Use variance metric for integral projection vector match

This commit replaces the SAD with variance as metric for the
integral projection vector match. It improves the search accuracy
in the presence of slight light change. The average speed -6
compression performance for rtc set is improved by 1.7%. No speed
changes are observed for the test clips.

Change-Id: I71c1d27e42de2aa429fb3564e6549bba1c7d6d4d

1 files changed, 15 insertions, 7 deletions

diff --git a/vp9/encoder/vp9_avg.c b/vp9/encoder/vp9_avg.c
index 8d6cf0667..50c8bca0b 100644
--- a/vp9/encoder/vp9_avg.c
+++ b/vp9/encoder/vp9_avg.c
@@ -37,6 +37,7 @@ void vp9_int_pro_row_c(int16_t *hbuf, uint8_t const *ref,
     hbuf[idx] = 0;
     for (i = 0; i < height; ++i)
       hbuf[idx] += ref[i * ref_stride];
+    hbuf[idx] /= 32;
     ++ref;
   }
 }
@@ -46,16 +47,23 @@ int16_t vp9_int_pro_col_c(uint8_t const *ref, const int width) {
   int16_t sum = 0;
   for (idx = 0; idx < width; ++idx)
     sum += ref[idx];
-  return sum;
+  return sum / 32;
 }
 
-int vp9_vector_sad_c(int16_t const *ref, int16_t const *src,
-                     const int width) {
+int vp9_vector_var_c(int16_t const *ref, int16_t const *src,
+                     const int bwl) {
   int i;
-  int this_sad = 0;
-  for (i = 0; i < width; ++i)
-    this_sad += abs(ref[i] - src[i]);
-  return this_sad;
+  int width = 4 << bwl;
+  int sse = 0, mean = 0, var;
+
+  for (i = 0; i < width; ++i) {
+    int diff = ref[i] - src[i];
+    mean += diff;
+    sse += diff * diff;
+  }
+
+  var = sse - ((mean * mean) >> (bwl + 2));
+  return var;
 }
 
 #if CONFIG_VP9_HIGHBITDEPTH