From 058aae3ce7626334013dbc9aef9136ba42464814 Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <michaelni@gmx.at>
Date: Fri, 9 May 2008 09:02:41 +0000
Subject: [PATCH] Improve motion estimation metric. Patch by Michael
 Niedermayer

Originally committed as revision 13090 to svn://svn.ffmpeg.org/ffmpeg/trunk
---
 libavcodec/zmbvenc.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/libavcodec/zmbvenc.c b/libavcodec/zmbvenc.c
index 2feeb66605..fbefa7cafc 100644
--- a/libavcodec/zmbvenc.c
+++ b/libavcodec/zmbvenc.c
@@ -54,6 +54,8 @@ typedef struct ZmbvEncContext {
     z_stream zstream;
 } ZmbvEncContext;
 
+static int score_tab[256];
+
 /** Block comparing function
  * XXX should be optimized and moved to DSPContext
  * TODO handle out of edge ME
@@ -62,13 +64,18 @@ static inline int block_cmp(uint8_t *src, int stride, uint8_t *src2, int stride2
 {
     int sum = 0;
     int i, j;
+    uint8_t histogram[256]={0};
 
     for(j = 0; j < bh; j++){
         for(i = 0; i < bw; i++)
-            sum += src[i] ^ src2[i];
+            histogram[src[i] ^ src2[i]]++;
         src += stride;
         src2 += stride2;
     }
+
+    for(i=1; i<256; i++)
+        sum+= score_tab[histogram[i]];
+
     return sum;
 }
 
@@ -235,8 +242,12 @@ static av_cold int encode_init(AVCodecContext *avctx)
 {
     ZmbvEncContext * const c = avctx->priv_data;
     int zret; // Zlib return code
+    int i;
     int lvl = 9;
 
+    for(i=1; i<256; i++)
+        score_tab[i]= -i * log2(i/256.0) * 256;
+
     c->avctx = avctx;
 
     c->pic.data[0] = NULL;