VP8: Inline traversing vp8_small_mvtree

Much faster read_mv_component, slightly faster overall

Originally committed as revision 24470 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/vp8.c

@@ -599,7 +599,7 @@ void find_near_mvs(VP8Context *s, VP8Macroblock *mb, int mb_x, int mb_y,
  */
 static int read_mv_component(VP56RangeCoder *c, const uint8_t *p)
 {
-    int x = 0;
+    int bit, x = 0;
 
     if (vp56_rac_get_prob_branchy(c, p[0])) {
         int i;
@@ -610,8 +610,17 @@ static int read_mv_component(VP56RangeCoder *c, const uint8_t *p)
             x += vp56_rac_get_prob(c, p[9 + i]) << i;
         if (!(x & 0xFFF0) || vp56_rac_get_prob(c, p[12]))
             x += 8;
-    } else
-        x = vp8_rac_get_tree(c, vp8_small_mvtree, &p[2]);
+    } else {
+        // small_mvtree
+        const uint8_t *ps = p+2;
+        bit = vp56_rac_get_prob(c, *ps);
+        ps += 1 + 3*bit;
+        x  += 4*bit;
+        bit = vp56_rac_get_prob(c, *ps);
+        ps += 1 + bit;
+        x  += 2*bit;
+        x  += vp56_rac_get_prob(c, *ps);
+    }
 
     return (x && vp56_rac_get_prob(c, p[1])) ? -x : x;
 }

libavcodec/vp8data.h

@@ -110,16 +110,6 @@ static const int8_t vp8_pred16x16_tree_mvinter[4][2] = {
        { -VP8_MVMODE_NEW, -VP8_MVMODE_SPLIT } // '1110', '1111'
 };
 
-static const int8_t vp8_small_mvtree[7][2] = {
-    {  1, 4 },
-     {  2, 3 },
-      { -0, -1 },                           // '000', '001'
-      { -2, -3 },                           // '010', '011'
-     {  5,  6 },
-      { -4, -5 },                           // '100', '101'
-      { -6, -7 }                            // '110', '111'
-};
-
 static const uint8_t vp8_mbsplits[5][16] = {
     {  0,  0,  0,  0,  0,  0,  0,  0,
        1,  1,  1,  1,  1,  1,  1,  1  },