[vlc-devel] [RFC PATCH] input: decoder: optimize dpb_size of H264

[Zhao Zhili]

Hi Francois,

On Fri, May 19, 2017 at 4:40 PM, Francois Cartegnie <fcvlcdev at free.fr>
wrote:

> Le 19/05/2017 à 10:31, Zhao Zhili a écrit :
>
> > +            {
> > +#define H264_MAX_DPB_SIZE   18
> > +                dpb_size = H264_MAX_DPB_SIZE;
> > +
> > +                int profile = -1;
> > +                int level = -1;
> > +
> > +                profile = p_dec->fmt_in.i_profile;
> > +                level = p_dec->fmt_in.i_level;
> > +                if( profile == -1 || level == -1 )
> > +                {
> > +                    if( h264_get_profile_level( &p_dec->fmt_in,
> &profile,
> > &level, NULL ) == false )
> > +                    {
> > +                        msg_Warn( p_dec, "get profile and level failed"
> );
> > +                        break;
> > +                    }
> > +                }
> > +                msg_Dbg( p_dec, "H264 profile %d, level %d", profile,
> > level );
> > +
> > +#define PROFILE_H264_MAIN                 77
> > +#define PROFILE_H264_HIGH                 100
> > +                if( profile != PROFILE_H264_MAIN && profile !=
> > PROFILE_H264_HIGH )
> > +                    break;
>
> Unfortunately, because of possible configuration changes, that max DPB
> will always be set to max.
>
> And in all cases, dpb value computation does not belong to core, and
> cannot be correct if relying on extradata.
>
>
Thanks for your review. I know this patch is ugly and not work in many
cases.
I just wonder how to reduce the memory usage when playing ultra high
definition
videos. Since ultra high definition videos have smaller dpb_size, a lot of
memory
can be saved. It would be better if we can use the number of reference
frames
directly. I don't know how to make this work and don't break anything. Any
suggestions would be appreciated.

Francois
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