Fix show existing frame

- Disable mode info update in case where current frame is coded
  as "show existing frame".
- Should fix issue 676.

Change-Id: Ibee681850eb307f982da6528d3e31cb94f881c08

vp9/common/vp9_onyxc_int.h

diff --git a/vp9/common/vp9_onyxc_int.h b/vp9/common/vp9_onyxc_int.h
index 751accf..b28d456 100644
--- a/vp9/common/vp9_onyxc_int.h
+++ b/vp9/common/vp9_onyxc_int.h
@@ -133,6 +133,7 @@
 
   int show_frame;
   int last_show_frame;
+  int show_existing_frame;
 
   // Flag signaling that the frame is encoded using only INTRA modes.
   int intra_only;

vp9/decoder/vp9_decodeframe.c

diff --git a/vp9/decoder/vp9_decodeframe.c b/vp9/decoder/vp9_decodeframe.c
index 9b6740e..9d82cac 100644
--- a/vp9/decoder/vp9_decodeframe.c
+++ b/vp9/decoder/vp9_decodeframe.c
@@ -1067,7 +1067,8 @@
   cm->version = vp9_rb_read_bit(rb);
   RESERVED;
 
-  if (vp9_rb_read_bit(rb)) {
+  cm->show_existing_frame = vp9_rb_read_bit(rb);
+  if (cm->show_existing_frame) {
     // show an existing frame directly
     int frame_to_show = cm->ref_frame_map[vp9_rb_read_literal(rb, 3)];
     ref_cnt_fb(cm->fb_idx_ref_cnt, &cm->new_fb_idx, frame_to_show);

vp9/decoder/vp9_onyxd_if.c

diff --git a/vp9/decoder/vp9_onyxd_if.c b/vp9/decoder/vp9_onyxd_if.c
index 740ad72..b06a50f 100644
--- a/vp9/decoder/vp9_onyxd_if.c
+++ b/vp9/decoder/vp9_onyxd_if.c
@@ -392,23 +392,25 @@
 
   cm->last_show_frame = cm->show_frame;
   if (cm->show_frame) {
-    // current mip will be the prev_mip for the next frame
-    MODE_INFO *temp = cm->prev_mip;
-    MODE_INFO **temp2 = cm->prev_mi_grid_base;
-    cm->prev_mip = cm->mip;
-    cm->mip = temp;
-    cm->prev_mi_grid_base = cm->mi_grid_base;
-    cm->mi_grid_base = temp2;
+    if (!cm->show_existing_frame) {
+      // current mip will be the prev_mip for the next frame
+      MODE_INFO *temp = cm->prev_mip;
+      MODE_INFO **temp2 = cm->prev_mi_grid_base;
+      cm->prev_mip = cm->mip;
+      cm->mip = temp;
+      cm->prev_mi_grid_base = cm->mi_grid_base;
+      cm->mi_grid_base = temp2;
 
-    // update the upper left visible macroblock ptrs
-    cm->mi = cm->mip + cm->mode_info_stride + 1;
-    cm->prev_mi = cm->prev_mip + cm->mode_info_stride + 1;
-    cm->mi_grid_visible = cm->mi_grid_base + cm->mode_info_stride + 1;
-    cm->prev_mi_grid_visible = cm->prev_mi_grid_base + cm->mode_info_stride + 1;
+      // update the upper left visible macroblock ptrs
+      cm->mi = cm->mip + cm->mode_info_stride + 1;
+      cm->prev_mi = cm->prev_mip + cm->mode_info_stride + 1;
+      cm->mi_grid_visible = cm->mi_grid_base + cm->mode_info_stride + 1;
+      cm->prev_mi_grid_visible = cm->prev_mi_grid_base +
+                                 cm->mode_info_stride + 1;
 
-    pbi->mb.mi_8x8 = cm->mi_grid_visible;
-    pbi->mb.mi_8x8[0] = cm->mi;
-
+      pbi->mb.mi_8x8 = cm->mi_grid_visible;
+      pbi->mb.mi_8x8[0] = cm->mi;
+    }
     cm->current_video_frame++;
   }