Deal correctly with 16x4/4x16 blocks in mvref_common.c

The logic that searches for motion vectors in scan_row_mbmi and
scan_col_mbmi steps in 4x4 units when the block size is less than
8x8. That test (bsize < BLOCK_8X8) doesn't work when you have 16X4 or
4X16 blocks, because they appear higher up in the enum.

Change-Id: Idb1a97f8a43b675fd78dbc76ae501fcdff7adbcd

av1/common/mvref_common.c

diff --git a/av1/common/mvref_common.c b/av1/common/mvref_common.c
index 7666000..9c72612 100644
--- a/av1/common/mvref_common.c
+++ b/av1/common/mvref_common.c
@@ -162,9 +162,11 @@
   int col_offset = 0;
 #if CONFIG_CB4X4
   const int bsize = xd->mi[0]->mbmi.sb_type;
-  const int mi_offset = bsize < BLOCK_8X8 || abs(row_offset) > 1
-                            ? mi_size_wide[BLOCK_4X4]
-                            : mi_size_wide[BLOCK_8X8];
+  const int mi_width = mi_size_wide[bsize];
+  const int mi_col_offset =
+      ((abs(row_offset) > 1) || (mi_width < mi_size_wide[BLOCK_8X8]))
+          ? mi_size_wide[BLOCK_4X4]
+          : mi_size_wide[BLOCK_8X8];
   // TODO(jingning): Revisit this part after cb4x4 is stable.
   if (abs(row_offset) > 1) {
     row_offset *= 2;
@@ -172,13 +174,12 @@
 
     col_offset = 1;
 
-    if (bsize < BLOCK_8X8) {
-      if (mi_row & 0x01) row_offset += 1;
-      if (mi_col & 0x01) col_offset -= 1;
-    }
+    if (mi_row & 0x01 && mi_size_high[bsize] < mi_size_high[BLOCK_8X8])
+      ++row_offset;
+    if (mi_col & 0x01 && mi_width < mi_size_wide[BLOCK_8X8]) --col_offset;
   }
 #else
-  const int mi_offset = mi_size_wide[BLOCK_8X8];
+  const int mi_col_offset = mi_size_wide[BLOCK_8X8];
 #endif
 
   for (i = 0; i < xd->n8_w && *refmv_count < MAX_REF_MV_STACK_SIZE;) {
@@ -204,9 +205,9 @@
       i += len;
     } else {
       if (use_step_16)
-        i += (mi_offset << 1);
+        i += (mi_col_offset << 1);
       else
-        i += mi_offset;
+        i += mi_col_offset;
     }
   }
 
@@ -223,22 +224,23 @@
   int row_offset = 0;
 #if CONFIG_CB4X4
   const BLOCK_SIZE bsize = xd->mi[0]->mbmi.sb_type;
-  const int mi_offset = (bsize < BLOCK_8X8) || (abs(col_offset) > 1)
-                            ? mi_size_high[BLOCK_4X4]
-                            : mi_size_high[BLOCK_8X8];
+  const int mi_height = mi_size_high[bsize];
+  const int mi_row_offset =
+      ((abs(col_offset) > 1) || (mi_height < mi_size_high[BLOCK_8X8]))
+          ? mi_size_high[BLOCK_4X4]
+          : mi_size_high[BLOCK_8X8];
   if (abs(col_offset) > 1) {
     col_offset *= 2;
     col_offset += 1;
 
     row_offset = 1;
 
-    if (bsize < BLOCK_8X8) {
-      if (mi_row & 0x01) row_offset -= 1;
-      if (mi_col & 0x01) col_offset += 1;
-    }
+    if (mi_row & 0x01 && mi_height < mi_size_high[BLOCK_8X8]) --row_offset;
+    if (mi_col & 0x01 && mi_size_wide[bsize] < mi_size_wide[BLOCK_8X8])
+      ++col_offset;
   }
 #else
-  const int mi_offset = mi_size_wide[BLOCK_8X8];
+  const int mi_row_offset = mi_size_wide[BLOCK_8X8];
 #endif
 
   for (i = 0; i < xd->n8_h && *refmv_count < MAX_REF_MV_STACK_SIZE;) {
@@ -264,9 +266,9 @@
       i += len;
     } else {
       if (use_step_16)
-        i += (mi_offset << 1);
+        i += (mi_row_offset << 1);
       else
-        i += mi_offset;
+        i += mi_row_offset;
     }
   }