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

[Vignesh Venkatasubramanian <vigneshv-at-google.com@ffmpeg.org>]

On Thu, Apr 21, 2022 at 9:18 PM Gyan Doshi <ffmpeg@gyani.pro> wrote:
>
>
>
> On 2022-04-21 09:46 pm, Vignesh Venkatasubramanian wrote:
> > On Thu, Apr 21, 2022 at 2:08 AM Gyan Doshi <ffmpeg@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@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
> Ok, these work.
>
> > 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!
>
> Add informative log msgs in the patchwelcome blocks.
>

Done.

> Are there plans to add support for transforms like cropping, rotation?
>

I have follow-up patches for fixing some of the AVERROR_PATCHWELCOME
cases. I don't have working code for transforms. It is something that
i will look into in the future once the basic AVIF encode/decode
support lands in ffmpeg.

> Regards,
> Gyan
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-- 
Vignesh
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