Line data    Source code

       1             : /*
       2             :   Copyright (c) 2010 The WebM project authors. All Rights Reserved.
       3             :  *
       4             :  *  Use of this source code is governed by a BSD-style license
       5             :  *  that can be found in the LICENSE file in the root of the source
       6             :  *  tree. An additional intellectual property rights grant can be found
       7             :  *  in the file PATENTS.  All contributing project authors may
       8             :  *  be found in the AUTHORS file in the root of the source tree.
       9             :  */
      10             : 
      11             : #include <assert.h>
      12             : 
      13             : #include "vp9/common/vp9_entropy.h"
      14             : 
      15             : #include "vp9/decoder/vp9_dsubexp.h"
      16             : 
      17           0 : static int inv_recenter_nonneg(int v, int m) {
      18           0 :   if (v > 2 * m) return v;
      19             : 
      20           0 :   return (v & 1) ? m - ((v + 1) >> 1) : m + (v >> 1);
      21             : }
      22             : 
      23           0 : static int decode_uniform(vpx_reader *r) {
      24           0 :   const int l = 8;
      25           0 :   const int m = (1 << l) - 191;
      26           0 :   const int v = vpx_read_literal(r, l - 1);
      27           0 :   return v < m ? v : (v << 1) - m + vpx_read_bit(r);
      28             : }
      29             : 
      30           0 : static int inv_remap_prob(int v, int m) {
      31             :   static uint8_t inv_map_table[MAX_PROB] = {
      32             :     7,   20,  33,  46,  59,  72,  85,  98,  111, 124, 137, 150, 163, 176, 189,
      33             :     202, 215, 228, 241, 254, 1,   2,   3,   4,   5,   6,   8,   9,   10,  11,
      34             :     12,  13,  14,  15,  16,  17,  18,  19,  21,  22,  23,  24,  25,  26,  27,
      35             :     28,  29,  30,  31,  32,  34,  35,  36,  37,  38,  39,  40,  41,  42,  43,
      36             :     44,  45,  47,  48,  49,  50,  51,  52,  53,  54,  55,  56,  57,  58,  60,
      37             :     61,  62,  63,  64,  65,  66,  67,  68,  69,  70,  71,  73,  74,  75,  76,
      38             :     77,  78,  79,  80,  81,  82,  83,  84,  86,  87,  88,  89,  90,  91,  92,
      39             :     93,  94,  95,  96,  97,  99,  100, 101, 102, 103, 104, 105, 106, 107, 108,
      40             :     109, 110, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 125,
      41             :     126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 138, 139, 140, 141,
      42             :     142, 143, 144, 145, 146, 147, 148, 149, 151, 152, 153, 154, 155, 156, 157,
      43             :     158, 159, 160, 161, 162, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173,
      44             :     174, 175, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 190,
      45             :     191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 203, 204, 205, 206,
      46             :     207, 208, 209, 210, 211, 212, 213, 214, 216, 217, 218, 219, 220, 221, 222,
      47             :     223, 224, 225, 226, 227, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238,
      48             :     239, 240, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 253
      49             :   };
      50           0 :   assert(v < (int)(sizeof(inv_map_table) / sizeof(inv_map_table[0])));
      51           0 :   v = inv_map_table[v];
      52           0 :   m--;
      53           0 :   if ((m << 1) <= MAX_PROB) {
      54           0 :     return 1 + inv_recenter_nonneg(v, m);
      55             :   } else {
      56           0 :     return MAX_PROB - inv_recenter_nonneg(v, MAX_PROB - 1 - m);
      57             :   }
      58             : }
      59             : 
      60           0 : static int decode_term_subexp(vpx_reader *r) {
      61           0 :   if (!vpx_read_bit(r)) return vpx_read_literal(r, 4);
      62           0 :   if (!vpx_read_bit(r)) return vpx_read_literal(r, 4) + 16;
      63           0 :   if (!vpx_read_bit(r)) return vpx_read_literal(r, 5) + 32;
      64           0 :   return decode_uniform(r) + 64;
      65             : }
      66             : 
      67           0 : void vp9_diff_update_prob(vpx_reader *r, vpx_prob *p) {
      68           0 :   if (vpx_read(r, DIFF_UPDATE_PROB)) {
      69           0 :     const int delp = decode_term_subexp(r);
      70           0 :     *p = (vpx_prob)inv_remap_prob(delp, *p);
      71             :   }
      72           0 : }