Re-arrange inter mode search order in RTC coding flow

This commit makes the ZEROMV mode first in the search order to
ensure that the zero mv is always checked in the RTC coding mode.
It improves the average speed -6 compression performance by 0.3%
in both PSNR and SSIM at no visible speed change.

Change-Id: I465a7e59f4e20cd84fee3f02ced6f98036945949

diff --git a/vp9/encoder/vp9_pickmode.c b/vp9/encoder/vp9_pickmode.c
index a34b1225836a3ce08a94315177fdbab51267e7ef..70e90b6e7bcbaee2561791476dcc936123456351 100644 (file)
--- a/vp9/encoder/vp9_pickmode.c
+++ b/vp9/encoder/vp9_pickmode.c
@@ -573,6 +573,10 @@ void vp9_pick_intra_mode(VP9_COMP *cpi, MACROBLOCK *x, RD_COST *rd_cost,
   *rd_cost = best_rdc;
 }
 
+static const PREDICTION_MODE inter_mode_set[INTER_MODES] = {
+    ZEROMV, NEARESTMV, NEARMV, NEWMV,
+};
+
 // TODO(jingning) placeholder for inter-frame non-RD mode decision.
 // this needs various further optimizations. to be continued..
 void vp9_pick_inter_mode(VP9_COMP *cpi, MACROBLOCK *x,
@@ -732,10 +736,12 @@ void vp9_pick_inter_mode(VP9_COMP *cpi, MACROBLOCK *x,
     mbmi->ref_frame[0] = ref_frame;
     set_ref_ptrs(cm, xd, ref_frame, NONE);
 
-    for (this_mode = NEARESTMV; this_mode <= NEWMV; ++this_mode) {
+    for (i = 0; i < INTER_MODES; ++i) {
       int rate_mv = 0;
       int mode_rd_thresh;
-      int mode_index = mode_idx[ref_frame][INTER_OFFSET(this_mode)];
+      int mode_index;
+      this_mode = inter_mode_set[i];
+      mode_index = mode_idx[ref_frame][INTER_OFFSET(this_mode)];
 
       if (const_motion[ref_frame] && this_mode == NEARMV)
         continue;