[FFmpeg-devel] [PATCH 1/2] lavc/vaapi_encode: correct the HRD buffer size calculate.

[Mark Thompson]

On 31/10/17 02:37, Jun Zhao wrote:
> From 7eef9be1c8a92bf625d62a0f97f762f1342c6d78 Mon Sep 17 00:00:00 2001
> From: Jun Zhao <jun.zhao at intel.com>
> Date: Tue, 31 Oct 2017 10:13:42 +0800
> Subject: [PATCH 1/2] lavc/vaapi_encode: correct the HRD buffer size calculate.
> 
> when rc_buffer_size didn't setting, always use the max bit rate
> per second as HRD buffer size.
> 
> Signed-off-by: Jun Zhao <jun.zhao at intel.com>
> Signed-off-by: Wang, Yi A <yi.a.wang at intel.com>
> ---
>  libavcodec/vaapi_encode.c | 21 ++++++++++-----------
>  1 file changed, 10 insertions(+), 11 deletions(-)
> 
> diff --git a/libavcodec/vaapi_encode.c b/libavcodec/vaapi_encode.c
> index 590f4be4ed..d5f89ef346 100644
> --- a/libavcodec/vaapi_encode.c
> +++ b/libavcodec/vaapi_encode.c
> @@ -1144,19 +1144,9 @@ static av_cold int vaapi_encode_init_rate_control(AVCodecContext *avctx)
>          return AVERROR(EINVAL);
>      }
>  
> -    if (avctx->rc_buffer_size)
> -        hrd_buffer_size = avctx->rc_buffer_size;
> -    else
> -        hrd_buffer_size = avctx->bit_rate;
> -    if (avctx->rc_initial_buffer_occupancy)
> -        hrd_initial_buffer_fullness = avctx->rc_initial_buffer_occupancy;
> -    else
> -        hrd_initial_buffer_fullness = hrd_buffer_size * 3 / 4;
> -
>      if (ctx->va_rc_mode == VA_RC_CBR) {
>          rc_bits_per_second   = avctx->bit_rate;
>          rc_target_percentage = 100;
> -        rc_window_size       = 1000;
>      } else {
>          if (avctx->rc_max_rate < avctx->bit_rate) {
>              // Max rate is unset or invalid, just use the normal bitrate.
> @@ -1166,8 +1156,17 @@ static av_cold int vaapi_encode_init_rate_control(AVCodecContext *avctx)
>              rc_bits_per_second   = avctx->rc_max_rate;
>              rc_target_percentage = (avctx->bit_rate * 100) / rc_bits_per_second;
>          }
> -        rc_window_size = (hrd_buffer_size * 1000) / avctx->bit_rate;
>      }
> +    rc_window_size = (rc_bits_per_second * 1000) / avctx->bit_rate;
> +
> +    if (avctx->rc_buffer_size)
> +        hrd_buffer_size = avctx->rc_buffer_size;
> +    else
> +        hrd_buffer_size = rc_bits_per_second;
> +    if (avctx->rc_initial_buffer_occupancy)
> +        hrd_initial_buffer_fullness = avctx->rc_initial_buffer_occupancy;
> +    else
> +        hrd_initial_buffer_fullness = hrd_buffer_size * 3 / 4;
>  
>      ctx->rc_params.misc.type = VAEncMiscParameterTypeRateControl;
>      ctx->rc_params.rc = (VAEncMiscParameterRateControl) {
> -- 
> 2.14.1
> 

Why?  If the RC buffer size is unset it currently guesses one second of the target bitrate - in what way is the peak bitrate any more appropriate as a guess?

- Mark