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 "vp9/common/vp9_header.h"
#include "vp9/encoder/vp9_encodemv.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/encoder/vp9_mcomp.h"
#include "vp9/common/vp9_systemdependent.h"
#include "vp9/common/vp9_pragmas.h"
#include "vpx/vpx_encoder.h"
#include "vpx_mem/vpx_mem.h"
#include "vp9/encoder/vp9_bitstream.h"
#include "vp9/encoder/vp9_segmentation.h"

#include "vp9/common/vp9_seg_common.h"
#include "vp9/common/vp9_pred_common.h"
#include "vp9/common/vp9_entropy.h"
#include "vp9/encoder/vp9_encodemv.h"
#include "vp9/common/vp9_entropymv.h"
#include "vp9/common/vp9_mvref_common.h"
#include "vp9/common/vp9_treecoder.h"

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

#ifdef ENTROPY_STATS
int intra_mode_stats[VP9_KF_BINTRAMODES]
                    [VP9_KF_BINTRAMODES]
                    [VP9_KF_BINTRAMODES];
vp9_coeff_stats tree_update_hist_4x4[BLOCK_TYPES];
vp9_coeff_stats tree_update_hist_8x8[BLOCK_TYPES];
vp9_coeff_stats tree_update_hist_16x16[BLOCK_TYPES];
vp9_coeff_stats tree_update_hist_32x32[BLOCK_TYPES];

extern unsigned int active_section;
#endif

#if CONFIG_CODE_ZEROGROUP
#ifdef ZPC_STATS
vp9_zpc_count zpc_stats_4x4;
vp9_zpc_count zpc_stats_8x8;
vp9_zpc_count zpc_stats_16x16;
vp9_zpc_count zpc_stats_32x32;
void init_zpcstats();
void update_zpcstats(VP9_COMMON *const cm);
void print_zpcstats();
#endif
#endif

#ifdef MODE_STATS
int count_mb_seg[4] = { 0, 0, 0, 0 };
#endif

#define vp9_cost_upd  ((int)(vp9_cost_one(upd) - vp9_cost_zero(upd)) >> 8)
#define vp9_cost_upd256  ((int)(vp9_cost_one(upd) - vp9_cost_zero(upd)))

#define SEARCH_NEWP
static int update_bits[255];

static INLINE void write_le16(uint8_t *p, int value) {
  p[0] = value;
  p[1] = value >> 8;
}

static INLINE void write_le32(uint8_t *p, int value) {
  p[0] = value;
  p[1] = value >> 8;
  p[2] = value >> 16;
  p[3] = value >> 24;
}

static void compute_update_table() {
  int i;
  for (i = 0; i < 255; i++)
    update_bits[i] = vp9_count_term_subexp(i, SUBEXP_PARAM, 255);
}

static int split_index(int i, int n, int modulus) {
  int max1 = (n - 1 - modulus / 2) / modulus + 1;
  if (i % modulus == modulus / 2) i = i / modulus;
  else i = max1 + i - (i + modulus - modulus / 2) / modulus;
  return i;
}

static int remap_prob(int v, int m) {
  const int n = 256;
  const int modulus = MODULUS_PARAM;
  int i;
  if ((m << 1) <= n)
    i = vp9_recenter_nonneg(v, m) - 1;
  else
    i = vp9_recenter_nonneg(n - 1 - v, n - 1 - m) - 1;

  i = split_index(i, n - 1, modulus);
  return i;
}

static void write_prob_diff_update(vp9_writer *const bc,
                                   vp9_prob newp, vp9_prob oldp) {
  int delp = remap_prob(newp, oldp);
  vp9_encode_term_subexp(bc, delp, SUBEXP_PARAM, 255);
}

static int prob_diff_update_cost(vp9_prob newp, vp9_prob oldp) {
  int delp = remap_prob(newp, oldp);
  return update_bits[delp] * 256;
}

static void update_mode(
  vp9_writer *const bc,
  int n,
  const struct vp9_token tok[/* 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 */]
) {
  unsigned int new_b = 0, old_b = 0;
  int i = 0;

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

  do {
    new_b += cost_branch(bct[i], Pnew[i]);
    old_b += cost_branch(bct[i], Pcur[i]);
  } while (++i < n);

  if (new_b + (n << 8) < old_b) {
    int i = 0;

    vp9_write_bit(bc, 1);

    do {
      const vp9_prob p = Pnew[i];

      vp9_write_literal(bc, Pcur[i] = p ? p : 1, 8);
    } while (++i < n);
  } else
    vp9_write_bit(bc, 0);
}

static void update_mbintra_mode_probs(VP9_COMP* const cpi,
                                      vp9_writer* const bc) {
  VP9_COMMON *const cm = &cpi->common;

  {
    vp9_prob Pnew   [VP9_YMODES - 1];
    unsigned int bct [VP9_YMODES - 1] [2];

    update_mode(
      bc, VP9_YMODES, vp9_ymode_encodings, vp9_ymode_tree,
      Pnew, cm->fc.ymode_prob, bct, (unsigned int *)cpi->ymode_count
    );
    update_mode(bc, VP9_I32X32_MODES, vp9_sb_ymode_encodings,
                vp9_sb_ymode_tree, Pnew, cm->fc.sb_ymode_prob, bct,
                (unsigned int *)cpi->sb_ymode_count);
  }
}

void vp9_update_skip_probs(VP9_COMP *cpi) {
  VP9_COMMON *const pc = &cpi->common;
  int k;

  for (k = 0; k < MBSKIP_CONTEXTS; ++k) {
    pc->mbskip_pred_probs[k] = get_binary_prob(cpi->skip_false_count[k],
                                               cpi->skip_true_count[k]);
  }
}

static void update_switchable_interp_probs(VP9_COMP *cpi,
                                           vp9_writer* const bc) {
  VP9_COMMON *const pc = &cpi->common;
  unsigned int branch_ct[32][2];
  int i, j;
  for (j = 0; j <= VP9_SWITCHABLE_FILTERS; ++j) {
    vp9_tree_probs_from_distribution(
        vp9_switchable_interp_tree,
        pc->fc.switchable_interp_prob[j], branch_ct,
        cpi->switchable_interp_count[j], 0);
    for (i = 0; i < VP9_SWITCHABLE_FILTERS - 1; ++i) {
      if (pc->fc.switchable_interp_prob[j][i] < 1)
        pc->fc.switchable_interp_prob[j][i] = 1;
      vp9_write_prob(bc, pc->fc.switchable_interp_prob[j][i]);
    }
  }
}

// This function updates the reference frame prediction stats
static void update_refpred_stats(VP9_COMP *cpi) {
  VP9_COMMON *const cm = &cpi->common;
  int i;
  vp9_prob new_pred_probs[PREDICTION_PROBS];
  int old_cost, new_cost;

  // Set the prediction probability structures to defaults
  if (cm->frame_type != KEY_FRAME) {
    // From the prediction counts set the probabilities for each context
    for (i = 0; i < PREDICTION_PROBS; i++) {
      new_pred_probs[i] = get_binary_prob(cpi->ref_pred_count[i][0],
                                          cpi->ref_pred_count[i][1]);

      // Decide whether or not to update the reference frame probs.
      // Returned costs are in 1/256 bit units.
      old_cost =
        (cpi->ref_pred_count[i][0] * vp9_cost_zero(cm->ref_pred_probs[i])) +
        (cpi->ref_pred_count[i][1] * vp9_cost_one(cm->ref_pred_probs[i]));

      new_cost =
        (cpi->ref_pred_count[i][0] * vp9_cost_zero(new_pred_probs[i])) +
        (cpi->ref_pred_count[i][1] * vp9_cost_one(new_pred_probs[i]));

      // Cost saving must be >= 8 bits (2048 in these units)
      if ((old_cost - new_cost) >= 2048) {
        cpi->ref_pred_probs_update[i] = 1;
        cm->ref_pred_probs[i] = new_pred_probs[i];
      } else
        cpi->ref_pred_probs_update[i] = 0;
    }
  }
}

// This function is called to update the mode probability context used to encode
// inter modes. It assumes the branch counts table has already been populated
// prior to the actual packing of the bitstream (in rd stage or dummy pack)
//
// The branch counts table is re-populated during the actual pack stage and in
// the decoder to facilitate backwards update of the context.
static void update_inter_mode_probs(VP9_COMMON *cm,
                                    int mode_context[INTER_MODE_CONTEXTS][4]) {
  int i, j;
  unsigned int (*mv_ref_ct)[4][2];

  vpx_memcpy(mode_context, cm->fc.vp9_mode_contexts,
             sizeof(cm->fc.vp9_mode_contexts));

  mv_ref_ct = cm->fc.mv_ref_ct;

  for (i = 0; i < INTER_MODE_CONTEXTS; i++) {
    for (j = 0; j < 4; j++) {
      int new_prob, old_cost, new_cost;

      // Work out cost of coding branches with the old and optimal probability
      old_cost = cost_branch256(mv_ref_ct[i][j], mode_context[i][j]);
      new_prob = get_binary_prob(mv_ref_ct[i][j][0], mv_ref_ct[i][j][1]);
      new_cost = cost_branch256(mv_ref_ct[i][j], new_prob);

      // If cost saving is >= 14 bits then update the mode probability.
      // This is the approximate net cost of updating one probability given
      // that the no update case ismuch more common than the update case.
      if (new_cost <= (old_cost - (14 << 8))) {
        mode_context[i][j] = new_prob;
      }
    }
  }
}

static void write_ymode(vp9_writer *bc, int m, const vp9_prob *p) {
  write_token(bc, vp9_ymode_tree, p, vp9_ymode_encodings + m);
}

static void kfwrite_ymode(vp9_writer *bc, int m, const vp9_prob *p) {
  write_token(bc, vp9_kf_ymode_tree, p, vp9_kf_ymode_encodings + m);
}

static void write_sb_ymode(vp9_writer *bc, int m, const vp9_prob *p) {
  write_token(bc, vp9_sb_ymode_tree, p, vp9_sb_ymode_encodings + m);
}

static void sb_kfwrite_ymode(vp9_writer *bc, int m, const vp9_prob *p) {
  write_token(bc, vp9_uv_mode_tree, p, vp9_sb_kf_ymode_encodings + m);
}

static void write_i8x8_mode(vp9_writer *bc, int m, const vp9_prob *p) {
  write_token(bc, vp9_i8x8_mode_tree, p, vp9_i8x8_mode_encodings + m);
}

static void write_uv_mode(vp9_writer *bc, int m, const vp9_prob *p) {
  write_token(bc, vp9_uv_mode_tree, p, vp9_uv_mode_encodings + m);
}


static void write_bmode(vp9_writer *bc, int m, const vp9_prob *p) {
#if CONFIG_NEWBINTRAMODES
  assert(m < B_CONTEXT_PRED - CONTEXT_PRED_REPLACEMENTS || m == B_CONTEXT_PRED);
  if (m == B_CONTEXT_PRED) m -= CONTEXT_PRED_REPLACEMENTS;
#endif
  write_token(bc, vp9_bmode_tree, p, vp9_bmode_encodings + m);
}

static void write_kf_bmode(vp9_writer *bc, int m, const vp9_prob *p) {
  write_token(bc, vp9_kf_bmode_tree, p, vp9_kf_bmode_encodings + m);
}

static void write_split(vp9_writer *bc, int x, const vp9_prob *p) {
  write_token(
    bc, vp9_mbsplit_tree, p, vp9_mbsplit_encodings + x);
}

static int prob_update_savings(const unsigned int *ct,
                               const vp9_prob oldp, const vp9_prob newp,
                               const vp9_prob upd) {
  const int old_b = cost_branch256(ct, oldp);
  const int new_b = cost_branch256(ct, newp);
  const int update_b = 2048 + vp9_cost_upd256;
  return (old_b - new_b - update_b);
}

static int prob_diff_update_savings(const unsigned int *ct,
                                    const vp9_prob oldp, const vp9_prob newp,
                                    const vp9_prob upd) {
  const int old_b = cost_branch256(ct, oldp);
  const int new_b = cost_branch256(ct, newp);
  const int update_b = (newp == oldp ? 0 :
                        prob_diff_update_cost(newp, oldp) + vp9_cost_upd256);
  return (old_b - new_b - update_b);
}

static int prob_diff_update_savings_search(const unsigned int *ct,
                                           const vp9_prob oldp, vp9_prob *bestp,
                                           const vp9_prob upd) {
  const int old_b = cost_branch256(ct, oldp);
  int new_b, update_b, savings, bestsavings, step;
  vp9_prob newp, bestnewp;

  bestsavings = 0;
  bestnewp = oldp;

  step = (*bestp > oldp ? -1 : 1);
  for (newp = *bestp; newp != oldp; newp += step) {
    new_b = cost_branch256(ct, newp);
    update_b = prob_diff_update_cost(newp, oldp) + vp9_cost_upd256;
    savings = old_b - new_b - update_b;
    if (savings > bestsavings) {
      bestsavings = savings;
      bestnewp = newp;
    }
  }
  *bestp = bestnewp;
  return bestsavings;
}

#if CONFIG_MODELCOEFPROB && MODEL_BASED_UPDATE
static int prob_diff_update_savings_search_model(const unsigned int *ct,
                                                 const vp9_prob *oldp,
                                                 vp9_prob *bestp,
                                                 const vp9_prob upd,
                                                 int b, int r, int q) {
  int i, old_b, new_b, update_b, savings, bestsavings, step;
  int newp;
  vp9_prob bestnewp, newplist[ENTROPY_NODES];
  for (i = UNCONSTRAINED_NODES - 1, old_b = 0; i < ENTROPY_NODES; ++i)
    old_b += cost_branch256(ct + 2 * i, oldp[i]);

  bestsavings = 0;
  bestnewp = oldp[UNCONSTRAINED_NODES - 1];

  step = (*bestp > oldp[UNCONSTRAINED_NODES - 1] ? -1 : 1);
  newp = *bestp;
  // newp = *bestp - step * (abs(*bestp - oldp[UNCONSTRAINED_NODES - 1]) >> 1);
  for (; newp != oldp[UNCONSTRAINED_NODES - 1]; newp += step) {
    if (newp < 1 || newp > 255) continue;
    newplist[UNCONSTRAINED_NODES - 1] = newp;
    vp9_get_model_distribution(newp, newplist, b, r);
    for (i = UNCONSTRAINED_NODES - 1, new_b = 0; i < ENTROPY_NODES; ++i)
      new_b += cost_branch256(ct + 2 * i, newplist[i]);
    update_b = prob_diff_update_cost(newp, oldp[UNCONSTRAINED_NODES - 1]) +
        vp9_cost_upd256;
    savings = old_b - new_b - update_b;
    if (savings > bestsavings) {
      bestsavings = savings;
      bestnewp = newp;
    }
  }
  *bestp = bestnewp;
  return bestsavings;
}
#endif

static void vp9_cond_prob_update(vp9_writer *bc, vp9_prob *oldp, vp9_prob upd,
                                 unsigned int *ct) {
  vp9_prob newp;
  int savings;
  newp = get_binary_prob(ct[0], ct[1]);
  savings = prob_update_savings(ct, *oldp, newp, upd);
  if (savings > 0) {
    vp9_write(bc, 1, upd);
    vp9_write_prob(bc, newp);
    *oldp = newp;
  } else {
    vp9_write(bc, 0, upd);
  }
}

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

  while (p < stop) {
    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 unsigned char *pp = p->context_tree;
    int v = a->value;
    int n = a->len;
    int ncount = n;

    if (t == EOSB_TOKEN)
    {
      ++p;
      break;
    }
    assert(pp != 0);
#if CONFIG_CODE_ZEROGROUP
    if (t == ZPC_ISOLATED || t == ZPC_EOORIENT) {
      assert((p - 1)->token == ZERO_TOKEN);
      encode_bool(bc, t == ZPC_ISOLATED, *pp);
      ++p;
      continue;
    } else if (p->skip_coef_val) {
      assert(p->skip_eob_node == 0);
      assert(t == DCT_EOB_TOKEN || t == ZERO_TOKEN);
      encode_bool(bc, t == ZERO_TOKEN, *pp);
      ++p;
      continue;
    }
#endif

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

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


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

      if (l) {
        const unsigned char *pp = 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, pp[i >> 1]);
          i = b->tree[i + bb];
        } while (n);
      }

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

  *tp = p;
}

static void write_mv_ref
(
  vp9_writer *bc, MB_PREDICTION_MODE m, const vp9_prob *p
) {
#if CONFIG_DEBUG
  assert(NEARESTMV <= m  &&  m <= SPLITMV);
#endif
  write_token(bc, vp9_mv_ref_tree, p,
              vp9_mv_ref_encoding_array - NEARESTMV + m);
}

static void write_sb_mv_ref(vp9_writer *bc, MB_PREDICTION_MODE m,
                            const vp9_prob *p) {
#if CONFIG_DEBUG
  assert(NEARESTMV <= m  &&  m < SPLITMV);
#endif
  write_token(bc, vp9_sb_mv_ref_tree, p,
              vp9_sb_mv_ref_encoding_array - NEARESTMV + m);
}

static void write_sub_mv_ref
(
  vp9_writer *bc, B_PREDICTION_MODE m, const vp9_prob *p
) {
#if CONFIG_DEBUG
  assert(LEFT4X4 <= m  &&  m <= NEW4X4);
#endif
  write_token(bc, vp9_sub_mv_ref_tree, p,
              vp9_sub_mv_ref_encoding_array - LEFT4X4 + m);
}

static void write_nmv(VP9_COMP *cpi, vp9_writer *bc,
                      const MV *mv, const int_mv *ref,
                      const nmv_context *nmvc, int usehp) {
  MV e;
  e.row = mv->row - ref->as_mv.row;
  e.col = mv->col - ref->as_mv.col;

  vp9_encode_nmv(bc, &e, &ref->as_mv, nmvc);
  vp9_encode_nmv_fp(bc, &e, &ref->as_mv, nmvc, usehp);
}

// This function writes the current macro block's segnment id to the bitstream
// It should only be called if a segment map update is indicated.
static void write_mb_segid(vp9_writer *bc,
                           const MB_MODE_INFO *mi, const MACROBLOCKD *xd) {
  // Encode the MB segment id.
  int seg_id = mi->segment_id;

  if (xd->segmentation_enabled && xd->update_mb_segmentation_map) {
    switch (seg_id) {
      case 0:
        vp9_write(bc, 0, xd->mb_segment_tree_probs[0]);
        vp9_write(bc, 0, xd->mb_segment_tree_probs[1]);
        vp9_write(bc, 0, xd->mb_segment_tree_probs[2]);
        break;
      case 1:
        vp9_write(bc, 0, xd->mb_segment_tree_probs[0]);
        vp9_write(bc, 0, xd->mb_segment_tree_probs[1]);
        vp9_write(bc, 1, xd->mb_segment_tree_probs[2]);
        break;
      case 2:
        vp9_write(bc, 0, xd->mb_segment_tree_probs[0]);
        vp9_write(bc, 1, xd->mb_segment_tree_probs[1]);
        vp9_write(bc, 0, xd->mb_segment_tree_probs[3]);
        break;
      case 3:
        vp9_write(bc, 0, xd->mb_segment_tree_probs[0]);
        vp9_write(bc, 1, xd->mb_segment_tree_probs[1]);
        vp9_write(bc, 1, xd->mb_segment_tree_probs[3]);
        break;
      case 4:
        vp9_write(bc, 1, xd->mb_segment_tree_probs[0]);
        vp9_write(bc, 0, xd->mb_segment_tree_probs[4]);
        vp9_write(bc, 0, xd->mb_segment_tree_probs[5]);
        break;
      case 5:
        vp9_write(bc, 1, xd->mb_segment_tree_probs[0]);
        vp9_write(bc, 0, xd->mb_segment_tree_probs[4]);
        vp9_write(bc, 1, xd->mb_segment_tree_probs[5]);
        break;
      case 6:
        vp9_write(bc, 1, xd->mb_segment_tree_probs[0]);
        vp9_write(bc, 1, xd->mb_segment_tree_probs[4]);
        vp9_write(bc, 0, xd->mb_segment_tree_probs[6]);
        break;
      case 7:
        vp9_write(bc, 1, xd->mb_segment_tree_probs[0]);
        vp9_write(bc, 1, xd->mb_segment_tree_probs[4]);
        vp9_write(bc, 1, xd->mb_segment_tree_probs[6]);
        break;

        // TRAP.. This should not happen
      default:
        vp9_write(bc, 0, xd->mb_segment_tree_probs[0]);
        vp9_write(bc, 0, xd->mb_segment_tree_probs[1]);
        vp9_write(bc, 0, xd->mb_segment_tree_probs[2]);
        break;
    }
  }
}

// This function encodes the reference frame
static void encode_ref_frame(vp9_writer *const bc,
                             VP9_COMMON *const cm,
                             MACROBLOCKD *xd,
                             int segment_id,
                             MV_REFERENCE_FRAME rf) {
  int seg_ref_active;
  int seg_ref_count = 0;
  seg_ref_active = vp9_segfeature_active(xd,
                                         segment_id,
                                         SEG_LVL_REF_FRAME);

  if (seg_ref_active) {
    seg_ref_count = vp9_check_segref(xd, segment_id, INTRA_FRAME) +
                    vp9_check_segref(xd, segment_id, LAST_FRAME) +
                    vp9_check_segref(xd, segment_id, GOLDEN_FRAME) +
                    vp9_check_segref(xd, segment_id, ALTREF_FRAME);
  }

  // If segment level coding of this signal is disabled...
  // or the segment allows multiple reference frame options
  if (!seg_ref_active || (seg_ref_count > 1)) {
    // Values used in prediction model coding
    unsigned char prediction_flag;
    vp9_prob pred_prob;
    MV_REFERENCE_FRAME pred_rf;

    // Get the context probability the prediction flag
    pred_prob = vp9_get_pred_prob(cm, xd, PRED_REF);

    // Get the predicted value.
    pred_rf = vp9_get_pred_ref(cm, xd);

    // Did the chosen reference frame match its predicted value.
    prediction_flag =
      (xd->mode_info_context->mbmi.ref_frame == pred_rf);

    vp9_set_pred_flag(xd, PRED_REF, prediction_flag);
    vp9_write(bc, prediction_flag, pred_prob);

    // If not predicted correctly then code value explicitly
    if (!prediction_flag) {
      vp9_prob mod_refprobs[PREDICTION_PROBS];

      vpx_memcpy(mod_refprobs,
                 cm->mod_refprobs[pred_rf], sizeof(mod_refprobs));

      // If segment coding enabled blank out options that cant occur by
      // setting the branch probability to 0.
      if (seg_ref_active) {
        mod_refprobs[INTRA_FRAME] *=
          vp9_check_segref(xd, segment_id, INTRA_FRAME);
        mod_refprobs[LAST_FRAME] *=
          vp9_check_segref(xd, segment_id, LAST_FRAME);
        mod_refprobs[GOLDEN_FRAME] *=
          (vp9_check_segref(xd, segment_id, GOLDEN_FRAME) *
           vp9_check_segref(xd, segment_id, ALTREF_FRAME));
      }

      if (mod_refprobs[0]) {
        vp9_write(bc, (rf != INTRA_FRAME), mod_refprobs[0]);
      }

      // Inter coded
      if (rf != INTRA_FRAME) {
        if (mod_refprobs[1]) {
          vp9_write(bc, (rf != LAST_FRAME), mod_refprobs[1]);
        }

        if (rf != LAST_FRAME) {
          if (mod_refprobs[2]) {
            vp9_write(bc, (rf != GOLDEN_FRAME), mod_refprobs[2]);
          }
        }
      }
    }
  }

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

// Update the probabilities used to encode reference frame data
static void update_ref_probs(VP9_COMP *const cpi) {
  VP9_COMMON *const cm = &cpi->common;

  const int *const rfct = cpi->count_mb_ref_frame_usage;
  const int rf_intra = rfct[INTRA_FRAME];
  const int rf_inter = rfct[LAST_FRAME] +
                       rfct[GOLDEN_FRAME] + rfct[ALTREF_FRAME];

  cm->prob_intra_coded = get_binary_prob(rf_intra, rf_inter);
  cm->prob_last_coded = get_prob(rfct[LAST_FRAME], rf_inter);
  cm->prob_gf_coded = get_binary_prob(rfct[GOLDEN_FRAME], rfct[ALTREF_FRAME]);

  // Compute a modified set of probabilities to use when prediction of the
  // reference frame fails
  vp9_compute_mod_refprobs(cm);
}

static void pack_inter_mode_mvs(VP9_COMP *cpi, MODE_INFO *m,
                                vp9_writer *bc,
                                int mb_rows_left, int mb_cols_left) {
  VP9_COMMON *const pc = &cpi->common;
  const nmv_context *nmvc = &pc->fc.nmvc;
  MACROBLOCK *const x = &cpi->mb;
  MACROBLOCKD *const xd = &x->e_mbd;
  const int mis = pc->mode_info_stride;
  MB_MODE_INFO *const mi = &m->mbmi;
  const MV_REFERENCE_FRAME rf = mi->ref_frame;
  const MB_PREDICTION_MODE mode = mi->mode;
  const int segment_id = mi->segment_id;
  const int bw = 1 << mb_width_log2(mi->sb_type);
  const int bh = 1 << mb_height_log2(mi->sb_type);
  int skip_coeff;

  int mb_row = pc->mb_rows - mb_rows_left;
  int mb_col = pc->mb_cols - mb_cols_left;
  xd->prev_mode_info_context = pc->prev_mi + (m - pc->mi);
  x->partition_info = x->pi + (m - pc->mi);

  // Distance of Mb to the various image edges.
  // These specified to 8th pel as they are always compared to MV
  // values that are in 1/8th pel units

  set_mb_row(pc, xd, mb_row, bh);
  set_mb_col(pc, xd, mb_col, bw);

#ifdef ENTROPY_STATS
  active_section = 9;
#endif

  if (cpi->mb.e_mbd.update_mb_segmentation_map) {
    // Is temporal coding of the segment map enabled
    if (pc->temporal_update) {
      unsigned char prediction_flag = vp9_get_pred_flag(xd, PRED_SEG_ID);
      vp9_prob pred_prob = vp9_get_pred_prob(pc, xd, PRED_SEG_ID);

      // Code the segment id prediction flag for this mb
      vp9_write(bc, prediction_flag, pred_prob);

      // If the mb segment id wasn't predicted code explicitly
      if (!prediction_flag)
        write_mb_segid(bc, mi, &cpi->mb.e_mbd);
    } else {
      // Normal unpredicted coding
      write_mb_segid(bc, mi, &cpi->mb.e_mbd);
    }
  }

  if (vp9_segfeature_active(xd, segment_id, SEG_LVL_SKIP)) {
    skip_coeff = 1;
  } else {
    skip_coeff = m->mbmi.mb_skip_coeff;
    vp9_write(bc, skip_coeff,
              vp9_get_pred_prob(pc, xd, PRED_MBSKIP));
  }

  // Encode the reference frame.
  encode_ref_frame(bc, pc, xd, segment_id, rf);

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

    if (m->mbmi.sb_type > BLOCK_SIZE_MB16X16)
      write_sb_ymode(bc, mode, pc->fc.sb_ymode_prob);
    else
      write_ymode(bc, mode, pc->fc.ymode_prob);

    if (mode == I4X4_PRED) {
      int j = 0;
      do {
        write_bmode(bc, m->bmi[j].as_mode.first,
                    pc->fc.bmode_prob);
      } while (++j < 16);
    }
    if (mode == I8X8_PRED) {
      write_i8x8_mode(bc, m->bmi[0].as_mode.first,
                      pc->fc.i8x8_mode_prob);
      write_i8x8_mode(bc, m->bmi[2].as_mode.first,
                      pc->fc.i8x8_mode_prob);
      write_i8x8_mode(bc, m->bmi[8].as_mode.first,
                      pc->fc.i8x8_mode_prob);
      write_i8x8_mode(bc, m->bmi[10].as_mode.first,
                      pc->fc.i8x8_mode_prob);
    } else {
      write_uv_mode(bc, mi->uv_mode,
                    pc->fc.uv_mode_prob[mode]);
    }
  } else {
    vp9_prob mv_ref_p[VP9_MVREFS - 1];

    vp9_mv_ref_probs(&cpi->common, mv_ref_p, mi->mb_mode_context[rf]);

#ifdef ENTROPY_STATS
    active_section = 3;
#endif

    // If segment skip is not enabled code the mode.
    if (!vp9_segfeature_active(xd, segment_id, SEG_LVL_SKIP)) {
      if (mi->sb_type > BLOCK_SIZE_MB16X16) {
        write_sb_mv_ref(bc, mode, mv_ref_p);
      } else {
        write_mv_ref(bc, mode, mv_ref_p);
      }
      vp9_accum_mv_refs(&cpi->common, mode, mi->mb_mode_context[rf]);
    }

    if (mode >= NEARESTMV && mode <= SPLITMV) {
      if (cpi->common.mcomp_filter_type == SWITCHABLE) {
        write_token(bc, vp9_switchable_interp_tree,
                    vp9_get_pred_probs(&cpi->common, xd,
                                       PRED_SWITCHABLE_INTERP),
                    vp9_switchable_interp_encodings +
                    vp9_switchable_interp_map[mi->interp_filter]);
      } else {
        assert(mi->interp_filter == cpi->common.mcomp_filter_type);
      }
    }

    // does the feature use compound prediction or not
    // (if not specified at the frame/segment level)
    if (cpi->common.comp_pred_mode == HYBRID_PREDICTION) {
      vp9_write(bc, mi->second_ref_frame > INTRA_FRAME,
                vp9_get_pred_prob(pc, xd, PRED_COMP));
    }
#if CONFIG_COMP_INTERINTRA_PRED
    if (cpi->common.use_interintra &&
        mode >= NEARESTMV && mode < SPLITMV &&
        mi->second_ref_frame <= INTRA_FRAME) {
      vp9_write(bc, mi->second_ref_frame == INTRA_FRAME,
                pc->fc.interintra_prob);
      // if (!cpi->dummy_packing)
      //   printf("-- %d (%d)\n", mi->second_ref_frame == INTRA_FRAME,
      //          pc->fc.interintra_prob);
      if (mi->second_ref_frame == INTRA_FRAME) {
        // if (!cpi->dummy_packing)
        //   printf("** %d %d\n", mi->interintra_mode,
        // mi->interintra_uv_mode);
        write_ymode(bc, mi->interintra_mode, pc->fc.ymode_prob);
#if SEPARATE_INTERINTRA_UV
        write_uv_mode(bc, mi->interintra_uv_mode,
                      pc->fc.uv_mode_prob[mi->interintra_mode]);
#endif
      }
    }
#endif

    switch (mode) { /* new, split require MVs */
      case NEWMV:
#ifdef ENTROPY_STATS
        active_section = 5;
#endif
        write_nmv(cpi, bc, &mi->mv[0].as_mv, &mi->best_mv,
                  (const nmv_context*) nmvc,
                  xd->allow_high_precision_mv);

        if (mi->second_ref_frame > 0) {
          write_nmv(cpi, bc, &mi->mv[1].as_mv, &mi->best_second_mv,
                    (const nmv_context*) nmvc,
                    xd->allow_high_precision_mv);
        }
        break;
      case SPLITMV: {
        int j = 0;

#ifdef MODE_STATS
        ++count_mb_seg[mi->partitioning];
#endif

        write_split(bc, mi->partitioning, cpi->common.fc.mbsplit_prob);
        cpi->mbsplit_count[mi->partitioning]++;

        do {
          B_PREDICTION_MODE blockmode;
          int_mv blockmv;
          const int *const  L = vp9_mbsplits[mi->partitioning];
          int k = -1;  /* first block in subset j */
          int mv_contz;
          int_mv leftmv, abovemv;

          blockmode = cpi->mb.partition_info->bmi[j].mode;
          blockmv = cpi->mb.partition_info->bmi[j].mv;
#if CONFIG_DEBUG
          while (j != L[++k])
            if (k >= 16)
              assert(0);
#else
          while (j != L[++k]);
#endif
          leftmv.as_int = left_block_mv(xd, m, k);
          abovemv.as_int = above_block_mv(m, k, mis);
          mv_contz = vp9_mv_cont(&leftmv, &abovemv);

          write_sub_mv_ref(bc, blockmode,
                           cpi->common.fc.sub_mv_ref_prob[mv_contz]);
          cpi->sub_mv_ref_count[mv_contz][blockmode - LEFT4X4]++;
          if (blockmode == NEW4X4) {
#ifdef ENTROPY_STATS
            active_section = 11;
#endif
            write_nmv(cpi, bc, &blockmv.as_mv, &mi->best_mv,
                      (const nmv_context*) nmvc,
                      xd->allow_high_precision_mv);

            if (mi->second_ref_frame > 0) {
              write_nmv(cpi, bc,
                        &cpi->mb.partition_info->bmi[j].second_mv.as_mv,
                        &mi->best_second_mv,
                        (const nmv_context*) nmvc,
                        xd->allow_high_precision_mv);
            }
          }
        } while (++j < cpi->mb.partition_info->count);
        break;
      }
      default:
        break;
    }
  }

  if (((rf == INTRA_FRAME && mode <= I8X8_PRED) ||
       (rf != INTRA_FRAME && !(mode == SPLITMV &&
                               mi->partitioning == PARTITIONING_4X4))) &&
      pc->txfm_mode == TX_MODE_SELECT &&
          !(skip_coeff || vp9_segfeature_active(xd, segment_id,
                                                SEG_LVL_SKIP))) {
    TX_SIZE sz = mi->txfm_size;
    // FIXME(rbultje) code ternary symbol once all experiments are merged
    vp9_write(bc, sz != TX_4X4, pc->prob_tx[0]);
    if (sz != TX_4X4 && mode != I8X8_PRED && mode != SPLITMV) {
      vp9_write(bc, sz != TX_8X8, pc->prob_tx[1]);
      if (mi->sb_type >= BLOCK_SIZE_SB32X32 && sz != TX_8X8)
        vp9_write(bc, sz != TX_16X16, pc->prob_tx[2]);
    }
  }
}

static void write_mb_modes_kf(const VP9_COMP *cpi,
                              MODE_INFO *m,
                              vp9_writer *bc,
                              int mb_rows_left, int mb_cols_left) {
  const VP9_COMMON *const c = &cpi->common;
  const MACROBLOCKD *const xd = &cpi->mb.e_mbd;
  const int mis = c->mode_info_stride;
  const int ym = m->mbmi.mode;
  const int segment_id = m->mbmi.segment_id;
  int skip_coeff;