Use SAD value to set chroma cost flag

This saves an extra 64x64 variance calculation and replaces two
32x32 variance functions with sad functions. The compression
performance change is unnoticeable.

Change-Id: I6d33868695664ec73b56c42945162ae61c484856

vp9/encoder/vp9_encodeframe.c

@@ -610,7 +610,6 @@ static unsigned int motion_estimation(VP9_COMP *cpi, MACROBLOCK *x,
   uint8_t const *ref_buf, *src_buf;
   MV *tmp_mv = &xd->mi[0].src_mi->mbmi.mv[0].as_mv;
   int best_sad;
-  unsigned int best_sse;
   MV this_mv;
 
   // Set up prediction 1-D reference set
@@ -659,13 +658,11 @@ static unsigned int motion_estimation(VP9_COMP *cpi, MACROBLOCK *x,
       tmp_mv->col = search_pos[idx].col + this_mv.col;
     }
   }
-
-  ref_buf = xd->plane[0].pre[0].buf + tmp_mv->row * ref_stride + tmp_mv->col;
-  cpi->fn_ptr[bsize].vf(src_buf, src_stride, ref_buf, ref_stride, &best_sse);
   tmp_mv->row *= 8;
   tmp_mv->col *= 8;
   x->pred_mv[LAST_FRAME] = *tmp_mv;
-  return best_sse;
+
+  return best_sad;
 }
 #endif
 
@@ -712,9 +709,9 @@ static void choose_partitioning(VP9_COMP *cpi,
 
   if (!is_key_frame) {
     MB_MODE_INFO *mbmi = &xd->mi[0].src_mi->mbmi;
-    unsigned int var = 0, uv_sse;
+    unsigned int uv_sad;
 #if GLOBAL_MOTION
-    unsigned int y_sse;
+    unsigned int y_sad;
     BLOCK_SIZE bsize;
 #endif
     vp9_setup_pre_planes(xd, 0, yv12, mi_row, mi_col,
@@ -735,7 +732,7 @@ static void choose_partitioning(VP9_COMP *cpi,
     else
       bsize = BLOCK_32X32;
 
-    y_sse = motion_estimation(cpi, x, bsize);
+    y_sad = motion_estimation(cpi, x, bsize);
 #endif
 
     vp9_build_inter_predictors_sb(xd, mi_row, mi_col, BLOCK_64X64);
@@ -744,13 +741,13 @@ static void choose_partitioning(VP9_COMP *cpi,
       struct macroblock_plane  *p = &x->plane[i];
       struct macroblockd_plane *pd = &xd->plane[i];
       const BLOCK_SIZE bs = get_plane_block_size(BLOCK_64X64, pd);
-      var += cpi->fn_ptr[bs].vf(p->src.buf, p->src.stride,
-                                pd->dst.buf, pd->dst.stride, &uv_sse);
+      uv_sad = cpi->fn_ptr[bs].sdf(p->src.buf, p->src.stride,
+                                   pd->dst.buf, pd->dst.stride);
 
 #if GLOBAL_MOTION
-      x->color_sensitivity[i - 1] = uv_sse * 6 > y_sse;
+      x->color_sensitivity[i - 1] = uv_sad * 4 > y_sad;
 #else
-      x->color_sensitivity[i - 1] = (uv_sse > 2048);
+      x->color_sensitivity[i - 1] = (uv_sad > 512);
 #endif
     }