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

[Jun Zhao]

On 2017/10/31 18:19, Mark Thompson wrote:
> 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?
In VBR mode, when rc_max_rate more than bit_rate, I think HDR size need
to use rc_max_rate, not the bit_rate.
>
> - Mark
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