Change to limit the mv search range

As the pixel values beyond image border are duplicates of pixels
on edge, the change limits the mv search range, any mv beyond
the limits no longer produce new/different prediction values
as entire block with pixels used for subpel interpolation are
outside image border.

Change-Id: I4c6fdf06e33c1cef1489f5470ce0fb4e5e01fb79

vp9/common/vp9_enums.h

@@ -16,11 +16,13 @@
 #define LOG2_MI_SIZE 3
 #define LOG2_MI_BLOCK_SIZE (6 - LOG2_MI_SIZE)  // 64 = 2^6
 
+#define MAX_BLOCK_SIZE (1 << 6)  // max block size in pixel
 #define MI_SIZE (1 << LOG2_MI_SIZE)  // pixels per mi-unit
 #define MI_BLOCK_SIZE (1 << LOG2_MI_BLOCK_SIZE)  // mi-units per max block
 
 #define MI_MASK (MI_BLOCK_SIZE - 1)
 
+
 typedef enum BLOCK_SIZE_TYPE {
   BLOCK_4X4,
   BLOCK_4X8,

vp9/encoder/vp9_encodeframe.c

@@ -516,14 +516,12 @@ static void set_offsets(VP9_COMP *cpi, int mi_row, int mi_col,
   // Set up destination pointers
   setup_dst_planes(xd, &cm->yv12_fb[dst_fb_idx], mi_row, mi_col);
 
-  /* Set up limit values for MV components to prevent them from
-   * extending beyond the UMV borders assuming 16x16 block size */
-  x->mv_row_min = -((mi_row * MI_SIZE)+ VP9BORDERINPIXELS - VP9_INTERP_EXTEND);
-  x->mv_col_min = -((mi_col * MI_SIZE)+ VP9BORDERINPIXELS - VP9_INTERP_EXTEND);
-  x->mv_row_max = ((cm->mi_rows - mi_row) * MI_SIZE
-      + (VP9BORDERINPIXELS - MI_SIZE * mi_height - VP9_INTERP_EXTEND));
-  x->mv_col_max = ((cm->mi_cols - mi_col) * MI_SIZE
-      + (VP9BORDERINPIXELS - MI_SIZE * mi_width - VP9_INTERP_EXTEND));
+  // Set up limit values for MV components
+  // mv beyond the range do not produce new/different prediction block
+  x->mv_row_min = -((mi_row * MI_SIZE) + MAX_BLOCK_SIZE + VP9_INTERP_EXTEND);
+  x->mv_col_min = -((mi_col * MI_SIZE) + MAX_BLOCK_SIZE + VP9_INTERP_EXTEND);
+  x->mv_row_max = (cm->mi_rows - mi_row) * MI_SIZE + VP9_INTERP_EXTEND;
+  x->mv_col_max = (cm->mi_cols - mi_col) * MI_SIZE + VP9_INTERP_EXTEND;
 
   // Set up distance of MB to edge of frame in 1/8th pel units
   assert(!(mi_col & (mi_width - 1)) && !(mi_row & (mi_height - 1)));