[FFmpeg-devel] [PATCH 28/42] lavc/hevc/ps: implement SPS parsing for nuh_layer_id>0

[Anton Khirnov]

Quoting James Almer (2024-08-30 04:52:39)
> On 8/27/2024 12:05 PM, Anton Khirnov wrote:
> > @@ -1167,16 +1167,26 @@ int ff_hevc_parse_sps(HEVCSPS *sps, GetBitContext *gb, unsigned int *sps_id,
> >       }
> >   
> >       sps->max_sub_layers = get_bits(gb, 3) + 1;
> > +    multi_layer_ext = nuh_layer_id > 0 &&
> > +                      sps->max_sub_layers == HEVC_MAX_SUB_LAYERS + 1;
> > +    if (multi_layer_ext) {
> > +        if (!sps->vps)
> > +            return AVERROR(EINVAL);
> > +
> > +        sps->max_sub_layers = sps->vps->vps_max_sub_layers;
> > +    }
> >       if (sps->max_sub_layers > HEVC_MAX_SUB_LAYERS) {
> 
> Not strictly related to this patch, but sps->max_sub_layers should 
> always be <= vps->vps_max_sub_layers (see F.7.4.3.2.1). So the presence 
> of vps should be checked for.
> 
> >           av_log(avctx, AV_LOG_ERROR, "sps_max_sub_layers out of range: %d\n",
> >                  sps->max_sub_layers);
> >           return AVERROR_INVALIDDATA;
> >       }
> >   
> > +    if (!multi_layer_ext) {
> >       sps->temporal_id_nesting = get_bits(gb, 1);
> 
> Similarly (not strictly related to this patch), this needs to be 1 if 
> sps->max_sub_layers is 0 or if vps->vps_temporal_id_nesting_flag is 1.
> 
> >   
> >       if ((ret = parse_ptl(gb, avctx, 1, &sps->ptl, sps->max_sub_layers)) < 0)
> >           return ret;
> > +    }
> 
> (Actually related this time) If multi_layer_ext is true, 
> sps->temporal_id_nesting needs to be set to 
> vps->vps_temporal_id_nesting_flag when sps->max_sub_layers > 1, or 
> hardcoded to 1 if it's 1.

Honestly this feels like pointless churn. We don't support any of this
temporal id stuff in the decoder, so why bother?

-- 
Anton Khirnov