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