[FFmpeg-devel] [PATCH] avformat/movenc: Support alpha channel for AVIF

[Vignesh Venkatasubramanian]

On Tue, Jun 21, 2022 at 10:12 AM Vignesh Venkatasubramanian
<vigneshv at google.com> wrote:
>
> On Mon, Jun 13, 2022 at 10:17 AM James Zern
> <jzern-at-google.com at ffmpeg.org> wrote:
> >
> > On Wed, Jun 1, 2022 at 11:06 AM Vignesh Venkatasubramanian
> > <vigneshv-at-google.com at ffmpeg.org> wrote:
> > >
> > > AVIF specification allows for alpha channel as an auxiliary item (in
> > > case of still images) or as an auxiliary track (in case of animated
> > > images).  Add support for both of these. The AVIF muxer will take
> > > exactly two streams (when alpha is present) as input (first one being
> > > the YUV planes and the second one being the alpha plane).
> > >
> > > The input has to come from two different images (one of it color and
> > > the other one being alpha), or it can come from a single file
> > > source with the alpha channel extracted using the "alphaextract"
> > > filter.
> > >
> > > Example using alphaextract:
> > > ffmpeg -i rgba.png -filter_complex "[0:v]alphaextract[a]" -map 0 -map "[a]" -still-picture 1 avif_with_alpha.avif
> > >
> > > Example using two sources (first source can be in any pixel format and
> > > the second source has to be in monochrome grey pixel format):
> > > ffmpeg -i color.avif -i grey.avif -map 0 -map 1 -c copy avif_with_alpha.avif
> > >
> > > The generated files pass the compliance checks in Compliance Warden:
> > > https://github.com/gpac/ComplianceWarden
> > >
> > > libavif (the reference avif library) is able to decode the files
> > > generated using this patch.
> > >
> > > They also play back properly (with transparent background) in:
> > > 1) Chrome
> > > 2) Firefox (only still AVIF, no animation support)
> > >
> > > Signed-off-by: Vignesh Venkatasubramanian <vigneshv at google.com>
> > > ---
> > >  libavformat/movenc.c | 188 +++++++++++++++++++++++++++++--------------
> > >  libavformat/movenc.h |   4 +-
> > >  2 files changed, 130 insertions(+), 62 deletions(-)
> > >
> >
> > lgtm.
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>
> Any more comments on this? If not can this be merged please? :)
>

Another ping on this please.

> --
> Vignesh



-- 
Vignesh