vp9_bitstream.c

/*
 *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE 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.
 */

#include <assert.h>
#include <stdio.h>
#include <limits.h>

#include "vpx/vpx_encoder.h"
#include "vpx_mem/vpx_mem.h"

#include "vp9/common/vp9_entropymode.h"
#include "vp9/common/vp9_entropymv.h"
#include "vp9/common/vp9_findnearmv.h"
#include "vp9/common/vp9_tile_common.h"
#include "vp9/common/vp9_seg_common.h"
#include "vp9/common/vp9_pred_common.h"
#include "vp9/common/vp9_entropy.h"
#include "vp9/common/vp9_entropymv.h"
#include "vp9/common/vp9_mvref_common.h"
#include "vp9/common/vp9_treecoder.h"
#include "vp9/common/vp9_systemdependent.h"
#include "vp9/common/vp9_pragmas.h"

#include "vp9/encoder/vp9_mcomp.h"
#include "vp9/encoder/vp9_encodemv.h"
#include "vp9/encoder/vp9_bitstream.h"
#include "vp9/encoder/vp9_segmentation.h"
#include "vp9/encoder/vp9_subexp.h"
#include "vp9/encoder/vp9_write_bit_buffer.h"


#if defined(SECTIONBITS_OUTPUT)
unsigned __int64 Sectionbits[500];
#endif

#ifdef ENTROPY_STATS
int intra_mode_stats[INTRA_MODES]
                    [INTRA_MODES]
                    [INTRA_MODES];
vp9_coeff_stats tree_update_hist[TX_SIZES][BLOCK_TYPES];

extern unsigned int active_section;
#endif


#ifdef MODE_STATS
int64_t tx_count_32x32p_stats[TX_SIZE_CONTEXTS][TX_SIZES];
int64_t tx_count_16x16p_stats[TX_SIZE_CONTEXTS][TX_SIZES - 1];
int64_t tx_count_8x8p_stats[TX_SIZE_CONTEXTS][TX_SIZES - 2];
int64_t switchable_interp_stats[SWITCHABLE_FILTERS+1]
                               [SWITCHABLE_FILTERS];

void init_tx_count_stats() {
  vp9_zero(tx_count_32x32p_stats);
  vp9_zero(tx_count_16x16p_stats);
  vp9_zero(tx_count_8x8p_stats);
}

void init_switchable_interp_stats() {
  vp9_zero(switchable_interp_stats);
}

static void update_tx_count_stats(VP9_COMMON *cm) {
  int i, j;
  for (i = 0; i < TX_SIZE_CONTEXTS; i++) {
    for (j = 0; j < TX_SIZES; j++) {
      tx_count_32x32p_stats[i][j] += cm->fc.tx_count_32x32p[i][j];
    }
  }
  for (i = 0; i < TX_SIZE_CONTEXTS; i++) {
    for (j = 0; j < TX_SIZES - 1; j++) {
      tx_count_16x16p_stats[i][j] += cm->fc.tx_count_16x16p[i][j];
    }
  }
  for (i = 0; i < TX_SIZE_CONTEXTS; i++) {
    for (j = 0; j < TX_SIZES - 2; j++) {
      tx_count_8x8p_stats[i][j] += cm->fc.tx_count_8x8p[i][j];
    }
  }
}

static void update_switchable_interp_stats(VP9_COMMON *cm) {
  int i, j;
  for (i = 0; i < SWITCHABLE_FILTERS+1; ++i)
    for (j = 0; j < SWITCHABLE_FILTERS; ++j) {
      switchable_interp_stats[i][j] += cm->fc.switchable_interp_count[i][j];
    }
}

void write_tx_count_stats() {
  int i, j;
  FILE *fp = fopen("tx_count.bin", "wb");
  fwrite(tx_count_32x32p_stats, sizeof(tx_count_32x32p_stats), 1, fp);
  fwrite(tx_count_16x16p_stats, sizeof(tx_count_16x16p_stats), 1, fp);
  fwrite(tx_count_8x8p_stats, sizeof(tx_count_8x8p_stats), 1, fp);
  fclose(fp);

  printf(
      "vp9_default_tx_count_32x32p[TX_SIZE_CONTEXTS][TX_SIZES] = {\n");
  for (i = 0; i < TX_SIZE_CONTEXTS; i++) {
    printf("  { ");
    for (j = 0; j < TX_SIZES; j++) {
      printf("%"PRId64", ", tx_count_32x32p_stats[i][j]);
    }
    printf("},\n");
  }
  printf("};\n");
  printf(
      "vp9_default_tx_count_16x16p[TX_SIZE_CONTEXTS][TX_SIZES-1] = {\n");
  for (i = 0; i < TX_SIZE_CONTEXTS; i++) {
    printf("  { ");
    for (j = 0; j < TX_SIZES - 1; j++) {
      printf("%"PRId64", ", tx_count_16x16p_stats[i][j]);
    }
    printf("},\n");
  }
  printf("};\n");
  printf(
      "vp9_default_tx_count_8x8p[TX_SIZE_CONTEXTS][TX_SIZES-2] = {\n");
  for (i = 0; i < TX_SIZE_CONTEXTS; i++) {
    printf("  { ");
    for (j = 0; j < TX_SIZES - 2; j++) {
      printf("%"PRId64", ", tx_count_8x8p_stats[i][j]);
    }
    printf("},\n");
  }
  printf("};\n");
}

void write_switchable_interp_stats() {
  int i, j;
  FILE *fp = fopen("switchable_interp.bin", "wb");
  fwrite(switchable_interp_stats, sizeof(switchable_interp_stats), 1, fp);
  fclose(fp);

  printf(
      "vp9_default_switchable_filter_count[SWITCHABLE_FILTERS+1]"
      "[SWITCHABLE_FILTERS] = {\n");
  for (i = 0; i < SWITCHABLE_FILTERS+1; i++) {
    printf("  { ");
    for (j = 0; j < SWITCHABLE_FILTERS; j++) {
      printf("%"PRId64", ", switchable_interp_stats[i][j]);
    }
    printf("},\n");
  }
  printf("};\n");
}
#endif

static INLINE void write_be32(uint8_t *p, int value) {
  p[0] = value >> 24;
  p[1] = value >> 16;
  p[2] = value >> 8;
  p[3] = value;
}

void vp9_encode_unsigned_max(struct vp9_write_bit_buffer *wb,
                             int data, int max) {
  vp9_wb_write_literal(wb, data, get_unsigned_bits(max));
}

static void update_mode(
  vp9_writer *w,
  int n,
  vp9_tree tree,
  vp9_prob Pnew[/* n-1 */],
  vp9_prob Pcur[/* n-1 */],
  unsigned int bct[/* n-1 */] [2],
  const unsigned int num_events[/* n */]
) {
  int i = 0;

  vp9_tree_probs_from_distribution(tree, Pnew, bct, num_events, 0);
  n--;

  for (i = 0; i < n; ++i) {
    vp9_cond_prob_diff_update(w, &Pcur[i], MODE_UPDATE_PROB, bct[i]);
  }
}

static void update_mbintra_mode_probs(VP9_COMP* const cpi,
                                      vp9_writer* const bc) {
  VP9_COMMON *const cm = &cpi->common;
  int j;
  vp9_prob pnew[INTRA_MODES - 1];
  unsigned int bct[INTRA_MODES - 1][2];

  for (j = 0; j < BLOCK_SIZE_GROUPS; j++)
    update_mode(bc, INTRA_MODES, vp9_intra_mode_tree, pnew,
                cm->fc.y_mode_prob[j], bct,
                (unsigned int *)cpi->y_mode_count[j]);
}

static void write_selected_tx_size(const VP9_COMP *cpi, MODE_INFO *m,
                                   TX_SIZE tx_size, BLOCK_SIZE bsize,
                                   vp9_writer *w) {
  const MACROBLOCKD *const xd = &cpi->mb.e_mbd;
  const vp9_prob *tx_probs = get_tx_probs2(xd, &cpi->common.fc.tx_probs, m);
  vp9_write(w, tx_size != TX_4X4, tx_probs[0]);
  if (bsize >= BLOCK_16X16 && tx_size != TX_4X4) {
    vp9_write(w, tx_size != TX_8X8, tx_probs[1]);
    if (bsize >= BLOCK_32X32 && tx_size != TX_8X8)
      vp9_write(w, tx_size != TX_16X16, tx_probs[2]);
  }
}

static int write_skip_coeff(const VP9_COMP *cpi, int segment_id, MODE_INFO *m,
                            vp9_writer *w) {
  const MACROBLOCKD *const xd = &cpi->mb.e_mbd;
  if (vp9_segfeature_active(&cpi->common.seg, segment_id, SEG_LVL_SKIP)) {
    return 1;
  } else {
    const int skip_coeff = m->mbmi.skip_coeff;
    vp9_write(w, skip_coeff, vp9_get_pred_prob_mbskip(&cpi->common, xd));
    return skip_coeff;
  }
}

void vp9_update_skip_probs(VP9_COMP *cpi, vp9_writer *w) {
  VP9_COMMON *cm = &cpi->common;
  int k;

  for (k = 0; k < MBSKIP_CONTEXTS; ++k)
    vp9_cond_prob_diff_update(w, &cm->fc.mbskip_probs[k],
                              MODE_UPDATE_PROB, cm->counts.mbskip[k]);
}

static void write_intra_mode(vp9_writer *bc, int m, const vp9_prob *p) {
  write_token(bc, vp9_intra_mode_tree, p, vp9_intra_mode_encodings + m);
}

static void update_switchable_interp_probs(VP9_COMP *const cpi,
                                           vp9_writer* const bc) {
  VP9_COMMON *const cm = &cpi->common;
  unsigned int branch_ct[SWITCHABLE_FILTERS + 1]
                        [SWITCHABLE_FILTERS - 1][2];
  vp9_prob new_prob[SWITCHABLE_FILTERS + 1][SWITCHABLE_FILTERS - 1];
  int i, j;
  for (j = 0; j <= SWITCHABLE_FILTERS; ++j) {
    vp9_tree_probs_from_distribution(
        vp9_switchable_interp_tree,
        new_prob[j], branch_ct[j],
        cm->counts.switchable_interp[j], 0);
  }
  for (j = 0; j <= SWITCHABLE_FILTERS; ++j) {
    for (i = 0; i < SWITCHABLE_FILTERS - 1; ++i) {
      vp9_cond_prob_diff_update(bc, &cm->fc.switchable_interp_prob[j][i],
                                MODE_UPDATE_PROB, branch_ct[j][i]);
    }
  }
#ifdef MODE_STATS
  if (!cpi->dummy_packing)
    update_switchable_interp_stats(cm);
#endif
}

static void update_inter_mode_probs(VP9_COMMON *cm, vp9_writer* const bc) {
  int i, j;

  for (i = 0; i < INTER_MODE_CONTEXTS; ++i) {
    unsigned int branch_ct[INTER_MODES - 1][2];
    vp9_prob new_prob[INTER_MODES - 1];

    vp9_tree_probs_from_distribution(vp9_inter_mode_tree,
                                     new_prob, branch_ct,
                                     cm->counts.inter_mode[i], NEARESTMV);

    for (j = 0; j < INTER_MODES - 1; ++j)
      vp9_cond_prob_diff_update(bc, &cm->fc.inter_mode_probs[i][j],
                                MODE_UPDATE_PROB, branch_ct[j]);
  }
}

static void pack_mb_tokens(vp9_writer* const bc,
                           TOKENEXTRA **tp,
                           const TOKENEXTRA *const stop) {
  TOKENEXTRA *p = *tp;

  while (p < stop && p->token != EOSB_TOKEN) {
    const int t = p->token;
    const struct vp9_token *const a = vp9_coef_encodings + t;
    const vp9_extra_bit *const b = vp9_extra_bits + t;
    int i = 0;
    const vp9_prob *pp;
    int v = a->value;
    int n = a->len;
    vp9_prob probs[ENTROPY_NODES];

    if (t >= TWO_TOKEN) {
      vp9_model_to_full_probs(p->context_tree, probs);
      pp = probs;
    } else {
      pp = p->context_tree;
    }
    assert(pp != 0);

    /* skip one or two nodes */
    if (p->skip_eob_node) {
      n -= p->skip_eob_node;
      i = 2 * p->skip_eob_node;
    }

    do {
      const int bb = (v >> --n) & 1;
      vp9_write(bc, bb, pp[i >> 1]);
      i = vp9_coef_tree[i + bb];
    } while (n);

    if (b->base_val) {
      const int e = p->extra, l = b->len;

      if (l) {
        const unsigned char *pb = b->prob;
        int v = e >> 1;
        int n = l;              /* number of bits in v, assumed nonzero */
        int i = 0;

        do {
          const int bb = (v >> --n) & 1;
          vp9_write(bc, bb, pb[i >> 1]);
          i = b->tree[i + bb];
        } while (n);
      }

      vp9_write_bit(bc, e & 1);
    }
    ++p;
  }

  *tp = p + (p->token == EOSB_TOKEN);
}

static void write_sb_mv_ref(vp9_writer *w, MB_PREDICTION_MODE mode,
                            const vp9_prob *p) {
  assert(is_inter_mode(mode));
  write_token(w, vp9_inter_mode_tree, p,
              &vp9_inter_mode_encodings[mode - NEARESTMV]);
}


static void write_segment_id(vp9_writer *w, const struct segmentation *seg,
                             int segment_id) {
  if (seg->enabled && seg->update_map)
    treed_write(w, vp9_segment_tree, seg->tree_probs, segment_id, 3);
}

// This function encodes the reference frame
static void encode_ref_frame(VP9_COMP *cpi, vp9_writer *bc) {
  VP9_COMMON *const cm = &cpi->common;
  MACROBLOCK *const x = &cpi->mb;
  MACROBLOCKD *const xd = &x->e_mbd;
  MB_MODE_INFO *mi = &xd->this_mi->mbmi;
  const int segment_id = mi->segment_id;
  int seg_ref_active = vp9_segfeature_active(&cm->seg, segment_id,
                                             SEG_LVL_REF_FRAME);
  // If segment level coding of this signal is disabled...
  // or the segment allows multiple reference frame options
  if (!seg_ref_active) {
    // does the feature use compound prediction or not
    // (if not specified at the frame/segment level)
    if (cm->comp_pred_mode == HYBRID_PREDICTION) {
      vp9_write(bc, mi->ref_frame[1] > INTRA_FRAME,
                vp9_get_pred_prob_comp_inter_inter(cm, xd));
    } else {
      assert((mi->ref_frame[1] <= INTRA_FRAME) ==
                 (cm->comp_pred_mode == SINGLE_PREDICTION_ONLY));
    }

    if (mi->ref_frame[1] > INTRA_FRAME) {
      vp9_write(bc, mi->ref_frame[0] == GOLDEN_FRAME,
                vp9_get_pred_prob_comp_ref_p(cm, xd));
    } else {
      vp9_write(bc, mi->ref_frame[0] != LAST_FRAME,
                vp9_get_pred_prob_single_ref_p1(cm, xd));
      if (mi->ref_frame[0] != LAST_FRAME)
        vp9_write(bc, mi->ref_frame[0] != GOLDEN_FRAME,
                  vp9_get_pred_prob_single_ref_p2(cm, xd));
    }
  } else {
    assert(mi->ref_frame[1] <= INTRA_FRAME);
    assert(vp9_get_segdata(&cm->seg, segment_id, SEG_LVL_REF_FRAME) ==
           mi->ref_frame[0]);
  }

  // if using the prediction mdoel we have nothing further to do because
  // the reference frame is fully coded by the segment
}

static void pack_inter_mode_mvs(VP9_COMP *cpi, MODE_INFO *m, vp9_writer *bc) {
  VP9_COMMON *const cm = &cpi->common;
  const nmv_context *nmvc = &cm->fc.nmvc;
  MACROBLOCK *const x = &cpi->mb;
  MACROBLOCKD *const xd = &x->e_mbd;
  struct segmentation *seg = &cm->seg;
  MB_MODE_INFO *const mi = &m->mbmi;
  const MV_REFERENCE_FRAME rf = mi->ref_frame[0];
  const MB_PREDICTION_MODE mode = mi->mode;
  const int segment_id = mi->segment_id;
  int skip_coeff;
  const BLOCK_SIZE bsize = mi->sb_type;
  const int allow_hp = xd->allow_high_precision_mv;

  x->partition_info = x->pi + (m - cm->mi);

#ifdef ENTROPY_STATS
  active_section = 9;
#endif

  if (seg->update_map) {
    if (seg->temporal_update) {
      const int pred_flag = mi->seg_id_predicted;
      vp9_prob pred_prob = vp9_get_pred_prob_seg_id(seg, xd);
      vp9_write(bc, pred_flag, pred_prob);
      if (!pred_flag)
        write_segment_id(bc, seg, segment_id);
    } else {
      write_segment_id(bc, seg, segment_id);
    }
  }

  skip_coeff = write_skip_coeff(cpi, segment_id, m, bc);

  if (!vp9_segfeature_active(seg, segment_id, SEG_LVL_REF_FRAME))
    vp9_write(bc, rf != INTRA_FRAME,
              vp9_get_pred_prob_intra_inter(cm, xd));

  if (bsize >= BLOCK_8X8 && cm->tx_mode == TX_MODE_SELECT &&
      !(rf != INTRA_FRAME &&
        (skip_coeff || vp9_segfeature_active(seg, segment_id, SEG_LVL_SKIP)))) {
    write_selected_tx_size(cpi, m, mi->tx_size, bsize, bc);
  }

  if (rf == INTRA_FRAME) {
#ifdef ENTROPY_STATS
    active_section = 6;
#endif

    if (bsize >= BLOCK_8X8) {
      write_intra_mode(bc, mode, cm->fc.y_mode_prob[size_group_lookup[bsize]]);
    } else {
      int idx, idy;
      const int num_4x4_blocks_wide = num_4x4_blocks_wide_lookup[bsize];
      const int num_4x4_blocks_high = num_4x4_blocks_high_lookup[bsize];
      for (idy = 0; idy < 2; idy += num_4x4_blocks_high) {
        for (idx = 0; idx < 2; idx += num_4x4_blocks_wide) {
          const MB_PREDICTION_MODE bm = m->bmi[idy * 2 + idx].as_mode;
          write_intra_mode(bc, bm, cm->fc.y_mode_prob[0]);
        }
      }
    }
    write_intra_mode(bc, mi->uv_mode, cm->fc.uv_mode_prob[mode]);
  } else {
    vp9_prob *mv_ref_p;
    encode_ref_frame(cpi, bc);
    mv_ref_p = cpi->common.fc.inter_mode_probs[mi->mode_context[rf]];

#ifdef ENTROPY_STATS
    active_section = 3;
#endif

    // If segment skip is not enabled code the mode.
    if (!vp9_segfeature_active(seg, segment_id, SEG_LVL_SKIP)) {
      if (bsize >= BLOCK_8X8) {
        write_sb_mv_ref(bc, mode, mv_ref_p);
        ++cm->counts.inter_mode[mi->mode_context[rf]]
                               [inter_mode_offset(mode)];
      }
    }

    if (cm->mcomp_filter_type == SWITCHABLE) {
      const int ctx = vp9_get_pred_context_switchable_interp(xd);
      write_token(bc, vp9_switchable_interp_tree,
                  cm->fc.switchable_interp_prob[ctx],
                  &vp9_switchable_interp_encodings[mi->interp_filter]);
    } else {
      assert(mi->interp_filter == cm->mcomp_filter_type);
    }

    if (bsize < BLOCK_8X8) {
      const int num_4x4_blocks_wide = num_4x4_blocks_wide_lookup[bsize];
      const int num_4x4_blocks_high = num_4x4_blocks_high_lookup[bsize];
      int idx, idy;
      for (idy = 0; idy < 2; idy += num_4x4_blocks_high) {
        for (idx = 0; idx < 2; idx += num_4x4_blocks_wide) {
          const int j = idy * 2 + idx;
          const MB_PREDICTION_MODE blockmode = x->partition_info->bmi[j].mode;
          write_sb_mv_ref(bc, blockmode, mv_ref_p);
          ++cm->counts.inter_mode[mi->mode_context[rf]]
                                 [inter_mode_offset(blockmode)];

          if (blockmode == NEWMV) {
#ifdef ENTROPY_STATS
            active_section = 11;
#endif
            vp9_encode_mv(cpi, bc, &m->bmi[j].as_mv[0].as_mv,
                          &mi->best_mv[0].as_mv, nmvc, allow_hp);

            if (has_second_ref(mi))
              vp9_encode_mv(cpi, bc, &m->bmi[j].as_mv[1].as_mv,
                            &mi->best_mv[1].as_mv, nmvc, allow_hp);
          }
        }
      }
    } else if (mode == NEWMV) {
#ifdef ENTROPY_STATS
      active_section = 5;
#endif
      vp9_encode_mv(cpi, bc, &mi->mv[0].as_mv,
                    &mi->best_mv[0].as_mv, nmvc, allow_hp);

      if (has_second_ref(mi))
        vp9_encode_mv(cpi, bc, &mi->mv[1].as_mv,
                      &mi->best_mv[1].as_mv, nmvc, allow_hp);
    }
  }
}

static void write_mb_modes_kf(const VP9_COMP *cpi, MODE_INFO **mi_8x8,
                              vp9_writer *bc) {
  const VP9_COMMON *const cm = &cpi->common;
  const MACROBLOCKD *const xd = &cpi->mb.e_mbd;
  const struct segmentation *const seg = &cm->seg;
  MODE_INFO *m = mi_8x8[0];
  const int ym = m->mbmi.mode;
  const int segment_id = m->mbmi.segment_id;
  MODE_INFO *above_mi = mi_8x8[-xd->mode_info_stride];
  MODE_INFO *left_mi = mi_8x8[-1];

  if (seg->update_map)
    write_segment_id(bc, seg, m->mbmi.segment_id);

  write_skip_coeff(cpi, segment_id, m, bc);

  if (m->mbmi.sb_type >= BLOCK_8X8 && cm->tx_mode == TX_MODE_SELECT)
    write_selected_tx_size(cpi, m, m->mbmi.tx_size, m->mbmi.sb_type, bc);

  if (m->mbmi.sb_type >= BLOCK_8X8) {
    const MB_PREDICTION_MODE A = above_block_mode(m, above_mi, 0);
    const MB_PREDICTION_MODE L = xd->left_available ?
                                 left_block_mode(m, left_mi, 0) : DC_PRED;
    write_intra_mode(bc, ym, vp9_kf_y_mode_prob[A][L]);
  } else {
    int idx, idy;
    const int num_4x4_blocks_wide = num_4x4_blocks_wide_lookup[m->mbmi.sb_type];
    const int num_4x4_blocks_high = num_4x4_blocks_high_lookup[m->mbmi.sb_type];
    for (idy = 0; idy < 2; idy += num_4x4_blocks_high) {
      for (idx = 0; idx < 2; idx += num_4x4_blocks_wide) {
        int i = idy * 2 + idx;
        const MB_PREDICTION_MODE A = above_block_mode(m, above_mi, i);
        const MB_PREDICTION_MODE L = (xd->left_available || idx) ?
                                     left_block_mode(m, left_mi, i) : DC_PRED;
        const int bm = m->bmi[i].as_mode;
#ifdef ENTROPY_STATS
        ++intra_mode_stats[A][L][bm];
#endif
        write_intra_mode(bc, bm, vp9_kf_y_mode_prob[A][L]);
      }
    }
  }

  write_intra_mode(bc, m->mbmi.uv_mode, vp9_kf_uv_mode_prob[ym]);
}

static void write_modes_b(VP9_COMP *cpi, MODE_INFO **mi_8x8, vp9_writer *bc,
                          TOKENEXTRA **tok, TOKENEXTRA *tok_end,
                          int mi_row, int mi_col) {
  VP9_COMMON *const cm = &cpi->common;
  MACROBLOCKD *const xd = &cpi->mb.e_mbd;
  MODE_INFO *m = mi_8x8[0];

  if (m->mbmi.sb_type < BLOCK_8X8)
    if (xd->ab_index > 0)
      return;

  xd->this_mi = mi_8x8[0];
  xd->mi_8x8 = mi_8x8;

  set_mi_row_col(&cpi->common, xd,
                 mi_row, num_8x8_blocks_high_lookup[m->mbmi.sb_type],
                 mi_col, num_8x8_blocks_wide_lookup[m->mbmi.sb_type]);
  if ((cm->frame_type == KEY_FRAME) || cm->intra_only) {
    write_mb_modes_kf(cpi, mi_8x8, bc);
#ifdef ENTROPY_STATS
    active_section = 8;
#endif
  } else {
    pack_inter_mode_mvs(cpi, m, bc);
#ifdef ENTROPY_STATS
    active_section = 1;
#endif
  }

  assert(*tok < tok_end);
  pack_mb_tokens(bc, tok, tok_end);
}

static void write_modes_sb(VP9_COMP *cpi, MODE_INFO **mi_8x8, vp9_writer *bc,
                           TOKENEXTRA **tok, TOKENEXTRA *tok_end,
                           int mi_row, int mi_col, BLOCK_SIZE bsize) {
  VP9_COMMON *const cm = &cpi->common;
  MACROBLOCKD *xd = &cpi->mb.e_mbd;
  const int mis = cm->mode_info_stride;
  int bsl = b_width_log2(bsize);
  int bs = (1 << bsl) / 4;  // mode_info step for subsize
  int n;
  PARTITION_TYPE partition = PARTITION_NONE;
  BLOCK_SIZE subsize;
  MODE_INFO *m = mi_8x8[0];

  if (mi_row >= cm->mi_rows || mi_col >= cm->mi_cols)
    return;

  partition = partition_lookup[bsl][m->mbmi.sb_type];

  if (bsize < BLOCK_8X8)
    if (xd->ab_index > 0)
      return;

  if (bsize >= BLOCK_8X8) {
    int pl;
    const int idx = check_bsize_coverage(bs, cm->mi_rows, cm->mi_cols,
                                         mi_row, mi_col);
    set_partition_seg_context(cm, xd, mi_row, mi_col);
    pl = partition_plane_context(xd, bsize);
    // encode the partition information
    if (idx == 0)
      write_token(bc, vp9_partition_tree,
                  cm->fc.partition_prob[cm->frame_type][pl],
                  vp9_partition_encodings + partition);
    else if (idx > 0)
      vp9_write(bc, partition == PARTITION_SPLIT,
                cm->fc.partition_prob[cm->frame_type][pl][idx]);
  }

  subsize = get_subsize(bsize, partition);
  *(get_sb_index(xd, subsize)) = 0;

  switch (partition) {
    case PARTITION_NONE:
      write_modes_b(cpi, mi_8x8, bc, tok, tok_end, mi_row, mi_col);
      break;
    case PARTITION_HORZ:
      write_modes_b(cpi, mi_8x8, bc, tok, tok_end, mi_row, mi_col);
      *(get_sb_index(xd, subsize)) = 1;
      if ((mi_row + bs) < cm->mi_rows)
        write_modes_b(cpi, mi_8x8 + bs * mis, bc, tok, tok_end, mi_row + bs,
                      mi_col);
      break;
    case PARTITION_VERT:
      write_modes_b(cpi, mi_8x8, bc, tok, tok_end, mi_row, mi_col);
      *(get_sb_index(xd, subsize)) = 1;
      if ((mi_col + bs) < cm->mi_cols)
        write_modes_b(cpi, mi_8x8 + bs, bc, tok, tok_end, mi_row, mi_col + bs);
      break;
    case PARTITION_SPLIT:
      for (n = 0; n < 4; n++) {
        int j = n >> 1, i = n & 0x01;
        *(get_sb_index(xd, subsize)) = n;
        write_modes_sb(cpi, mi_8x8 + j * bs * mis + i * bs, bc, tok, tok_end,
                       mi_row + j * bs, mi_col + i * bs, subsize);
      }
      break;
    default:
      assert(0);
  }

  // update partition context
  if (bsize >= BLOCK_8X8 &&
      (bsize == BLOCK_8X8 || partition != PARTITION_SPLIT)) {
    set_partition_seg_context(cm, xd, mi_row, mi_col);
    update_partition_context(xd, subsize, bsize);
  }
}

static void write_modes(VP9_COMP *cpi, vp9_writer* const bc,
                        TOKENEXTRA **tok, TOKENEXTRA *tok_end) {
  VP9_COMMON *const cm = &cpi->common;
  const int mis = cm->mode_info_stride;
  int mi_row, mi_col;
  MODE_INFO **mi_8x8 = cm->mi_grid_visible;
  MODE_INFO **m_8x8;

  mi_8x8 += cm->cur_tile_mi_col_start + cm->cur_tile_mi_row_start * mis;

  for (mi_row = cm->cur_tile_mi_row_start; mi_row < cm->cur_tile_mi_row_end;
       mi_row += 8, mi_8x8 += 8 * mis) {
    m_8x8 = mi_8x8;
    vp9_zero(cm->left_seg_context);
    for (mi_col = cm->cur_tile_mi_col_start; mi_col < cm->cur_tile_mi_col_end;
         mi_col += MI_BLOCK_SIZE, m_8x8 += MI_BLOCK_SIZE) {
      write_modes_sb(cpi, m_8x8, bc, tok, tok_end, mi_row, mi_col,
                     BLOCK_64X64);
    }
  }
}

/* This function is used for debugging probability trees. */
static void print_prob_tree(vp9_coeff_probs *coef_probs, int block_types) {
  /* print coef probability tree */
  int i, j, k, l, m;
  FILE *f = fopen("enc_tree_probs.txt", "a");
  fprintf(f, "{\n");
  for (i = 0; i < block_types; i++) {
    fprintf(f, "  {\n");
    for (j = 0; j < REF_TYPES; ++j) {
      fprintf(f, "  {\n");
      for (k = 0; k < COEF_BANDS; k++) {
        fprintf(f, "    {\n");
        for (l = 0; l < PREV_COEF_CONTEXTS; l++) {
          fprintf(f, "      {");
          for (m = 0; m < ENTROPY_NODES; m++) {
            fprintf(f, "%3u, ",
                    (unsigned int)(coef_probs[i][j][k][l][m]));
          }
        }
        fprintf(f, " }\n");
      }
      fprintf(f, "    }\n");
    }
    fprintf(f, "  }\n");
  }
  fprintf(f, "}\n");
  fclose(f);
}

static void build_tree_distribution(VP9_COMP *cpi, TX_SIZE tx_size) {
  vp9_coeff_probs_model *coef_probs = cpi->frame_coef_probs[tx_size];
  vp9_coeff_count *coef_counts = cpi->coef_counts[tx_size];
  unsigned int (*eob_branch_ct)[REF_TYPES][COEF_BANDS][PREV_COEF_CONTEXTS] =
      cpi->common.counts.eob_branch[tx_size];
  vp9_coeff_stats *coef_branch_ct = cpi->frame_branch_ct[tx_size];
  vp9_prob full_probs[ENTROPY_NODES];
  int i, j, k, l;

  for (i = 0; i < BLOCK_TYPES; ++i) {
    for (j = 0; j < REF_TYPES; ++j) {
      for (k = 0; k < COEF_BANDS; ++k) {
        for (l = 0; l < PREV_COEF_CONTEXTS; ++l) {
          if (l >= 3 && k == 0)
            continue;
          vp9_tree_probs_from_distribution(vp9_coef_tree,
                                           full_probs,
                                           coef_branch_ct[i][j][k][l],
                                           coef_counts[i][j][k][l], 0);
          vpx_memcpy(coef_probs[i][j][k][l], full_probs,
                     sizeof(vp9_prob) * UNCONSTRAINED_NODES);
          coef_branch_ct[i][j][k][l][0][1] = eob_branch_ct[i][j][k][l] -
                                             coef_branch_ct[i][j][k][l][0][0];
          coef_probs[i][j][k][l][0] =
              get_binary_prob(coef_branch_ct[i][j][k][l][0][0],
                              coef_branch_ct[i][j][k][l][0][1]);
#ifdef ENTROPY_STATS
          if (!cpi->dummy_packing) {
            int t;
            for (t = 0; t < MAX_ENTROPY_TOKENS; ++t)
              context_counters[tx_size][i][j][k][l][t] +=
                  coef_counts[</