[x265] fix chroma lambda weighting

[Deepthi Nandakumar]

Thanks, very interesting fix. Can you give us some background here? Where
did we the divide by 3.0 come from?


On Tue, Mar 25, 2014 at 9:01 AM, Satoshi Nakagawa <nakagawa424 at oki.com>wrote:

> # HG changeset patch
> # User Satoshi Nakagawa <nakagawa424 at oki.com>
> # Date 1395672158 -32400
> #      Mon Mar 24 23:42:38 2014 +0900
> # Node ID 08584b5913bce6a5f9d2f0d408fcdace6aa83a65
> # Parent  fdd7c6168cf42a11240ff1c7fc7b401605524db2
> fix chroma lambda weighting
>
> diff -r fdd7c6168cf4 -r 08584b5913bc source/encoder/frameencoder.cpp
> --- a/source/encoder/frameencoder.cpp   Fri Mar 21 14:44:35 2014 -0500
> +++ b/source/encoder/frameencoder.cpp   Mon Mar 24 23:42:38 2014 +0900
> @@ -335,11 +335,10 @@
>      // instead we weight the distortion of chroma.
>      int chromaQPOffset = slice->getPPS()->getChromaCbQpOffset() +
> slice->getSliceQpDeltaCb();
>      int qpc = Clip3(0, MAX_MAX_QP, qp + chromaQPOffset);
> -    double cbWeight = pow(2.0, (qp - g_chromaScale[chFmt][qpc])); //
> takes into account of the chroma qp mapping and chroma qp Offset
> -
> +    double cbWeight = pow(2.0, (qp - g_chromaScale[chFmt][qpc]) / 3.0);
> // takes into account of the chroma qp mapping and chroma qp Offset
>      chromaQPOffset = slice->getPPS()->getChromaCrQpOffset() +
> slice->getSliceQpDeltaCr();
>      qpc = Clip3(0, MAX_MAX_QP, qp + chromaQPOffset);
> -    double crWeight = pow(2.0, (qp - g_chromaScale[chFmt][qpc])); //
> takes into account of the chroma qp mapping and chroma qp Offset
> +    double crWeight = pow(2.0, (qp - g_chromaScale[chFmt][qpc]) / 3.0);
> // takes into account of the chroma qp mapping and chroma qp Offset
>      double chromaLambda = lambda / crWeight;
>
>      m_rows[row].m_search.setQPLambda(qp, lambda, chromaLambda);
> @@ -376,10 +375,10 @@
>      int qpc;
>      int chromaQPOffset = slice->getPPS()->getChromaCbQpOffset() +
> slice->getSliceQpDeltaCb();
>      qpc = Clip3(0, MAX_MAX_QP, qp + chromaQPOffset);
> -    double cbWeight = pow(2.0, (qp - g_chromaScale[chFmt][qpc])); //
> takes into account of the chroma qp mapping and chroma qp Offset
> +    double cbWeight = pow(2.0, (qp - g_chromaScale[chFmt][qpc]) / 3.0);
> // takes into account of the chroma qp mapping and chroma qp Offset
>      chromaQPOffset = slice->getPPS()->getChromaCrQpOffset() +
> slice->getSliceQpDeltaCr();
>      qpc = Clip3(0, MAX_MAX_QP, qp + chromaQPOffset);
> -    double crWeight = pow(2.0, (qp - g_chromaScale[chFmt][qpc])); //
> takes into account of the chroma qp mapping and chroma qp Offset
> +    double crWeight = pow(2.0, (qp - g_chromaScale[chFmt][qpc]) / 3.0);
> // takes into account of the chroma qp mapping and chroma qp Offset
>      double chromaLambda = lambda / crWeight;
>
>      // NOTE: set SAO lambda every Frame
> _______________________________________________
> x265-devel mailing list
> x265-devel at videolan.org
> https://mailman.videolan.org/listinfo/x265-devel
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.videolan.org/pipermail/x265-devel/attachments/20140325/2776e76b/attachment.html>