shithub: libvpx

Download patch

ref: 10ed60dc718aa6133508c2fb5183cfc7dc67e920
parent: a60fc419f50eefbef568ceecb93233471e894fa5
author: Yaowu Xu <yaowu@google.com>
date: Mon Jun 20 12:30:26 EDT 2011

adjusting the calculation of errorperbit

RDMULT/RDDIV defines a bit worth of distortion in term of sum squared
difference. This has also been used as errorperbit in subpixel motion
search, where the distortions computed as variance of the difference.
The variance of differences is different from sum squared differences
by amount of DC squared. Typically, for inter predicted MBs, this
difference averages around 10% between the two distortion, so this patch
introduces a 110% constant in deriving errorperbit from RDMULT/RDDIV.

Test on CIF set shows small but positive gain on overall PSNR (.03%)
and SSIM (.07%), overall impact on average PSNR is 0.

Change-Id: I95425f922d037b4d96083064a10c7cdd4948ee62

--- a/vp8/encoder/encodeframe.c
+++ b/vp8/encoder/encodeframe.c
@@ -335,7 +335,8 @@
 {
 #if USE_ACT_INDEX
     x->rdmult += *(x->mb_activity_ptr) * (x->rdmult >> 2);
-    x->errorperbit = x->rdmult/x->rddiv;
+    x->errorperbit = x->rdmult * 100 /(110 * x->rddiv);
+    x->errorperbit += (x->errorperbit==0);
 #else
     INT64 a;
     INT64 b;
@@ -346,8 +347,8 @@
     b = (2*act) + cpi->activity_avg;
 
     x->rdmult = (unsigned int)(((INT64)x->rdmult*b + (a>>1))/a);
-    x->errorperbit = x->rdmult/x->rddiv;
-
+    x->errorperbit = x->rdmult * 100 /(110 * x->rddiv);
+    x->errorperbit += (x->errorperbit==0);
 #endif
 
     // Activity based Zbin adjustment
--- a/vp8/encoder/rdopt.c
+++ b/vp8/encoder/rdopt.c
@@ -238,7 +238,7 @@
                 (cpi->RDMULT * rd_iifactor[cpi->twopass.next_iiratio]) >> 4;
     }
 
-    cpi->mb.errorperbit = (cpi->RDMULT / 100);
+    cpi->mb.errorperbit = (cpi->RDMULT / 110);
     cpi->mb.errorperbit += (cpi->mb.errorperbit==0);
 
     vp8_set_speed_features(cpi);
--