[x265] fix chroma lambda weighting

[Satoshi Nakagawa]

# 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