Nearest / Zero Mv default entropy tweak.

Tweak to default mode context to account for the fact
that when there are no non zero motion candidates
Nearest is now the preferred mode for coding a 0,0
vector.

Also resolve duplicate function name and typos.

Change-Id: I76802788d46c84e3d1c771be216a537ab7b12817

vp9/common/vp9_modecont.c

@@ -12,7 +12,7 @@
 #include "vp9/common/vp9_entropy.h"
 
 const int vp9_default_mode_contexts[INTER_MODE_CONTEXTS][4] = {
-  {223,     1,     1,    237},  // 0,0 best: Only candidate
+  {1,       223,   1,    237},  // 0,0 best: Only candidate
   {87,      166,   26,   219},  // 0,0 best: non zero candidates
   {89,      67,    18,   125},  // 0,0 best: non zero candidates, split
   {16,      141,   69,   226},  // strong nz candidate(s), no split

vp9/decoder/vp9_decodemv.c

@@ -792,7 +792,7 @@ static void read_mb_modes_mv(VP9D_COMP *pbi, MODE_INFO *mi, MB_MODE_INFO *mbmi,
       }
       */
 
-      // Is the segment level skip mode enabled
+      // If the segment level skip mode enabled
       if (vp9_segfeature_active(xd, mbmi->segment_id, SEG_LVL_SKIP)) {
         mbmi->mode = ZEROMV;
       } else {

vp9/encoder/vp9_bitstream.c

@@ -221,8 +221,8 @@ static void update_refpred_stats(VP9_COMP *cpi) {
 //
 // The branch counts table is re-populated during the actual pack stage and in
 // the decoder to facilitate backwards update of the context.
-static void update_mode_probs(VP9_COMMON *cm,
-                              int mode_context[INTER_MODE_CONTEXTS][4]) {
+static void update_inter_mode_probs(VP9_COMMON *cm,
+                                    int mode_context[INTER_MODE_CONTEXTS][4]) {
   int i, j;
   unsigned int (*mv_ref_ct)[4][2];
 
@@ -813,7 +813,7 @@ static void pack_inter_mode_mvs(VP9_COMP *cpi, MODE_INFO *m,
     active_section = 3;
 #endif
 
-    // Is segment skip is not enabled code the mode.
+    // If segment skip is not enabled code the mode.
     if (!vp9_segfeature_active(xd, segment_id, SEG_LVL_SKIP)) {
       if (mi->sb_type) {
         write_sb_mv_ref(bc, mode, mv_ref_p);
@@ -1871,7 +1871,13 @@ void vp9_pack_bitstream(VP9_COMP *cpi, unsigned char *dest,
   if (pc->frame_type != KEY_FRAME) {
     int i, j;
     int new_context[INTER_MODE_CONTEXTS][4];
-    update_mode_probs(pc, new_context);
+    if (!cpi->dummy_packing) {
+      update_inter_mode_probs(pc, new_context);
+    } else {
+      // In dummy pack assume context unchanged.
+      vpx_memcpy(new_context, pc->fc.vp9_mode_contexts,
+                 sizeof(pc->fc.vp9_mode_contexts));
+    }
 
     for (i = 0; i < INTER_MODE_CONTEXTS; i++) {
       for (j = 0; j < 4; j++) {