// 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 <assert.h>

#include <math.h>

#include <stdlib.h> // for abs()

#include "src/dsp/quant.h"

#include "src/enc/vp8i_enc.h"

#include "src/enc/cost_enc.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.

// number of non-zero coeffs below which we consider the block very flat

// (and apply a penalty to complex predictions)

#define FLATNESS_LIMIT_I16 0 // I16 mode (special case)

#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 RD_DISTO_MULT 256 // distortion multiplier (equivalent of lambda)

// #define DEBUG_BLOCK

//------------------------------------------------------------------------------

#if defined(DEBUG_BLOCK)

#include <stdio.h>

#include <stdlib.h>

static void PrintBlockInfo(const VP8EncIterator* const it,

const VP8ModeScore* const rd) {

int i, j;

const int is_i16 = (it->mb_->type_ == 1);

const uint8_t* const y_in = it->yuv_in_ + Y_OFF_ENC;

const uint8_t* const y_out = it->yuv_out_ + Y_OFF_ENC;

const uint8_t* const uv_in = it->yuv_in_ + U_OFF_ENC;

const uint8_t* const uv_out = it->yuv_out_ + U_OFF_ENC;

printf("SOURCE / OUTPUT / ABS DELTA\n");

for (j = 0; j < 16; ++j) {

for (i = 0; i < 16; ++i) printf("%3d ", y_in[i + j * BPS]);

printf(" ");

for (i = 0; i < 16; ++i) printf("%3d ", y_out[i + j * BPS]);

printf(" ");

for (i = 0; i < 16; ++i) {

printf("%1d ", abs(y_in[i + j * BPS] - y_out[i + j * BPS]));

}

printf("\n");

}

printf("\n"); // newline before the U/V block

for (j = 0; j < 8; ++j) {

for (i = 0; i < 8; ++i) printf("%3d ", uv_in[i + j * BPS]);

printf(" ");

for (i = 8; i < 16; ++i) printf("%3d ", uv_in[i + j * BPS]);

printf(" ");

for (i = 0; i < 8; ++i) printf("%3d ", uv_out[i + j * BPS]);

printf(" ");

for (i = 8; i < 16; ++i) printf("%3d ", uv_out[i + j * BPS]);

printf(" ");

for (i = 0; i < 8; ++i) {

printf("%1d ", abs(uv_out[i + j * BPS] - uv_in[i + j * BPS]));

}

printf(" ");

for (i = 8; i < 16; ++i) {

printf("%1d ", abs(uv_out[i + j * BPS] - uv_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 CheckLambdaValue(int* const v) { if (*v < 1) *v = 1; }

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 q_i4, q_i16, q_uv;

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)];

q_i4 = ExpandMatrix(&m->y1_, 0);

q_i16 = ExpandMatrix(&m->y2_, 1);

q_uv = ExpandMatrix(&m->uv_, 2);

m->lambda_i4_ = (3 * q_i4 * q_i4) >> 7;

m->lambda_i16_ = (3 * q_i16 * q_i16);

m->lambda_uv_ = (3 * q_uv * q_uv) >> 6;

m->lambda_mode_ = (1 * q_i4 * q_i4) >> 7;

m->lambda_trellis_i4_ = (7 * q_i4 * q_i4) >> 3;

m->lambda_trellis_i16_ = (q_i16 * q_i16) >> 2;

m->lambda_trellis_uv_ = (q_uv * q_uv) << 1;

m->tlambda_ = (tlambda_scale * q_i4) >> 5;

// none of these constants should be < 1

CheckLambdaValue(&m->lambda_i4_);

CheckLambdaValue(&m->lambda_i16_);

CheckLambdaValue(&m->lambda_uv_);

CheckLambdaValue(&m->lambda_mode_);

CheckLambdaValue(&m->lambda_trellis_i4_);

CheckLambdaValue(&m->lambda_trellis_i16_);

CheckLambdaValue(&m->lambda_trellis_uv_);

CheckLambdaValue(&m->tlambda_);

m->min_disto_ = 20 * m->y1_.q_[0]; // quantization-aware min disto

m->max_edge_ = 0;

m->i4_penalty_ = 1000 * q_i4 * q_i4;

}

}

//------------------------------------------------------------------------------

// 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 };

// 'num_segments_' is previously validated and <= NUM_MB_SEGMENTS, but an

// explicit check is needed to avoid a spurious warning about 'i' exceeding

// array bounds of 'dqm_' with some compilers (noticed with gcc-4.9).

const int num_segments = (enc->segment_hdr_.num_segments_ < NUM_MB_SEGMENTS)

? enc->segment_hdr_.num_segments_

: NUM_MB_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 uint16_t VP8I16ModeOffsets[4] = { I16DC16, I16TM16, I16VE16, I16HE16 };

const uint16_t VP8UVModeOffsets[4] = { C8DC8, C8TM8, C8VE8, C8HE8 };

// Must be indexed using {B_DC_PRED -> B_HU_PRED} as index

const uint16_t 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 uint16_t 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 uint16_t 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) {

rd->score = (rd->R + rd->H) * lambda + RD_DISTO_MULT * (rd->D + rd->SD);

}

static WEBP_INLINE score_t RDScoreTrellis(int lambda, score_t rate,

score_t distortion) {

return rate * lambda + RD_DISTO_MULT * 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);

int thresh_level = QUANTDIV(coeff0, iQ, BIAS(0x80));

if (thresh_level > MAX_LEVEL) thresh_level = MAX_LEVEL;

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;

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 < 0 || level > thresh_level) {

// Node is dead.

continue;

}

{

// 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 last_pos_cost =

(n < 15) ? VP8BitCost(0, probas[band][ctx][0]) : 0;

const score_t last_pos_score = RDScoreTrellis(lambda, last_pos_cost, 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;

}

//------------------------------------------------------------------------------

// DC-error diffusion

// Diffusion weights. We under-correct a bit (15/16th of the error is actually

// diffused) to avoid 'rainbow' chessboard pattern of blocks at q~=0.

#define C1 7 // fraction of error sent to the 4x4 block below

#define C2 8 // fraction of error sent to the 4x4 block on the right

#define DSHIFT 4

#define DSCALE 1 // storage descaling, needed to make the error fit int8_t

// Quantize as usual, but also compute and return the quantization error.

// Error is already divided by DSHIFT.

static int QuantizeSingle(int16_t* const v, const VP8Matrix* const mtx) {

int V = *v;

const int sign = (V < 0);

if (sign) V = -V;

if (V > (int)mtx->zthresh_[0]) {

const int qV = QUANTDIV(V, mtx->iq_[0], mtx->bias_[0]) * mtx->q_[0];

const int err = (V - qV);

*v = sign ? -qV : qV;

return (sign ? -err : err) >> DSCALE;

}

*v = 0;

return (sign ? -V : V) >> DSCALE;

}

static void CorrectDCValues(const VP8EncIterator* const it,

const VP8Matrix* const mtx,

int16_t tmp[][16], VP8ModeScore* const rd) {

// | top[0] | top[1]

// --------+--------+---------

// left[0] | tmp[0] tmp[1] <-> err0 err1

// left[1] | tmp[2] tmp[3] err2 err3

//

// Final errors {err1,err2,err3} are preserved and later restored

// as top[]/left[] on the next block.

int ch;

for (ch = 0; ch <= 1; ++ch) {

const int8_t* const top = it->top_derr_[it->x_][ch];

const int8_t* const left = it->left_derr_[ch];

int16_t (* const c)[16] = &tmp[ch * 4];

int err0, err1, err2, err3;

c[0][0] += (C1 * top[0] + C2 * left[0]) >> (DSHIFT - DSCALE);

err0 = QuantizeSingle(&c[0][0], mtx);

c[1][0] += (C1 * top[1] + C2 * err0) >> (DSHIFT - DSCALE);

err1 = QuantizeSingle(&c[1][0], mtx);

c[2][0] += (C1 * err0 + C2 * left[1]) >> (DSHIFT - DSCALE);

err2 = QuantizeSingle(&c[2][0], mtx);

c[3][0] += (C1 * err1 + C2 * err2) >> (DSHIFT - DSCALE);

err3 = QuantizeSingle(&c[3][0], mtx);

// error 'err' is bounded by mtx->q_[0] which is 132 at max. Hence

// err >> DSCALE will fit in an int8_t type if DSCALE>=1.

assert(abs(err1) <= 127 && abs(err2) <= 127 && abs(err3) <= 127);

rd->derr[ch][0] = (int8_t)err1;

rd->derr[ch][1] = (int8_t)err2;

rd->derr[ch][2] = (int8_t)err3;

}

}

static void StoreDiffusionErrors(VP8EncIterator* const it,

const VP8ModeScore* const rd) {

int ch;

for (ch = 0; ch <= 1; ++ch) {

int8_t* const top = it->top_derr_[it->x_][ch];

int8_t* const left = it->left_derr_[ch];

left[0] = rd->derr[ch][0]; // restore err1

left[1] = 3 * rd->derr[ch][2] >> 2; // ... 3/4th of err3

top[0] = rd->derr[ch][1]; // ... err2

top[1] = rd->derr[ch][2] - left[1]; // ... 1/4th of err3.

}

}

#undef C1

#undef C2

#undef DSHIFT

#undef DSCALE

//------------------------------------------------------------------------------

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 (it->top_derr_ != NULL) CorrectDCValues(it, &dqm->uv_, tmp, rd);

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[2]);

const int v2 = abs(DCs[4]);

int max_v = (v1 > v0) ? 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 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;

int is_flat = IsFlatSource16(it->yuv_in_ + Y_OFF_ENC);

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);