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 (at) gmail.com) 13 14 #include "./vp8i.h" 15 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 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
