[x265] [PATCH STABLE] rdcost: use FIX16 for psyrd scale multiplier

[Steve Borho]

# HG changeset patch
# User Steve Borho <steve at borho.org>
# Date 1423084119 21600
#      Wed Feb 04 15:08:39 2015 -0600
# Branch stable
# Node ID 24642eec8f6b4fe29de4c25c43e2b4ece42ef541
# Parent  18cb1eef8cd500c6db074fac838844d5c3f0f531
rdcost: use FIX16 for psyrd scale multiplier

Gives us more resolution at the lower end of the range of psy-rd values. The
max value of m_psyRdBase after the 0.33 scaling of [0..2] is less than 1.

diff -r 18cb1eef8cd5 -r 24642eec8f6b source/encoder/rdcost.h
--- a/source/encoder/rdcost.h	Wed Feb 04 15:00:31 2015 -0600
+++ b/source/encoder/rdcost.h	Wed Feb 04 15:08:39 2015 -0600
@@ -42,7 +42,7 @@
     uint32_t  m_psyRd;
     int       m_qp;
 
-    void setPsyRdScale(double scale)                { m_psyRdBase = (uint32_t)floor(256.0 * scale * 0.33); }
+    void setPsyRdScale(double scale)                { m_psyRdBase = (uint32_t)floor(65536.0 * scale * 0.33); }
 
     void setQP(const Slice& slice, int qp)
     {
@@ -106,7 +106,7 @@
     /* return the RD cost of this prediction, including the effect of psy-rd */
     inline uint64_t calcPsyRdCost(uint32_t distortion, uint32_t bits, uint32_t psycost) const
     {
-        return distortion + ((m_lambda * m_psyRd * psycost) >> 16) + ((bits * m_lambda2) >> 8);
+        return distortion + ((m_lambda * m_psyRd * psycost) >> 24) + ((bits * m_lambda2) >> 8);
     }
 
     inline uint64_t calcRdSADCost(uint32_t sadCost, uint32_t bits) const