[x265] [PATCH] rd Level: improve bitrate and psnr in rd level 2

[Deepthi Nandakumar]

On Fri, Jan 10, 2014 at 2:10 PM, <sumalatha at multicorewareinc.com> wrote:

> # HG changeset patch
> # User Sumalatha Polureddy
> # Date 1389343212 -19800
> # Node ID 104fb077a9813f0f3bb94c370e134d0d6d180809
> # Parent  80b63c3ee144e6edbafbbe281ad3d1d8505be1f6
> rd Level: improve bitrate and psnr in rd level 2
>
> a. Always allow intra mode for mode decision
> b. increase more merge skips at each depth
>
> Results are below
> CLI: input.y4m -o bitstream.hevc -r recon.y4m --preset veryfast --rd 2
>
> rd3 / previous rd2 / latest rd2
> BasketballDrive_1920x1080_50
> fps: 4.24/5.615.7
> psnr: 33.67/33.95/33.677
> birate: 2211/2272/2188
>
> Kimono1_1920x1080_24
> fps: 5.45/6.11/6.1
> psnr: 35.004/35.144/34.835
> birate: 713/740/692
>
> FourPeople_1280x720_60
> fps: 7.99/10.86/11.46
> psnr: 34.93/35.17/34.931
> birate: 320/341/341
>
> big_buck_bunny_360p24
> fps: 38.98/49.32/44.46
> psnr: 33.21/33.36/33.167
> birate: 56/60/56
>
> Johnny_1280x720_60
> fps: 8.21/9.58/11.32
> psnr: 36.74/37.238/37.01
> birate: 203/204/206
>
> diff -r 80b63c3ee144 -r 104fb077a981 source/encoder/compress.cpp
> --- a/source/encoder/compress.cpp       Thu Jan 09 12:50:16 2014 +0550
> +++ b/source/encoder/compress.cpp       Fri Jan 10 14:10:12 2014 +0530
> @@ -517,12 +517,6 @@
>                          bdoIntra = (outBestCU->getCbf(0, TEXT_LUMA) ||
>  outBestCU->getCbf(0, TEXT_CHROMA_U) ||
>                                      outBestCU->getCbf(0, TEXT_CHROMA_V));
>                      }
> -                    else
> -                    {
> -                        uint32_t threshold[4] = { 20000, 6000, 1600, 500
> };
> -                        int index = 4 -
> g_convertToBit[outBestCU->getWidth(0)];
> -                        bdoIntra = (outBestCU->m_totalDistortion >
> threshold[index]);
> -                    }
>

This change is valid.


>                      if (bdoIntra)
>                      {
>                          xComputeCostIntraInInter(m_intraInInterCU[depth],
> SIZE_2Nx2N);
> @@ -587,8 +581,12 @@
>                          }
>
>  m_search->encodeResAndCalcRdInterCU(m_mergeCU[depth], m_origYuv[depth],
> bestMergePred, m_tmpResiYuv[depth],
>
>  m_bestResiYuv[depth], m_tmpRecoYuv[depth], true);
> -
> -                        if (m_mergeCU[depth]->m_totalCost <
> outBestCU->m_totalCost)
> +                        double lambda[4];
> +                        lambda[0] = 1.06;
> +                        lambda[1] = 1.5;
> +                        lambda[2] = 1.1;
> +                        lambda[3] = 1.0;
>

This part looks like an artificial way of forcing more skips. I'd like to
understand why merge-skips have reduced so much in the first place in rd 2,
and then fix the root cause.

+                        if (m_mergeCU[depth]->m_totalCost < lambda[depth]
> * outBestCU->m_totalCost)
>                          {
>                              outBestCU = m_mergeCU[depth];
>                              tempYuv = m_bestRecoYuv[depth];
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>
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