quant.c revision a2415724fb3466168b2af5b08bd94ba732c0e753 
1// Copyright 2010 Google Inc. All Rights Reserved.
2//
3// This code is licensed under the same terms as WebM:
4//  Software License Agreement:  http://www.webmproject.org/license/software/
5//  Additional IP Rights Grant:  http://www.webmproject.org/license/additional/
6// -----------------------------------------------------------------------------
7//
8// Quantizer initialization
9//
10// Author: Skal (pascal.massimino@gmail.com)
11
12#include "./vp8i.h"
13
14#if defined(__cplusplus) || defined(c_plusplus)
15extern "C" {
16#endif
17
18static WEBP_INLINE int clip(int v, int M) {
19  return v < 0 ? 0 : v > M ? M : v;
20}
21
22// Paragraph 14.1
23static const uint8_t kDcTable[128] = {
24  4,     5,   6,   7,   8,   9,  10,  10,
25  11,   12,  13,  14,  15,  16,  17,  17,
26  18,   19,  20,  20,  21,  21,  22,  22,
27  23,   23,  24,  25,  25,  26,  27,  28,
28  29,   30,  31,  32,  33,  34,  35,  36,
29  37,   37,  38,  39,  40,  41,  42,  43,
30  44,   45,  46,  46,  47,  48,  49,  50,
31  51,   52,  53,  54,  55,  56,  57,  58,
32  59,   60,  61,  62,  63,  64,  65,  66,
33  67,   68,  69,  70,  71,  72,  73,  74,
34  75,   76,  76,  77,  78,  79,  80,  81,
35  82,   83,  84,  85,  86,  87,  88,  89,
36  91,   93,  95,  96,  98, 100, 101, 102,
37  104, 106, 108, 110, 112, 114, 116, 118,
38  122, 124, 126, 128, 130, 132, 134, 136,
39  138, 140, 143, 145, 148, 151, 154, 157
40};
41
42static const uint16_t kAcTable[128] = {
43  4,     5,   6,   7,   8,   9,  10,  11,
44  12,   13,  14,  15,  16,  17,  18,  19,
45  20,   21,  22,  23,  24,  25,  26,  27,
46  28,   29,  30,  31,  32,  33,  34,  35,
47  36,   37,  38,  39,  40,  41,  42,  43,
48  44,   45,  46,  47,  48,  49,  50,  51,
49  52,   53,  54,  55,  56,  57,  58,  60,
50  62,   64,  66,  68,  70,  72,  74,  76,
51  78,   80,  82,  84,  86,  88,  90,  92,
52  94,   96,  98, 100, 102, 104, 106, 108,
53  110, 112, 114, 116, 119, 122, 125, 128,
54  131, 134, 137, 140, 143, 146, 149, 152,
55  155, 158, 161, 164, 167, 170, 173, 177,
56  181, 185, 189, 193, 197, 201, 205, 209,
57  213, 217, 221, 225, 229, 234, 239, 245,
58  249, 254, 259, 264, 269, 274, 279, 284
59};
60
61//------------------------------------------------------------------------------
62// Paragraph 9.6
63
64void VP8ParseQuant(VP8Decoder* const dec) {
65  VP8BitReader* const br = &dec->br_;
66  const int base_q0 = VP8GetValue(br, 7);
67  const int dqy1_dc = VP8Get(br) ? VP8GetSignedValue(br, 4) : 0;
68  const int dqy2_dc = VP8Get(br) ? VP8GetSignedValue(br, 4) : 0;
69  const int dqy2_ac = VP8Get(br) ? VP8GetSignedValue(br, 4) : 0;
70  const int dquv_dc = VP8Get(br) ? VP8GetSignedValue(br, 4) : 0;
71  const int dquv_ac = VP8Get(br) ? VP8GetSignedValue(br, 4) : 0;
72
73  const VP8SegmentHeader* const hdr = &dec->segment_hdr_;
74  int i;
75
76  for (i = 0; i < NUM_MB_SEGMENTS; ++i) {
77    int q;
78    if (hdr->use_segment_) {
79      q = hdr->quantizer_[i];
80      if (!hdr->absolute_delta_) {
81        q += base_q0;
82      }
83    } else {
84      if (i > 0) {
85        dec->dqm_[i] = dec->dqm_[0];
86        continue;
87      } else {
88        q = base_q0;
89      }
90    }
91    {
92      VP8QuantMatrix* const m = &dec->dqm_[i];
93      m->y1_mat_[0] = kDcTable[clip(q + dqy1_dc, 127)];
94      m->y1_mat_[1] = kAcTable[clip(q + 0,       127)];
95
96      m->y2_mat_[0] = kDcTable[clip(q + dqy2_dc, 127)] * 2;
97      // For all x in [0..284], x*155/100 is bitwise equal to (x*101581) >> 16.
98      // The smallest precision for that is '(x*6349) >> 12' but 16 is a good
99      // word size.
100      m->y2_mat_[1] = (kAcTable[clip(q + dqy2_ac, 127)] * 101581) >> 16;
101      if (m->y2_mat_[1] < 8) m->y2_mat_[1] = 8;
102
103      m->uv_mat_[0] = kDcTable[clip(q + dquv_dc, 117)];
104      m->uv_mat_[1] = kAcTable[clip(q + dquv_ac, 127)];
105    }
106  }
107}
108
109//------------------------------------------------------------------------------
110
111#if defined(__cplusplus) || defined(c_plusplus)
112}    // extern "C"
113#endif
114