shithub: libvpx

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Do joint motion search iteratively

Allow motion search multiple times iteratively, and break out
the loop if this search couldn't find better motion vectors.
Limit the maximum number of search to 2.

Tests results:
1. stdhd set: 0.311%(overall psnr); 0.346%(ssim).
positive gain on 10 out of 16 clips(best: 2.746% on sunflower;
worst: -0.434% on old_town_cross).
2. derf set: 0.016%(overall psnr); 0.062%(ssim).
positive gain on half of the clips(best: 0.499% on bowing;
worst: -0.387 on city).

Change-Id: Ibf0a51776d4caf7707be0586346db08128117559

--- a/vp9/encoder/vp9_rdopt.c

+++ b/vp9/encoder/vp9_rdopt.c

@@ -1863,6 +1863,7 @@

         struct buf_2d backup_yv12[MAX_MB_PLANE] = {{0}};

         struct buf_2d backup_second_yv12[MAX_MB_PLANE] = {{0}};

         struct buf_2d scaled_first_yv12;

+        int last_besterr[2] = {INT_MAX, INT_MAX};

         if (scaled_ref_frame[0]) {

           int i;

@@ -1897,11 +1898,9 @@

         frame_mv[NEWMV][refs[0]].as_int = single_newmv[refs[0]].as_int;

         frame_mv[NEWMV][refs[1]].as_int = single_newmv[refs[1]].as_int;

-        // Iteration: joint search is done once for each ref frame.

-        // Tried allowing search multiple times iteratively, and break out if

-        // it couldn't find better mv. But tests didn't show noticeable

-        // improvement.

-        for (ite = 0; ite < 2; ite++) {

+        // Allow joint search multiple times iteratively for each ref frame, and

+        // break out the search loop if it couldn't find better mv.

+        for (ite = 0; ite < 4; ite++) {

           struct buf_2d ref_yv12[2] = {xd->plane[0].pre[0],

                                        xd->plane[0].pre[1]};

           int bestsme = INT_MAX;

@@ -1952,19 +1951,26 @@

             int dis; /* TODO: use dis in distortion calculation later. */

             unsigned int sse;

-            vp9_find_best_sub_pixel_comp(x, &tmp_mv,

-                                         &ref_mv[id],

-                                         x->errorperbit,

-                                         &cpi->fn_ptr[block_size],

-                                         x->nmvjointcost, x->mvcost,

-                                         &dis, &sse, second_pred,

-                                         b_sz[bsize][0], b_sz[bsize][1]);

+            bestsme = vp9_find_best_sub_pixel_comp(x, &tmp_mv,

+                                                   &ref_mv[id],

+                                                   x->errorperbit,

+                                                   &cpi->fn_ptr[block_size],

+                                                   x->nmvjointcost, x->mvcost,

+                                                   &dis, &sse, second_pred,

+                                                   b_sz[bsize][0],

+                                                   b_sz[bsize][1]);

           }

-          frame_mv[NEWMV][refs[id]].as_int =

-              xd->mode_info_context->bmi[0].as_mv[1].as_int = tmp_mv.as_int;

           if (id)

             xd->plane[0].pre[0] = scaled_first_yv12;

+

+          if (bestsme < last_besterr[id]) {

+            frame_mv[NEWMV][refs[id]].as_int =

+                xd->mode_info_context->bmi[0].as_mv[1].as_int = tmp_mv.as_int;

+            last_besterr[id] = bestsme;

+          } else {

+            break;

+          }

         }

         // restore the predictor

-- 

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