/*

  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 "vp9/common/vp9_common.h"

#include "vp9/common/vp9_entropy.h"

#include "vp9/common/vp9_entropymode.h"

#include "vp9/common/vp9_entropymv.h"

#include "vp9/common/vp9_mvref_common.h"

#include "vp9/common/vp9_pred_common.h"

#include "vp9/common/vp9_reconinter.h"

#include "vp9/common/vp9_seg_common.h"

#include "vp9/decoder/vp9_decodemv.h"

#include "vp9/decoder/vp9_decodeframe.h"

#include "vpx_dsp/vpx_dsp_common.h"

static PREDICTION_MODE read_intra_mode(vpx_reader *r, const vpx_prob *p) {

  return (PREDICTION_MODE)vpx_read_tree(r, vp9_intra_mode_tree, p);

}

static PREDICTION_MODE read_intra_mode_y(VP9_COMMON *cm, MACROBLOCKD *xd,

                                         vpx_reader *r, int size_group) {

  const PREDICTION_MODE y_mode =

      read_intra_mode(r, cm->fc->y_mode_prob[size_group]);

  FRAME_COUNTS *counts = xd->counts;

  if (counts) ++counts->y_mode[size_group][y_mode];

  return y_mode;

}

static PREDICTION_MODE read_intra_mode_uv(VP9_COMMON *cm, MACROBLOCKD *xd,

                                          vpx_reader *r,

                                          PREDICTION_MODE y_mode) {

  const PREDICTION_MODE uv_mode =

      read_intra_mode(r, cm->fc->uv_mode_prob[y_mode]);

  FRAME_COUNTS *counts = xd->counts;

  if (counts) ++counts->uv_mode[y_mode][uv_mode];

  return uv_mode;

}

static PREDICTION_MODE read_inter_mode(VP9_COMMON *cm, MACROBLOCKD *xd,

                                       vpx_reader *r, int ctx) {

  const int mode =

      vpx_read_tree(r, vp9_inter_mode_tree, cm->fc->inter_mode_probs[ctx]);

  FRAME_COUNTS *counts = xd->counts;

  if (counts) ++counts->inter_mode[ctx][mode];

  return NEARESTMV + mode;

}

static int read_segment_id(vpx_reader *r, const struct segmentation *seg) {

  return vpx_read_tree(r, vp9_segment_tree, seg->tree_probs);

}

static TX_SIZE read_selected_tx_size(VP9_COMMON *cm, MACROBLOCKD *xd,

                                     TX_SIZE max_tx_size, vpx_reader *r) {

  FRAME_COUNTS *counts = xd->counts;

  const int ctx = get_tx_size_context(xd);

  const vpx_prob *tx_probs = get_tx_probs(max_tx_size, ctx, &cm->fc->tx_probs);

  int tx_size = vpx_read(r, tx_probs[0]);

  if (tx_size != TX_4X4 && max_tx_size >= TX_16X16) {

    tx_size += vpx_read(r, tx_probs[1]);

    if (tx_size != TX_8X8 && max_tx_size >= TX_32X32)

      tx_size += vpx_read(r, tx_probs[2]);

  }

  if (counts) ++get_tx_counts(max_tx_size, ctx, &counts->tx)[tx_size];

  return (TX_SIZE)tx_size;

}

static INLINE TX_SIZE read_tx_size(VP9_COMMON *cm, MACROBLOCKD *xd,

                                   int allow_select, vpx_reader *r) {

  TX_MODE tx_mode = cm->tx_mode;

  BLOCK_SIZE bsize = xd->mi[0]->sb_type;

  const TX_SIZE max_tx_size = max_txsize_lookup[bsize];

  if (allow_select && tx_mode == TX_MODE_SELECT && bsize >= BLOCK_8X8)

    return read_selected_tx_size(cm, xd, max_tx_size, r);

  else

    return VPXMIN(max_tx_size, tx_mode_to_biggest_tx_size[tx_mode]);

}

static int dec_get_segment_id(const VP9_COMMON *cm, const uint8_t *segment_ids,

                              int mi_offset, int x_mis, int y_mis) {

  int x, y, segment_id = INT_MAX;

  for (y = 0; y < y_mis; y++)

    for (x = 0; x < x_mis; x++)

      segment_id =

          VPXMIN(segment_id, segment_ids[mi_offset + y * cm->mi_cols + x]);

  assert(segment_id >= 0 && segment_id < MAX_SEGMENTS);

  return segment_id;

}

static void set_segment_id(VP9_COMMON *cm, int mi_offset, int x_mis, int y_mis,

                           int segment_id) {

  int x, y;

  assert(segment_id >= 0 && segment_id < MAX_SEGMENTS);

  for (y = 0; y < y_mis; y++)

    for (x = 0; x < x_mis; x++)

      cm->current_frame_seg_map[mi_offset + y * cm->mi_cols + x] = segment_id;

}

static void copy_segment_id(const VP9_COMMON *cm,

                            const uint8_t *last_segment_ids,

                            uint8_t *current_segment_ids, int mi_offset,

                            int x_mis, int y_mis) {

  int x, y;

  for (y = 0; y < y_mis; y++)

    for (x = 0; x < x_mis; x++)

      current_segment_ids[mi_offset + y * cm->mi_cols + x] =

          last_segment_ids ? last_segment_ids[mi_offset + y * cm->mi_cols + x]

                           : 0;

}

static int read_intra_segment_id(VP9_COMMON *const cm, int mi_offset, int x_mis,

                                 int y_mis, vpx_reader *r) {

  struct segmentation *const seg = &cm->seg;

  int segment_id;

  if (!seg->enabled) return 0;  // Default for disabled segmentation

  if (!seg->update_map) {

    copy_segment_id(cm, cm->last_frame_seg_map, cm->current_frame_seg_map,

                    mi_offset, x_mis, y_mis);

    return 0;

  }

  segment_id = read_segment_id(r, seg);

  set_segment_id(cm, mi_offset, x_mis, y_mis, segment_id);

  return segment_id;

}

static int read_inter_segment_id(VP9_COMMON *const cm, MACROBLOCKD *const xd,

                                 int mi_row, int mi_col, vpx_reader *r,

                                 int x_mis, int y_mis) {

  struct segmentation *const seg = &cm->seg;

  MODE_INFO *const mi = xd->mi[0];

  int predicted_segment_id, segment_id;

  const int mi_offset = mi_row * cm->mi_cols + mi_col;

  if (!seg->enabled) return 0;  // Default for disabled segmentation

  predicted_segment_id = cm->last_frame_seg_map

                             ? dec_get_segment_id(cm, cm->last_frame_seg_map,

                                                  mi_offset, x_mis, y_mis)

                             : 0;

  if (!seg->update_map) {

    copy_segment_id(cm, cm->last_frame_seg_map, cm->current_frame_seg_map,

                    mi_offset, x_mis, y_mis);

    return predicted_segment_id;

  }

  if (seg->temporal_update) {

    const vpx_prob pred_prob = vp9_get_pred_prob_seg_id(seg, xd);

    mi->seg_id_predicted = vpx_read(r, pred_prob);

    segment_id =

        mi->seg_id_predicted ? predicted_segment_id : read_segment_id(r, seg);

  } else {

    segment_id = read_segment_id(r, seg);

  }

  set_segment_id(cm, mi_offset, x_mis, y_mis, segment_id);

  return segment_id;

}

static int read_skip(VP9_COMMON *cm, const MACROBLOCKD *xd, int segment_id,

                     vpx_reader *r) {

  if (segfeature_active(&cm->seg, segment_id, SEG_LVL_SKIP)) {

    return 1;

  } else {

    const int ctx = vp9_get_skip_context(xd);

    const int skip = vpx_read(r, cm->fc->skip_probs[ctx]);

    FRAME_COUNTS *counts = xd->counts;

    if (counts) ++counts->skip[ctx][skip];

    return skip;

  }

}

static void read_intra_frame_mode_info(VP9_COMMON *const cm,

                                       MACROBLOCKD *const xd, int mi_row,

                                       int mi_col, vpx_reader *r, int x_mis,

                                       int y_mis) {

  MODE_INFO *const mi = xd->mi[0];

  const MODE_INFO *above_mi = xd->above_mi;

  const MODE_INFO *left_mi = xd->left_mi;

  const BLOCK_SIZE bsize = mi->sb_type;

  int i;

  const int mi_offset = mi_row * cm->mi_cols + mi_col;

  mi->segment_id = read_intra_segment_id(cm, mi_offset, x_mis, y_mis, r);

  mi->skip = read_skip(cm, xd, mi->segment_id, r);

  mi->tx_size = read_tx_size(cm, xd, 1, r);

  mi->ref_frame[0] = INTRA_FRAME;

  mi->ref_frame[1] = NO_REF_FRAME;

  switch (bsize) {

    case BLOCK_4X4:

      for (i = 0; i < 4; ++i)

        mi->bmi[i].as_mode =

            read_intra_mode(r, get_y_mode_probs(mi, above_mi, left_mi, i));

      mi->mode = mi->bmi[3].as_mode;

      break;

    case BLOCK_4X8:

      mi->bmi[0].as_mode = mi->bmi[2].as_mode =

          read_intra_mode(r, get_y_mode_probs(mi, above_mi, left_mi, 0));

      mi->bmi[1].as_mode = mi->bmi[3].as_mode = mi->mode =

          read_intra_mode(r, get_y_mode_probs(mi, above_mi, left_mi, 1));

      break;

    case BLOCK_8X4:

      mi->bmi[0].as_mode = mi->bmi[1].as_mode =

          read_intra_mode(r, get_y_mode_probs(mi, above_mi, left_mi, 0));

      mi->bmi[2].as_mode = mi->bmi[3].as_mode = mi->mode =

          read_intra_mode(r, get_y_mode_probs(mi, above_mi, left_mi, 2));

      break;

    default:

      mi->mode = read_intra_mode(r, get_y_mode_probs(mi, above_mi, left_mi, 0));

  }

  mi->uv_mode = read_intra_mode(r, vp9_kf_uv_mode_prob[mi->mode]);

}

static int read_mv_component(vpx_reader *r, const nmv_component *mvcomp,

                             int usehp) {

  int mag, d, fr, hp;

  const int sign = vpx_read(r, mvcomp->sign);

  const int mv_class = vpx_read_tree(r, vp9_mv_class_tree, mvcomp->classes);

  const int class0 = mv_class == MV_CLASS_0;

  // Integer part

  if (class0) {

    d = vpx_read(r, mvcomp->class0[0]);

    mag = 0;

  } else {

    int i;

    const int n = mv_class + CLASS0_BITS - 1;  // number of bits

    d = 0;

    for (i = 0; i < n; ++i) d |= vpx_read(r, mvcomp->bits[i]) << i;

    mag = CLASS0_SIZE << (mv_class + 2);

  }

  // Fractional part

  fr = vpx_read_tree(r, vp9_mv_fp_tree,

                     class0 ? mvcomp->class0_fp[d] : mvcomp->fp);

  // High precision part (if hp is not used, the default value of the hp is 1)

  hp = usehp ? vpx_read(r, class0 ? mvcomp->class0_hp : mvcomp->hp) : 1;

  // Result

  mag += ((d << 3) | (fr << 1) | hp) + 1;

  return sign ? -mag : mag;

}

static INLINE void read_mv(vpx_reader *r, MV *mv, const MV *ref,

                           const nmv_context *ctx, nmv_context_counts *counts,

                           int allow_hp) {

  const MV_JOINT_TYPE joint_type =

      (MV_JOINT_TYPE)vpx_read_tree(r, vp9_mv_joint_tree, ctx->joints);

  const int use_hp = allow_hp && use_mv_hp(ref);

  MV diff = { 0, 0 };

  if (mv_joint_vertical(joint_type))

    diff.row = read_mv_component(r, &ctx->comps[0], use_hp);

  if (mv_joint_horizontal(joint_type))

    diff.col = read_mv_component(r, &ctx->comps[1], use_hp);

  vp9_inc_mv(&diff, counts);

  mv->row = ref->row + diff.row;

  mv->col = ref->col + diff.col;

}

static REFERENCE_MODE read_block_reference_mode(VP9_COMMON *cm,

                                                const MACROBLOCKD *xd,

                                                vpx_reader *r) {

  if (cm->reference_mode == REFERENCE_MODE_SELECT) {

    const int ctx = vp9_get_reference_mode_context(cm, xd);

    const REFERENCE_MODE mode =

        (REFERENCE_MODE)vpx_read(r, cm->fc->comp_inter_prob[ctx]);

    FRAME_COUNTS *counts = xd->counts;

    if (counts) ++counts->comp_inter[ctx][mode];

    return mode;  // SINGLE_REFERENCE or COMPOUND_REFERENCE

  } else {

    return cm->reference_mode;

  }

}

// Read the reference frame

static void read_ref_frames(VP9_COMMON *const cm, MACROBLOCKD *const xd,

                            vpx_reader *r, int segment_id,

                            MV_REFERENCE_FRAME ref_frame[2]) {

  FRAME_CONTEXT *const fc = cm->fc;

  FRAME_COUNTS *counts = xd->counts;

  if (segfeature_active(&cm->seg, segment_id, SEG_LVL_REF_FRAME)) {

    ref_frame[0] = (MV_REFERENCE_FRAME)get_segdata(&cm->seg, segment_id,

                                                   SEG_LVL_REF_FRAME);

    ref_frame[1] = NO_REF_FRAME;

  } else {

    const REFERENCE_MODE mode = read_block_reference_mode(cm, xd, r);

    // FIXME(rbultje) I'm pretty sure this breaks segmentation ref frame coding

    if (mode == COMPOUND_REFERENCE) {

      const int idx = cm->ref_frame_sign_bias[cm->comp_fixed_ref];

      const int ctx = vp9_get_pred_context_comp_ref_p(cm, xd);

      const int bit = vpx_read(r, fc->comp_ref_prob[ctx]);

      if (counts) ++counts->comp_ref[ctx][bit];

      ref_frame[idx] = cm->comp_fixed_ref;

      ref_frame[!idx] = cm->comp_var_ref[bit];

    } else if (mode == SINGLE_REFERENCE) {

      const int ctx0 = vp9_get_pred_context_single_ref_p1(xd);

      const int bit0 = vpx_read(r, fc->single_ref_prob[ctx0][0]);

      if (counts) ++counts->single_ref[ctx0][0][bit0];

      if (bit0) {

        const int ctx1 = vp9_get_pred_context_single_ref_p2(xd);

        const int bit1 = vpx_read(r, fc->single_ref_prob[ctx1][1]);

        if (counts) ++counts->single_ref[ctx1][1][bit1];

        ref_frame[0] = bit1 ? ALTREF_FRAME : GOLDEN_FRAME;

      } else {

        ref_frame[0] = LAST_FRAME;

      }

      ref_frame[1] = NO_REF_FRAME;

    } else {

      assert(0 && "Invalid prediction mode.");

    }

  }

}

static INLINE INTERP_FILTER read_switchable_interp_filter(VP9_COMMON *const cm,

                                                          MACROBLOCKD *const xd,

                                                          vpx_reader *r) {

  const int ctx = get_pred_context_switchable_interp(xd);

  const INTERP_FILTER type = (INTERP_FILTER)vpx_read_tree(

      r, vp9_switchable_interp_tree, cm->fc->switchable_interp_prob[ctx]);

  FRAME_COUNTS *counts = xd->counts;

  if (counts) ++counts->switchable_interp[ctx][type];

  return type;

}

static void read_intra_block_mode_info(VP9_COMMON *const cm,

                                       MACROBLOCKD *const xd, MODE_INFO *mi,

                                       vpx_reader *r) {

  const BLOCK_SIZE bsize = mi->sb_type;

  int i;

  switch (bsize) {

    case BLOCK_4X4:

      for (i = 0; i < 4; ++i)

        mi->bmi[i].as_mode = read_intra_mode_y(cm, xd, r, 0);

      mi->mode = mi->bmi[3].as_mode;

      break;

    case BLOCK_4X8:

      mi->bmi[0].as_mode = mi->bmi[2].as_mode = read_intra_mode_y(cm, xd, r, 0);

      mi->bmi[1].as_mode = mi->bmi[3].as_mode = mi->mode =

          read_intra_mode_y(cm, xd, r, 0);

      break;

    case BLOCK_8X4:

      mi->bmi[0].as_mode = mi->bmi[1].as_mode = read_intra_mode_y(cm, xd, r, 0);

      mi->bmi[2].as_mode = mi->bmi[3].as_mode = mi->mode =

          read_intra_mode_y(cm, xd, r, 0);

      break;

    default: mi->mode = read_intra_mode_y(cm, xd, r, size_group_lookup[bsize]);

  }

  mi->uv_mode = read_intra_mode_uv(cm, xd, r, mi->mode);

  // Initialize interp_filter here so we do not have to check for inter block

  // modes in get_pred_context_switchable_interp()

  mi->interp_filter = SWITCHABLE_FILTERS;

  mi->ref_frame[0] = INTRA_FRAME;

  mi->ref_frame[1] = NO_REF_FRAME;

}

static INLINE int is_mv_valid(const MV *mv) {

  return mv->row > MV_LOW && mv->row < MV_UPP && mv->col > MV_LOW &&

         mv->col < MV_UPP;

}

static INLINE void copy_mv_pair(int_mv *dst, const int_mv *src) {

  memcpy(dst, src, sizeof(*dst) * 2);

}

static INLINE void zero_mv_pair(int_mv *dst) {

  memset(dst, 0, sizeof(*dst) * 2);

}

static INLINE int assign_mv(VP9_COMMON *cm, MACROBLOCKD *xd,

                            PREDICTION_MODE mode, int_mv mv[2],

                            int_mv ref_mv[2], int_mv near_nearest_mv[2],

                            int is_compound, int allow_hp, vpx_reader *r) {

  int i;

  int ret = 1;

  switch (mode) {

    case NEWMV: {

      FRAME_COUNTS *counts = xd->counts;

      nmv_context_counts *const mv_counts = counts ? &counts->mv : NULL;

      for (i = 0; i < 1 + is_compound; ++i) {

        read_mv(r, &mv[i].as_mv, &ref_mv[i].as_mv, &cm->fc->nmvc, mv_counts,

                allow_hp);

        ret = ret && is_mv_valid(&mv[i].as_mv);

      }

      break;

    }

    case NEARMV:

    case NEARESTMV: {

      copy_mv_pair(mv, near_nearest_mv);

      break;

    }

    case ZEROMV: {

      zero_mv_pair(mv);

      break;

    }

    default: {

      return 0;

    }

  }

  return ret;

}

static int read_is_inter_block(VP9_COMMON *const cm, MACROBLOCKD *const xd,

                               int segment_id, vpx_reader *r) {

  if (segfeature_active(&cm->seg, segment_id, SEG_LVL_REF_FRAME)) {

    return get_segdata(&cm->seg, segment_id, SEG_LVL_REF_FRAME) != INTRA_FRAME;

  } else {

    const int ctx = get_intra_inter_context(xd);

    const int is_inter = vpx_read(r, cm->fc->intra_inter_prob[ctx]);

    FRAME_COUNTS *counts = xd->counts;

    if (counts) ++counts->intra_inter[ctx][is_inter];

    return is_inter;

  }

}

// This macro is used to add a motion vector mv_ref list if it isn't

// already in the list.  If it's the second motion vector or early_break

// it will also skip all additional processing and jump to Done!

#define ADD_MV_REF_LIST_EB(mv, refmv_count, mv_ref_list, Done) \

  do {                                                         \

    if (refmv_count) {                                         \

      if ((mv).as_int != (mv_ref_list)[0].as_int) {            \

        (mv_ref_list)[(refmv_count)] = (mv);                   \

        refmv_count++;                                         \

        goto Done;                                             \

      }                                                        \

    } else {                                                   \

      (mv_ref_list)[(refmv_count)++] = (mv);                   \

      if (early_break) goto Done;                              \

    }                                                          \

  } while (0)

// If either reference frame is different, not INTRA, and they

// are different from each other scale and add the mv to our list.

#define IF_DIFF_REF_FRAME_ADD_MV_EB(mbmi, ref_frame, ref_sign_bias,       \

                                    refmv_count, mv_ref_list, Done)       \

  do {                                                                    \

    if (is_inter_block(mbmi)) {                                           \

      if ((mbmi)->ref_frame[0] != ref_frame)                              \

        ADD_MV_REF_LIST_EB(scale_mv((mbmi), 0, ref_frame, ref_sign_bias), \

                           refmv_count, mv_ref_list, Done);               \

      if (has_second_ref(mbmi) && (mbmi)->ref_frame[1] != ref_frame &&    \

          (mbmi)->mv[1].as_int != (mbmi)->mv[0].as_int)                   \

        ADD_MV_REF_LIST_EB(scale_mv((mbmi), 1, ref_frame, ref_sign_bias), \

                           refmv_count, mv_ref_list, Done);               \

    }                                                                     \

  } while (0)

// This function searches the neighborhood of a given MB/SB

// to try and find candidate reference vectors.

static int dec_find_mv_refs(const VP9_COMMON *cm, const MACROBLOCKD *xd,

                            PREDICTION_MODE mode, MV_REFERENCE_FRAME ref_frame,

                            const POSITION *const mv_ref_search,

                            int_mv *mv_ref_list, int mi_row, int mi_col,

                            int block) {

  const int *ref_sign_bias = cm->ref_frame_sign_bias;

  int i, refmv_count = 0;

  int different_ref_found = 0;

  const MV_REF *const prev_frame_mvs =

      cm->use_prev_frame_mvs

          ? cm->prev_frame->mvs + mi_row * cm->mi_cols + mi_col

          : NULL;

  const TileInfo *const tile = &xd->tile;

  // If mode is nearestmv or newmv (uses nearestmv as a reference) then stop

  // searching after the first mv is found.

  const int early_break = (mode != NEARMV);

  // Blank the reference vector list

  memset(mv_ref_list, 0, sizeof(*mv_ref_list) * MAX_MV_REF_CANDIDATES);

  i = 0;

  if (block >= 0) {

    // If the size < 8x8 we get the mv from the bmi substructure for the

    // nearest two blocks.

    for (i = 0; i < 2; ++i) {

      const POSITION *const mv_ref = &mv_ref_search[i];

      if (is_inside(tile, mi_col, mi_row, cm->mi_rows, mv_ref)) {

        const MODE_INFO *const candidate_mi =

            xd->mi[mv_ref->col + mv_ref->row * xd->mi_stride];

        different_ref_found = 1;

        if (candidate_mi->ref_frame[0] == ref_frame)

          ADD_MV_REF_LIST_EB(

              get_sub_block_mv(candidate_mi, 0, mv_ref->col, block),

              refmv_count, mv_ref_list, Done);

        else if (candidate_mi->ref_frame[1] == ref_frame)

          ADD_MV_REF_LIST_EB(

              get_sub_block_mv(candidate_mi, 1, mv_ref->col, block),

              refmv_count, mv_ref_list, Done);

      }

    }

  }

  // Check the rest of the neighbors in much the same way

  // as before except we don't need to keep track of sub blocks or

  // mode counts.

  for (; i < MVREF_NEIGHBOURS; ++i) {

    const POSITION *const mv_ref = &mv_ref_search[i];

    if (is_inside(tile, mi_col, mi_row, cm->mi_rows, mv_ref)) {

      const MODE_INFO *const candidate =

          xd->mi[mv_ref->col + mv_ref->row * xd->mi_stride];

      different_ref_found = 1;

      if (candidate->ref_frame[0] == ref_frame)

        ADD_MV_REF_LIST_EB(candidate->mv[0], refmv_count, mv_ref_list, Done);

      else if (candidate->ref_frame[1] == ref_frame)

        ADD_MV_REF_LIST_EB(candidate->mv[1], refmv_count, mv_ref_list, Done);

    }

  }

  // Check the last frame's mode and mv info.

  if (prev_frame_mvs) {

    if (prev_frame_mvs->ref_frame[0] == ref_frame) {

      ADD_MV_REF_LIST_EB(prev_frame_mvs->mv[0], refmv_count, mv_ref_list, Done);

    } else if (prev_frame_mvs->ref_frame[1] == ref_frame) {

      ADD_MV_REF_LIST_EB(prev_frame_mvs->mv[1], refmv_count, mv_ref_list, Done);

    }

  }

  // Since we couldn't find 2 mvs from the same reference frame

  // go back through the neighbors and find motion vectors from

  // different reference frames.

  if (different_ref_found) {

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

      const POSITION *mv_ref = &mv_ref_search[i];

      if (is_inside(tile, mi_col, mi_row, cm->mi_rows, mv_ref)) {

        const MODE_INFO *const candidate =

            xd->mi[mv_ref->col + mv_ref->row * xd->mi_stride];

        // If the candidate is INTRA we don't want to consider its mv.

        IF_DIFF_REF_FRAME_ADD_MV_EB(candidate, ref_frame, ref_sign_bias,

                                    refmv_count, mv_ref_list, Done);

      }

    }

  }

  // Since we still don't have a candidate we'll try the last frame.

  if (prev_frame_mvs) {

    if (prev_frame_mvs->ref_frame[0] != ref_frame &&

        prev_frame_mvs->ref_frame[0] > INTRA_FRAME) {

      int_mv mv = prev_frame_mvs->mv[0];

      if (ref_sign_bias[prev_frame_mvs->ref_frame[0]] !=

          ref_sign_bias[ref_frame]) {

        mv.as_mv.row *= -1;

        mv.as_mv.col *= -1;

      }

      ADD_MV_REF_LIST_EB(mv, refmv_count, mv_ref_list, Done);

    }

    if (prev_frame_mvs->ref_frame[1] > INTRA_FRAME &&

        prev_frame_mvs->ref_frame[1] != ref_frame &&

        prev_frame_mvs->mv[1].as_int != prev_frame_mvs->mv[0].as_int) {

      int_mv mv = prev_frame_mvs->mv[1];

      if (ref_sign_bias[prev_frame_mvs->ref_frame[1]] !=

          ref_sign_bias[ref_frame]) {

        mv.as_mv.row *= -1;

        mv.as_mv.col *= -1;

      }

      ADD_MV_REF_LIST_EB(mv, refmv_count, mv_ref_list, Done);

    }

  }

  if (mode == NEARMV)

    refmv_count = MAX_MV_REF_CANDIDATES;

  else

    // we only care about the nearestmv for the remaining modes

    refmv_count = 1;

Done:

  // Clamp vectors

  for (i = 0; i < refmv_count; ++i) clamp_mv_ref(&mv_ref_list[i].as_mv, xd);

  return refmv_count;

}

static void append_sub8x8_mvs_for_idx(VP9_COMMON *cm, MACROBLOCKD *xd,

                                      const POSITION *const mv_ref_search,

                                      PREDICTION_MODE b_mode, int block,

                                      int ref, int mi_row, int mi_col,

                                      int_mv *best_sub8x8) {

  int_mv mv_list[MAX_MV_REF_CANDIDATES];

  MODE_INFO *const mi = xd->mi[0];

  b_mode_info *bmi = mi->bmi;

  int n;

  int refmv_count;

  assert(MAX_MV_REF_CANDIDATES == 2);

  switch (block) {

    case 0:

      refmv_count =

          dec_find_mv_refs(cm, xd, b_mode, mi->ref_frame[ref], mv_ref_search,

                           mv_list, mi_row, mi_col, block);

      best_sub8x8->as_int = mv_list[refmv_count - 1].as_int;

      break;

    case 1:

    case 2:

      if (b_mode == NEARESTMV) {

        best_sub8x8->as_int = bmi[0].as_mv[ref].as_int;

      } else {

        dec_find_mv_refs(cm, xd, b_mode, mi->ref_frame[ref], mv_ref_search,

                         mv_list, mi_row, mi_col, block);

        best_sub8x8->as_int = 0;

        for (n = 0; n < 2; ++n)

          if (bmi[0].as_mv[ref].as_int != mv_list[n].as_int) {

            best_sub8x8->as_int = mv_list[n].as_int;

            break;

          }

      }

      break;

    case 3:

      if (b_mode == NEARESTMV) {

        best_sub8x8->as_int = bmi[2].as_mv[ref].as_int;

      } else {

        best_sub8x8->as_int = 0;

        if (bmi[2].as_mv[ref].as_int != bmi[1].as_mv[ref].as_int) {

          best_sub8x8->as_int = bmi[1].as_mv[ref].as_int;

          break;

        }

        if (bmi[2].as_mv[ref].as_int != bmi[0].as_mv[ref].as_int) {

          best_sub8x8->as_int = bmi[0].as_mv[ref].as_int;

          break;

        }

        dec_find_mv_refs(cm, xd, b_mode, mi->ref_frame[ref], mv_ref_search,

                         mv_list, mi_row, mi_col, block);

        for (n = 0; n < 2; ++n)

          if (bmi[2].as_mv[ref].as_int != mv_list[n].as_int) {

            best_sub8x8->as_int = mv_list[n].as_int;

            break;

          }

      }

      break;

    default: assert(0 && "Invalid block index.");

  }

}

static uint8_t get_mode_context(const VP9_COMMON *cm, const MACROBLOCKD *xd,

                                const POSITION *const mv_ref_search, int mi_row,

                                int mi_col) {

  int i;

  int context_counter = 0;

  const TileInfo *const tile = &xd->tile;

  // Get mode count from nearest 2 blocks

  for (i = 0; i < 2; ++i) {

    const POSITION *const mv_ref = &mv_ref_search[i];

    if (is_inside(tile, mi_col, mi_row, cm->mi_rows, mv_ref)) {

      const MODE_INFO *const candidate =

          xd->mi[mv_ref->col + mv_ref->row * xd->mi_stride];

      // Keep counts for entropy encoding.

      context_counter += mode_2_counter[candidate->mode];

    }

  }

  return counter_to_context[context_counter];

}

static void read_inter_block_mode_info(VP9Decoder *const pbi,

                                       MACROBLOCKD *const xd,

                                       MODE_INFO *const mi, int mi_row,

                                       int mi_col, vpx_reader *r) {

  VP9_COMMON *const cm = &pbi->common;

  const BLOCK_SIZE bsize = mi->sb_type;

  const int allow_hp = cm->allow_high_precision_mv;

  int_mv best_ref_mvs[2] = { { 0 }, { 0 } };

  int ref, is_compound;

  uint8_t inter_mode_ctx;

  const POSITION *const mv_ref_search = mv_ref_blocks[bsize];

  read_ref_frames(cm, xd, r, mi->segment_id, mi->ref_frame);

  is_compound = has_second_ref(mi);

  inter_mode_ctx = get_mode_context(cm, xd, mv_ref_search, mi_row, mi_col);

  if (segfeature_active(&cm->seg, mi->segment_id, SEG_LVL_SKIP)) {

    mi->mode = ZEROMV;

    if (bsize < BLOCK_8X8) {

      vpx_internal_error(xd->error_info, VPX_CODEC_UNSUP_BITSTREAM,

                         "Invalid usage of segment feature on small blocks");

      return;

    }

  } else {

    if (bsize >= BLOCK_8X8)

      mi->mode = read_inter_mode(cm, xd, r, inter_mode_ctx);

  }

  mi->interp_filter = (cm->interp_filter == SWITCHABLE)

                          ? read_switchable_interp_filter(cm, xd, r)

                          : cm->interp_filter;

  if (bsize < BLOCK_8X8) {

    const int num_4x4_w = 1 << xd->bmode_blocks_wl;

    const int num_4x4_h = 1 << xd->bmode_blocks_hl;

    int idx, idy;

    PREDICTION_MODE b_mode;

    int got_mv_refs_for_new = 0;

    int_mv best_sub8x8[2];

    const uint32_t invalid_mv = 0x80008000;

    // Initialize the 2nd element as even though it won't be used meaningfully

    // if is_compound is false, copying/clamping it may trigger a MSan warning.

    best_sub8x8[1].as_int = invalid_mv;

    for (idy = 0; idy < 2; idy += num_4x4_h) {

      for (idx = 0; idx < 2; idx += num_4x4_w) {

        const int j = idy * 2 + idx;

        b_mode = read_inter_mode(cm, xd, r, inter_mode_ctx);

        if (b_mode == NEARESTMV || b_mode == NEARMV) {

          for (ref = 0; ref < 1 + is_compound; ++ref)

            append_sub8x8_mvs_for_idx(cm, xd, mv_ref_search, b_mode, j, ref,

                                      mi_row, mi_col, &best_sub8x8[ref]);

        } else if (b_mode == NEWMV && !got_mv_refs_for_new) {

          for (ref = 0; ref < 1 + is_compound; ++ref) {

            int_mv tmp_mvs[MAX_MV_REF_CANDIDATES];

            const MV_REFERENCE_FRAME frame = mi->ref_frame[ref];

            dec_find_mv_refs(cm, xd, NEWMV, frame, mv_ref_search, tmp_mvs,

                             mi_row, mi_col, -1);

            lower_mv_precision(&tmp_mvs[0].as_mv, allow_hp);

            best_ref_mvs[ref] = tmp_mvs[0];

            got_mv_refs_for_new = 1;

          }

        }

        if (!assign_mv(cm, xd, b_mode, mi->bmi[j].as_mv, best_ref_mvs,

                       best_sub8x8, is_compound, allow_hp, r)) {

          xd->corrupted |= 1;

          return;

        }

        if (num_4x4_h == 2) mi->bmi[j + 2] = mi->bmi[j];

        if (num_4x4_w == 2) mi->bmi[j + 1] = mi->bmi[j];

      }

    }

    mi->mode = b_mode;

    copy_mv_pair(mi->mv, mi->bmi[3].as_mv);

  } else {

    if (mi->mode != ZEROMV) {

      for (ref = 0; ref < 1 + is_compound; ++ref) {

        int_mv tmp_mvs[MAX_MV_REF_CANDIDATES];

        const MV_REFERENCE_FRAME frame = mi->ref_frame[ref];

        int refmv_count =

            dec_find_mv_refs(cm, xd, mi->mode, frame, mv_ref_search, tmp_mvs,

                             mi_row, mi_col, -1);

        lower_mv_precision(&tmp_mvs[refmv_count - 1].as_mv, allow_hp);

        best_ref_mvs[ref] = tmp_mvs[refmv_count - 1];

      }

    }

    xd->corrupted |= !assign_mv(cm, xd, mi->mode, mi->mv, best_ref_mvs,

                                best_ref_mvs, is_compound, allow_hp, r);

  }

}

static void read_inter_frame_mode_info(VP9Decoder *const pbi,

                                       MACROBLOCKD *const xd, int mi_row,

                                       int mi_col, vpx_reader *r, int x_mis,

                                       int y_mis) {

  VP9_COMMON *const cm = &pbi->common;

  MODE_INFO *const mi = xd->mi[0];

  int inter_block;

  mi->segment_id =

      read_inter_segment_id(cm, xd, mi_row, mi_col, r, x_mis, y_mis);

  mi->skip = read_skip(cm, xd, mi->segment_id, r);

  inter_block = read_is_inter_block(cm, xd, mi->segment_id, r);

  mi->tx_size = read_tx_size(cm, xd, !mi->skip || !inter_block, r);

  if (inter_block)

    read_inter_block_mode_info(pbi, xd, mi, mi_row, mi_col, r);

  else

    read_intra_block_mode_info(cm, xd, mi, r);

}

static INLINE void copy_ref_frame_pair(MV_REFERENCE_FRAME *dst,

                                       const MV_REFERENCE_FRAME *src) {

  memcpy(dst, src, sizeof(*dst) * 2);

}

void vp9_read_mode_info(TileWorkerData *twd, VP9Decoder *const pbi, int mi_row,

                        int mi_col, int x_mis, int y_mis) {

  vpx_reader *r = &twd->bit_reader;

  MACROBLOCKD *const xd = &twd->xd;

  VP9_COMMON *const cm = &pbi->common;

  MODE_INFO *const mi = xd->mi[0];

  MV_REF *frame_mvs = cm->cur_frame->mvs + mi_row * cm->mi_cols + mi_col;

  int w, h;

  if (frame_is_intra_only(cm)) {

    read_intra_frame_mode_info(cm, xd, mi_row, mi_col, r, x_mis, y_mis);

  } else {

    // Cache mi->ref_frame and mi->mv so that the compiler can prove that they

    // are constant for the duration of the loop and avoids reloading them.

    MV_REFERENCE_FRAME mi_ref_frame[2];

    int_mv mi_mv[2];

    read_inter_frame_mode_info(pbi, xd, mi_row, mi_col, r, x_mis, y_mis);

    copy_ref_frame_pair(mi_ref_frame, mi->ref_frame);

    copy_mv_pair(mi_mv, mi->mv);

    for (h = 0; h < y_mis; ++h) {

      for (w = 0; w < x_mis; ++w) {

        MV_REF *const mv = frame_mvs + w;

        copy_ref_frame_pair(mv->ref_frame, mi_ref_frame);

        copy_mv_pair(mv->mv, mi_mv);

      }

      frame_mvs += cm->mi_cols;

    }

  }

#if 0   // CONFIG_BETTER_HW_COMPATIBILITY && CONFIG_VP9_HIGHBITDEPTH

  if ((xd->cur_buf->flags & YV12_FLAG_HIGHBITDEPTH) &&

      (xd->above_mi == NULL || xd->left_mi == NULL) &&

      !is_inter_block(mi) && need_top_left[mi->uv_mode])

    assert(0);

#endif  // CONFIG_BETTER_HW_COMPATIBILITY && CONFIG_VP9_HIGHBITDEPTH

}