[FFmpeg-devel] [PATCH v2] lavc/vaapi_encode: Enable Macroblock based bitrate control

[Mark Thompson]

On 23/02/2024 07:14, fei.w.wang-at-intel.com at ffmpeg.org wrote:
> From: Fei Wang <fei.w.wang at intel.com>
> 
> Signed-off-by: Fei Wang <fei.w.wang at intel.com>
> ---
> update:
> Print mbbrc status with "ON/OFF" instead of "0/1".
> 
>   doc/encoders.texi         |  3 +++
>   libavcodec/vaapi_encode.c | 11 ++++++++++-
>   libavcodec/vaapi_encode.h |  9 ++++++++-
>   3 files changed, 21 insertions(+), 2 deletions(-)

Can you explain what the option actually does?  The current documentation doesn't really give any hint of whether a user would want it on or off.

It also seems like this is a legacy name and maybe should have a more generic name to make sense - the iHD driver at least accepts the option for H.265 and VP9, neither of which have macroblocks.

> diff --git a/doc/encoders.texi b/doc/encoders.texi
> index 9f477d7c53..3f11a80039 100644
> --- a/doc/encoders.texi
> +++ b/doc/encoders.texi
> @@ -4086,6 +4086,9 @@ Quality-defined variable-bitrate.
>   Average variable bitrate.
>   @end table
>   
> + at item mbbrc
> +Enable Macroblock based rate control. Invalid for CQP mode.
> +
>   @end table
>   
>   Each encoder also has its own specific options:
> diff --git a/libavcodec/vaapi_encode.c b/libavcodec/vaapi_encode.c
> index 86f4110cd2..e4bf15fea0 100644
> --- a/libavcodec/vaapi_encode.c
> +++ b/libavcodec/vaapi_encode.c
> @@ -1806,6 +1806,9 @@ static av_cold int vaapi_encode_init_rate_control(AVCodecContext *avctx)
>           int i, first = 1, res;
>   
>           supported_va_rc_modes = rc_attr.value;
> +        if (ctx->mbbrc && !(supported_va_rc_modes & VA_RC_MB))
> +            ctx->mbbrc = 0;

Probably not a good idea to silently disable what the user explicitly requested.

> +
>           for (i = 0; i < FF_ARRAY_ELEMS(vaapi_encode_rc_modes); i++) {
>               rc_mode = &vaapi_encode_rc_modes[i];
>               if (supported_va_rc_modes & rc_mode->va_mode) {
> @@ -2017,13 +2020,18 @@ rc_mode_found:
>       ctx->va_bit_rate = rc_bits_per_second;
>   
>       av_log(avctx, AV_LOG_VERBOSE, "RC mode: %s.\n", rc_mode->name);
> +
> +    if (ctx->mbbrc && ctx->va_rc_mode == VA_RC_CQP)
> +        ctx->mbbrc = 0;
> +    av_log(avctx, AV_LOG_VERBOSE, "MB bitrate control: %s.\n", ctx->mbbrc ? "ON" : "OFF");
> +
>       if (rc_attr.value == VA_ATTRIB_NOT_SUPPORTED) {
>           // This driver does not want the RC mode attribute to be set.
>       } else {
>           ctx->config_attributes[ctx->nb_config_attributes++] =
>               (VAConfigAttrib) {
>               .type  = VAConfigAttribRateControl,
> -            .value = ctx->va_rc_mode,
> +            .value = ctx->mbbrc ? ctx->va_rc_mode | VA_RC_MB : ctx->va_rc_mode,
>           };
>       }
>   
> @@ -2052,6 +2060,7 @@ rc_mode_found:
>   #if VA_CHECK_VERSION(1, 1, 0)
>               .ICQ_quality_factor = av_clip(rc_quality, 1, 51),
>               .max_qp             = (avctx->qmax > 0 ? avctx->qmax : 0),
> +            .rc_flags.bits.mb_rate_control = ctx->mbbrc ? 1 : 2,

What did the previous 0 "use default" do here?

>   #endif
>   #if VA_CHECK_VERSION(1, 3, 0)
>               .quality_factor     = rc_quality,
> diff --git a/libavcodec/vaapi_encode.h b/libavcodec/vaapi_encode.h
> index 6964055b93..9774cc86b1 100644
> --- a/libavcodec/vaapi_encode.h
> +++ b/libavcodec/vaapi_encode.h
> @@ -216,6 +216,9 @@ typedef struct VAAPIEncodeContext {
>       // available modes).
>       int             explicit_rc_mode;
>   
> +    // Macroblock based rate control.
> +    int             mbbrc;
> +
>       // Explicitly-set QP, for use with the "qp" options.
>       // (Forces CQP mode when set, overriding everything else.)
>       int             explicit_qp;
> @@ -538,7 +541,11 @@ int ff_vaapi_encode_close(AVCodecContext *avctx);
>       VAAPI_ENCODE_RC_MODE(VBR,  "Variable-bitrate"), \
>       VAAPI_ENCODE_RC_MODE(ICQ,  "Intelligent constant-quality"), \
>       VAAPI_ENCODE_RC_MODE(QVBR, "Quality-defined variable-bitrate"), \
> -    VAAPI_ENCODE_RC_MODE(AVBR, "Average variable-bitrate")
> +    VAAPI_ENCODE_RC_MODE(AVBR, "Average variable-bitrate"), \
> +    { "mbbrc", \
> +      "Macroblock based bitrate control",\
> +      OFFSET(common.mbbrc), AV_OPT_TYPE_BOOL, \
> +      { .i64 = 0 }, 0, 1, FLAGS }
>   
>   
>   #endif /* AVCODEC_VAAPI_ENCODE_H */

Thanks,

- Mark