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