[FFmpeg-devel] [PATCH] avformat/mov: Add support for still image AVIF parsing

[Vignesh Venkatasubramanian]

On Thu, Apr 21, 2022 at 2:08 AM Gyan Doshi <ffmpeg at gyani.pro> wrote:
>
>
>
> On 2022-04-20 09:54 am, Gyan Doshi wrote:
> >
> >
> > On 2022-04-20 02:49 am, Paul B Mahol wrote:
> >> On Tue, Apr 19, 2022 at 10:57 PM Vignesh Venkatasubramanian <
> >> vigneshv-at-google.com at ffmpeg.org> wrote:
> >>
> >>> Add support for parsing AVIF still images. This patches supports
> >>> AVIF still images that have exactly 1 item (i.e.) no alpha channel.
> >>> Essentially, we will have to parse the "iloc" box and populate
> >>> the mov index.
> >>>
> >>> With this patch, we can decode still AVIF images like so:
> >>> ffmpeg -i image.avif image.png
> >>>
> >>> Partially fixes trac ticket #7621
> >>>
> >> LGTM
> >
> > Will push tomorrow if no one else has.
>
> Can you provide a sample AVIF image and command that this patch allows
> decoding of?
>
> I tried a couple of samples from Netflix[1] and MS[2] and none worked,
> even with forcing MOV demuxer ("moov atom not found" or "error reading
> header").

Thanks for verifying. The test files you tried are invalid/not
supported by this patch. Please see the explanation below.

>
> [1]: http://download.opencontent.netflix.com/?prefix=AV1/Chimera/AVIF/

These files are not valid AVIF since they don't have the major brand
set to "mif1" and not "avif". They are also missing a few other
mandatory boxes. libavif (the reference AVIF library) also is not able
to parse these files. These files were likely made when the AVIF
specification was not yet finalized.

$ ./avifdec --info Chimera-AV1-8bit-1280x720-3363kbps-100.avif
ERROR: Failed to decode image: BMFF parsing failed
Diagnostics:
 * [Strict] Item ID 1 of type 'av01' is missing mandatory pixi property

> [2]:
> https://github.com/AOMediaCodec/av1-avif/tree/master/testFiles/Microsoft
>

These files have EXIF metadata and will contain more than one item
entry in the iloc box. This patch does not support that (however, i
have a follow-up patch to fix this). The files in this directory
return AVERROR_PATCHWELCOME as intended.

For a set of working AVIF files that are supported by this patch you
can try the files under "Link-U" and "Netflix" subdirectories of this repo:

https://github.com/AOMediaCodec/av1-avif/tree/master/testFiles/Link-U

https://github.com/AOMediaCodec/av1-avif/tree/master/testFiles/Netflix/avif

The command is as mentioned in the commit message:
./ffmpeg -i <avif file> output.png

Please let me know if you have more questions. Thank you!


> Regards,
> Gyan
>
>
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--
Vignesh