third_party/libwebp/enc/frame.c

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This source file includes following definitions.
InitPassStats
Clamp
ComputeNextQ
ResetStats
CalcSkipProba
FinalizeSkipProba
ResetTokenStats
Record
RecordCoeffs
CalcTokenProba
BranchCost
FinalizeTokenProbas
GetProba
SetSegmentProbas
InitResidual
SetResidualCoeffs
GetResidualCost
VP8GetCostLuma4
VP8GetCostLuma16
VP8GetCostUV
PutCoeffs
CodeResiduals
RecordResiduals
RecordTokens
SetBlock
ResetSSE
StoreSSE
StoreSideInfo
GetPSNR
SetLoopParams
OneStatPass
StatLoop
PreLoopInitialize
PostLoopFinalize
ResetAfterSkip
VP8EncLoop
VP8EncTokenLoop
VP8EncTokenLoop
// 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.
// -----------------------------------------------------------------------------
//
//   frame coding and analysis
//
// Author: Skal (pascal.massimino@gmail.com)

#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>

#include "./vp8enci.h"
#include "./cost.h"
#include "../webp/format_constants.h"  // RIFF constants

#define SEGMENT_VISU 0
#define DEBUG_SEARCH 0    // useful to track search convergence

// On-the-fly info about the current set of residuals. Handy to avoid
// passing zillions of params.
typedef struct {
  int first;
  int last;
  const int16_t* coeffs;

  int coeff_type;
  ProbaArray* prob;
  StatsArray* stats;
  CostArray*  cost;
} VP8Residual;

//------------------------------------------------------------------------------
// multi-pass convergence

#define HEADER_SIZE_ESTIMATE (RIFF_HEADER_SIZE + CHUNK_HEADER_SIZE +  \
                              VP8_FRAME_HEADER_SIZE)
#define DQ_LIMIT 0.4  // convergence is considered reached if dq < DQ_LIMIT
// we allow 2k of extra head-room in PARTITION0 limit.
#define PARTITION0_SIZE_LIMIT ((VP8_MAX_PARTITION0_SIZE - 2048ULL) << 11)

typedef struct {  // struct for organizing convergence in either size or PSNR
  int is_first;
  float dq;
  float q, last_q;
  double value, last_value;   // PSNR or size
  double target;
  int do_size_search;
} PassStats;

static int InitPassStats(const VP8Encoder* const enc, PassStats* const s) {
  const uint64_t target_size = (uint64_t)enc->config_->target_size;
  const int do_size_search = (target_size != 0);
  const float target_PSNR = enc->config_->target_PSNR;

  s->is_first = 1;
  s->dq = 10.f;
  s->q = s->last_q = enc->config_->quality;
  s->target = do_size_search ? (double)target_size
            : (target_PSNR > 0.) ? target_PSNR
            : 40.;   // default, just in case
  s->value = s->last_value = 0.;
  s->do_size_search = do_size_search;
  return do_size_search;
}

static float Clamp(float v, float min, float max) {
  return (v < min) ? min : (v > max) ? max : v;
}

static float ComputeNextQ(PassStats* const s) {
  float dq;
  if (s->is_first) {
    dq = (s->value > s->target) ? -s->dq : s->dq;
    s->is_first = 0;
  } else if (s->value != s->last_value) {
    const double slope = (s->target - s->value) / (s->last_value - s->value);
    dq = (float)(slope * (s->last_q - s->q));
  } else {
    dq = 0.;  // we're done?!
  }
  // Limit variable to avoid large swings.
  s->dq = Clamp(dq, -30.f, 30.f);
  s->last_q = s->q;
  s->last_value = s->value;
  s->q = Clamp(s->q + s->dq, 0.f, 100.f);
  return s->q;
}

//------------------------------------------------------------------------------
// Tables for level coding

const uint8_t VP8EncBands[16 + 1] = {
  0, 1, 2, 3, 6, 4, 5, 6, 6, 6, 6, 6, 6, 6, 6, 7,
  0  // sentinel
};

const uint8_t VP8Cat3[] = { 173, 148, 140 };
const uint8_t VP8Cat4[] = { 176, 155, 140, 135 };
const uint8_t VP8Cat5[] = { 180, 157, 141, 134, 130 };
const uint8_t VP8Cat6[] =
    { 254, 254, 243, 230, 196, 177, 153, 140, 133, 130, 129 };

//------------------------------------------------------------------------------
// Reset the statistics about: number of skips, token proba, level cost,...

static void ResetStats(VP8Encoder* const enc) {
  VP8Proba* const proba = &enc->proba_;
  VP8CalculateLevelCosts(proba);
  proba->nb_skip_ = 0;
}

//------------------------------------------------------------------------------
// Skip decision probability

#define SKIP_PROBA_THRESHOLD 250  // value below which using skip_proba is OK.

static int CalcSkipProba(uint64_t nb, uint64_t total) {
  return (int)(total ? (total - nb) * 255 / total : 255);
}

// Returns the bit-cost for coding the skip probability.
static int FinalizeSkipProba(VP8Encoder* const enc) {
  VP8Proba* const proba = &enc->proba_;
  const int nb_mbs = enc->mb_w_ * enc->mb_h_;
  const int nb_events = proba->nb_skip_;
  int size;
  proba->skip_proba_ = CalcSkipProba(nb_events, nb_mbs);
  proba->use_skip_proba_ = (proba->skip_proba_ < SKIP_PROBA_THRESHOLD);
  size = 256;   // 'use_skip_proba' bit
  if (proba->use_skip_proba_) {
    size +=  nb_events * VP8BitCost(1, proba->skip_proba_)
         + (nb_mbs - nb_events) * VP8BitCost(0, proba->skip_proba_);
    size += 8 * 256;   // cost of signaling the skip_proba_ itself.
  }
  return size;
}

//------------------------------------------------------------------------------
// Recording of token probabilities.

static void ResetTokenStats(VP8Encoder* const enc) {
  VP8Proba* const proba = &enc->proba_;
  memset(proba->stats_, 0, sizeof(proba->stats_));
}

// Record proba context used
static int Record(int bit, proba_t* const stats) {
  proba_t p = *stats;
  if (p >= 0xffff0000u) {               // an overflow is inbound.
    p = ((p + 1u) >> 1) & 0x7fff7fffu;  // -> divide the stats by 2.
  }
  // record bit count (lower 16 bits) and increment total count (upper 16 bits).
  p += 0x00010000u + bit;
  *stats = p;
  return bit;
}

// We keep the table free variant around for reference, in case.
#define USE_LEVEL_CODE_TABLE

// Simulate block coding, but only record statistics.
// Note: no need to record the fixed probas.
static int RecordCoeffs(int ctx, const VP8Residual* const res) {
  int n = res->first;
  // should be stats[VP8EncBands[n]], but it's equivalent for n=0 or 1
  proba_t* s = res->stats[n][ctx];
  if (res->last  < 0) {
    Record(0, s + 0);
    return 0;
  }
  while (n <= res->last) {
    int v;
    Record(1, s + 0);  // order of record doesn't matter
    while ((v = res->coeffs[n++]) == 0) {
      Record(0, s + 1);
      s = res->stats[VP8EncBands[n]][0];
    }
    Record(1, s + 1);
    if (!Record(2u < (unsigned int)(v + 1), s + 2)) {  // v = -1 or 1
      s = res->stats[VP8EncBands[n]][1];
    } else {
      v = abs(v);
#if !defined(USE_LEVEL_CODE_TABLE)
      if (!Record(v > 4, s + 3)) {
        if (Record(v != 2, s + 4))
          Record(v == 4, s + 5);
      } else if (!Record(v > 10, s + 6)) {
        Record(v > 6, s + 7);
      } else if (!Record((v >= 3 + (8 << 2)), s + 8)) {
        Record((v >= 3 + (8 << 1)), s + 9);
      } else {
        Record((v >= 3 + (8 << 3)), s + 10);
      }
#else
      if (v > MAX_VARIABLE_LEVEL)
        v = MAX_VARIABLE_LEVEL;

      {
        const int bits = VP8LevelCodes[v - 1][1];
        int pattern = VP8LevelCodes[v - 1][0];
        int i;
        for (i = 0; (pattern >>= 1) != 0; ++i) {
          const int mask = 2 << i;
          if (pattern & 1) Record(!!(bits & mask), s + 3 + i);
        }
      }
#endif
      s = res->stats[VP8EncBands[n]][2];
    }
  }
  if (n < 16) Record(0, s + 0);
  return 1;
}

// Collect statistics and deduce probabilities for next coding pass.
// Return the total bit-cost for coding the probability updates.
static int CalcTokenProba(int nb, int total) {
  assert(nb <= total);
  return nb ? (255 - nb * 255 / total) : 255;
}

// Cost of coding 'nb' 1's and 'total-nb' 0's using 'proba' probability.
static int BranchCost(int nb, int total, int proba) {
  return nb * VP8BitCost(1, proba) + (total - nb) * VP8BitCost(0, proba);
}

static int FinalizeTokenProbas(VP8Proba* const proba) {
  int has_changed = 0;
  int size = 0;
  int t, b, c, p;
  for (t = 0; t < NUM_TYPES; ++t) {
    for (b = 0; b < NUM_BANDS; ++b) {
      for (c = 0; c < NUM_CTX; ++c) {
        for (p = 0; p < NUM_PROBAS; ++p) {
          const proba_t stats = proba->stats_[t][b][c][p];
          const int nb = (stats >> 0) & 0xffff;
          const int total = (stats >> 16) & 0xffff;
          const int update_proba = VP8CoeffsUpdateProba[t][b][c][p];
          const int old_p = VP8CoeffsProba0[t][b][c][p];
          const int new_p = CalcTokenProba(nb, total);
          const int old_cost = BranchCost(nb, total, old_p)
                             + VP8BitCost(0, update_proba);
          const int new_cost = BranchCost(nb, total, new_p)
                             + VP8BitCost(1, update_proba)
                             + 8 * 256;
          const int use_new_p = (old_cost > new_cost);
          size += VP8BitCost(use_new_p, update_proba);
          if (use_new_p) {  // only use proba that seem meaningful enough.
            proba->coeffs_[t][b][c][p] = new_p;
            has_changed |= (new_p != old_p);
            size += 8 * 256;
          } else {
            proba->coeffs_[t][b][c][p] = old_p;
          }
        }
      }
    }
  }
  proba->dirty_ = has_changed;
  return size;
}

//------------------------------------------------------------------------------
// Finalize Segment probability based on the coding tree

static int GetProba(int a, int b) {
  const int total = a + b;
  return (total == 0) ? 255     // that's the default probability.
                      : (255 * a + total / 2) / total;  // rounded proba
}

static void SetSegmentProbas(VP8Encoder* const enc) {
  int p[NUM_MB_SEGMENTS] = { 0 };
  int n;

  for (n = 0; n < enc->mb_w_ * enc->mb_h_; ++n) {
    const VP8MBInfo* const mb = &enc->mb_info_[n];
    p[mb->segment_]++;
  }
  if (enc->pic_->stats != NULL) {
    for (n = 0; n < NUM_MB_SEGMENTS; ++n) {
      enc->pic_->stats->segment_size[n] = p[n];
    }
  }
  if (enc->segment_hdr_.num_segments_ > 1) {
    uint8_t* const probas = enc->proba_.segments_;
    probas[0] = GetProba(p[0] + p[1], p[2] + p[3]);
    probas[1] = GetProba(p[0], p[1]);
    probas[2] = GetProba(p[2], p[3]);

    enc->segment_hdr_.update_map_ =
        (probas[0] != 255) || (probas[1] != 255) || (probas[2] != 255);
    enc->segment_hdr_.size_ =
        p[0] * (VP8BitCost(0, probas[0]) + VP8BitCost(0, probas[1])) +
        p[1] * (VP8BitCost(0, probas[0]) + VP8BitCost(1, probas[1])) +
        p[2] * (VP8BitCost(1, probas[0]) + VP8BitCost(0, probas[2])) +
        p[3] * (VP8BitCost(1, probas[0]) + VP8BitCost(1, probas[2]));
  } else {
    enc->segment_hdr_.update_map_ = 0;
    enc->segment_hdr_.size_ = 0;
  }
}

//------------------------------------------------------------------------------
// helper functions for residuals struct VP8Residual.

static void InitResidual(int first, int coeff_type,
                         VP8Encoder* const enc, VP8Residual* const res) {
  res->coeff_type = coeff_type;
  res->prob  = enc->proba_.coeffs_[coeff_type];
  res->stats = enc->proba_.stats_[coeff_type];
  res->cost  = enc->proba_.level_cost_[coeff_type];
  res->first = first;
}

static void SetResidualCoeffs(const int16_t* const coeffs,
                              VP8Residual* const res) {
  int n;
  res->last = -1;
  for (n = 15; n >= res->first; --n) {
    if (coeffs[n]) {
      res->last = n;
      break;
    }
  }
  res->coeffs = coeffs;
}

//------------------------------------------------------------------------------
// Mode costs

static int GetResidualCost(int ctx0, const VP8Residual* const res) {
  int n = res->first;
  // should be prob[VP8EncBands[n]], but it's equivalent for n=0 or 1
  int p0 = res->prob[n][ctx0][0];
  const uint16_t* t = res->cost[n][ctx0];
  int cost;

  if (res->last < 0) {
    return VP8BitCost(0, p0);
  }
  cost = VP8BitCost(1, p0);
  for (; n < res->last; ++n) {
    const int v = abs(res->coeffs[n]);
    const int b = VP8EncBands[n + 1];
    const int ctx = (v >= 2) ? 2 : v;
    cost += VP8LevelCost(t, v);
    t = res->cost[b][ctx];
    // the masking trick is faster than "if (v) cost += ..." with clang
    cost += (v ? ~0U : 0) & VP8BitCost(1, res->prob[b][ctx][0]);
  }
  // Last coefficient is always non-zero
  {
    const int v = abs(res->coeffs[n]);
    assert(v != 0);
    cost += VP8LevelCost(t, v);
    if (n < 15) {
      const int b = VP8EncBands[n + 1];
      const int ctx = (v == 1) ? 1 : 2;
      const int last_p0 = res->prob[b][ctx][0];
      cost += VP8BitCost(0, last_p0);
    }
  }
  return cost;
}

int VP8GetCostLuma4(VP8EncIterator* const it, const int16_t levels[16]) {
  const int x = (it->i4_ & 3), y = (it->i4_ >> 2);
  VP8Residual res;
  VP8Encoder* const enc = it->enc_;
  int R = 0;
  int ctx;

  InitResidual(0, 3, enc, &res);
  ctx = it->top_nz_[x] + it->left_nz_[y];
  SetResidualCoeffs(levels, &res);
  R += GetResidualCost(ctx, &res);
  return R;
}

int VP8GetCostLuma16(VP8EncIterator* const it, const VP8ModeScore* const rd) {
  VP8Residual res;
  VP8Encoder* const enc = it->enc_;
  int x, y;
  int R = 0;

  VP8IteratorNzToBytes(it);   // re-import the non-zero context

  // DC
  InitResidual(0, 1, enc, &res);
  SetResidualCoeffs(rd->y_dc_levels, &res);
  R += GetResidualCost(it->top_nz_[8] + it->left_nz_[8], &res);

  // AC
  InitResidual(1, 0, enc, &res);
  for (y = 0; y < 4; ++y) {
    for (x = 0; x < 4; ++x) {
      const int ctx = it->top_nz_[x] + it->left_nz_[y];
      SetResidualCoeffs(rd->y_ac_levels[x + y * 4], &res);
      R += GetResidualCost(ctx, &res);
      it->top_nz_[x] = it->left_nz_[y] = (res.last >= 0);
    }
  }
  return R;
}

int VP8GetCostUV(VP8EncIterator* const it, const VP8ModeScore* const rd) {
  VP8Residual res;
  VP8Encoder* const enc = it->enc_;
  int ch, x, y;
  int R = 0;

  VP8IteratorNzToBytes(it);  // re-import the non-zero context

  InitResidual(0, 2, enc, &res);
  for (ch = 0; ch <= 2; ch += 2) {
    for (y = 0; y < 2; ++y) {
      for (x = 0; x < 2; ++x) {
        const int ctx = it->top_nz_[4 + ch + x] + it->left_nz_[4 + ch + y];
        SetResidualCoeffs(rd->uv_levels[ch * 2 + x + y * 2], &res);
        R += GetResidualCost(ctx, &res);
        it->top_nz_[4 + ch + x] = it->left_nz_[4 + ch + y] = (res.last >= 0);
      }
    }
  }
  return R;
}

//------------------------------------------------------------------------------
// Coefficient coding

static int PutCoeffs(VP8BitWriter* const bw, int ctx, const VP8Residual* res) {
  int n = res->first;
  // should be prob[VP8EncBands[n]], but it's equivalent for n=0 or 1
  const uint8_t* p = res->prob[n][ctx];
  if (!VP8PutBit(bw, res->last >= 0, p[0])) {
    return 0;
  }

  while (n < 16) {
    const int c = res->coeffs[n++];
    const int sign = c < 0;
    int v = sign ? -c : c;
    if (!VP8PutBit(bw, v != 0, p[1])) {
      p = res->prob[VP8EncBands[n]][0];
      continue;
    }
    if (!VP8PutBit(bw, v > 1, p[2])) {
      p = res->prob[VP8EncBands[n]][1];
    } else {
      if (!VP8PutBit(bw, v > 4, p[3])) {
        if (VP8PutBit(bw, v != 2, p[4]))
          VP8PutBit(bw, v == 4, p[5]);
      } else if (!VP8PutBit(bw, v > 10, p[6])) {
        if (!VP8PutBit(bw, v > 6, p[7])) {
          VP8PutBit(bw, v == 6, 159);
        } else {
          VP8PutBit(bw, v >= 9, 165);
          VP8PutBit(bw, !(v & 1), 145);
        }
      } else {
        int mask;
        const uint8_t* tab;
        if (v < 3 + (8 << 1)) {          // VP8Cat3  (3b)
          VP8PutBit(bw, 0, p[8]);
          VP8PutBit(bw, 0, p[9]);
          v -= 3 + (8 << 0);
          mask = 1 << 2;
          tab = VP8Cat3;
        } else if (v < 3 + (8 << 2)) {   // VP8Cat4  (4b)
          VP8PutBit(bw, 0, p[8]);
          VP8PutBit(bw, 1, p[9]);
          v -= 3 + (8 << 1);
          mask = 1 << 3;
          tab = VP8Cat4;
        } else if (v < 3 + (8 << 3)) {   // VP8Cat5  (5b)
          VP8PutBit(bw, 1, p[8]);
          VP8PutBit(bw, 0, p[10]);
          v -= 3 + (8 << 2);
          mask = 1 << 4;
          tab = VP8Cat5;
        } else {                         // VP8Cat6 (11b)
          VP8PutBit(bw, 1, p[8]);
          VP8PutBit(bw, 1, p[10]);
          v -= 3 + (8 << 3);
          mask = 1 << 10;
          tab = VP8Cat6;
        }
        while (mask) {
          VP8PutBit(bw, !!(v & mask), *tab++);
          mask >>= 1;
        }
      }
      p = res->prob[VP8EncBands[n]][2];
    }
    VP8PutBitUniform(bw, sign);
    if (n == 16 || !VP8PutBit(bw, n <= res->last, p[0])) {
      return 1;   // EOB
    }
  }
  return 1;
}

static void CodeResiduals(VP8BitWriter* const bw, VP8EncIterator* const it,
                          const VP8ModeScore* const rd) {
  int x, y, ch;
  VP8Residual res;
  uint64_t pos1, pos2, pos3;
  const int i16 = (it->mb_->type_ == 1);
  const int segment = it->mb_->segment_;
  VP8Encoder* const enc = it->enc_;

  VP8IteratorNzToBytes(it);

  pos1 = VP8BitWriterPos(bw);
  if (i16) {
    InitResidual(0, 1, enc, &res);
    SetResidualCoeffs(rd->y_dc_levels, &res);
    it->top_nz_[8] = it->left_nz_[8] =
      PutCoeffs(bw, it->top_nz_[8] + it->left_nz_[8], &res);
    InitResidual(1, 0, enc, &res);
  } else {
    InitResidual(0, 3, enc, &res);
  }

  // luma-AC
  for (y = 0; y < 4; ++y) {
    for (x = 0; x < 4; ++x) {
      const int ctx = it->top_nz_[x] + it->left_nz_[y];
      SetResidualCoeffs(rd->y_ac_levels[x + y * 4], &res);
      it->top_nz_[x] = it->left_nz_[y] = PutCoeffs(bw, ctx, &res);
    }
  }
  pos2 = VP8BitWriterPos(bw);

  // U/V
  InitResidual(0, 2, enc, &res);
  for (ch = 0; ch <= 2; ch += 2) {
    for (y = 0; y < 2; ++y) {
      for (x = 0; x < 2; ++x) {
        const int ctx = it->top_nz_[4 + ch + x] + it->left_nz_[4 + ch + y];
        SetResidualCoeffs(rd->uv_levels[ch * 2 + x + y * 2], &res);
        it->top_nz_[4 + ch + x] = it->left_nz_[4 + ch + y] =
            PutCoeffs(bw, ctx, &res);
      }
    }
  }
  pos3 = VP8BitWriterPos(bw);
  it->luma_bits_ = pos2 - pos1;
  it->uv_bits_ = pos3 - pos2;
  it->bit_count_[segment][i16] += it->luma_bits_;
  it->bit_count_[segment][2] += it->uv_bits_;
  VP8IteratorBytesToNz(it);
}

// Same as CodeResiduals, but doesn't actually write anything.
// Instead, it just records the event distribution.
static void RecordResiduals(VP8EncIterator* const it,
                            const VP8ModeScore* const rd) {
  int x, y, ch;
  VP8Residual res;
  VP8Encoder* const enc = it->enc_;

  VP8IteratorNzToBytes(it);

  if (it->mb_->type_ == 1) {   // i16x16
    InitResidual(0, 1, enc, &res);
    SetResidualCoeffs(rd->y_dc_levels, &res);
    it->top_nz_[8] = it->left_nz_[8] =
      RecordCoeffs(it->top_nz_[8] + it->left_nz_[8], &res);
    InitResidual(1, 0, enc, &res);
  } else {
    InitResidual(0, 3, enc, &res);
  }

  // luma-AC
  for (y = 0; y < 4; ++y) {
    for (x = 0; x < 4; ++x) {
      const int ctx = it->top_nz_[x] + it->left_nz_[y];
      SetResidualCoeffs(rd->y_ac_levels[x + y * 4], &res);
      it->top_nz_[x] = it->left_nz_[y] = RecordCoeffs(ctx, &res);
    }
  }

  // U/V
  InitResidual(0, 2, enc, &res);
  for (ch = 0; ch <= 2; ch += 2) {
    for (y = 0; y < 2; ++y) {
      for (x = 0; x < 2; ++x) {
        const int ctx = it->top_nz_[4 + ch + x] + it->left_nz_[4 + ch + y];
        SetResidualCoeffs(rd->uv_levels[ch * 2 + x + y * 2], &res);
        it->top_nz_[4 + ch + x] = it->left_nz_[4 + ch + y] =
            RecordCoeffs(ctx, &res);
      }
    }
  }

  VP8IteratorBytesToNz(it);
}

//------------------------------------------------------------------------------
// Token buffer

#if !defined(DISABLE_TOKEN_BUFFER)

static void RecordTokens(VP8EncIterator* const it, const VP8ModeScore* const rd,
                         VP8TBuffer* const tokens) {
  int x, y, ch;
  VP8Residual res;
  VP8Encoder* const enc = it->enc_;

  VP8IteratorNzToBytes(it);
  if (it->mb_->type_ == 1) {   // i16x16
    const int ctx = it->top_nz_[8] + it->left_nz_[8];
    InitResidual(0, 1, enc, &res);
    SetResidualCoeffs(rd->y_dc_levels, &res);
    it->top_nz_[8] = it->left_nz_[8] =
        VP8RecordCoeffTokens(ctx, 1,
                             res.first, res.last, res.coeffs, tokens);
    RecordCoeffs(ctx, &res);
    InitResidual(1, 0, enc, &res);
  } else {
    InitResidual(0, 3, enc, &res);
  }

  // luma-AC
  for (y = 0; y < 4; ++y) {
    for (x = 0; x < 4; ++x) {
      const int ctx = it->top_nz_[x] + it->left_nz_[y];
      SetResidualCoeffs(rd->y_ac_levels[x + y * 4], &res);
      it->top_nz_[x] = it->left_nz_[y] =
          VP8RecordCoeffTokens(ctx, res.coeff_type,
                               res.first, res.last, res.coeffs, tokens);
      RecordCoeffs(ctx, &res);
    }
  }

  // U/V
  InitResidual(0, 2, enc, &res);
  for (ch = 0; ch <= 2; ch += 2) {
    for (y = 0; y < 2; ++y) {
      for (x = 0; x < 2; ++x) {
        const int ctx = it->top_nz_[4 + ch + x] + it->left_nz_[4 + ch + y];
        SetResidualCoeffs(rd->uv_levels[ch * 2 + x + y * 2], &res);
        it->top_nz_[4 + ch + x] = it->left_nz_[4 + ch + y] =
            VP8RecordCoeffTokens(ctx, 2,
                                 res.first, res.last, res.coeffs, tokens);
        RecordCoeffs(ctx, &res);
      }
    }
  }
  VP8IteratorBytesToNz(it);
}

#endif    // !DISABLE_TOKEN_BUFFER

//------------------------------------------------------------------------------
// ExtraInfo map / Debug function

#if SEGMENT_VISU
static void SetBlock(uint8_t* p, int value, int size) {
  int y;
  for (y = 0; y < size; ++y) {
    memset(p, value, size);
    p += BPS;
  }
}
#endif

static void ResetSSE(VP8Encoder* const enc) {
  enc->sse_[0] = 0;
  enc->sse_[1] = 0;
  enc->sse_[2] = 0;
  // Note: enc->sse_[3] is managed by alpha.c
  enc->sse_count_ = 0;
}

static void StoreSSE(const VP8EncIterator* const it) {
  VP8Encoder* const enc = it->enc_;
  const uint8_t* const in = it->yuv_in_;
  const uint8_t* const out = it->yuv_out_;
  // Note: not totally accurate at boundary. And doesn't include in-loop filter.
  enc->sse_[0] += VP8SSE16x16(in + Y_OFF, out + Y_OFF);
  enc->sse_[1] += VP8SSE8x8(in + U_OFF, out + U_OFF);
  enc->sse_[2] += VP8SSE8x8(in + V_OFF, out + V_OFF);
  enc->sse_count_ += 16 * 16;
}

static void StoreSideInfo(const VP8EncIterator* const it) {
  VP8Encoder* const enc = it->enc_;
  const VP8MBInfo* const mb = it->mb_;
  WebPPicture* const pic = enc->pic_;

  if (pic->stats != NULL) {
    StoreSSE(it);
    enc->block_count_[0] += (mb->type_ == 0);
    enc->block_count_[1] += (mb->type_ == 1);
    enc->block_count_[2] += (mb->skip_ != 0);
  }

  if (pic->extra_info != NULL) {
    uint8_t* const info = &pic->extra_info[it->x_ + it->y_ * enc->mb_w_];
    switch (pic->extra_info_type) {
      case 1: *info = mb->type_; break;
      case 2: *info = mb->segment_; break;
      case 3: *info = enc->dqm_[mb->segment_].quant_; break;
      case 4: *info = (mb->type_ == 1) ? it->preds_[0] : 0xff; break;
      case 5: *info = mb->uv_mode_; break;
      case 6: {
        const int b = (int)((it->luma_bits_ + it->uv_bits_ + 7) >> 3);
        *info = (b > 255) ? 255 : b; break;
      }
      case 7: *info = mb->alpha_; break;
      default: *info = 0; break;
    };
  }
#if SEGMENT_VISU  // visualize segments and prediction modes
  SetBlock(it->yuv_out_ + Y_OFF, mb->segment_ * 64, 16);
  SetBlock(it->yuv_out_ + U_OFF, it->preds_[0] * 64, 8);
  SetBlock(it->yuv_out_ + V_OFF, mb->uv_mode_ * 64, 8);
#endif
}

static double GetPSNR(uint64_t mse, uint64_t size) {
  return (mse > 0 && size > 0) ? 10. * log10(255. * 255. * size / mse) : 99;
}

//------------------------------------------------------------------------------
//  StatLoop(): only collect statistics (number of skips, token usage, ...).
//  This is used for deciding optimal probabilities. It also modifies the
//  quantizer value if some target (size, PSNR) was specified.

static void SetLoopParams(VP8Encoder* const enc, float q) {
  // Make sure the quality parameter is inside valid bounds
  q = Clamp(q, 0.f, 100.f);

  VP8SetSegmentParams(enc, q);      // setup segment quantizations and filters
  SetSegmentProbas(enc);            // compute segment probabilities

  ResetStats(enc);
  ResetSSE(enc);
}

static uint64_t OneStatPass(VP8Encoder* const enc, VP8RDLevel rd_opt,
                            int nb_mbs, int percent_delta,
                            PassStats* const s) {
  VP8EncIterator it;
  uint64_t size = 0;
  uint64_t size_p0 = 0;
  uint64_t distortion = 0;
  const uint64_t pixel_count = nb_mbs * 384;

  VP8IteratorInit(enc, &it);
  SetLoopParams(enc, s->q);
  do {
    VP8ModeScore info;
    VP8IteratorImport(&it, NULL);
    if (VP8Decimate(&it, &info, rd_opt)) {
      // Just record the number of skips and act like skip_proba is not used.
      enc->proba_.nb_skip_++;
    }
    RecordResiduals(&it, &info);
    size += info.R + info.H;
    size_p0 += info.H;
    distortion += info.D;
    if (percent_delta && !VP8IteratorProgress(&it, percent_delta))
      return 0;
    VP8IteratorSaveBoundary(&it);
  } while (VP8IteratorNext(&it) && --nb_mbs > 0);

  size_p0 += enc->segment_hdr_.size_;
  if (s->do_size_search) {
    size += FinalizeSkipProba(enc);
    size += FinalizeTokenProbas(&enc->proba_);
    size = ((size + size_p0 + 1024) >> 11) + HEADER_SIZE_ESTIMATE;
    s->value = (double)size;
  } else {
    s->value = GetPSNR(distortion, pixel_count);
  }
  return size_p0;
}

static int StatLoop(VP8Encoder* const enc) {
  const int method = enc->method_;
  const int do_search = enc->do_search_;
  const int fast_probe = ((method == 0 || method == 3) && !do_search);
  int num_pass_left = enc->config_->pass;
  const int task_percent = 20;
  const int percent_per_pass =
      (task_percent + num_pass_left / 2) / num_pass_left;
  const int final_percent = enc->percent_ + task_percent;
  const VP8RDLevel rd_opt =
      (method >= 3 || do_search) ? RD_OPT_BASIC : RD_OPT_NONE;
  int nb_mbs = enc->mb_w_ * enc->mb_h_;
  PassStats stats;

  InitPassStats(enc, &stats);
  ResetTokenStats(enc);

  // Fast mode: quick analysis pass over few mbs. Better than nothing.
  if (fast_probe) {
    if (method == 3) {  // we need more stats for method 3 to be reliable.
      nb_mbs = (nb_mbs > 200) ? nb_mbs >> 1 : 100;
    } else {
      nb_mbs = (nb_mbs > 200) ? nb_mbs >> 2 : 50;
    }
  }

  while (num_pass_left-- > 0) {
    const int is_last_pass = (fabs(stats.dq) <= DQ_LIMIT) ||
                             (num_pass_left == 0) ||
                             (enc->max_i4_header_bits_ == 0);
    const uint64_t size_p0 =
        OneStatPass(enc, rd_opt, nb_mbs, percent_per_pass, &stats);
    if (size_p0 == 0) return 0;
#if (DEBUG_SEARCH > 0)
    printf("#%d value:%.1lf -> %.1lf   q:%.2f -> %.2f\n",
           num_pass_left, stats.last_value, stats.value, stats.last_q, stats.q);
#endif
    if (enc->max_i4_header_bits_ > 0 && size_p0 > PARTITION0_SIZE_LIMIT) {
      ++num_pass_left;
      enc->max_i4_header_bits_ >>= 1;  // strengthen header bit limitation...
      continue;                        // ...and start over
    }
    if (is_last_pass) {
      break;
    }
    // If no target size: just do several pass without changing 'q'
    if (do_search) {
      ComputeNextQ(&stats);
      if (fabs(stats.dq) <= DQ_LIMIT) break;
    }
  }
  if (!do_search || !stats.do_size_search) {
    // Need to finalize probas now, since it wasn't done during the search.
    FinalizeSkipProba(enc);
    FinalizeTokenProbas(&enc->proba_);
  }
  VP8CalculateLevelCosts(&enc->proba_);  // finalize costs
  return WebPReportProgress(enc->pic_, final_percent, &enc->percent_);
}

//------------------------------------------------------------------------------
// Main loops
//

static const int kAverageBytesPerMB[8] = { 50, 24, 16, 9, 7, 5, 3, 2 };

static int PreLoopInitialize(VP8Encoder* const enc) {
  int p;
  int ok = 1;
  const int average_bytes_per_MB = kAverageBytesPerMB[enc->base_quant_ >> 4];
  const int bytes_per_parts =
      enc->mb_w_ * enc->mb_h_ * average_bytes_per_MB / enc->num_parts_;
  // Initialize the bit-writers
  for (p = 0; ok && p < enc->num_parts_; ++p) {
    ok = VP8BitWriterInit(enc->parts_ + p, bytes_per_parts);
  }
  if (!ok) VP8EncFreeBitWriters(enc);  // malloc error occurred
  return ok;
}

static int PostLoopFinalize(VP8EncIterator* const it, int ok) {
  VP8Encoder* const enc = it->enc_;
  if (ok) {      // Finalize the partitions, check for extra errors.
    int p;
    for (p = 0; p < enc->num_parts_; ++p) {
      VP8BitWriterFinish(enc->parts_ + p);
      ok &= !enc->parts_[p].error_;
    }
  }

  if (ok) {      // All good. Finish up.
    if (enc->pic_->stats != NULL) {  // finalize byte counters...
      int i, s;
      for (i = 0; i <= 2; ++i) {
        for (s = 0; s < NUM_MB_SEGMENTS; ++s) {
          enc->residual_bytes_[i][s] = (int)((it->bit_count_[s][i] + 7) >> 3);
        }
      }
    }
    VP8AdjustFilterStrength(it);     // ...and store filter stats.
  } else {
    // Something bad happened -> need to do some memory cleanup.
    VP8EncFreeBitWriters(enc);
  }
  return ok;
}

//------------------------------------------------------------------------------
//  VP8EncLoop(): does the final bitstream coding.

static void ResetAfterSkip(VP8EncIterator* const it) {
  if (it->mb_->type_ == 1) {
    *it->nz_ = 0;  // reset all predictors
    it->left_nz_[8] = 0;
  } else {
    *it->nz_ &= (1 << 24);  // preserve the dc_nz bit
  }
}

int VP8EncLoop(VP8Encoder* const enc) {
  VP8EncIterator it;
  int ok = PreLoopInitialize(enc);
  if (!ok) return 0;

  StatLoop(enc);  // stats-collection loop

  VP8IteratorInit(enc, &it);
  VP8InitFilter(&it);
  do {
    VP8ModeScore info;
    const int dont_use_skip = !enc->proba_.use_skip_proba_;
    const VP8RDLevel rd_opt = enc->rd_opt_level_;

    VP8IteratorImport(&it, NULL);
    // Warning! order is important: first call VP8Decimate() and
    // *then* decide how to code the skip decision if there's one.
    if (!VP8Decimate(&it, &info, rd_opt) || dont_use_skip) {
      CodeResiduals(it.bw_, &it, &info);
    } else {   // reset predictors after a skip
      ResetAfterSkip(&it);
    }
#ifdef WEBP_EXPERIMENTAL_FEATURES
    if (enc->use_layer_) {
      VP8EncCodeLayerBlock(&it);
    }
#endif
    StoreSideInfo(&it);
    VP8StoreFilterStats(&it);
    VP8IteratorExport(&it);
    ok = VP8IteratorProgress(&it, 20);
    VP8IteratorSaveBoundary(&it);
  } while (ok && VP8IteratorNext(&it));

  return PostLoopFinalize(&it, ok);
}

//------------------------------------------------------------------------------
// Single pass using Token Buffer.

#if !defined(DISABLE_TOKEN_BUFFER)

#define MIN_COUNT 96  // minimum number of macroblocks before updating stats

int VP8EncTokenLoop(VP8Encoder* const enc) {
  // Roughly refresh the proba eight times per pass
  int max_count = (enc->mb_w_ * enc->mb_h_) >> 3;
  int num_pass_left = enc->config_->pass;
  const int do_search = enc->do_search_;
  VP8EncIterator it;
  VP8Proba* const proba = &enc->proba_;
  const VP8RDLevel rd_opt = enc->rd_opt_level_;
  const uint64_t pixel_count = enc->mb_w_ * enc->mb_h_ * 384;
  PassStats stats;
  int ok;

  InitPassStats(enc, &stats);
  ok = PreLoopInitialize(enc);
  if (!ok) return 0;

  if (max_count < MIN_COUNT) max_count = MIN_COUNT;

  assert(enc->num_parts_ == 1);
  assert(enc->use_tokens_);
  assert(proba->use_skip_proba_ == 0);
  assert(rd_opt >= RD_OPT_BASIC);   // otherwise, token-buffer won't be useful
  assert(num_pass_left > 0);

  while (ok && num_pass_left-- > 0) {
    const int is_last_pass = (fabs(stats.dq) <= DQ_LIMIT) ||
                             (num_pass_left == 0) ||
                             (enc->max_i4_header_bits_ == 0);
    uint64_t size_p0 = 0;
    uint64_t distortion = 0;
    int cnt = max_count;
    VP8IteratorInit(enc, &it);
    SetLoopParams(enc, stats.q);
    if (is_last_pass) {
      ResetTokenStats(enc);
      VP8InitFilter(&it);  // don't collect stats until last pass (too costly)
    }
    VP8TBufferClear(&enc->tokens_);
    do {
      VP8ModeScore info;
      VP8IteratorImport(&it, NULL);
      if (--cnt < 0) {
        FinalizeTokenProbas(proba);
        VP8CalculateLevelCosts(proba);  // refresh cost tables for rd-opt
        cnt = max_count;
      }
      VP8Decimate(&it, &info, rd_opt);
      RecordTokens(&it, &info, &enc->tokens_);
      size_p0 += info.H;
      distortion += info.D;
#ifdef WEBP_EXPERIMENTAL_FEATURES
      if (enc->use_layer_) {
        VP8EncCodeLayerBlock(&it);
      }
#endif
      if (is_last_pass) {
        StoreSideInfo(&it);
        VP8StoreFilterStats(&it);
        VP8IteratorExport(&it);
        ok = VP8IteratorProgress(&it, 20);
      }
      VP8IteratorSaveBoundary(&it);
    } while (ok && VP8IteratorNext(&it));
    if (!ok) break;

    size_p0 += enc->segment_hdr_.size_;
    if (stats.do_size_search) {
      uint64_t size = FinalizeTokenProbas(&enc->proba_);
      size += VP8EstimateTokenSize(&enc->tokens_,
                                   (const uint8_t*)proba->coeffs_);
      size = (size + size_p0 + 1024) >> 11;  // -> size in bytes
      size += HEADER_SIZE_ESTIMATE;
      stats.value = (double)size;
    } else {  // compute and store PSNR
      stats.value = GetPSNR(distortion, pixel_count);
    }

#if (DEBUG_SEARCH > 0)
    printf("#%2d metric:%.1lf -> %.1lf   last_q=%.2lf q=%.2lf dq=%.2lf\n",
           num_pass_left, stats.last_value, stats.value,
           stats.last_q, stats.q, stats.dq);
#endif
    if (size_p0 > PARTITION0_SIZE_LIMIT) {
      ++num_pass_left;
      enc->max_i4_header_bits_ >>= 1;  // strengthen header bit limitation...
      continue;                        // ...and start over
    }
    if (is_last_pass) {
      break;   // done
    }
    if (do_search) {
      ComputeNextQ(&stats);  // Adjust q
    }
  }
  if (ok) {
    if (!stats.do_size_search) {
      FinalizeTokenProbas(&enc->proba_);
    }
    ok = VP8EmitTokens(&enc->tokens_, enc->parts_ + 0,
                       (const uint8_t*)proba->coeffs_, 1);
  }
  ok = ok && WebPReportProgress(enc->pic_, enc->percent_ + 20, &enc->percent_);
  return PostLoopFinalize(&it, ok);
}

#else

int VP8EncTokenLoop(VP8Encoder* const enc) {
  (void)enc;
  return 0;   // we shouldn't be here.
}

#endif    // DISABLE_TOKEN_BUFFER

//------------------------------------------------------------------------------
/* [<][>][^][v][top][bottom][index][help] */
root/third_party/libwebp/enc/frame.c

DEFINITIONS
