Correct the mode decisions in special cases

The rate costs calculated for inter modes are not precise in some
cases, which causes NEWMV is chosen instead of NEARESTMV, NEARMV,
and ZEROMV. This patch added checks for these cases, and corrected
the mode decisions.

Borg tests at speed 3 showed:
1. stdhd set: 0.102% PSNR gain and 0.088% SSIM gain.
2. derf set:  0.147% PSNR gain and 0.132% SSIM gain.
No speed change.

Change-Id: I35d17684b89ad4734fb610942d707899146426db

diff --git a/vp9/encoder/vp9_rdopt.c b/vp9/encoder/vp9_rdopt.c
index a70669f84e6dacd1cd4cd2eb7ffc069383babfa9..9f9bed691b9d6c2948b656e2d6ed380e4028ca11 100644 (file)
--- a/vp9/encoder/vp9_rdopt.c
+++ b/vp9/encoder/vp9_rdopt.c
@@ -2850,6 +2850,8 @@ int64_t vp9_rd_pick_inter_mode_sb(VP9_COMP *cpi, MACROBLOCK *x,
     // them for this frame.
     mbmi->interp_filter = cm->interp_filter == SWITCHABLE ? EIGHTTAP
                                                           : cm->interp_filter;
+    mbmi->mv[0].as_int = mbmi->mv[1].as_int = 0;
+
     x->skip = 0;
     set_ref_ptrs(cm, xd, ref_frame, second_ref_frame);
 
@@ -3095,6 +3097,28 @@ int64_t vp9_rd_pick_inter_mode_sb(VP9_COMP *cpi, MACROBLOCK *x,
       break;
   }
 
+  // The inter modes' rate costs are not calculated precisely in some cases.
+  // Therefore, sometimes, NEWMV is chosen instead of NEARESTMV, NEARMV, and
+  // ZEROMV. Here, checks are added for those cases, and the mode decisions
+  // are corrected.
+  if (best_mbmode.mode == NEWMV) {
+    const MV_REFERENCE_FRAME refs[2] = {best_mbmode.ref_frame[0],
+        best_mbmode.ref_frame[1]};
+    int comp_pred_mode = refs[1] > INTRA_FRAME;
+
+    if (frame_mv[NEARESTMV][refs[0]].as_int == best_mbmode.mv[0].as_int &&
+        ((comp_pred_mode && frame_mv[NEARESTMV][refs[1]].as_int ==
+            best_mbmode.mv[1].as_int) || !comp_pred_mode))
+      best_mbmode.mode = NEARESTMV;
+    else if (frame_mv[NEARMV][refs[0]].as_int == best_mbmode.mv[0].as_int &&
+        ((comp_pred_mode && frame_mv[NEARMV][refs[1]].as_int ==
+            best_mbmode.mv[1].as_int) || !comp_pred_mode))
+      best_mbmode.mode = NEARMV;
+    else if (best_mbmode.mv[0].as_int == 0 &&
+        ((comp_pred_mode && best_mbmode.mv[1].as_int == 0) || !comp_pred_mode))
+      best_mbmode.mode = ZEROMV;
+  }
+
   if (best_mode_index < 0 || best_rd >= best_rd_so_far)
     return INT64_MAX;