[FFmpeg-devel] lavc/vaapi_encode_h264: respect "slices" option in h264 vaapi encoder

[Mark Thompson]

On 02/08/17 06:56, Jun Zhao wrote:
> From f9b42385faedd64dacf613785c393c7b025237c9 Mon Sep 17 00:00:00 2001
> From: Jun Zhao <jun.zhao at intel.com>
> Date: Tue, 1 Aug 2017 23:05:44 -0400
> Subject: [PATCH V2 3/4] lavc/vaapi_encode_h264: respect "slices" option in
>  h264 vaapi encoder
> 
> Enable multi-slice support in AVC/H.264 vaapi encoder.
> 
> Signed-off-by: Wang, Yi A <yi.a.wang at intel.com>
> Signed-off-by: Jun Zhao <jun.zhao at intel.com>
> ---
>  libavcodec/vaapi_encode_h264.c | 38 +++++++++++++++++++++++++++++++++-----
>  1 file changed, 33 insertions(+), 5 deletions(-)
> 
> diff --git a/libavcodec/vaapi_encode_h264.c b/libavcodec/vaapi_encode_h264.c
> index f9fcd805a4..5dad6d10a5 100644
> --- a/libavcodec/vaapi_encode_h264.c
> +++ b/libavcodec/vaapi_encode_h264.c
> @@ -141,6 +141,10 @@ typedef struct VAAPIEncodeH264Context {
>      int mb_width;
>      int mb_height;
>  
> +    int slice_of_mbs;
> +    int slice_mod_mbs;
> +    int last_mb_index;
> +
>      int fixed_qp_idr;
>      int fixed_qp_p;
>      int fixed_qp_b;
> @@ -957,6 +961,7 @@ static int vaapi_encode_h264_init_picture_params(AVCodecContext *avctx,
>      VAEncPictureParameterBufferH264  *vpic = pic->codec_picture_params;
>      VAAPIEncodeH264Context           *priv = ctx->priv_data;
>      int i;
> +    int max_slices;
>  
>      if (pic->type == PICTURE_TYPE_IDR) {
>          av_assert0(pic->display_order == pic->encode_order);
> @@ -1002,7 +1007,22 @@ static int vaapi_encode_h264_init_picture_params(AVCodecContext *avctx,
>      vpic->pic_fields.bits.idr_pic_flag = (pic->type == PICTURE_TYPE_IDR);
>      vpic->pic_fields.bits.reference_pic_flag = (pic->type != PICTURE_TYPE_B);
>  
> -    pic->nb_slices = 1;
> +    max_slices = 1;
> +    if (ctx->max_slices) {
> +        max_slices = FFMIN(priv->mb_height, ctx->max_slices);

Where is this coming from?  You don't enforce anything about rows below.

> +        if (avctx->slices > max_slices) {
> +            av_log(avctx, AV_LOG_WARNING, "The max slices number per frame "
> +                   "cannot more than %d.\n", max_slices);

So if you pass a value which is too high, you get some lower number instead?  It should probably hard fail here - I'm not sure what your use case is for this option, but I imagine it being for conforming to the some specific stream requirements (like bluray or whatever), so just ignoring the option in that case is probably bad.

> +        } else {
> +            max_slices = avctx->slices;
> +        }
> +    }
> +
> +    pic->nb_slices = max_slices;
> +
> +    priv->slice_of_mbs  = (priv->mb_width * priv->mb_height) / pic->nb_slices;
> +    priv->slice_mod_mbs = (priv->mb_width * priv->mb_height) % pic->nb_slices;
> +    priv->last_mb_index = 0;
>  
>      return 0;
>  }
> @@ -1052,14 +1072,18 @@ static int vaapi_encode_h264_init_slice_params(AVCodecContext *avctx,
>          av_assert0(0 && "invalid picture type");
>      }
>  
> -    // Only one slice per frame.
> -    vslice->macroblock_address = 0;
> -    vslice->num_macroblocks = priv->mb_width * priv->mb_height;
> +    vslice->macroblock_address = priv->last_mb_index;
> +    vslice->num_macroblocks = priv->slice_of_mbs + (priv->slice_mod_mbs > 0 ? 1 : 0);
> +    if (priv->slice_mod_mbs > 0)
> +        priv->slice_mod_mbs--;
> +    priv->last_mb_index += vslice->num_macroblocks;

I'm still unconfortable about this method of distributing the macroblocks equally to slices with rounding error at the top - slice boundaries are not invisible at low bitrates.  I don't have anything better to suggest, though.

>  
>      vslice->macroblock_info = VA_INVALID_ID;
>  
>      vslice->pic_parameter_set_id = vpic->pic_parameter_set_id;
> -    vslice->idr_pic_id = priv->idr_pic_count++;
> +    vslice->idr_pic_id = priv->idr_pic_count;
> +    if (priv->last_mb_index == priv->mb_width * priv->mb_height)
> +        priv->idr_pic_count++;
>  
>      vslice->pic_order_cnt_lsb = (pic->display_order - priv->last_idr_frame) &
>          ((1 << (4 + vseq->seq_fields.bits.log2_max_pic_order_cnt_lsb_minus4)) - 1);
> @@ -1157,6 +1181,10 @@ static av_cold int vaapi_encode_h264_configure(AVCodecContext *avctx)
>  #endif
>      }
>  
> +    if (!ctx->max_slices && avctx->slices > 0)
> +        av_log(avctx, AV_LOG_WARNING, "The encode slice option is not "
> +               "supported with this VAAPI version.\n");

It's a driver constraint, not a VAAPI version one.

> +
>      return 0;
>  }
>  
> -- 
> 2.11.0
>