Re: [FFmpeg-devel] [PATCH v1] avcodec/av1dec: Add tile list OBU to decompose list

["Wang, Fei W" <fei.w.wang-at-intel.com@ffmpeg.org>]

On Fri, 2023-12-22 at 08:41 +0100, Andreas Rheinhardt wrote:
> Wang, Fei W:
> > On Thu, 2023-12-21 at 20:14 +0100, Andreas Rheinhardt wrote:
> > > Wang, Fei W:
> > > > On Wed, 2023-12-20 at 17:11 +0100, Andreas Rheinhardt wrote:
> > > > > fei.w.wang-at-intel.com@ffmpeg.org:
> > > > > > From: Fei Wang <fei.w.wang@intel.com>
> > > > > > 
> > > > > > Show the unsupported message and return unsupported for
> > > > > > clips
> > > > > > contain
> > > > > > tile list OBU since it hasn't been implemented. Otherwise,
> > > > > > decoding
> > > > > > maybe successful but result is incorrect.
> > > > > > 
> > > > > > Signed-off-by: Fei Wang <fei.w.wang@intel.com>
> > > > > > ---
> > > > > >  libavcodec/av1dec.c | 5 +++++
> > > > > >  1 file changed, 5 insertions(+)
> > > > > > 
> > > > > > diff --git a/libavcodec/av1dec.c b/libavcodec/av1dec.c
> > > > > > index 4dcde234c6..629e37c3f8 100644
> > > > > > --- a/libavcodec/av1dec.c
> > > > > > +++ b/libavcodec/av1dec.c
> > > > > > @@ -805,6 +805,7 @@ static const CodedBitstreamUnitType
> > > > > > decompose_unit_types[] = {
> > > > > >      AV1_OBU_SEQUENCE_HEADER,
> > > > > >      AV1_OBU_TEMPORAL_DELIMITER,
> > > > > >      AV1_OBU_TILE_GROUP,
> > > > > > +    AV1_OBU_TILE_LIST,
> > > > > 
> > > > > What do you need this for? Decomposing it would only change
> > > > > whether
> > > > > CodedBitstreamUnit.content is available, but you are only
> > > > > reading
> > > > > CodedBitstreamUnit.type.
> > > > 
> > > > To show the unsupported error and let user know that there are
> > > > tile
> > > > list OBUs in bitstream that decoder can't handle them.
> > > > Otherwise,
> > > > like
> > > > my commit mentioned, tile list obu bitsteam may be decoded
> > > > 'successful'
> > > > according to log.
> > > > 
> > > 
> > > As I said: You do not need CodedBitstreamUnit.content for the
> > > error
> > > message.
> > 
> > No, obu will be filtered if it is not listed in decompose, decoder
> > can't receive its type neither.
> > 
> 
> Did you test this? If so, this would be a violation of the
> documentation
> of decompose_unit_types: "Types not in this list will be available in
> bitstream form only." My reading of the code of
> cbs_read_fragment_content() in cbs.c is that it does what it is
> supposed
> to do.

I was misled by the incomplete log. Decoder can receive tile list OBU
bitstream. Fixed it together with another version. Sorry for the noise.

https://patchwork.ffmpeg.org/project/ffmpeg/list/?series=10358

Thanks
Fei

> 
> If you were right, it would also mean that the current case for
> AV1_OBU_TILE_LIST and AV1_OBU_PADDING is redundant (and that the
> default
> case will be used instead).
> 
> - Andreas
> 
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