Re: [FFmpeg-devel] [PATCH v3 2/2] lavc/vaapi_encode_h265: Set general_*_constriaint flags with profile

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

On Mon, 2024-03-18 at 21:22 +0000, Mark Thompson wrote:
> On 18/03/2024 04:21, fei.w.wang-at-intel.com@ffmpeg.org wrote:
> > From: Fei Wang <fei.w.wang@intel.com>
> > 
> > According to Table A.2 in spec.
> > 
> > Signed-off-by: Fei Wang <fei.w.wang@intel.com>
> > ---
> >   libavcodec/vaapi_encode_h265.c | 176 +++++++++++++++++++++++-----
> > -----
> >   1 file changed, 123 insertions(+), 53 deletions(-)
> > 
> > diff --git a/libavcodec/vaapi_encode_h265.c
> > b/libavcodec/vaapi_encode_h265.c
> > index 43755e2188..5ed317ce11 100644
> > --- a/libavcodec/vaapi_encode_h265.c
> > +++ b/libavcodec/vaapi_encode_h265.c
> > @@ -258,6 +258,124 @@ fail:
> >       return err;
> >   }
> >   
> > +static int vaapi_encode_h265_init_ptl(AVCodecContext *avctx)
> > +{
> > +    VAAPIEncodeContext      *ctx = avctx->priv_data;
> > +    VAAPIEncodeH265Context *priv = avctx->priv_data;
> > +    H265RawVPS              *vps = &priv->raw_vps;
> > +    H265RawProfileTierLevel *ptl = &vps->profile_tier_level;
> > +
> > +    ptl->general_profile_space = 0;
> > +    ptl->general_profile_idc   = avctx->profile;
> > +    ptl->general_tier_flag     = priv->tier;
> > +
> > +    ptl->general_profile_compatibility_flag[ptl-
> > >general_profile_idc] = 1;
> > +
> > +    if (ptl->general_profile_compatibility_flag[1])
> > +        ptl->general_profile_compatibility_flag[2] = 1;
> > +    if (ptl->general_profile_compatibility_flag[3]) {
> > +        ptl->general_profile_compatibility_flag[1] = 1;
> > +        ptl->general_profile_compatibility_flag[2] = 1;
> > +    }
> > +
> > +    ptl->general_progressive_source_flag    = 1;
> > +    ptl->general_interlaced_source_flag     = 0;
> > +    ptl->general_non_packed_constraint_flag = 1;
> > +    ptl->general_frame_only_constraint_flag = 1;
> > +
> > +    if (avctx->profile >= 4) {
> > +        ptl->general_intra_constraint_flag            = ctx-
> > >gop_size == 1;
> > +        ptl->general_one_picture_only_constraint_flag = 0;
> > +        ptl->general_lower_bit_rate_constraint_flag   = 1;
> > +        ptl->general_max_14bit_constraint_flag        = 0;
> > +
> > +        switch (ctx->va_profile) {
> > +#if VA_CHECK_VERSION(1, 2, 0)
> > +        case VAProfileHEVCMain12:
> > +            // Main 12
> > +            ptl->general_max_12bit_constraint_flag      = 1;
> > +            ptl->general_max_10bit_constraint_flag      = 0;
> > +            ptl->general_max_8bit_constraint_flag       = 0;
> > +            ptl->general_max_422chroma_constraint_flag  = 1;
> > +            ptl->general_max_420chroma_constraint_flag  = 1;
> > +            ptl->general_max_monochrome_constraint_flag = 0;
> > +            break;
> > +        case VAProfileHEVCMain422_10:
> > +            // Main 4:2:2 10
> > +            ptl->general_max_12bit_constraint_flag      = 1;
> > +            ptl->general_max_10bit_constraint_flag      = 1;
> > +            ptl->general_max_8bit_constraint_flag       = 0;
> > +            ptl->general_max_422chroma_constraint_flag  = 1;
> > +            ptl->general_max_420chroma_constraint_flag  = 0;
> > +            ptl->general_max_monochrome_constraint_flag = 0;
> > +            break;
> > +        case VAProfileHEVCMain422_12:
> > +            // Main 4:2:2 12
> > +            ptl->general_max_12bit_constraint_flag      = 1;
> > +            ptl->general_max_10bit_constraint_flag      = 0;
> > +            ptl->general_max_8bit_constraint_flag       = 0;
> > +            ptl->general_max_422chroma_constraint_flag  = 1;
> > +            ptl->general_max_420chroma_constraint_flag  = 0;
> > +            ptl->general_max_monochrome_constraint_flag = 0;
> > +            break;
> > +        case VAProfileHEVCMain444:
> > +            // Main 4:4:4
> > +            ptl->general_max_12bit_constraint_flag      = 1;
> > +            ptl->general_max_10bit_constraint_flag      = 1;
> > +            ptl->general_max_8bit_constraint_flag       = 1;
> > +            ptl->general_max_422chroma_constraint_flag  = 0;
> > +            ptl->general_max_420chroma_constraint_flag  = 0;
> > +            ptl->general_max_monochrome_constraint_flag = 0;
> > +            break;
> > +        case VAProfileHEVCMain444_10:
> > +            // Main 4:4:4 10
> > +            ptl->general_max_12bit_constraint_flag      = 1;
> > +            ptl->general_max_10bit_constraint_flag      = 1;
> > +            ptl->general_max_8bit_constraint_flag       = 0;
> > +            ptl->general_max_422chroma_constraint_flag  = 0;
> > +            ptl->general_max_420chroma_constraint_flag  = 0;
> > +            ptl->general_max_monochrome_constraint_flag = 0;
> > +            break;
> > +        case VAProfileHEVCMain444_12:
> > +            // Main 4:4:4 12
> > +            ptl->general_max_12bit_constraint_flag      = 1;
> > +            ptl->general_max_10bit_constraint_flag      = 0;
> > +            ptl->general_max_8bit_constraint_flag       = 0;
> > +            ptl->general_max_422chroma_constraint_flag  = 0;
> > +            ptl->general_max_420chroma_constraint_flag  = 0;
> > +            ptl->general_max_monochrome_constraint_flag = 0;
> > +            break;
> > +#endif
> > +        default:
> > +            av_log(avctx, AV_LOG_ERROR, "Unknown profile to init
> > PTL.\n");
> > +            return AVERROR(EINVAL);
> > +        }
> > +    }
> 
> Why is this an improvement over the current code which sets the
> constraint flags based on the actual content of the stream?
> 
> Note the requirement in A.3.5 for decoder support:
> 
> general_profile_idc is equal to 4 or
> general_profile_compatibility_flag[ 4 ] is equal to 1 for the
> bitstream, and
> the value of each constraint flag listed in Table A.2 is greater than
> or equal to the value(s) specified in the row
> of Table A.2 for the format range extensions profile for which the
> decoder conformance is evaluated.
> 
> which says that decoders must be able to support streams which set
> additional constraint flags beyond those which are specified for a
> particular profile (in particular, an 8-bit 4:2:2 stream must be
> decodable by any decoder supporting either "Main 4:2:2 10" or "Main
> 4:4:4", so ideally it shouldn't be marked to require one of those in
> particular).

That's a capability request for decoder. For encoder side, I'd prefer
to use the most typical values. The constraint flags in Table A.2/3/5
are strictly checked to get rext profile in ff_h265_get_profile(), and
seems the constraint flags is the only way to distinguish profiles in
rext(all the rext profiles shares same general_profile_idc or
general_profile_compatibility_flag[ 4 ]).

Thanks
Fei

> 
> Thanks,
> 
> - Mark
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