[FFmpeg-devel] [PATCH] libavcodec/qsvenc: Enable fixed QP configure in qsv CQP runtime

[Xiang, Haihao]

On Wed, 2022-06-15 at 15:25 +0800, Wenbin Chen wrote:
> From: Yue Heng <yue.heng at intel.com>
> 
> Enable dynamic QP configuration in runtime on qsv encoder. Through
> AVFrame->metadata, we can set key "qsv_config_qp" to change QP
> configuration when we encode video in CQP mode.
> 
> Signed-off-by: Yue Heng <yue.heng at intel.com>
> Signed-off-by: Wenbin Chen <wenbin.chen at intel.com>
> ---
>  doc/encoders.texi   |  9 +++++++
>  libavcodec/qsvenc.c | 59 +++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 68 insertions(+)
> 
> diff --git a/doc/encoders.texi b/doc/encoders.texi
> index 9796a606fa..1eb75e199a 100644
> --- a/doc/encoders.texi
> +++ b/doc/encoders.texi
> @@ -3333,6 +3333,15 @@ Forcing I frames as IDR frames.
>  For encoders set this flag to ON to reduce power consumption and GPU usage.
>  @end table
>  
> + at subsection Runtime Options
> +Following options can be used durning qsv encoding.
> +
> + at table @option
> + at item @var{qsv_config_qp}
> +This option can be set in per-frame metadata. QP parameter can be dynamically
> +changed when encode in CQP mode.
> + at end table
> +
>  @subsection H264 options
>  These options are used by h264_qsv
>  
> diff --git a/libavcodec/qsvenc.c b/libavcodec/qsvenc.c
> index 2b3b06767d..52462950be 100644
> --- a/libavcodec/qsvenc.c
> +++ b/libavcodec/qsvenc.c
> @@ -146,6 +146,14 @@ static const struct {
>      { MFX_RATECONTROL_QVBR,    "QVBR" },
>  };
>  
> +#define UPDATE_PARAM(a, b)  \
> +do {                        \
> +    if ((a) != (b)) {       \
> +        a = b;              \
> +        updated = 1;        \
> +    }                       \
> +} while (0)                 \
> +
>  static const char *print_ratecontrol(mfxU16 rc_mode)
>  {
>      int i;
> @@ -1520,6 +1528,53 @@ static void print_interlace_msg(AVCodecContext *avctx,
> QSVEncContext *q)
>      }
>  }
>  
> +static int update_qp(AVCodecContext *avctx, QSVEncContext *q,
> +                     const AVFrame *frame)
> +{
> +    int updated = 0, qp = 0, new_qp;
> +    AVDictionaryEntry *entry = av_dict_get(frame->metadata, "qsv_config_qp",
> +                                           NULL, 0);
> +    if (entry && q->param.mfx.RateControlMethod == MFX_RATECONTROL_CQP) {
> +        qp = atoi(entry->value);

I think it is better to use strtol() because atoi() doesn't detect errors. See
`man atoi`


> +        av_log(avctx, AV_LOG_DEBUG, "Configure qp: %d\n",qp);
> +        if (qp < 0 || qp > 51)
> +            av_log(avctx, AV_LOG_WARNING, "Invalid qp, clip to 0 ~ 51\n");

Is this feature for H264 and H265 only ?

> +
> +        qp = av_clip(qp, 0, 51);
> +        UPDATE_PARAM(q->param.mfx.QPP, qp);
> +        new_qp = av_clip(qp * fabs(avctx->i_quant_factor) +
> +                            avctx->i_quant_offset, 0, 51);
> +        UPDATE_PARAM(q->param.mfx.QPI, new_qp);
> +        new_qp = av_clip(qp * fabs(avctx->b_quant_factor) +
> +                            avctx->b_quant_offset, 0, 51);
> +        UPDATE_PARAM(q->param.mfx.QPB, new_qp);
> +        av_log(avctx, AV_LOG_DEBUG,
> +                "using fixed qp = %d/%d/%d for idr/p/b frames\n",
> +                q->param.mfx.QPI, q->param.mfx.QPP, q->param.mfx.QPB);
> +    }
> +    return updated;
> +}
> +
> +static int update_parameters(AVCodecContext *avctx, QSVEncContext *q,
> +                             const AVFrame *frame)
> +{
> +    int needReset = 0, ret = 0;
> +
> +    if (!frame)
> +        return 0;
> +
> +    needReset = update_qp(avctx, q, frame);
> +    if (needReset) {
> +        q->param.ExtParam    = q->extparam_internal;
> +        q->param.NumExtParam = q->nb_extparam_internal;

User might provide external parameters in avctx->hwaccel_context. Are these
parameters not required in MFXVideoENCODE_Reset() ? 

Thanks
Haihao

> +        av_log(avctx, AV_LOG_DEBUG, "Parameter change, call msdk reset.\n");
> +        ret = MFXVideoENCODE_Reset(q->session, &q->param);
> +        if (ret < 0)
> +            return ff_qsv_print_error(avctx, ret, "Error during resetting");
> +    }
> +    return 0;
> +}
> +
>  static int encode_frame(AVCodecContext *avctx, QSVEncContext *q,
>                          const AVFrame *frame)
>  {
> @@ -1630,6 +1685,10 @@ int ff_qsv_encode(AVCodecContext *avctx, QSVEncContext
> *q,
>  {
>      int ret;
>  
> +    ret = update_parameters(avctx, q, frame);
> +    if (ret < 0)
> +        return ret;
> +
>      ret = encode_frame(avctx, q, frame);
>      if (ret < 0)
>          return ret;