller than those using the native muxer using
>> the default
>> encoding and muxing settings.
>> Is this because the muxing done by libwebpmux is different, or are the
>> quality defaults
>> changed in any way when using this codepath? If the former then that's
>> pretty good, but
>> if the latter then it should probably be fixed.
> Short answer: muxing done by libwebpmux is different, so it's expected
> that it generates smaller WebP files.
> Detailed answer:
> The native muxer is naive, and it always uses X offset and Y offset of 0
> for all frames. This means the full width x height of all frames are
> encoded.
> libwebpmux muxer is smart on the other hand: for example, it only encodes
> the part of the frame which has changed from previous frame.
> This and other optimizations result in smaller WebP files.
> Thanks,
> Urvang
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A gentle reminder to review the patch.


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