[x265] [PATCH 2 of 2] rc: restrict low tolerance for bitrate fluctuations to strict-cbr option

[Steve Borho]

On 01/07, aarthi at multicorewareinc.com wrote:
> # HG changeset patch
> # User Aarthi Thirumalai
> # Date 1419064540 -19800
> #      Sat Dec 20 14:05:40 2014 +0530
> # Node ID 5d658640bcf115f2add4da1619eeaec50177973f
> # Parent  9b30c4b16dfc4c673b57ee4c567fa8956a41e2fc
> rc: restrict low tolerance for bitrate fluctuations to strict-cbr option

this patch isn't applying; perhaps it depends on the RCstart/stop patch

> diff -r 9b30c4b16dfc -r 5d658640bcf1 source/encoder/ratecontrol.cpp
> --- a/source/encoder/ratecontrol.cpp	Tue Dec 23 16:32:30 2014 +0530
> +++ b/source/encoder/ratecontrol.cpp	Sat Dec 20 14:05:40 2014 +0530
> @@ -1759,7 +1759,7 @@
>                  for (int j = 0; bufferFillCur >= 0; j++)
>                  {
>                      int type = curFrame->m_lowres.plannedType[j];
> -                    if (type == X265_TYPE_AUTO)
> +                    if (type == X265_TYPE_AUTO || totalDuration >= 1.0)
>                          break;
>                      totalDuration += m_frameDuration;
>                      double wantedFrameSize = m_vbvMaxRate * m_frameDuration;
> @@ -1773,17 +1773,21 @@
>                      bufferFillCur -= curBits;
>                  }
>  
> -                /* Try to get the buffer no more than 80% filled, but don't set an impossible goal. */
> -                double tol = isIFramePresent ? 1 / totalDuration : totalDuration < 0.5 ? 2 : 1;
> -                targetFill = X265_MIN(m_bufferFill + totalDuration * m_vbvMaxRate * 0.5 , m_bufferSize * (1 - 0.8 * totalDuration * tol));
> +                /* Try to get the buffer at least 50% filled, but don't set an impossible goal. */
> +                double finalDur = 1;
> +                if (m_param->rc.bStrictCbr)
> +                {
> +                    finalDur = Clip3(0.4, 1.0, totalDuration);
> +                }
> +                targetFill = X265_MIN(m_bufferFill + totalDuration * m_vbvMaxRate * 0.5 , m_bufferSize * (1 - 0.5 * finalDur));
>                  if (bufferFillCur < targetFill)
>                  {
>                      q *= 1.01;
>                      loopTerminate |= 1;
>                      continue;
>                  }
> -                /* Try to get the buffer atleast 50% filled, but don't set an impossible goal. */
> -                targetFill = Clip3(m_bufferSize - (m_bufferSize * totalDuration * 0.5), m_bufferSize, m_bufferFill - totalDuration * m_vbvMaxRate * 0.5);
> +                /* Try to get the buffer not more than 80% filled, but don't set an impossible goal. */
> +                targetFill = Clip3(m_bufferSize * (1 - 0.2 * finalDur) , m_bufferSize, m_bufferFill - totalDuration * m_vbvMaxRate * 0.5);
>                  if (m_isCbr && bufferFillCur > targetFill)
>                  {
>                      q /= 1.01;
> @@ -1976,7 +1980,7 @@
>      if (row < sps.numCuInHeight - 1)
>      {
>          /* More threads means we have to be more cautious in letting ratecontrol use up extra bits. */
> -        double rcTol = (bufferLeftPlanned * 0.2) / m_param->frameNumThreads * m_param->rc.rateTolerance;
> +        double rcTol = bufferLeftPlanned / m_param->frameNumThreads * m_param->rc.rateTolerance;
>          int32_t encodedBitsSoFar = 0;
>          double accFrameBits = predictRowsSizeSum(curFrame, rce, qpVbv, encodedBitsSoFar);
>  
> @@ -1994,7 +1998,7 @@
>  
>          while (qpVbv < qpMax
>                 && ((accFrameBits > rce->frameSizePlanned + rcTol) ||
> -                   (rce->bufferFill - accFrameBits < bufferLeftPlanned * 0.2) ||
> +                   (rce->bufferFill - accFrameBits < bufferLeftPlanned * 0.5) ||
>                     (accFrameBits > rce->frameSizePlanned && qpVbv < rce->qpNoVbv)))
>          {
>              qpVbv += stepSize;
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-- 
Steve Borho