Change to MV reference search.

This patch reduces the cpu cost of the MV ref
search by only allowing insert for candidates
that would be in the current top 4.

This could alter the outcome and slightly favors
near candidates which are tested first but also
limits the worst case loop count to 4 and means in
many cases it will drop out and not happen.

Change-Id: Idd795a825f9fd681f30f4fcd550c34c38939e113
diff --git a/vp9/common/vp9_blockd.h b/vp9/common/vp9_blockd.h
index 17e8474..27ef22f 100644
--- a/vp9/common/vp9_blockd.h
+++ b/vp9/common/vp9_blockd.h
@@ -45,6 +45,7 @@
 #define SEGMENT_DELTADATA   0
 #define SEGMENT_ABSDATA     1
 #define MAX_MV_REFS 9
+#define MAX_MV_REF_CANDIDATES 4
 
 typedef struct {
   int r, c;
@@ -238,7 +239,7 @@
   MV_REFERENCE_FRAME ref_frame, second_ref_frame;
   TX_SIZE txfm_size;
   int_mv mv[2]; // for each reference frame used
-  int_mv ref_mvs[MAX_REF_FRAMES][MAX_MV_REFS];
+  int_mv ref_mvs[MAX_REF_FRAMES][MAX_MV_REF_CANDIDATES];
   int_mv best_mv, best_second_mv;
 #if CONFIG_NEW_MVREF
   int best_index, best_second_index;
diff --git a/vp9/common/vp9_findnearmv.c b/vp9/common/vp9_findnearmv.c
index 02c28fb..4fd4689 100644
--- a/vp9/common/vp9_findnearmv.c
+++ b/vp9/common/vp9_findnearmv.c
@@ -139,8 +139,8 @@
 #if CONFIG_SUBPELREFMV
   unsigned int sse;
 #endif
-  unsigned int ref_scores[MAX_MV_REFS] = {0};
-  int_mv sorted_mvs[MAX_MV_REFS];
+  unsigned int ref_scores[MAX_MV_REF_CANDIDATES] = {0};
+  int_mv sorted_mvs[MAX_MV_REF_CANDIDATES];
   int zero_seen = FALSE;
 
   // Default all to 0,0 if nothing else available
@@ -159,9 +159,8 @@
   left_ref  = ref_y_buffer - 3;
 #endif
 
-  //for(i = 0; i < MAX_MV_REFS; ++i) {
-  // Limit search to the predicted best 4
-  for(i = 0; i < 4; ++i) {
+  // Limit search to the predicted best few candidates
+  for(i = 0; i < MAX_MV_REF_CANDIDATES; ++i) {
     int_mv this_mv;
     int offset = 0;
     int row_offset, col_offset;
@@ -268,7 +267,7 @@
   }
 
   // Make sure all the candidates are properly clamped etc
-  for (i = 0; i < 4; ++i) {
+  for (i = 0; i < MAX_MV_REF_CANDIDATES; ++i) {
     lower_mv_precision(&sorted_mvs[i], xd->allow_high_precision_mv);
     clamp_mv2(&sorted_mvs[i], xd);
   }
diff --git a/vp9/common/vp9_mvref_common.c b/vp9/common/vp9_mvref_common.c
index bf60630..bbed055 100644
--- a/vp9/common/vp9_mvref_common.c
+++ b/vp9/common/vp9_mvref_common.c
@@ -170,14 +170,20 @@
   int weight
 ) {
 
-  int i = *index;
+  int i;
+  int insert_point;
   int duplicate_found = FALSE;
 
-  // Check for duplicates. If there is one increment its score.
-  // Duplicate defined as being the same full pel vector with rounding.
+  // Check for duplicates. If there is one increase its score.
+  // We only compare vs the current top candidates.
+  insert_point = (*index < (MAX_MV_REF_CANDIDATES - 1))
+                 ? *index : (MAX_MV_REF_CANDIDATES - 1);
+
+  i = insert_point;
+  if (*index > i)
+    i++;
   while (i > 0) {
     i--;
-
     if (candidate_mv.as_int == mv_list[i].as_int) {
       duplicate_found = TRUE;
       mv_scores[i] += weight;
@@ -185,11 +191,13 @@
     }
   }
 
-  // If no duplicate was found add the new vector and give it a weight
-  if (!duplicate_found) {
-    mv_list[*index].as_int = candidate_mv.as_int;
-    mv_scores[*index] = weight;
-    i = *index;
+  // If no duplicate and the new candidate is good enough then add it.
+  if (!duplicate_found ) {
+    if (weight > mv_scores[insert_point]) {
+      mv_list[insert_point].as_int = candidate_mv.as_int;
+      mv_scores[insert_point] = weight;
+      i = insert_point;
+    }
     (*index)++;
   }
 
@@ -224,12 +232,12 @@
   int i;
   MODE_INFO *candidate_mi;
   MB_MODE_INFO * mbmi = &xd->mode_info_context->mbmi;
-  int_mv candidate_mvs[MAX_MV_REFS];
+  int_mv candidate_mvs[MAX_MV_REF_CANDIDATES];
   int_mv c_refmv;
-  MV_REFERENCE_FRAME c_ref_frame;
   int_mv c2_refmv;
+  MV_REFERENCE_FRAME c_ref_frame;
   MV_REFERENCE_FRAME c2_ref_frame;
-  int candidate_scores[MAX_MV_REFS];
+  int candidate_scores[MAX_MV_REF_CANDIDATES];
   int index = 0;
   int split_count = 0;
   int ref_weight = 0;
@@ -238,8 +246,8 @@
   int *ref_distance_weight;
 
   // Blank the reference vector lists and other local structures.
-  vpx_memset(mv_ref_list, 0, sizeof(int_mv) * MAX_MV_REFS);
-  vpx_memset(candidate_mvs, 0, sizeof(int_mv) * MAX_MV_REFS);
+  vpx_memset(mv_ref_list, 0, sizeof(int_mv) * MAX_MV_REF_CANDIDATES);
+  vpx_memset(candidate_mvs, 0, sizeof(int_mv) * MAX_MV_REF_CANDIDATES);
   vpx_memset(candidate_scores, 0, sizeof(candidate_scores));
 
 #if CONFIG_SUPERBLOCKS
@@ -349,11 +357,6 @@
     }
   }
 
-  // Make sure we are able to add 0,0
-  if (index > (MAX_MV_REFS - 1)) {
-    index = (MAX_MV_REFS - 1);
-  }
-
   // Define inter mode coding context.
   // 0,0 was best
   if (candidate_mvs[0].as_int == 0) {
@@ -383,14 +386,12 @@
   }
 
   // 0,0 is always a valid reference.
-  for (i = 0; i < index; ++i) {
+  for (i = 0; i < MAX_MV_REF_CANDIDATES; ++i) {
     if (candidate_mvs[i].as_int == 0)
       break;
   }
-  if (i == index) {
-    c_refmv.as_int = 0;
-    addmv_and_shuffle(candidate_mvs, candidate_scores,
-                      &index, c_refmv, candidate_scores[3]+1 );
+  if (i == MAX_MV_REF_CANDIDATES) {
+    candidate_mvs[MAX_MV_REF_CANDIDATES-1].as_int = 0;
   }
 
   // Copy over the candidate list.
diff --git a/vp9/encoder/vp9_block.h b/vp9/encoder/vp9_block.h
index d5bf89c..4669d2e 100644
--- a/vp9/encoder/vp9_block.h
+++ b/vp9/encoder/vp9_block.h
@@ -70,7 +70,7 @@
   PARTITION_INFO partition_info;
   int_mv best_ref_mv;
   int_mv second_best_ref_mv;
-  int_mv ref_mvs[MAX_REF_FRAMES][MAX_MV_REFS];
+  int_mv ref_mvs[MAX_REF_FRAMES][MAX_MV_REF_CANDIDATES];
   int rate;
   int distortion;
   int64_t intra_error;
diff --git a/vp9/encoder/vp9_encodeframe.c b/vp9/encoder/vp9_encodeframe.c
index b7f8cf4..76176be 100644
--- a/vp9/encoder/vp9_encodeframe.c
+++ b/vp9/encoder/vp9_encodeframe.c
@@ -395,8 +395,7 @@
          vp9_mv_bit_cost(&target_mv, &mv_ref_list[0], x->nmvjointcost,
                          x->mvcost, 96, xd->allow_high_precision_mv);
 
-  // Use 4 for now : for (i = 1; i < MAX_MV_REFS; ++i ) {
-  for (i = 1; i < 4; ++i) {
+  for (i = 1; i < MAX_MV_REF_CANDIDATES; ++i) {
     // If we see a 0,0 reference vector for a second time we have reached
     // the end of the list of valid candidate vectors.
     if (!mv_ref_list[i].as_int) {
diff --git a/vp9/encoder/vp9_onyx_if.c b/vp9/encoder/vp9_onyx_if.c
index 8cabed9..448b56a 100644
--- a/vp9/encoder/vp9_onyx_if.c
+++ b/vp9/encoder/vp9_onyx_if.c
@@ -3821,7 +3821,7 @@
   {
     FILE *f = fopen("mv_ref_dist.stt", "a");
     unsigned int i;
-    for (i = 0; i < MAX_MV_REFS; ++i) {
+    for (i = 0; i < MAX_MV_REF_CANDIDATES; ++i) {
       fprintf(f, "%10d", cpi->best_ref_index_counts[0][i]);
     }
     fprintf(f, "\n" );
diff --git a/vp9/encoder/vp9_onyx_int.h b/vp9/encoder/vp9_onyx_int.h
index 8180d16..511e62f 100644
--- a/vp9/encoder/vp9_onyx_int.h
+++ b/vp9/encoder/vp9_onyx_int.h
@@ -790,7 +790,7 @@
   unsigned int switchable_interp_count[VP9_SWITCHABLE_FILTERS + 1]
                                       [VP9_SWITCHABLE_FILTERS];
 #if CONFIG_NEW_MVREF
-  unsigned int best_ref_index_counts[MAX_REF_FRAMES][MAX_MV_REFS];
+  unsigned int best_ref_index_counts[MAX_REF_FRAMES][MAX_MV_REF_CANDIDATES];
 #endif
 
 } VP9_COMP;