// Copyright 2011 Google Inc. All Rights Reserved. // // Use of this source code is governed by a BSD-style license // that can be found in the COPYING file in the root of the source // tree. An additional intellectual property rights grant can be found // in the file PATENTS. All contributing project authors may // be found in the AUTHORS file in the root of the source tree. // ----------------------------------------------------------------------------- // // Quantization // // Author: Skal (pascal.massimino@gmail.com) #include #include #include // for abs() #include "./vp8enci.h" #include "./cost.h" #define DO_TRELLIS_I4 1 #define DO_TRELLIS_I16 1 // not a huge gain, but ok at low bitrate. #define DO_TRELLIS_UV 0 // disable trellis for UV. Risky. Not worth. #define USE_TDISTO 1 #define MID_ALPHA 64 // neutral value for susceptibility #define MIN_ALPHA 30 // lowest usable value for susceptibility #define MAX_ALPHA 100 // higher meaningful value for susceptibility #define SNS_TO_DQ 0.9 // Scaling constant between the sns value and the QP // power-law modulation. Must be strictly less than 1. #define I4_PENALTY 4000 // Rate-penalty for quick i4/i16 decision // number of non-zero coeffs below which we consider the block very flat // (and apply a penalty to complex predictions) #define FLATNESS_LIMIT_I16 10 // I16 mode #define FLATNESS_LIMIT_I4 3 // I4 mode #define FLATNESS_LIMIT_UV 2 // UV mode #define FLATNESS_PENALTY 140 // roughly ~1bit per block #define MULT_8B(a, b) (((a) * (b) + 128) >> 8) // #define DEBUG_BLOCK //------------------------------------------------------------------------------ #if defined(DEBUG_BLOCK) #include #include static void PrintBlockInfo(const VP8EncIterator* const it, const VP8ModeScore* const rd) { int i, j; const int is_i16 = (it->mb_->type_ == 1); printf("SOURCE / OUTPUT / ABS DELTA\n"); for (j = 0; j < 24; ++j) { if (j == 16) printf("\n"); // newline before the U/V block for (i = 0; i < 16; ++i) printf("%3d ", it->yuv_in_[i + j * BPS]); printf(" "); for (i = 0; i < 16; ++i) printf("%3d ", it->yuv_out_[i + j * BPS]); printf(" "); for (i = 0; i < 16; ++i) { printf("%1d ", abs(it->yuv_out_[i + j * BPS] - it->yuv_in_[i + j * BPS])); } printf("\n"); } printf("\nD:%d SD:%d R:%d H:%d nz:0x%x score:%d\n", (int)rd->D, (int)rd->SD, (int)rd->R, (int)rd->H, (int)rd->nz, (int)rd->score); if (is_i16) { printf("Mode: %d\n", rd->mode_i16); printf("y_dc_levels:"); for (i = 0; i < 16; ++i) printf("%3d ", rd->y_dc_levels[i]); printf("\n"); } else { printf("Modes[16]: "); for (i = 0; i < 16; ++i) printf("%d ", rd->modes_i4[i]); printf("\n"); } printf("y_ac_levels:\n"); for (j = 0; j < 16; ++j) { for (i = is_i16 ? 1 : 0; i < 16; ++i) { printf("%4d ", rd->y_ac_levels[j][i]); } printf("\n"); } printf("\n"); printf("uv_levels (mode=%d):\n", rd->mode_uv); for (j = 0; j < 8; ++j) { for (i = 0; i < 16; ++i) { printf("%4d ", rd->uv_levels[j][i]); } printf("\n"); } } #endif // DEBUG_BLOCK //------------------------------------------------------------------------------ static WEBP_INLINE int clip(int v, int m, int M) { return v < m ? m : v > M ? M : v; } static const uint8_t kZigzag[16] = { 0, 1, 4, 8, 5, 2, 3, 6, 9, 12, 13, 10, 7, 11, 14, 15 }; static const uint8_t kDcTable[128] = { 4, 5, 6, 7, 8, 9, 10, 10, 11, 12, 13, 14, 15, 16, 17, 17, 18, 19, 20, 20, 21, 21, 22, 22, 23, 23, 24, 25, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 91, 93, 95, 96, 98, 100, 101, 102, 104, 106, 108, 110, 112, 114, 116, 118, 122, 124, 126, 128, 130, 132, 134, 136, 138, 140, 143, 145, 148, 151, 154, 157 }; static const uint16_t kAcTable[128] = { 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110, 112, 114, 116, 119, 122, 125, 128, 131, 134, 137, 140, 143, 146, 149, 152, 155, 158, 161, 164, 167, 170, 173, 177, 181, 185, 189, 193, 197, 201, 205, 209, 213, 217, 221, 225, 229, 234, 239, 245, 249, 254, 259, 264, 269, 274, 279, 284 }; static const uint16_t kAcTable2[128] = { 8, 8, 9, 10, 12, 13, 15, 17, 18, 20, 21, 23, 24, 26, 27, 29, 31, 32, 34, 35, 37, 38, 40, 41, 43, 44, 46, 48, 49, 51, 52, 54, 55, 57, 58, 60, 62, 63, 65, 66, 68, 69, 71, 72, 74, 75, 77, 79, 80, 82, 83, 85, 86, 88, 89, 93, 96, 99, 102, 105, 108, 111, 114, 117, 120, 124, 127, 130, 133, 136, 139, 142, 145, 148, 151, 155, 158, 161, 164, 167, 170, 173, 176, 179, 184, 189, 193, 198, 203, 207, 212, 217, 221, 226, 230, 235, 240, 244, 249, 254, 258, 263, 268, 274, 280, 286, 292, 299, 305, 311, 317, 323, 330, 336, 342, 348, 354, 362, 370, 379, 385, 393, 401, 409, 416, 424, 432, 440 }; static const uint8_t kBiasMatrices[3][2] = { // [luma-ac,luma-dc,chroma][dc,ac] { 96, 110 }, { 96, 108 }, { 110, 115 } }; // Sharpening by (slightly) raising the hi-frequency coeffs. // Hack-ish but helpful for mid-bitrate range. Use with care. #define SHARPEN_BITS 11 // number of descaling bits for sharpening bias static const uint8_t kFreqSharpening[16] = { 0, 30, 60, 90, 30, 60, 90, 90, 60, 90, 90, 90, 90, 90, 90, 90 }; //------------------------------------------------------------------------------ // Initialize quantization parameters in VP8Matrix // Returns the average quantizer static int ExpandMatrix(VP8Matrix* const m, int type) { int i, sum; for (i = 0; i < 2; ++i) { const int is_ac_coeff = (i > 0); const int bias = kBiasMatrices[type][is_ac_coeff]; m->iq_[i] = (1 << QFIX) / m->q_[i]; m->bias_[i] = BIAS(bias); // zthresh_ is the exact value such that QUANTDIV(coeff, iQ, B) is: // * zero if coeff <= zthresh // * non-zero if coeff > zthresh m->zthresh_[i] = ((1 << QFIX) - 1 - m->bias_[i]) / m->iq_[i]; } for (i = 2; i < 16; ++i) { m->q_[i] = m->q_[1]; m->iq_[i] = m->iq_[1]; m->bias_[i] = m->bias_[1]; m->zthresh_[i] = m->zthresh_[1]; } for (sum = 0, i = 0; i < 16; ++i) { if (type == 0) { // we only use sharpening for AC luma coeffs m->sharpen_[i] = (kFreqSharpening[i] * m->q_[i]) >> SHARPEN_BITS; } else { m->sharpen_[i] = 0; } sum += m->q_[i]; } return (sum + 8) >> 4; } static void SetupMatrices(VP8Encoder* enc) { int i; const int tlambda_scale = (enc->method_ >= 4) ? enc->config_->sns_strength : 0; const int num_segments = enc->segment_hdr_.num_segments_; for (i = 0; i < num_segments; ++i) { VP8SegmentInfo* const m = &enc->dqm_[i]; const int q = m->quant_; int q4, q16, quv; m->y1_.q_[0] = kDcTable[clip(q + enc->dq_y1_dc_, 0, 127)]; m->y1_.q_[1] = kAcTable[clip(q, 0, 127)]; m->y2_.q_[0] = kDcTable[ clip(q + enc->dq_y2_dc_, 0, 127)] * 2; m->y2_.q_[1] = kAcTable2[clip(q + enc->dq_y2_ac_, 0, 127)]; m->uv_.q_[0] = kDcTable[clip(q + enc->dq_uv_dc_, 0, 117)]; m->uv_.q_[1] = kAcTable[clip(q + enc->dq_uv_ac_, 0, 127)]; q4 = ExpandMatrix(&m->y1_, 0); q16 = ExpandMatrix(&m->y2_, 1); quv = ExpandMatrix(&m->uv_, 2); m->lambda_i4_ = (3 * q4 * q4) >> 7; m->lambda_i16_ = (3 * q16 * q16); m->lambda_uv_ = (3 * quv * quv) >> 6; m->lambda_mode_ = (1 * q4 * q4) >> 7; m->lambda_trellis_i4_ = (7 * q4 * q4) >> 3; m->lambda_trellis_i16_ = (q16 * q16) >> 2; m->lambda_trellis_uv_ = (quv *quv) << 1; m->tlambda_ = (tlambda_scale * q4) >> 5; m->min_disto_ = 10 * m->y1_.q_[0]; // quantization-aware min disto m->max_edge_ = 0; } } //------------------------------------------------------------------------------ // Initialize filtering parameters // Very small filter-strength values have close to no visual effect. So we can // save a little decoding-CPU by turning filtering off for these. #define FSTRENGTH_CUTOFF 2 static void SetupFilterStrength(VP8Encoder* const enc) { int i; // level0 is in [0..500]. Using '-f 50' as filter_strength is mid-filtering. const int level0 = 5 * enc->config_->filter_strength; for (i = 0; i < NUM_MB_SEGMENTS; ++i) { VP8SegmentInfo* const m = &enc->dqm_[i]; // We focus on the quantization of AC coeffs. const int qstep = kAcTable[clip(m->quant_, 0, 127)] >> 2; const int base_strength = VP8FilterStrengthFromDelta(enc->filter_hdr_.sharpness_, qstep); // Segments with lower complexity ('beta') will be less filtered. const int f = base_strength * level0 / (256 + m->beta_); m->fstrength_ = (f < FSTRENGTH_CUTOFF) ? 0 : (f > 63) ? 63 : f; } // We record the initial strength (mainly for the case of 1-segment only). enc->filter_hdr_.level_ = enc->dqm_[0].fstrength_; enc->filter_hdr_.simple_ = (enc->config_->filter_type == 0); enc->filter_hdr_.sharpness_ = enc->config_->filter_sharpness; } //------------------------------------------------------------------------------ // Note: if you change the values below, remember that the max range // allowed by the syntax for DQ_UV is [-16,16]. #define MAX_DQ_UV (6) #define MIN_DQ_UV (-4) // We want to emulate jpeg-like behaviour where the expected "good" quality // is around q=75. Internally, our "good" middle is around c=50. So we // map accordingly using linear piece-wise function static double QualityToCompression(double c) { const double linear_c = (c < 0.75) ? c * (2. / 3.) : 2. * c - 1.; // The file size roughly scales as pow(quantizer, 3.). Actually, the // exponent is somewhere between 2.8 and 3.2, but we're mostly interested // in the mid-quant range. So we scale the compressibility inversely to // this power-law: quant ~= compression ^ 1/3. This law holds well for // low quant. Finer modeling for high-quant would make use of kAcTable[] // more explicitly. const double v = pow(linear_c, 1 / 3.); return v; } static double QualityToJPEGCompression(double c, double alpha) { // We map the complexity 'alpha' and quality setting 'c' to a compression // exponent empirically matched to the compression curve of libjpeg6b. // On average, the WebP output size will be roughly similar to that of a // JPEG file compressed with same quality factor. const double amin = 0.30; const double amax = 0.85; const double exp_min = 0.4; const double exp_max = 0.9; const double slope = (exp_min - exp_max) / (amax - amin); // Linearly interpolate 'expn' from exp_min to exp_max // in the [amin, amax] range. const double expn = (alpha > amax) ? exp_min : (alpha < amin) ? exp_max : exp_max + slope * (alpha - amin); const double v = pow(c, expn); return v; } static int SegmentsAreEquivalent(const VP8SegmentInfo* const S1, const VP8SegmentInfo* const S2) { return (S1->quant_ == S2->quant_) && (S1->fstrength_ == S2->fstrength_); } static void SimplifySegments(VP8Encoder* const enc) { int map[NUM_MB_SEGMENTS] = { 0, 1, 2, 3 }; const int num_segments = enc->segment_hdr_.num_segments_; int num_final_segments = 1; int s1, s2; for (s1 = 1; s1 < num_segments; ++s1) { // find similar segments const VP8SegmentInfo* const S1 = &enc->dqm_[s1]; int found = 0; // check if we already have similar segment for (s2 = 0; s2 < num_final_segments; ++s2) { const VP8SegmentInfo* const S2 = &enc->dqm_[s2]; if (SegmentsAreEquivalent(S1, S2)) { found = 1; break; } } map[s1] = s2; if (!found) { if (num_final_segments != s1) { enc->dqm_[num_final_segments] = enc->dqm_[s1]; } ++num_final_segments; } } if (num_final_segments < num_segments) { // Remap int i = enc->mb_w_ * enc->mb_h_; while (i-- > 0) enc->mb_info_[i].segment_ = map[enc->mb_info_[i].segment_]; enc->segment_hdr_.num_segments_ = num_final_segments; // Replicate the trailing segment infos (it's mostly cosmetics) for (i = num_final_segments; i < num_segments; ++i) { enc->dqm_[i] = enc->dqm_[num_final_segments - 1]; } } } void VP8SetSegmentParams(VP8Encoder* const enc, float quality) { int i; int dq_uv_ac, dq_uv_dc; const int num_segments = enc->segment_hdr_.num_segments_; const double amp = SNS_TO_DQ * enc->config_->sns_strength / 100. / 128.; const double Q = quality / 100.; const double c_base = enc->config_->emulate_jpeg_size ? QualityToJPEGCompression(Q, enc->alpha_ / 255.) : QualityToCompression(Q); for (i = 0; i < num_segments; ++i) { // We modulate the base coefficient to accommodate for the quantization // susceptibility and allow denser segments to be quantized more. const double expn = 1. - amp * enc->dqm_[i].alpha_; const double c = pow(c_base, expn); const int q = (int)(127. * (1. - c)); assert(expn > 0.); enc->dqm_[i].quant_ = clip(q, 0, 127); } // purely indicative in the bitstream (except for the 1-segment case) enc->base_quant_ = enc->dqm_[0].quant_; // fill-in values for the unused segments (required by the syntax) for (i = num_segments; i < NUM_MB_SEGMENTS; ++i) { enc->dqm_[i].quant_ = enc->base_quant_; } // uv_alpha_ is normally spread around ~60. The useful range is // typically ~30 (quite bad) to ~100 (ok to decimate UV more). // We map it to the safe maximal range of MAX/MIN_DQ_UV for dq_uv. dq_uv_ac = (enc->uv_alpha_ - MID_ALPHA) * (MAX_DQ_UV - MIN_DQ_UV) / (MAX_ALPHA - MIN_ALPHA); // we rescale by the user-defined strength of adaptation dq_uv_ac = dq_uv_ac * enc->config_->sns_strength / 100; // and make it safe. dq_uv_ac = clip(dq_uv_ac, MIN_DQ_UV, MAX_DQ_UV); // We also boost the dc-uv-quant a little, based on sns-strength, since // U/V channels are quite more reactive to high quants (flat DC-blocks // tend to appear, and are unpleasant). dq_uv_dc = -4 * enc->config_->sns_strength / 100; dq_uv_dc = clip(dq_uv_dc, -15, 15); // 4bit-signed max allowed enc->dq_y1_dc_ = 0; // TODO(skal): dq-lum enc->dq_y2_dc_ = 0; enc->dq_y2_ac_ = 0; enc->dq_uv_dc_ = dq_uv_dc; enc->dq_uv_ac_ = dq_uv_ac; SetupFilterStrength(enc); // initialize segments' filtering, eventually if (num_segments > 1) SimplifySegments(enc); SetupMatrices(enc); // finalize quantization matrices } //------------------------------------------------------------------------------ // Form the predictions in cache // Must be ordered using {DC_PRED, TM_PRED, V_PRED, H_PRED} as index const int VP8I16ModeOffsets[4] = { I16DC16, I16TM16, I16VE16, I16HE16 }; const int VP8UVModeOffsets[4] = { C8DC8, C8TM8, C8VE8, C8HE8 }; // Must be indexed using {B_DC_PRED -> B_HU_PRED} as index const int VP8I4ModeOffsets[NUM_BMODES] = { I4DC4, I4TM4, I4VE4, I4HE4, I4RD4, I4VR4, I4LD4, I4VL4, I4HD4, I4HU4 }; void VP8MakeLuma16Preds(const VP8EncIterator* const it) { const uint8_t* const left = it->x_ ? it->y_left_ : NULL; const uint8_t* const top = it->y_ ? it->y_top_ : NULL; VP8EncPredLuma16(it->yuv_p_, left, top); } void VP8MakeChroma8Preds(const VP8EncIterator* const it) { const uint8_t* const left = it->x_ ? it->u_left_ : NULL; const uint8_t* const top = it->y_ ? it->uv_top_ : NULL; VP8EncPredChroma8(it->yuv_p_, left, top); } void VP8MakeIntra4Preds(const VP8EncIterator* const it) { VP8EncPredLuma4(it->yuv_p_, it->i4_top_); } //------------------------------------------------------------------------------ // Quantize // Layout: // +----+----+ // |YYYY|UUVV| 0 // |YYYY|UUVV| 4 // |YYYY|....| 8 // |YYYY|....| 12 // +----+----+ const int VP8Scan[16] = { // Luma 0 + 0 * BPS, 4 + 0 * BPS, 8 + 0 * BPS, 12 + 0 * BPS, 0 + 4 * BPS, 4 + 4 * BPS, 8 + 4 * BPS, 12 + 4 * BPS, 0 + 8 * BPS, 4 + 8 * BPS, 8 + 8 * BPS, 12 + 8 * BPS, 0 + 12 * BPS, 4 + 12 * BPS, 8 + 12 * BPS, 12 + 12 * BPS, }; static const int VP8ScanUV[4 + 4] = { 0 + 0 * BPS, 4 + 0 * BPS, 0 + 4 * BPS, 4 + 4 * BPS, // U 8 + 0 * BPS, 12 + 0 * BPS, 8 + 4 * BPS, 12 + 4 * BPS // V }; //------------------------------------------------------------------------------ // Distortion measurement static const uint16_t kWeightY[16] = { 38, 32, 20, 9, 32, 28, 17, 7, 20, 17, 10, 4, 9, 7, 4, 2 }; static const uint16_t kWeightTrellis[16] = { #if USE_TDISTO == 0 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16 #else 30, 27, 19, 11, 27, 24, 17, 10, 19, 17, 12, 8, 11, 10, 8, 6 #endif }; // Init/Copy the common fields in score. static void InitScore(VP8ModeScore* const rd) { rd->D = 0; rd->SD = 0; rd->R = 0; rd->H = 0; rd->nz = 0; rd->score = MAX_COST; } static void CopyScore(VP8ModeScore* const dst, const VP8ModeScore* const src) { dst->D = src->D; dst->SD = src->SD; dst->R = src->R; dst->H = src->H; dst->nz = src->nz; // note that nz is not accumulated, but just copied. dst->score = src->score; } static void AddScore(VP8ModeScore* const dst, const VP8ModeScore* const src) { dst->D += src->D; dst->SD += src->SD; dst->R += src->R; dst->H += src->H; dst->nz |= src->nz; // here, new nz bits are accumulated. dst->score += src->score; } //------------------------------------------------------------------------------ // Performs trellis-optimized quantization. // Trellis node typedef struct { int8_t prev; // best previous node int8_t sign; // sign of coeff_i int16_t level; // level } Node; // Score state typedef struct { score_t score; // partial RD score const uint16_t* costs; // shortcut to cost tables } ScoreState; // If a coefficient was quantized to a value Q (using a neutral bias), // we test all alternate possibilities between [Q-MIN_DELTA, Q+MAX_DELTA] // We don't test negative values though. #define MIN_DELTA 0 // how much lower level to try #define MAX_DELTA 1 // how much higher #define NUM_NODES (MIN_DELTA + 1 + MAX_DELTA) #define NODE(n, l) (nodes[(n)][(l) + MIN_DELTA]) #define SCORE_STATE(n, l) (score_states[n][(l) + MIN_DELTA]) static WEBP_INLINE void SetRDScore(int lambda, VP8ModeScore* const rd) { // TODO: incorporate the "* 256" in the tables? rd->score = (rd->R + rd->H) * lambda + 256 * (rd->D + rd->SD); } static WEBP_INLINE score_t RDScoreTrellis(int lambda, score_t rate, score_t distortion) { return rate * lambda + 256 * distortion; } static int TrellisQuantizeBlock(const VP8Encoder* const enc, int16_t in[16], int16_t out[16], int ctx0, int coeff_type, const VP8Matrix* const mtx, int lambda) { const ProbaArray* const probas = enc->proba_.coeffs_[coeff_type]; CostArrayPtr const costs = (CostArrayPtr)enc->proba_.remapped_costs_[coeff_type]; const int first = (coeff_type == 0) ? 1 : 0; Node nodes[16][NUM_NODES]; ScoreState score_states[2][NUM_NODES]; ScoreState* ss_cur = &SCORE_STATE(0, MIN_DELTA); ScoreState* ss_prev = &SCORE_STATE(1, MIN_DELTA); int best_path[3] = {-1, -1, -1}; // store best-last/best-level/best-previous score_t best_score; int n, m, p, last; { score_t cost; const int thresh = mtx->q_[1] * mtx->q_[1] / 4; const int last_proba = probas[VP8EncBands[first]][ctx0][0]; // compute the position of the last interesting coefficient last = first - 1; for (n = 15; n >= first; --n) { const int j = kZigzag[n]; const int err = in[j] * in[j]; if (err > thresh) { last = n; break; } } // we don't need to go inspect up to n = 16 coeffs. We can just go up // to last + 1 (inclusive) without losing much. if (last < 15) ++last; // compute 'skip' score. This is the max score one can do. cost = VP8BitCost(0, last_proba); best_score = RDScoreTrellis(lambda, cost, 0); // initialize source node. for (m = -MIN_DELTA; m <= MAX_DELTA; ++m) { const score_t rate = (ctx0 == 0) ? VP8BitCost(1, last_proba) : 0; ss_cur[m].score = RDScoreTrellis(lambda, rate, 0); ss_cur[m].costs = costs[first][ctx0]; } } // traverse trellis. for (n = first; n <= last; ++n) { const int j = kZigzag[n]; const uint32_t Q = mtx->q_[j]; const uint32_t iQ = mtx->iq_[j]; const uint32_t B = BIAS(0x00); // neutral bias // note: it's important to take sign of the _original_ coeff, // so we don't have to consider level < 0 afterward. const int sign = (in[j] < 0); const uint32_t coeff0 = (sign ? -in[j] : in[j]) + mtx->sharpen_[j]; int level0 = QUANTDIV(coeff0, iQ, B); if (level0 > MAX_LEVEL) level0 = MAX_LEVEL; { // Swap current and previous score states ScoreState* const tmp = ss_cur; ss_cur = ss_prev; ss_prev = tmp; } // test all alternate level values around level0. for (m = -MIN_DELTA; m <= MAX_DELTA; ++m) { Node* const cur = &NODE(n, m); int level = level0 + m; const int ctx = (level > 2) ? 2 : level; const int band = VP8EncBands[n + 1]; score_t base_score, last_pos_score; score_t best_cur_score = MAX_COST; int best_prev = 0; // default, in case ss_cur[m].score = MAX_COST; ss_cur[m].costs = costs[n + 1][ctx]; if (level > MAX_LEVEL || level < 0) { // node is dead? continue; } // Compute extra rate cost if last coeff's position is < 15 { const score_t last_pos_cost = (n < 15) ? VP8BitCost(0, probas[band][ctx][0]) : 0; last_pos_score = RDScoreTrellis(lambda, last_pos_cost, 0); } { // Compute delta_error = how much coding this level will // subtract to max_error as distortion. // Here, distortion = sum of (|coeff_i| - level_i * Q_i)^2 const int new_error = coeff0 - level * Q; const int delta_error = kWeightTrellis[j] * (new_error * new_error - coeff0 * coeff0); base_score = RDScoreTrellis(lambda, 0, delta_error); } // Inspect all possible non-dead predecessors. Retain only the best one. for (p = -MIN_DELTA; p <= MAX_DELTA; ++p) { // Dead nodes (with ss_prev[p].score >= MAX_COST) are automatically // eliminated since their score can't be better than the current best. const score_t cost = VP8LevelCost(ss_prev[p].costs, level); // Examine node assuming it's a non-terminal one. const score_t score = base_score + ss_prev[p].score + RDScoreTrellis(lambda, cost, 0); if (score < best_cur_score) { best_cur_score = score; best_prev = p; } } // Store best finding in current node. cur->sign = sign; cur->level = level; cur->prev = best_prev; ss_cur[m].score = best_cur_score; // Now, record best terminal node (and thus best entry in the graph). if (level != 0) { const score_t score = best_cur_score + last_pos_score; if (score < best_score) { best_score = score; best_path[0] = n; // best eob position best_path[1] = m; // best node index best_path[2] = best_prev; // best predecessor } } } } // Fresh start memset(in + first, 0, (16 - first) * sizeof(*in)); memset(out + first, 0, (16 - first) * sizeof(*out)); if (best_path[0] == -1) { return 0; // skip! } { // Unwind the best path. // Note: best-prev on terminal node is not necessarily equal to the // best_prev for non-terminal. So we patch best_path[2] in. int nz = 0; int best_node = best_path[1]; n = best_path[0]; NODE(n, best_node).prev = best_path[2]; // force best-prev for terminal for (; n >= first; --n) { const Node* const node = &NODE(n, best_node); const int j = kZigzag[n]; out[n] = node->sign ? -node->level : node->level; nz |= node->level; in[j] = out[n] * mtx->q_[j]; best_node = node->prev; } return (nz != 0); } } #undef NODE //------------------------------------------------------------------------------ // Performs: difference, transform, quantize, back-transform, add // all at once. Output is the reconstructed block in *yuv_out, and the // quantized levels in *levels. static int ReconstructIntra16(VP8EncIterator* const it, VP8ModeScore* const rd, uint8_t* const yuv_out, int mode) { const VP8Encoder* const enc = it->enc_; const uint8_t* const ref = it->yuv_p_ + VP8I16ModeOffsets[mode]; const uint8_t* const src = it->yuv_in_ + Y_OFF_ENC; const VP8SegmentInfo* const dqm = &enc->dqm_[it->mb_->segment_]; int nz = 0; int n; int16_t tmp[16][16], dc_tmp[16]; for (n = 0; n < 16; n += 2) { VP8FTransform2(src + VP8Scan[n], ref + VP8Scan[n], tmp[n]); } VP8FTransformWHT(tmp[0], dc_tmp); nz |= VP8EncQuantizeBlockWHT(dc_tmp, rd->y_dc_levels, &dqm->y2_) << 24; if (DO_TRELLIS_I16 && it->do_trellis_) { int x, y; VP8IteratorNzToBytes(it); for (y = 0, n = 0; y < 4; ++y) { for (x = 0; x < 4; ++x, ++n) { const int ctx = it->top_nz_[x] + it->left_nz_[y]; const int non_zero = TrellisQuantizeBlock(enc, tmp[n], rd->y_ac_levels[n], ctx, 0, &dqm->y1_, dqm->lambda_trellis_i16_); it->top_nz_[x] = it->left_nz_[y] = non_zero; rd->y_ac_levels[n][0] = 0; nz |= non_zero << n; } } } else { for (n = 0; n < 16; n += 2) { // Zero-out the first coeff, so that: a) nz is correct below, and // b) finding 'last' non-zero coeffs in SetResidualCoeffs() is simplified. tmp[n][0] = tmp[n + 1][0] = 0; nz |= VP8EncQuantize2Blocks(tmp[n], rd->y_ac_levels[n], &dqm->y1_) << n; assert(rd->y_ac_levels[n + 0][0] == 0); assert(rd->y_ac_levels[n + 1][0] == 0); } } // Transform back VP8TransformWHT(dc_tmp, tmp[0]); for (n = 0; n < 16; n += 2) { VP8ITransform(ref + VP8Scan[n], tmp[n], yuv_out + VP8Scan[n], 1); } return nz; } static int ReconstructIntra4(VP8EncIterator* const it, int16_t levels[16], const uint8_t* const src, uint8_t* const yuv_out, int mode) { const VP8Encoder* const enc = it->enc_; const uint8_t* const ref = it->yuv_p_ + VP8I4ModeOffsets[mode]; const VP8SegmentInfo* const dqm = &enc->dqm_[it->mb_->segment_]; int nz = 0; int16_t tmp[16]; VP8FTransform(src, ref, tmp); if (DO_TRELLIS_I4 && it->do_trellis_) { const int x = it->i4_ & 3, y = it->i4_ >> 2; const int ctx = it->top_nz_[x] + it->left_nz_[y]; nz = TrellisQuantizeBlock(enc, tmp, levels, ctx, 3, &dqm->y1_, dqm->lambda_trellis_i4_); } else { nz = VP8EncQuantizeBlock(tmp, levels, &dqm->y1_); } VP8ITransform(ref, tmp, yuv_out, 0); return nz; } static int ReconstructUV(VP8EncIterator* const it, VP8ModeScore* const rd, uint8_t* const yuv_out, int mode) { const VP8Encoder* const enc = it->enc_; const uint8_t* const ref = it->yuv_p_ + VP8UVModeOffsets[mode]; const uint8_t* const src = it->yuv_in_ + U_OFF_ENC; const VP8SegmentInfo* const dqm = &enc->dqm_[it->mb_->segment_]; int nz = 0; int n; int16_t tmp[8][16]; for (n = 0; n < 8; n += 2) { VP8FTransform2(src + VP8ScanUV[n], ref + VP8ScanUV[n], tmp[n]); } if (DO_TRELLIS_UV && it->do_trellis_) { int ch, x, y; for (ch = 0, n = 0; ch <= 2; ch += 2) { for (y = 0; y < 2; ++y) { for (x = 0; x < 2; ++x, ++n) { const int ctx = it->top_nz_[4 + ch + x] + it->left_nz_[4 + ch + y]; const int non_zero = TrellisQuantizeBlock(enc, tmp[n], rd->uv_levels[n], ctx, 2, &dqm->uv_, dqm->lambda_trellis_uv_); it->top_nz_[4 + ch + x] = it->left_nz_[4 + ch + y] = non_zero; nz |= non_zero << n; } } } } else { for (n = 0; n < 8; n += 2) { nz |= VP8EncQuantize2Blocks(tmp[n], rd->uv_levels[n], &dqm->uv_) << n; } } for (n = 0; n < 8; n += 2) { VP8ITransform(ref + VP8ScanUV[n], tmp[n], yuv_out + VP8ScanUV[n], 1); } return (nz << 16); } //------------------------------------------------------------------------------ // RD-opt decision. Reconstruct each modes, evalue distortion and bit-cost. // Pick the mode is lower RD-cost = Rate + lambda * Distortion. static void StoreMaxDelta(VP8SegmentInfo* const dqm, const int16_t DCs[16]) { // We look at the first three AC coefficients to determine what is the average // delta between each sub-4x4 block. const int v0 = abs(DCs[1]); const int v1 = abs(DCs[4]); const int v2 = abs(DCs[5]); int max_v = (v0 > v1) ? v1 : v0; max_v = (v2 > max_v) ? v2 : max_v; if (max_v > dqm->max_edge_) dqm->max_edge_ = max_v; } static void SwapModeScore(VP8ModeScore** a, VP8ModeScore** b) { VP8ModeScore* const tmp = *a; *a = *b; *b = tmp; } static void SwapPtr(uint8_t** a, uint8_t** b) { uint8_t* const tmp = *a; *a = *b; *b = tmp; } static void SwapOut(VP8EncIterator* const it) { SwapPtr(&it->yuv_out_, &it->yuv_out2_); } static score_t IsFlat(const int16_t* levels, int num_blocks, score_t thresh) { score_t score = 0; while (num_blocks-- > 0) { // TODO(skal): refine positional scoring? int i; for (i = 1; i < 16; ++i) { // omit DC, we're only interested in AC score += (levels[i] != 0); if (score > thresh) return 0; } levels += 16; } return 1; } static void PickBestIntra16(VP8EncIterator* const it, VP8ModeScore* rd) { const int kNumBlocks = 16; VP8SegmentInfo* const dqm = &it->enc_->dqm_[it->mb_->segment_]; const int lambda = dqm->lambda_i16_; const int tlambda = dqm->tlambda_; const uint8_t* const src = it->yuv_in_ + Y_OFF_ENC; VP8ModeScore rd_tmp; VP8ModeScore* rd_cur = &rd_tmp; VP8ModeScore* rd_best = rd; int mode; rd->mode_i16 = -1; for (mode = 0; mode < NUM_PRED_MODES; ++mode) { uint8_t* const tmp_dst = it->yuv_out2_ + Y_OFF_ENC; // scratch buffer rd_cur->mode_i16 = mode; // Reconstruct rd_cur->nz = ReconstructIntra16(it, rd_cur, tmp_dst, mode); // Measure RD-score rd_cur->D = VP8SSE16x16(src, tmp_dst); rd_cur->SD = tlambda ? MULT_8B(tlambda, VP8TDisto16x16(src, tmp_dst, kWeightY)) : 0; rd_cur->H = VP8FixedCostsI16[mode]; rd_cur->R = VP8GetCostLuma16(it, rd_cur); if (mode > 0 && IsFlat(rd_cur->y_ac_levels[0], kNumBlocks, FLATNESS_LIMIT_I16)) { // penalty to avoid flat area to be mispredicted by complex mode rd_cur->R += FLATNESS_PENALTY * kNumBlocks; } // Since we always examine Intra16 first, we can overwrite *rd directly. SetRDScore(lambda, rd_cur); if (mode == 0 || rd_cur->score < rd_best->score) { SwapModeScore(&rd_cur, &rd_best); SwapOut(it); } } if (rd_best != rd) { memcpy(rd, rd_best, sizeof(*rd)); } SetRDScore(dqm->lambda_mode_, rd); // finalize score for mode decision. VP8SetIntra16Mode(it, rd->mode_i16); // we have a blocky macroblock (only DCs are non-zero) with fairly high // distortion, record max delta so we can later adjust the minimal filtering // strength needed to smooth these blocks out. if ((rd->nz & 0xffff) == 0 && rd->D > dqm->min_disto_) { StoreMaxDelta(dqm, rd->y_dc_levels); } } //------------------------------------------------------------------------------ // return the cost array corresponding to the surrounding prediction modes. static const uint16_t* GetCostModeI4(VP8EncIterator* const it, const uint8_t modes[16]) { const int preds_w = it->enc_->preds_w_; const int x = (it->i4_ & 3), y = it->i4_ >> 2; const int left = (x == 0) ? it->preds_[y * preds_w - 1] : modes[it->i4_ - 1]; const int top = (y == 0) ? it->preds_[-preds_w + x] : modes[it->i4_ - 4]; return VP8FixedCostsI4[top][left]; } static int PickBestIntra4(VP8EncIterator* const it, VP8ModeScore* const rd) { const VP8Encoder* const enc = it->enc_; const VP8SegmentInfo* const dqm = &enc->dqm_[it->mb_->segment_]; const int lambda = dqm->lambda_i4_; const int tlambda = dqm->tlambda_; const uint8_t* const src0 = it->yuv_in_ + Y_OFF_ENC; uint8_t* const best_blocks = it->yuv_out2_ + Y_OFF_ENC; int total_header_bits = 0; VP8ModeScore rd_best; if (enc->max_i4_header_bits_ == 0) { return 0; } InitScore(&rd_best); rd_best.H = 211; // '211' is the value of VP8BitCost(0, 145) SetRDScore(dqm->lambda_mode_, &rd_best); VP8IteratorStartI4(it); do { const int kNumBlocks = 1; VP8ModeScore rd_i4; int mode; int best_mode = -1; const uint8_t* const src = src0 + VP8Scan[it->i4_]; const uint16_t* const mode_costs = GetCostModeI4(it, rd->modes_i4); uint8_t* best_block = best_blocks + VP8Scan[it->i4_]; uint8_t* tmp_dst = it->yuv_p_ + I4TMP; // scratch buffer. InitScore(&rd_i4); VP8MakeIntra4Preds(it); for (mode = 0; mode < NUM_BMODES; ++mode) { VP8ModeScore rd_tmp; int16_t tmp_levels[16]; // Reconstruct rd_tmp.nz = ReconstructIntra4(it, tmp_levels, src, tmp_dst, mode) << it->i4_; // Compute RD-score rd_tmp.D = VP8SSE4x4(src, tmp_dst); rd_tmp.SD = tlambda ? MULT_8B(tlambda, VP8TDisto4x4(src, tmp_dst, kWeightY)) : 0; rd_tmp.H = mode_costs[mode]; // Add flatness penalty if (mode > 0 && IsFlat(tmp_levels, kNumBlocks, FLATNESS_LIMIT_I4)) { rd_tmp.R = FLATNESS_PENALTY * kNumBlocks; } else { rd_tmp.R = 0; } // early-out check SetRDScore(lambda, &rd_tmp); if (best_mode >= 0 && rd_tmp.score >= rd_i4.score) continue; // finish computing score rd_tmp.R += VP8GetCostLuma4(it, tmp_levels); SetRDScore(lambda, &rd_tmp); if (best_mode < 0 || rd_tmp.score < rd_i4.score) { CopyScore(&rd_i4, &rd_tmp); best_mode = mode; SwapPtr(&tmp_dst, &best_block); memcpy(rd_best.y_ac_levels[it->i4_], tmp_levels, sizeof(rd_best.y_ac_levels[it->i4_])); } } SetRDScore(dqm->lambda_mode_, &rd_i4); AddScore(&rd_best, &rd_i4); if (rd_best.score >= rd->score) { return 0; } total_header_bits += (int)rd_i4.H; // <- equal to mode_costs[best_mode]; if (total_header_bits > enc->max_i4_header_bits_) { return 0; } // Copy selected samples if not in the right place already. if (best_block != best_blocks + VP8Scan[it->i4_]) { VP8Copy4x4(best_block, best_blocks + VP8Scan[it->i4_]); } rd->modes_i4[it->i4_] = best_mode; it->top_nz_[it->i4_ & 3] = it->left_nz_[it->i4_ >> 2] = (rd_i4.nz ? 1 : 0); } while (VP8IteratorRotateI4(it, best_blocks)); // finalize state CopyScore(rd, &rd_best); VP8SetIntra4Mode(it, rd->modes_i4); SwapOut(it); memcpy(rd->y_ac_levels, rd_best.y_ac_levels, sizeof(rd->y_ac_levels)); return 1; // select intra4x4 over intra16x16 } //------------------------------------------------------------------------------ static void PickBestUV(VP8EncIterator* const it, VP8ModeScore* const rd) { const int kNumBlocks = 8; const VP8SegmentInfo* const dqm = &it->enc_->dqm_[it->mb_->segment_]; const int lambda = dqm->lambda_uv_; const uint8_t* const src = it->yuv_in_ + U_OFF_ENC; uint8_t* tmp_dst = it->yuv_out2_ + U_OFF_ENC; // scratch buffer uint8_t* dst0 = it->yuv_out_ + U_OFF_ENC; uint8_t* dst = dst0; VP8ModeScore rd_best; int mode; rd->mode_uv = -1; InitScore(&rd_best); for (mode = 0; mode < NUM_PRED_MODES; ++mode) { VP8ModeScore rd_uv; // Reconstruct rd_uv.nz = ReconstructUV(it, &rd_uv, tmp_dst, mode); // Compute RD-score rd_uv.D = VP8SSE16x8(src, tmp_dst); rd_uv.SD = 0; // TODO: should we call TDisto? it tends to flatten areas. rd_uv.H = VP8FixedCostsUV[mode]; rd_uv.R = VP8GetCostUV(it, &rd_uv); if (mode > 0 && IsFlat(rd_uv.uv_levels[0], kNumBlocks, FLATNESS_LIMIT_UV)) { rd_uv.R += FLATNESS_PENALTY * kNumBlocks; } SetRDScore(lambda, &rd_uv); if (mode == 0 || rd_uv.score < rd_best.score) { CopyScore(&rd_best, &rd_uv); rd->mode_uv = mode; memcpy(rd->uv_levels, rd_uv.uv_levels, sizeof(rd->uv_levels)); SwapPtr(&dst, &tmp_dst); } } VP8SetIntraUVMode(it, rd->mode_uv); AddScore(rd, &rd_best); if (dst != dst0) { // copy 16x8 block if needed VP8Copy16x8(dst, dst0); } } //------------------------------------------------------------------------------ // Final reconstruction and quantization. static void SimpleQuantize(VP8EncIterator* const it, VP8ModeScore* const rd) { const VP8Encoder* const enc = it->enc_; const int is_i16 = (it->mb_->type_ == 1); int nz = 0; if (is_i16) { nz = ReconstructIntra16(it, rd, it->yuv_out_ + Y_OFF_ENC, it->preds_[0]); } else { VP8IteratorStartI4(it); do { const int mode = it->preds_[(it->i4_ & 3) + (it->i4_ >> 2) * enc->preds_w_]; const uint8_t* const src = it->yuv_in_ + Y_OFF_ENC + VP8Scan[it->i4_]; uint8_t* const dst = it->yuv_out_ + Y_OFF_ENC + VP8Scan[it->i4_]; VP8MakeIntra4Preds(it); nz |= ReconstructIntra4(it, rd->y_ac_levels[it->i4_], src, dst, mode) << it->i4_; } while (VP8IteratorRotateI4(it, it->yuv_out_ + Y_OFF_ENC)); } nz |= ReconstructUV(it, rd, it->yuv_out_ + U_OFF_ENC, it->mb_->uv_mode_); rd->nz = nz; } // Refine intra16/intra4 sub-modes based on distortion only (not rate). static void DistoRefine(VP8EncIterator* const it, int try_both_i4_i16) { const int is_i16 = (it->mb_->type_ == 1); score_t best_score = MAX_COST; if (try_both_i4_i16 || is_i16) { int mode; int best_mode = -1; for (mode = 0; mode < NUM_PRED_MODES; ++mode) { const uint8_t* const ref = it->yuv_p_ + VP8I16ModeOffsets[mode]; const uint8_t* const src = it->yuv_in_ + Y_OFF_ENC; const score_t score = VP8SSE16x16(src, ref); if (score < best_score) { best_mode = mode; best_score = score; } } VP8SetIntra16Mode(it, best_mode); } if (try_both_i4_i16 || !is_i16) { uint8_t modes_i4[16]; // We don't evaluate the rate here, but just account for it through a // constant penalty (i4 mode usually needs more bits compared to i16). score_t score_i4 = (score_t)I4_PENALTY; VP8IteratorStartI4(it); do { int mode; int best_sub_mode = -1; score_t best_sub_score = MAX_COST; const uint8_t* const src = it->yuv_in_ + Y_OFF_ENC + VP8Scan[it->i4_]; // TODO(skal): we don't really need the prediction pixels here, // but just the distortion against 'src'. VP8MakeIntra4Preds(it); for (mode = 0; mode < NUM_BMODES; ++mode) { const uint8_t* const ref = it->yuv_p_ + VP8I4ModeOffsets[mode]; const score_t score = VP8SSE4x4(src, ref); if (score < best_sub_score) { best_sub_mode = mode; best_sub_score = score; } } modes_i4[it->i4_] = best_sub_mode; score_i4 += best_sub_score; if (score_i4 >= best_score) break; } while (VP8IteratorRotateI4(it, it->yuv_in_ + Y_OFF_ENC)); if (score_i4 < best_score) { VP8SetIntra4Mode(it, modes_i4); } } } //------------------------------------------------------------------------------ // Entry point int VP8Decimate(VP8EncIterator* const it, VP8ModeScore* const rd, VP8RDLevel rd_opt) { int is_skipped; const int method = it->enc_->method_; InitScore(rd); // We can perform predictions for Luma16x16 and Chroma8x8 already. // Luma4x4 predictions needs to be done as-we-go. VP8MakeLuma16Preds(it); VP8MakeChroma8Preds(it); if (rd_opt > RD_OPT_NONE) { it->do_trellis_ = (rd_opt >= RD_OPT_TRELLIS_ALL); PickBestIntra16(it, rd); if (method >= 2) { PickBestIntra4(it, rd); } PickBestUV(it, rd); if (rd_opt == RD_OPT_TRELLIS) { // finish off with trellis-optim now it->do_trellis_ = 1; SimpleQuantize(it, rd); } } else { // For method == 2, pick the best intra4/intra16 based on SSE (~tad slower). // For method <= 1, we refine intra4 or intra16 (but don't re-examine mode). DistoRefine(it, (method >= 2)); SimpleQuantize(it, rd); } is_skipped = (rd->nz == 0); VP8SetSkip(it, is_skipped); return is_skipped; }