[FFmpeg-devel] [FFmpeg-cvslog] lavc/qsvenc: add support for external bitrate control for HEVC

[Mark Thompson]

On 18/02/2020 02:32, Linjie Fu wrote:
> ffmpeg | branch: master | Linjie Fu <linjie.fu at intel.com> | Thu Feb 13 20:47:24 2020 +0800| [ebee8085952de079946d903f0cc6e37aee3bc035] | committer: Zhong Li
> 
> lavc/qsvenc: add support for external bitrate control for HEVC
> 
> Enables option for hevc_qsv encoder:
>     -extbrc
> 
> Improvements in BD-Rate could be observed with extbrc on.
> 
> Signed-off-by: Linjie Fu <linjie.fu at intel.com>
> Signed-off-by: Zhong Li <zhongli_dev at 126.com>
> 
>> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=ebee8085952de079946d903f0cc6e37aee3bc035
> ---
> 
>  libavcodec/qsvenc.c | 18 ++++++++++++------
>  1 file changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/libavcodec/qsvenc.c b/libavcodec/qsvenc.c
> index 40904af388..52b4e43979 100644
> --- a/libavcodec/qsvenc.c
> +++ b/libavcodec/qsvenc.c
> @@ -687,11 +687,8 @@ FF_ENABLE_DEPRECATION_WARNINGS
>  
>          q->extparam_internal[q->nb_extparam_internal++] = (mfxExtBuffer *)&q->extco;
>  
> -        if (avctx->codec_id == AV_CODEC_ID_H264) {
>  #if QSV_HAVE_CO2
> -            q->extco2.Header.BufferId     = MFX_EXTBUFF_CODING_OPTION2;
> -            q->extco2.Header.BufferSz     = sizeof(q->extco2);
> -
> +        if (avctx->codec_id == AV_CODEC_ID_H264) {
>              if (q->int_ref_type >= 0)
>                  q->extco2.IntRefType = q->int_ref_type;
>              if (q->int_ref_cycle_size >= 0)
> @@ -703,8 +700,6 @@ FF_ENABLE_DEPRECATION_WARNINGS
>                  q->extco2.BitrateLimit = q->bitrate_limit ? MFX_CODINGOPTION_ON : MFX_CODINGOPTION_OFF;
>              if (q->mbbrc >= 0)
>                  q->extco2.MBBRC = q->mbbrc ? MFX_CODINGOPTION_ON : MFX_CODINGOPTION_OFF;
> -            if (q->extbrc >= 0)
> -                q->extco2.ExtBRC = q->extbrc ? MFX_CODINGOPTION_ON : MFX_CODINGOPTION_OFF;
>  
>              if (q->max_frame_size >= 0)
>                  q->extco2.MaxFrameSize = q->max_frame_size;
> @@ -752,9 +747,20 @@ FF_ENABLE_DEPRECATION_WARNINGS
>                  q->extco2.MaxQPP = q->extco2.MaxQPB = q->extco2.MaxQPI;
>              }
>  #endif
> +        }
> +
> +        if (avctx->codec_id == AV_CODEC_ID_H264 || avctx->codec_id == AV_CODEC_ID_HEVC) {
> +            if (q->extbrc >= 0)
> +                q->extco2.ExtBRC = q->extbrc ? MFX_CODINGOPTION_ON : MFX_CODINGOPTION_OFF;
> +
> +            q->extco2.Header.BufferId = MFX_EXTBUFF_CODING_OPTION2;
> +            q->extco2.Header.BufferSz = sizeof(q->extco2);
> +
>              q->extparam_internal[q->nb_extparam_internal++] = (mfxExtBuffer *)&q->extco2;
> +        }
>  #endif
>  
> +        if (avctx->codec_id == AV_CODEC_ID_H264) {
>  #if QSV_HAVE_MF
>              if (QSV_RUNTIME_VERSION_ATLEAST(q->ver, 1, 25)) {
>                  q->extmfp.Header.BufferId     = MFX_EXTBUFF_MULTI_FRAME_PARAM;

I am very confused by this.  Where is the implementation of the mfxExtBRC callbacks?  Who is actually doing the rate control which gives you this 20% better result?

- Mark