/*
 * Copyright (c) 2016, Alliance for Open Media. All rights reserved
 *
 * This source code is subject to the terms of the BSD 2 Clause License and
 * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
 * was not distributed with this source code in the LICENSE file, you can
 * obtain it at www.aomedia.org/license/software. If the Alliance for Open
 * Media Patent License 1.0 was not distributed with this source code in the
 * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
 */

#include "av1/common/mvref_common.h"
#include "av1/common/warped_motion.h"

#define USE_CUR_GM_REFMV 1

void av1_copy_frame_mvs(const AV1_COMMON *const cm, MODE_INFO *mi, int mi_row,
                        int mi_col, int x_mis, int y_mis) {
#if CONFIG_TMV || CONFIG_MFMV
  const int frame_mvs_stride = ROUND_POWER_OF_TWO(cm->mi_cols, 1);
  MV_REF *frame_mvs =
      cm->cur_frame->mvs + (mi_row >> 1) * frame_mvs_stride + (mi_col >> 1);
  x_mis = ROUND_POWER_OF_TWO(x_mis, 1);
  y_mis = ROUND_POWER_OF_TWO(y_mis, 1);
#else
  const int frame_mvs_stride = cm->mi_cols;
  MV_REF *frame_mvs = cm->cur_frame->mvs +
                      (mi_row & 0xfffe) * frame_mvs_stride + (mi_col & 0xfffe);
  x_mis = AOMMAX(x_mis, 2);
  y_mis = AOMMAX(y_mis, 2);
#endif  // CONFIG_TMV
  int w, h;

  for (h = 0; h < y_mis; h++) {
    MV_REF *mv = frame_mvs;
    for (w = 0; w < x_mis; w++) {
#if CONFIG_MFMV
      mv->ref_frame[0] = NONE_FRAME;
      mv->ref_frame[1] = NONE_FRAME;
      mv->mv[0].as_int = 0;
      mv->mv[1].as_int = 0;

      for (int idx = 0; idx < 2; ++idx) {
        MV_REFERENCE_FRAME ref_frame = mi->mbmi.ref_frame[idx];
        if (ref_frame > INTRA_FRAME) {
          int8_t ref_idx = cm->ref_frame_side[ref_frame];
          if (ref_idx < 0) continue;
          mv->ref_frame[ref_idx] = ref_frame;
          mv->mv[ref_idx].as_int = mi->mbmi.mv[idx].as_int;
        }
      }
#else
      mv->ref_frame[0] = mi->mbmi.ref_frame[0];
      mv->ref_frame[1] = mi->mbmi.ref_frame[1];
      mv->mv[0].as_int = mi->mbmi.mv[0].as_int;
      mv->mv[1].as_int = mi->mbmi.mv[1].as_int;
#endif
      // (TODO:yunqing) The following 2 lines won't be used and can be removed.
      mv->pred_mv[0].as_int = mi->mbmi.pred_mv[0].as_int;
      mv->pred_mv[1].as_int = mi->mbmi.pred_mv[1].as_int;
      mv++;
    }
    frame_mvs += frame_mvs_stride;
  }
}

static uint8_t add_ref_mv_candidate(
    const MODE_INFO *const candidate_mi, const MB_MODE_INFO *const candidate,
    const MV_REFERENCE_FRAME rf[2], uint8_t *refmv_count,
    uint8_t *ref_match_count, CANDIDATE_MV *ref_mv_stack, const int use_hp,
    int len, int block,
#if USE_CUR_GM_REFMV
    int_mv *gm_mv_candidates, const WarpedMotionParams *gm_params,
#endif  // USE_CUR_GM_REFMV
    int col, int weight,
#if CONFIG_AMVR
    int is_integer,
#endif
    BLOCK_SIZE bsize, int mi_row, int mi_col, int subsampling_x,
    int subsampling_y, int do_warping) {
#if CONFIG_INTRABC
  if (!is_inter_block(candidate)) return 0;
#endif  // CONFIG_INTRABC
  int index = 0, ref;
  int newmv_count = 0;
  assert(weight % 2 == 0);
  (void)ref_match_count;
#if !CONFIG_EXT_WARPED_MOTION
  (void)bsize;
  (void)mi_row;
  (void)mi_col;
  (void)subsampling_x;
  (void)subsampling_y;
  (void)do_warping;
#endif  // CONFIG_EXT_WARPED_MOTION

  if (rf[1] == NONE_FRAME) {
    // single reference frame
    for (ref = 0; ref < 2; ++ref) {
      if (candidate->ref_frame[ref] == rf[0]) {
        int_mv this_refmv;
#if CONFIG_EXT_WARPED_MOTION
        if (candidate->motion_mode == WARPED_CAUSAL && do_warping) {
          const WarpedMotionParams wm = candidate->wm_params[0];
          const int bw = block_size_wide[bsize];
          const int bh = block_size_high[bsize];
          int global_offset_c = mi_col * MI_SIZE;
          int global_offset_r = mi_row * MI_SIZE;
          int cc_offset = bw / 2 - 1;
          int cr_offset = bh / 2 - 1;
          int xc0 = cc_offset + global_offset_c;
          int yc0 = cr_offset + global_offset_r;
          int xc1 = xc0 + 1;
          int yc1 = yc0 + 1;
          int in[4] = { xc0, yc0, xc1, yc1 };
          int out[4] = { 0, 0, 0, 0 };

          assert(ref == 0);
          // For WARPED_CAUSAL, wmtype is always AFFINE.
          assert(wm.wmtype == AFFINE);
          project_points_affine(wm.wmmat, in, out, 2, 2, 2, subsampling_x,
                                subsampling_y);

          // assert(x_scale == 1024 && y_scale == 1024);
          // out[]'s precision is 1/64, adjust xc, yc accordingly.
          out[0] -= (xc0 << (3 + SCALING_FCT));
          out[1] -= (yc0 << (3 + SCALING_FCT));
          out[2] -= (xc1 << (3 + SCALING_FCT));
          out[3] -= (yc1 << (3 + SCALING_FCT));

          this_refmv.as_mv.col =
              ROUND_POWER_OF_TWO_SIGNED(out[0] + out[2], SCALING_FCT + 1);
          this_refmv.as_mv.row =
              ROUND_POWER_OF_TWO_SIGNED(out[1] + out[3], SCALING_FCT + 1);
#if CONFIG_AMVR
          lower_mv_precision(&this_refmv.as_mv, use_hp, is_integer);
#else
          lower_mv_precision(&this_refmv.as_mv, use_hp);
#endif
        } else {
#endif  // CONFIG_EXT_WARPED_MOTION
#if USE_CUR_GM_REFMV
          if (is_global_mv_block(candidate_mi, block, gm_params[rf[0]].wmtype))
            this_refmv = gm_mv_candidates[0];
          else
#endif  // USE_CUR_GM_REFMV
            this_refmv = get_sub_block_mv(candidate_mi, ref, col, block);
#if CONFIG_AMVR
          lower_mv_precision(&this_refmv.as_mv, use_hp, is_integer);
#else
        lower_mv_precision(&this_refmv.as_mv, use_hp);
#endif  // CONFIG_AMVR
#if CONFIG_EXT_WARPED_MOTION
        }
#endif  // CONFIG_EXT_WARPED_MOTION

        for (index = 0; index < *refmv_count; ++index)
          if (ref_mv_stack[index].this_mv.as_int == this_refmv.as_int) break;

        if (index < *refmv_count) ref_mv_stack[index].weight += weight * len;

        // Add a new item to the list.
        if (index == *refmv_count && *refmv_count < MAX_REF_MV_STACK_SIZE) {
          ref_mv_stack[index].this_mv = this_refmv;
          ref_mv_stack[index].pred_diff[0] = av1_get_pred_diff_ctx(
              get_sub_block_pred_mv(candidate_mi, ref, col, block), this_refmv);
          ref_mv_stack[index].weight = weight * len;
          ++(*refmv_count);

#if !CONFIG_OPT_REF_MV
          if (candidate->mode == NEWMV) ++newmv_count;
#endif
        }
#if CONFIG_OPT_REF_MV
        if (candidate->mode == NEWMV) ++newmv_count;
        ++*ref_match_count;
#endif
      }
    }
  } else {
    // compound reference frame
    if (candidate->ref_frame[0] == rf[0] && candidate->ref_frame[1] == rf[1]) {
      int_mv this_refmv[2];

      for (ref = 0; ref < 2; ++ref) {
#if USE_CUR_GM_REFMV
        if (is_global_mv_block(candidate_mi, block, gm_params[rf[ref]].wmtype))
          this_refmv[ref] = gm_mv_candidates[ref];
        else
#endif  // USE_CUR_GM_REFMV
          this_refmv[ref] = get_sub_block_mv(candidate_mi, ref, col, block);
#if CONFIG_AMVR
        lower_mv_precision(&this_refmv[ref].as_mv, use_hp, is_integer);
#else
        lower_mv_precision(&this_refmv[ref].as_mv, use_hp);
#endif
      }

      for (index = 0; index < *refmv_count; ++index)
        if ((ref_mv_stack[index].this_mv.as_int == this_refmv[0].as_int) &&
            (ref_mv_stack[index].comp_mv.as_int == this_refmv[1].as_int))
          break;

      if (index < *refmv_count) ref_mv_stack[index].weight += weight * len;

      // Add a new item to the list.
      if (index == *refmv_count && *refmv_count < MAX_REF_MV_STACK_SIZE) {
        ref_mv_stack[index].this_mv = this_refmv[0];
        ref_mv_stack[index].comp_mv = this_refmv[1];
        ref_mv_stack[index].pred_diff[0] = av1_get_pred_diff_ctx(
            get_sub_block_pred_mv(candidate_mi, 0, col, block), this_refmv[0]);
        ref_mv_stack[index].pred_diff[1] = av1_get_pred_diff_ctx(
            get_sub_block_pred_mv(candidate_mi, 1, col, block), this_refmv[1]);
        ref_mv_stack[index].weight = weight * len;
        ++(*refmv_count);

#if !CONFIG_OPT_REF_MV
        if (candidate->mode == NEW_NEWMV) ++newmv_count;
#endif
      }
#if CONFIG_OPT_REF_MV
      if (candidate->mode == NEW_NEWMV) ++newmv_count;
      ++*ref_match_count;
#endif
    }
  }
  return newmv_count;
}

static uint8_t scan_row_mbmi(const AV1_COMMON *cm, const MACROBLOCKD *xd,
                             int mi_row, int mi_col, int block,
                             const MV_REFERENCE_FRAME rf[2], int row_offset,
                             CANDIDATE_MV *ref_mv_stack, uint8_t *refmv_count,
                             uint8_t *ref_match_count,
#if USE_CUR_GM_REFMV
                             int_mv *gm_mv_candidates,
#endif  // USE_CUR_GM_REFMV
                             int max_row_offset, int *processed_rows) {
  const int end_mi = AOMMIN(xd->n8_w, cm->mi_cols - mi_col);
  const int n8_w_8 = mi_size_wide[BLOCK_8X8];
  const int n8_w_16 = mi_size_wide[BLOCK_16X16];
  int i;
  uint8_t newmv_count = 0;
  int col_offset = 0;
  const int shift = 0;
  // TODO(jingning): Revisit this part after cb4x4 is stable.
  if (abs(row_offset) > 1) {
    col_offset = 1;
    if (mi_col & 0x01 && xd->n8_w < n8_w_8) --col_offset;
  }
  const int use_step_16 = (xd->n8_w >= 16);
  MODE_INFO **const candidate_mi0 = xd->mi + row_offset * xd->mi_stride;
  const int do_warping = (row_offset == -1);

  for (i = 0; i < end_mi;) {
    const MODE_INFO *const candidate_mi = candidate_mi0[col_offset + i];
    const MB_MODE_INFO *const candidate = &candidate_mi->mbmi;
    const int candidate_bsize = candidate->sb_type;
    const int n8_w = mi_size_wide[candidate_bsize];
    int len = AOMMIN(xd->n8_w, n8_w);
    if (use_step_16)
      len = AOMMAX(n8_w_16, len);
    else if (abs(row_offset) > 1)
      len = AOMMAX(len, n8_w_8);

    int weight = 2;
    if (xd->n8_w >= n8_w_8 && xd->n8_w <= n8_w) {
      int inc = AOMMIN(-max_row_offset + row_offset + 1,
                       mi_size_high[candidate_bsize]);
      // Obtain range used in weight calculation.
      weight = AOMMAX(weight, (inc << shift));
      // Update processed rows.
      *processed_rows = inc - row_offset - 1;
    }

#if CONFIG_AMVR
    newmv_count += add_ref_mv_candidate(
        candidate_mi, candidate, rf, refmv_count, ref_match_count, ref_mv_stack,
        cm->allow_high_precision_mv, len, block,
#if USE_CUR_GM_REFMV
        gm_mv_candidates, cm->global_motion,
#endif  // USE_CUR_GM_REFMV
        col_offset + i, weight, cm->cur_frame_force_integer_mv,
        xd->mi[0]->mbmi.sb_type, mi_row, mi_col, xd->plane[0].subsampling_x,
        xd->plane[0].subsampling_y, do_warping);
#else
    newmv_count += add_ref_mv_candidate(
        candidate_mi, candidate, rf, refmv_count, ref_match_count, ref_mv_stack,
        cm->allow_high_precision_mv, len, block,
#if USE_CUR_GM_REFMV
        gm_mv_candidates, cm->global_motion,
#endif  // USE_CUR_GM_REFMV
        col_offset + i, weight, xd->mi[0]->mbmi.sb_type, mi_row, mi_col,
        xd->plane[0].subsampling_x, xd->plane[0].subsampling_y, do_warping);
#endif

    i += len;
  }

  return newmv_count;
}

static uint8_t scan_col_mbmi(const AV1_COMMON *cm, const MACROBLOCKD *xd,
                             int mi_row, int mi_col, int block,
                             const MV_REFERENCE_FRAME rf[2], int col_offset,
                             CANDIDATE_MV *ref_mv_stack, uint8_t *refmv_count,
                             uint8_t *ref_match_count,
#if USE_CUR_GM_REFMV
                             int_mv *gm_mv_candidates,
#endif  // USE_CUR_GM_REFMV
                             int max_col_offset, int *processed_cols) {
  const int end_mi = AOMMIN(xd->n8_h, cm->mi_rows - mi_row);
  const int n8_h_8 = mi_size_high[BLOCK_8X8];
  const int n8_h_16 = mi_size_high[BLOCK_16X16];
  int i;
  uint8_t newmv_count = 0;
  int row_offset = 0;
  const int shift = 0;
  if (abs(col_offset) > 1) {
    row_offset = 1;
    if (mi_row & 0x01 && xd->n8_h < n8_h_8) --row_offset;
  }
  const int use_step_16 = (xd->n8_h >= 16);
  const int do_warping = (col_offset == -1);

  for (i = 0; i < end_mi;) {
    const MODE_INFO *const candidate_mi =
        xd->mi[(row_offset + i) * xd->mi_stride + col_offset];
    const MB_MODE_INFO *const candidate = &candidate_mi->mbmi;
    const int candidate_bsize = candidate->sb_type;
    const int n8_h = mi_size_high[candidate_bsize];
    int len = AOMMIN(xd->n8_h, n8_h);
    if (use_step_16)
      len = AOMMAX(n8_h_16, len);
    else if (abs(col_offset) > 1)
      len = AOMMAX(len, n8_h_8);

    int weight = 2;
    if (xd->n8_h >= n8_h_8 && xd->n8_h <= n8_h) {
      int inc = AOMMIN(-max_col_offset + col_offset + 1,
                       mi_size_wide[candidate_bsize]);
      // Obtain range used in weight calculation.
      weight = AOMMAX(weight, (inc << shift));
      // Update processed cols.
      *processed_cols = inc - col_offset - 1;
    }

#if CONFIG_AMVR
    newmv_count += add_ref_mv_candidate(
        candidate_mi, candidate, rf, refmv_count, ref_match_count, ref_mv_stack,
        cm->allow_high_precision_mv, len, block,
#if USE_CUR_GM_REFMV
        gm_mv_candidates, cm->global_motion,
#endif  // USE_CUR_GM_REFMV
        col_offset, weight, cm->cur_frame_force_integer_mv,
        xd->mi[0]->mbmi.sb_type, mi_row, mi_col, xd->plane[0].subsampling_x,
        xd->plane[0].subsampling_y, do_warping);
#else
    newmv_count += add_ref_mv_candidate(
        candidate_mi, candidate, rf, refmv_count, ref_match_count, ref_mv_stack,
        cm->allow_high_precision_mv, len, block,
#if USE_CUR_GM_REFMV
        gm_mv_candidates, cm->global_motion,
#endif  // USE_CUR_GM_REFMV
        col_offset, weight, xd->mi[0]->mbmi.sb_type, mi_row, mi_col,
        xd->plane[0].subsampling_x, xd->plane[0].subsampling_y, do_warping);
#endif
    i += len;
  }

  return newmv_count;
}

static uint8_t scan_blk_mbmi(const AV1_COMMON *cm, const MACROBLOCKD *xd,
                             const int mi_row, const int mi_col, int block,
                             const MV_REFERENCE_FRAME rf[2], int row_offset,
                             int col_offset, CANDIDATE_MV *ref_mv_stack,
                             uint8_t *ref_match_count,
#if USE_CUR_GM_REFMV
                             int_mv *gm_mv_candidates,
#endif  // USE_CUR_GM_REFMV
                             uint8_t *refmv_count) {
  const TileInfo *const tile = &xd->tile;
  POSITION mi_pos;
  uint8_t newmv_count = 0;
  const int do_warping = 1;

  mi_pos.row = row_offset;
  mi_pos.col = col_offset;

  if (is_inside(tile, mi_col, mi_row, cm->mi_rows, cm, &mi_pos)) {
    const MODE_INFO *const candidate_mi =
        xd->mi[mi_pos.row * xd->mi_stride + mi_pos.col];
    const MB_MODE_INFO *const candidate = &candidate_mi->mbmi;
    const int len = mi_size_wide[BLOCK_8X8];

#if CONFIG_AMVR
    newmv_count += add_ref_mv_candidate(
        candidate_mi, candidate, rf, refmv_count, ref_match_count, ref_mv_stack,
        cm->allow_high_precision_mv, len, block,
#if USE_CUR_GM_REFMV
        gm_mv_candidates, cm->global_motion,
#endif  // USE_CUR_GM_REFMV
        mi_pos.col, 2, cm->cur_frame_force_integer_mv, xd->mi[0]->mbmi.sb_type,
        mi_row, mi_col, xd->plane[0].subsampling_x, xd->plane[0].subsampling_y,
        do_warping);
#else
    newmv_count += add_ref_mv_candidate(
        candidate_mi, candidate, rf, refmv_count, ref_match_count, ref_mv_stack,
        cm->allow_high_precision_mv, len, block,
#if USE_CUR_GM_REFMV
        gm_mv_candidates, cm->global_motion,
#endif  // USE_CUR_GM_REFMV
        mi_pos.col, 2, xd->mi[0]->mbmi.sb_type, mi_row, mi_col,
        xd->plane[0].subsampling_x, xd->plane[0].subsampling_y, do_warping);
#endif
  }  // Analyze a single 8x8 block motion information.

  return newmv_count;
}

static int has_top_right(const AV1_COMMON *cm, const MACROBLOCKD *xd,
                         int mi_row, int mi_col, int bs) {
  const int sb_mi_size = mi_size_wide[cm->sb_size];
  const int mask_row = mi_row & (sb_mi_size - 1);
  const int mask_col = mi_col & (sb_mi_size - 1);

  // In a split partition all apart from the bottom right has a top right
  int has_tr = !((mask_row & bs) && (mask_col & bs));

  // bs > 0 and bs is a power of 2
  assert(bs > 0 && !(bs & (bs - 1)));

  // For each 4x4 group of blocks, when the bottom right is decoded the blocks
  // to the right have not been decoded therefore the bottom right does
  // not have a top right
  while (bs < sb_mi_size) {
    if (mask_col & bs) {
      if ((mask_col & (2 * bs)) && (mask_row & (2 * bs))) {
        has_tr = 0;
        break;
      }
    } else {
      break;
    }
    bs <<= 1;
  }

  // The left hand of two vertical rectangles always has a top right (as the
  // block above will have been decoded)
  if (xd->n8_w < xd->n8_h)
    if (!xd->is_sec_rect) has_tr = 1;

  // The bottom of two horizontal rectangles never has a top right (as the block
  // to the right won't have been decoded)
  if (xd->n8_w > xd->n8_h)
    if (xd->is_sec_rect) has_tr = 0;

#if CONFIG_EXT_PARTITION_TYPES && !CONFIG_EXT_PARTITION_TYPES_AB
  // The bottom left square of a Vertical A (in the old format) does
  // not have a top right as it is decoded before the right hand
  // rectangle of the partition
  if (xd->mi[0]->mbmi.partition == PARTITION_VERT_A)
    if ((mask_row & bs) && !(mask_col & bs)) has_tr = 0;
#endif  // CONFIG_EXT_PARTITION_TYPES

  return has_tr;
}

#if CONFIG_MFMV
static int check_sb_border(const AV1_COMMON *cm, const int mi_row,
                           const int mi_col, const int row_offset,
                           const int col_offset) {
  const int sb_mi_size = mi_size_wide[cm->sb_size];
  const int row = mi_row & (sb_mi_size - 1);
  const int col = mi_col & (sb_mi_size - 1);

  if (row + row_offset < 0 || row + row_offset >= sb_mi_size ||
      col + col_offset < 0 || col + col_offset >= sb_mi_size)
    return 0;

  return 1;
}

static int add_tpl_ref_mv(const AV1_COMMON *cm,
                          const MV_REF *prev_frame_mvs_base,
                          const MACROBLOCKD *xd, int mi_row, int mi_col,
                          MV_REFERENCE_FRAME ref_frame, int blk_row,
                          int blk_col, uint8_t *refmv_count,
                          CANDIDATE_MV *ref_mv_stack, int16_t *mode_context) {
  (void)prev_frame_mvs_base;
  POSITION mi_pos;
  int idx;
  int coll_blk_count = 0;
  const int weight_unit = 1;  // mi_size_wide[BLOCK_8X8];

#if CONFIG_MV_COMPRESS
  mi_pos.row = (mi_row & 0x01) ? blk_row : blk_row + 1;
  mi_pos.col = (mi_col & 0x01) ? blk_col : blk_col + 1;
#else
  mi_pos.row = blk_row;
  mi_pos.col = blk_col;
#endif

  if (!is_inside(&xd->tile, mi_col, mi_row, cm->mi_rows, cm, &mi_pos))
    return coll_blk_count;

  const TPL_MV_REF *prev_frame_mvs =
      cm->tpl_mvs + ((mi_row + mi_pos.row) >> 1) * (cm->mi_stride >> 1) +
      ((mi_col + mi_pos.col) >> 1);

  MV_REFERENCE_FRAME rf[2];
  av1_set_ref_frame(rf, ref_frame);

  if (rf[1] == NONE_FRAME) {
    for (int i = 0; i < MFMV_STACK_SIZE; ++i) {
      if (prev_frame_mvs->mfmv[ref_frame - LAST_FRAME][i].as_int !=
          INVALID_MV) {
        int_mv this_refmv = prev_frame_mvs->mfmv[ref_frame - LAST_FRAME][i];
#if CONFIG_AMVR
        lower_mv_precision(&this_refmv.as_mv, cm->allow_high_precision_mv,
                           cm->cur_frame_force_integer_mv);
#else
        lower_mv_precision(&this_refmv.as_mv, cm->allow_high_precision_mv);
#endif

        if (blk_row == 0 && blk_col == 0)
          if (abs(this_refmv.as_mv.row) >= 16 ||
              abs(this_refmv.as_mv.col) >= 16)
            mode_context[ref_frame] |= (1 << GLOBALMV_OFFSET);

        for (idx = 0; idx < *refmv_count; ++idx)
          if (abs(this_refmv.as_mv.row - ref_mv_stack[idx].this_mv.as_mv.row) <
                  4 &&
              abs(this_refmv.as_mv.col - ref_mv_stack[idx].this_mv.as_mv.col) <
                  4)
            break;

        if (idx < *refmv_count) ref_mv_stack[idx].weight += 2 * weight_unit;

        if (idx == *refmv_count && *refmv_count < MAX_REF_MV_STACK_SIZE) {
          ref_mv_stack[idx].this_mv.as_int = this_refmv.as_int;
          // TODO(jingning): Hard coded context number. Need to make it better
          // sense.
          ref_mv_stack[idx].pred_diff[0] = 1;
          ref_mv_stack[idx].weight = 2 * weight_unit;
          ++(*refmv_count);
        }

        ++coll_blk_count;
      }
    }
  } else {
    // Process compound inter mode
    for (int i = 0; i < MFMV_STACK_SIZE; ++i) {
      if (prev_frame_mvs->mfmv[rf[0] - LAST_FRAME][i].as_int != INVALID_MV &&
          prev_frame_mvs->mfmv[rf[1] - LAST_FRAME][i].as_int != INVALID_MV) {
        int_mv this_refmv = prev_frame_mvs->mfmv[rf[0] - LAST_FRAME][i];
        int_mv comp_refmv = prev_frame_mvs->mfmv[rf[1] - LAST_FRAME][i];
#if CONFIG_AMVR
        lower_mv_precision(&this_refmv.as_mv, cm->allow_high_precision_mv,
                           cm->cur_frame_force_integer_mv);
        lower_mv_precision(&comp_refmv.as_mv, cm->allow_high_precision_mv,
                           cm->cur_frame_force_integer_mv);
#else
        lower_mv_precision(&this_refmv.as_mv, cm->allow_high_precision_mv);
        lower_mv_precision(&comp_refmv.as_mv, cm->allow_high_precision_mv);
#endif
        if (blk_row == 0 && blk_col == 0)
          if (abs(this_refmv.as_mv.row) >= 16 ||
              abs(this_refmv.as_mv.col) >= 16 ||
              abs(comp_refmv.as_mv.row) >= 16 ||
              abs(comp_refmv.as_mv.col) >= 16)
            mode_context[ref_frame] |= (1 << GLOBALMV_OFFSET);

        for (idx = 0; idx < *refmv_count; ++idx)
          if (abs(this_refmv.as_mv.row - ref_mv_stack[idx].this_mv.as_mv.row) <
                  4 &&
              abs(this_refmv.as_mv.col - ref_mv_stack[idx].this_mv.as_mv.col) <
                  4 &&
              abs(comp_refmv.as_mv.row - ref_mv_stack[idx].comp_mv.as_mv.row) <
                  4 &&
              abs(comp_refmv.as_mv.col - ref_mv_stack[idx].comp_mv.as_mv.col) <
                  4)
            break;

        if (idx < *refmv_count) ref_mv_stack[idx].weight += 2 * weight_unit;

        if (idx == *refmv_count && *refmv_count < MAX_REF_MV_STACK_SIZE) {
          ref_mv_stack[idx].this_mv.as_int = this_refmv.as_int;
          ref_mv_stack[idx].comp_mv.as_int = comp_refmv.as_int;
          // TODO(jingning): Hard coded context number. Need to make it better
          // sense.
          ref_mv_stack[idx].pred_diff[0] = 1;
          ref_mv_stack[idx].pred_diff[1] = 1;
          ref_mv_stack[idx].weight = 2 * weight_unit;
          ++(*refmv_count);
        }

        ++coll_blk_count;
      }
    }
  }

  return coll_blk_count;
}
#else
static int add_col_ref_mv(const AV1_COMMON *cm,
                          const MV_REF *prev_frame_mvs_base,
                          int prev_frame_mvs_stride, const MACROBLOCKD *xd,
                          int mi_row, int mi_col, MV_REFERENCE_FRAME ref_frame,
                          int blk_row, int blk_col, uint8_t *refmv_count,
                          CANDIDATE_MV *ref_mv_stack, int16_t *mode_context) {
#if CONFIG_TMV
  const MV_REF *prev_frame_mvs = prev_frame_mvs_base +
                                 (blk_row >> 1) * prev_frame_mvs_stride +
                                 (blk_col >> 1);
#else
  const MV_REF *prev_frame_mvs =
      prev_frame_mvs_base + blk_row * prev_frame_mvs_stride + blk_col;
#endif
  POSITION mi_pos;
  int ref, idx;
  int coll_blk_count = 0;
  const int weight_unit = mi_size_wide[BLOCK_8X8];

#if CONFIG_TMV
  mi_pos.row = blk_row;
  mi_pos.col = blk_col;
#else
#if CONFIG_MV_COMPRESS
  mi_pos.row = (mi_row & 0x01) ? blk_row : blk_row + 1;
  mi_pos.col = (mi_col & 0x01) ? blk_col : blk_col + 1;
#else
  mi_pos.row = blk_row;
  mi_pos.col = blk_col;
#endif
#endif  // CONFIG_TMV

  if (!is_inside(&xd->tile, mi_col, mi_row, cm->mi_rows, cm, &mi_pos))
    return coll_blk_count;
  for (ref = 0; ref < 2; ++ref) {
    if (prev_frame_mvs->ref_frame[ref] == ref_frame) {
      int_mv this_refmv = prev_frame_mvs->mv[ref];
#if CONFIG_AMVR
      lower_mv_precision(&this_refmv.as_mv, cm->allow_high_precision_mv,
                         cm->cur_frame_force_integer_mv);
#else
      lower_mv_precision(&this_refmv.as_mv, cm->allow_high_precision_mv);
#endif

#if CONFIG_OPT_REF_MV
      if (blk_row == 0 && blk_col == 0)
#endif
      {
        if (abs(this_refmv.as_mv.row) >= 16 || abs(this_refmv.as_mv.col) >= 16)
          mode_context[ref_frame] |= (1 << GLOBALMV_OFFSET);
      }

      for (idx = 0; idx < *refmv_count; ++idx)
        if (this_refmv.as_int == ref_mv_stack[idx].this_mv.as_int) break;

      if (idx < *refmv_count) ref_mv_stack[idx].weight += 2 * weight_unit;

      if (idx == *refmv_count && *refmv_count < MAX_REF_MV_STACK_SIZE) {
        ref_mv_stack[idx].this_mv.as_int = this_refmv.as_int;
        ref_mv_stack[idx].pred_diff[0] =
            av1_get_pred_diff_ctx(prev_frame_mvs->pred_mv[ref], this_refmv);
        ref_mv_stack[idx].weight = 2 * weight_unit;
        ++(*refmv_count);
      }

      ++coll_blk_count;
    }
  }

  return coll_blk_count;
}
#endif  // CONFIG_MFMV

static void setup_ref_mv_list(const AV1_COMMON *cm, const MACROBLOCKD *xd,
                              MV_REFERENCE_FRAME ref_frame,
                              uint8_t *refmv_count, CANDIDATE_MV *ref_mv_stack,
                              int_mv *mv_ref_list,
#if USE_CUR_GM_REFMV
                              int_mv *gm_mv_candidates,
#endif  // USE_CUR_GM_REFMV
                              int block, int mi_row, int mi_col,
                              int16_t *mode_context) {
#if CONFIG_TMV
  const int prev_frame_mvs_stride = ROUND_POWER_OF_TWO(cm->mi_cols, 1);
  const int tmi_row = mi_row & 0xfffe;
  const int tmi_col = mi_col & 0xfffe;
  const MV_REF *const prev_frame_mvs_base =
      cm->use_prev_frame_mvs
          ? cm->prev_frame->mvs + (tmi_row >> 1) * prev_frame_mvs_stride +
                (tmi_col >> 1)
          : NULL;
#else
  const int prev_frame_mvs_stride = cm->mi_cols;
#if CONFIG_MV_COMPRESS
  const MV_REF *const prev_frame_mvs_base =
      cm->use_prev_frame_mvs
          ? cm->prev_frame->mvs +
                (((mi_row >> 1) << 1) + 1) * prev_frame_mvs_stride +
                ((mi_col >> 1) << 1) + 1
          : NULL;
#else
  const MV_REF *const prev_frame_mvs_base =
      cm->use_prev_frame_mvs
          ? cm->prev_frame->mvs + mi_row * prev_frame_mvs_stride + mi_col
          : NULL;
#endif
#endif  // CONFIG_TMV

  const int bs = AOMMAX(xd->n8_w, xd->n8_h);
  const int has_tr = has_top_right(cm, xd, mi_row, mi_col, bs);
  MV_REFERENCE_FRAME rf[2];

  const TileInfo *const tile = &xd->tile;
  int max_row_offset = 0, max_col_offset = 0;
  const int row_adj = (xd->n8_h < mi_size_high[BLOCK_8X8]) && (mi_row & 0x01);
  const int col_adj = (xd->n8_w < mi_size_wide[BLOCK_8X8]) && (mi_col & 0x01);
  int processed_rows = 0;
  int processed_cols = 0;

  av1_set_ref_frame(rf, ref_frame);
  mode_context[ref_frame] = 0;
  *refmv_count = 0;

  // Find valid maximum row/col offset.
  if (xd->up_available) {
    max_row_offset = -(MVREF_ROWS << 1) + row_adj;
    max_row_offset =
        find_valid_row_offset(tile, mi_row, cm->mi_rows, cm, max_row_offset);
  }

  if (xd->left_available) {
    max_col_offset = -(MVREF_COLS << 1) + col_adj;
    max_col_offset = find_valid_col_offset(tile, mi_col, max_col_offset);
  }

  uint8_t ref_match_count = 0;
  uint8_t newmv_count = 0;

  // Scan the first above row mode info. row_offset = -1;
  if (abs(max_row_offset) >= 1)
    newmv_count += scan_row_mbmi(cm, xd, mi_row, mi_col, block, rf, -1,
                                 ref_mv_stack, refmv_count, &ref_match_count,
#if USE_CUR_GM_REFMV
                                 gm_mv_candidates,
#endif  // USE_CUR_GM_REFMV
                                 max_row_offset, &processed_rows);
  // Scan the first left column mode info. col_offset = -1;
  if (abs(max_col_offset) >= 1)
    newmv_count += scan_col_mbmi(cm, xd, mi_row, mi_col, block, rf, -1,
                                 ref_mv_stack, refmv_count, &ref_match_count,
#if USE_CUR_GM_REFMV
                                 gm_mv_candidates,
#endif  // USE_CUR_GM_REFMV
                                 max_col_offset, &processed_cols);
  // Check top-right boundary
  if (has_tr)
    newmv_count += scan_blk_mbmi(cm, xd, mi_row, mi_col, block, rf, -1,
                                 xd->n8_w, ref_mv_stack, &ref_match_count,
#if USE_CUR_GM_REFMV
                                 gm_mv_candidates,
#endif  // USE_CUR_GM_REFMV
                                 refmv_count);

  const int nearest_match = ref_match_count;
  const int nearest_refmv_count = *refmv_count;

  ref_mv_stack[0].weight = 0;
  for (int idx = 0; idx < nearest_refmv_count; ++idx)
    ref_mv_stack[idx].weight += REF_CAT_LEVEL;

#if CONFIG_MFMV
  if (cm->use_ref_frame_mvs) {
    int coll_blk_count = 0;
    const int voffset = AOMMAX(mi_size_high[BLOCK_8X8], xd->n8_h);
    const int hoffset = AOMMAX(mi_size_wide[BLOCK_8X8], xd->n8_w);

    const int tpl_sample_pos[9][2] = {
      { -2, hoffset }, { 0, hoffset },  { voffset, hoffset },
      { voffset, 0 },  { voffset, -2 }, { voffset, -4 },
      { -4, hoffset }, { voffset, 4 },  { 2, hoffset + 4 },
    };

    for (int blk_row = 0; blk_row < xd->n8_h;
         blk_row += mi_size_high[BLOCK_8X8]) {
      for (int blk_col = 0; blk_col < xd->n8_w;
           blk_col += mi_size_wide[BLOCK_8X8]) {
        // (TODO: yunqing) prev_frame_mvs_base is not used here, tpl_mvs is
        // used.
        // Can be modified the same way.
        int is_available = add_tpl_ref_mv(
            cm, prev_frame_mvs_base, xd, mi_row, mi_col, ref_frame, blk_row,
            blk_col, refmv_count, ref_mv_stack, mode_context);
        if (blk_row == 0 && blk_col == 0) coll_blk_count = is_available;
      }
    }

    if (coll_blk_count == 0) mode_context[ref_frame] |= (1 << GLOBALMV_OFFSET);

    for (int i = 0; i < 9; ++i) {
      const int blk_row = tpl_sample_pos[i][0];
      const int blk_col = tpl_sample_pos[i][1];

      if (!check_sb_border(cm, mi_row, mi_col, blk_row, blk_col)) continue;
      // (TODO: yunqing) prev_frame_mvs_base is not used here, tpl_mvs is used.
      // Can be modified the same way.
      coll_blk_count += add_tpl_ref_mv(cm, prev_frame_mvs_base, xd, mi_row,
                                       mi_col, ref_frame, blk_row, blk_col,
                                       refmv_count, ref_mv_stack, mode_context);
    }
  }
#else
#if CONFIG_TEMPMV_SIGNALING
  if (cm->use_prev_frame_mvs && rf[1] == NONE_FRAME)
#else
  if (prev_frame_mvs_base && cm->show_frame && cm->last_show_frame &&
      rf[1] == NONE_FRAME)
#endif
  {
    int coll_blk_count = 0;
    const int mi_step = (xd->n8_w == 1 || xd->n8_h == 1)
                            ? mi_size_wide[BLOCK_8X8]
                            : mi_size_wide[BLOCK_16X16];

    for (int blk_row = 0; blk_row < xd->n8_h; blk_row += mi_step) {
      for (int blk_col = 0; blk_col < xd->n8_w; blk_col += mi_step) {
#if CONFIG_TMV
        int is_available =
            add_col_ref_mv(cm, prev_frame_mvs_base, prev_frame_mvs_stride, xd,
                           tmi_row, tmi_col, ref_frame, blk_row, blk_col,
                           refmv_count, ref_mv_stack, mode_context);
#else
        int is_available =
            add_col_ref_mv(cm, prev_frame_mvs_base, prev_frame_mvs_stride, xd,
                           mi_row, mi_col, ref_frame, blk_row, blk_col,
                           refmv_count, ref_mv_stack, mode_context);
#endif  // CONFIG_TMV
#if CONFIG_OPT_REF_MV
        if (blk_row == 0 && blk_col == 0) coll_blk_count = is_available;
#else
        coll_blk_count += is_available;
#endif
      }
    }

    if (coll_blk_count == 0) mode_context[ref_frame] |= (1 << GLOBALMV_OFFSET);
  } else {
    mode_context[ref_frame] |= (1 << GLOBALMV_OFFSET);
  }
#endif  // CONFIG_MFMV

  // Scan the second outer area.
  scan_blk_mbmi(cm, xd, mi_row, mi_col, block, rf, -1, -1, ref_mv_stack,
                &ref_match_count,
#if USE_CUR_GM_REFMV
                gm_mv_candidates,
#endif  // USE_CUR_GM_REFMV
                refmv_count);
  for (int idx = 2; idx <= MVREF_ROWS; ++idx) {
    const int row_offset = -(idx << 1) + 1 + row_adj;
    const int col_offset = -(idx << 1) + 1 + col_adj;

    if (abs(row_offset) <= abs(max_row_offset) &&
        abs(row_offset) > processed_rows)
      scan_row_mbmi(cm, xd, mi_row, mi_col, block, rf, row_offset, ref_mv_stack,
                    refmv_count, &ref_match_count,
#if USE_CUR_GM_REFMV
                    gm_mv_candidates,
#endif  // USE_CUR_GM_REFMV
                    max_row_offset, &processed_rows);

    if (abs(col_offset) <= abs(max_col_offset) &&
        abs(col_offset) > processed_cols)
      scan_col_mbmi(cm, xd, mi_row, mi_col, block, rf, col_offset, ref_mv_stack,
                    refmv_count, &ref_match_count,
#if USE_CUR_GM_REFMV
                    gm_mv_candidates,
#endif  // USE_CUR_GM_REFMV
                    max_col_offset, &processed_cols);
  }

  const int col_offset = -(MVREF_COLS << 1) + 1 + col_adj;
  if (abs(col_offset) <= abs(max_col_offset) &&
      abs(col_offset) > processed_cols)
    scan_col_mbmi(cm, xd, mi_row, mi_col, block, rf, col_offset, ref_mv_stack,
                  refmv_count, &ref_match_count,
#if USE_CUR_GM_REFMV
                  gm_mv_candidates,
#endif  // USE_CUR_GM_REFMV
                  max_col_offset, &processed_cols);

#if CONFIG_OPT_REF_MV
  switch (nearest_match)
#else
  switch (nearest_refmv_count)
#endif
  {
    case 0: mode_context[ref_frame] |= 0;
#if CONFIG_OPT_REF_MV
      if (ref_match_count >= 1) mode_context[ref_frame] |= 1;
      if (ref_match_count == 1)
        mode_context[ref_frame] |= (1 << REFMV_OFFSET);
      else if (ref_match_count >= 2)
        mode_context[ref_frame] |= (2 << REFMV_OFFSET);
#else
      if (*refmv_count >= 1) mode_context[ref_frame] |= 1;
      if (*refmv_count == 1)
        mode_context[ref_frame] |= (1 << REFMV_OFFSET);
      else if (*refmv_count >= 2)
        mode_context[ref_frame] |= (2 << REFMV_OFFSET);
#endif
      break;
    case 1: mode_context[ref_frame] |= (newmv_count > 0) ? 2 : 3;
#if CONFIG_OPT_REF_MV
      if (ref_match_count == 1)
        mode_context[ref_frame] |= (3 << REFMV_OFFSET);
      else if (ref_match_count >= 2)
        mode_context[ref_frame] |= (4 << REFMV_OFFSET);
#else
      if (*refmv_count == 1)
        mode_context[ref_frame] |= (3 << REFMV_OFFSET);
      else if (*refmv_count >= 2)
        mode_context[ref_frame] |= (4 << REFMV_OFFSET);
#endif
      break;

    case 2:
    default:
      if (newmv_count >= 2)
        mode_context[ref_frame] |= 4;
      else if (newmv_count == 1)
        mode_context[ref_frame] |= 5;
      else
        mode_context[ref_frame] |= 6;

      mode_context[ref_frame] |= (5 << REFMV_OFFSET);
      break;
  }

  // Rank the likelihood and assign nearest and near mvs.
  int len = nearest_refmv_count;
  while (len > 0) {
    int nr_len = 0;
    for (int idx = 1; idx < len; ++idx) {
      if (ref_mv_stack[idx - 1].weight < ref_mv_stack[idx].weight) {
        CANDIDATE_MV tmp_mv = ref_mv_stack[idx - 1];
        ref_mv_stack[idx - 1] = ref_mv_stack[idx];
        ref_mv_stack[idx] = tmp_mv;
        nr_len = idx;
      }
    }
    len = nr_len;
  }

  len = *refmv_count;
  while (len > nearest_refmv_count) {
    int nr_len = nearest_refmv_count;
    for (int idx = nearest_refmv_count + 1; idx < len; ++idx) {
      if (ref_mv_stack[idx - 1].weight < ref_mv_stack[idx].weight) {
        CANDIDATE_MV tmp_mv = ref_mv_stack[idx - 1];
        ref_mv_stack[idx - 1] = ref_mv_stack[idx];
        ref_mv_stack[idx] = tmp_mv;
        nr_len = idx;
      }
    }
    len = nr_len;
  }

  if (rf[1] > NONE_FRAME) {
    for (int idx = 0; idx < *refmv_count; ++idx) {
      clamp_mv_ref(&ref_mv_stack[idx].this_mv.as_mv, xd->n8_w << MI_SIZE_LOG2,
                   xd->n8_h << MI_SIZE_LOG2, xd);
      clamp_mv_ref(&ref_mv_stack[idx].comp_mv.as_mv, xd->n8_w << MI_SIZE_LOG2,
                   xd->n8_h << MI_SIZE_LOG2, xd);
    }
  } else {
    for (int idx = 0; idx < AOMMIN(MAX_MV_REF_CANDIDATES, *refmv_count);
         ++idx) {
      mv_ref_list[idx].as_int = ref_mv_stack[idx].this_mv.as_int;
      clamp_mv_ref(&mv_ref_list[idx].as_mv, xd->n8_w << MI_SIZE_LOG2,
                   xd->n8_h << MI_SIZE_LOG2, xd);
    }
  }
  (void)nearest_match;
}

// This function searches the neighbourhood of a given MB/SB
// to try and find candidate reference vectors.
static void find_mv_refs_idx(const AV1_COMMON *cm, const MACROBLOCKD *xd,
                             MODE_INFO *mi, MV_REFERENCE_FRAME ref_frame,
                             int_mv *mv_ref_list, int block, int mi_row,
                             int mi_col, find_mv_refs_sync sync,
                             void *const data, int16_t *mode_context,
                             int_mv zeromv) {
  const int *ref_sign_bias = cm->ref_frame_sign_bias;
  const int sb_mi_size = mi_size_wide[cm->sb_size];
  int i, refmv_count = 0;
  int different_ref_found = 0;
  int context_counter = 0;

#if CONFIG_MFMV
  (void)sync;
  (void)data;
#else
#if CONFIG_TMV
  int tmi_row = mi_row & 0xfffe;
  int tmi_col = mi_col & 0xfffe;
  POSITION mi_pos = { 0, 0 };
  int inside = is_inside(&xd->tile, tmi_col, tmi_row, cm->mi_rows, cm, &mi_pos);
  const MV_REF *const prev_frame_mvs =
      cm->use_prev_frame_mvs && inside
          ? cm->prev_frame->mvs + (tmi_row >> 1) * ((cm->mi_cols + 1) >> 1) +
                (tmi_col >> 1)
          : NULL;
#else
#if CONFIG_MV_COMPRESS
  const TileInfo *const tile_ = &xd->tile;
  int mi_row_end = tile_->mi_row_end;
  int mi_col_end = tile_->mi_col_end;
  const MV_REF *const prev_frame_mvs =
      cm->use_prev_frame_mvs
          ? cm->prev_frame->mvs +
                AOMMIN(((mi_row >> 1) << 1) + 1 + (((xd->n8_h - 1) >> 1) << 1),
                       mi_row_end - 1) *
                    cm->mi_cols +
                AOMMIN(((mi_col >> 1) << 1) + 1 + (((xd->n8_w - 1) >> 1) << 1),
                       mi_col_end - 1)
          : NULL;
#else
  const MV_REF *const prev_frame_mvs =
      cm->use_prev_frame_mvs
          ? cm->prev_frame->mvs + mi_row * cm->mi_cols + mi_col
          : NULL;
#endif  // CONFIG_MV_COMPRESS
#endif  // CONFIG_TMV
#endif  // CONFIG_MFMV

#if CONFIG_INTRABC
  assert(IMPLIES(ref_frame == INTRA_FRAME, cm->use_prev_frame_mvs == 0));
#endif
  const TileInfo *const tile = &xd->tile;
  const BLOCK_SIZE bsize = mi->mbmi.sb_type;
  const int bw = block_size_wide[AOMMAX(bsize, BLOCK_8X8)];
  const int bh = block_size_high[AOMMAX(bsize, BLOCK_8X8)];
  POSITION mv_ref_search[MVREF_NEIGHBOURS];
  const int num_8x8_blocks_wide = num_8x8_blocks_wide_lookup[bsize];
  const int num_8x8_blocks_high = num_8x8_blocks_high_lookup[bsize];
  mv_ref_search[0].row = num_8x8_blocks_high - 1;
  mv_ref_search[0].col = -1;
  mv_ref_search[1].row = -1;
  mv_ref_search[1].col = num_8x8_blocks_wide - 1;
  mv_ref_search[2].row = -1;
  mv_ref_search[2].col = (num_8x8_blocks_wide - 1) >> 1;
  mv_ref_search[3].row = (num_8x8_blocks_high - 1) >> 1;
  mv_ref_search[3].col = -1;
  mv_ref_search[4].row = -1;
  mv_ref_search[4].col = -1;
#if CONFIG_EXT_PARTITION_TYPES
  if (num_8x8_blocks_wide == num_8x8_blocks_high) {
    mv_ref_search[5].row = -1;
    mv_ref_search[5].col = 0;
    mv_ref_search[6].row = 0;
    mv_ref_search[6].col = -1;
  } else {
    mv_ref_search[5].row = -1;
    mv_ref_search[5].col = num_8x8_blocks_wide;
    mv_ref_search[6].row = num_8x8_blocks_high;
    mv_ref_search[6].col = -1;
  }
#else
  mv_ref_search[5].row = -1;
  mv_ref_search[5].col = num_8x8_blocks_wide;
  mv_ref_search[6].row = num_8x8_blocks_high;
  mv_ref_search[6].col = -1;
#endif  // CONFIG_EXT_PARTITION_TYPES
  mv_ref_search[7].row = -1;
  mv_ref_search[7].col = -3;
  mv_ref_search[8].row = num_8x8_blocks_high - 1;
  mv_ref_search[8].col = -3;

  for (i = 0; i < MVREF_NEIGHBOURS; ++i) {
    mv_ref_search[i].row *= 2;
    mv_ref_search[i].col *= 2;
  }

  // The nearest 2 blocks are treated differently
  // if the size < 8x8 we get the mv from the bmi substructure,
  // and we also need to keep a mode count.
  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, cm, mv_ref)) {
      const MODE_INFO *const candidate_mi =
          xd->mi[mv_ref->col + mv_ref->row * xd->mi_stride];
      const MB_MODE_INFO *const candidate = &candidate_mi->mbmi;
#if CONFIG_INTRABC
      if (ref_frame == INTRA_FRAME && !is_intrabc_block(candidate)) continue;
#endif  // CONFIG_INTRABC
      // Keep counts for entropy encoding.
      context_counter += mode_2_counter[candidate->mode];
      different_ref_found = 1;

      if (candidate->ref_frame[0] == ref_frame)
        ADD_MV_REF_LIST(get_sub_block_mv(candidate_mi, 0, mv_ref->col, block),
                        refmv_count, mv_ref_list, bw, bh, xd, Done);
      else if (candidate->ref_frame[1] == ref_frame)
        ADD_MV_REF_LIST(get_sub_block_mv(candidate_mi, 1, mv_ref->col, block),
                        refmv_count, mv_ref_list, bw, bh, xd, 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, cm, mv_ref)) {
      const MB_MODE_INFO *const candidate =
          !xd->mi[mv_ref->col + mv_ref->row * xd->mi_stride]
              ? NULL
              : &xd->mi[mv_ref->col + mv_ref->row * xd->mi_stride]->mbmi;
      if (candidate == NULL) continue;
#if CONFIG_INTRABC
      if (ref_frame == INTRA_FRAME && !is_intrabc_block(candidate)) continue;
#endif  // CONFIG_INTRABC
      if ((mi_row & (sb_mi_size - 1)) + mv_ref->row >= sb_mi_size ||
          (mi_col & (sb_mi_size - 1)) + mv_ref->col >= sb_mi_size)
        continue;
      different_ref_found = 1;

      if (candidate->ref_frame[0] == ref_frame)
        ADD_MV_REF_LIST(candidate->mv[0], refmv_count, mv_ref_list, bw, bh, xd,
                        Done);
      else if (candidate->ref_frame[1] == ref_frame)
        ADD_MV_REF_LIST(candidate->mv[1], refmv_count, mv_ref_list, bw, bh, xd,
                        Done);
    }
  }

// TODO(hkuang): Remove this sync after fixing pthread_cond_broadcast
// on windows platform. The sync here is unncessary if use_perv_frame_mvs
// is 0. But after removing it, there will be hang in the unit test on windows
// due to several threads waiting for a thread's signal.
#if defined(_WIN32) && !HAVE_PTHREAD_H
  if (cm->frame_parallel_decode && sync != NULL) {
    sync(data, mi_row);
  }
#endif

#if !CONFIG_MFMV
  // Check the last frame's mode and mv info.
  if (cm->use_prev_frame_mvs) {
    // Synchronize here for frame parallel decode if sync function is provided.
    if (cm->frame_parallel_decode && sync != NULL) {
      sync(data, mi_row);
    }

    if (prev_frame_mvs->ref_frame[0] == ref_frame) {
      ADD_MV_REF_LIST(prev_frame_mvs->mv[0], refmv_count, mv_ref_list, bw, bh,
                      xd, Done);
    } else if (prev_frame_mvs->ref_frame[1] == ref_frame) {
      ADD_MV_REF_LIST(prev_frame_mvs->mv[1], refmv_count, mv_ref_list, bw, bh,
                      xd, Done);
    }
  }
#endif  // !CONFIG_MFMV

  // 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
#if CONFIG_INTRABC
      && ref_frame != INTRA_FRAME
#endif  // CONFIG_INTRABC
      ) {
    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, cm, mv_ref)) {
        const MB_MODE_INFO *const candidate =
            !xd->mi[mv_ref->col + mv_ref->row * xd->mi_stride]
                ? NULL
                : &xd->mi[mv_ref->col + mv_ref->row * xd->mi_stride]->mbmi;
        if (candidate == NULL) continue;
        if ((mi_row & (sb_mi_size - 1)) + mv_ref->row >= sb_mi_size ||
            (mi_col & (sb_mi_size - 1)) + mv_ref->col >= sb_mi_size)
          continue;

        // If the candidate is INTRA we don't want to consider its mv.
        IF_DIFF_REF_FRAME_ADD_MV(candidate, ref_frame, ref_sign_bias,
                                 refmv_count, mv_ref_list, bw, bh, xd, Done);
      }
    }
  }

#if !CONFIG_MFMV
  // Since we still don't have a candidate we'll try the last frame.
  if (cm->use_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(mv, refmv_count, mv_ref_list, bw, bh, xd, Done);
    }

    if (prev_frame_mvs->ref_frame[1] > INTRA_FRAME &&
        prev_frame_mvs->ref_frame[1] != ref_frame) {
      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(mv, refmv_count, mv_ref_list, bw, bh, xd, Done);
    }
  }
#endif  // !CONFIG_MFMV

Done:
  if (mode_context)
    mode_context[ref_frame] = counter_to_context[context_counter];
  for (i = refmv_count; i < MAX_MV_REF_CANDIDATES; ++i)
    mv_ref_list[i].as_int = zeromv.as_int;
}

// This function keeps a mode count for a given MB/SB
void av1_update_mv_context(const AV1_COMMON *cm, const MACROBLOCKD *xd,
                           MODE_INFO *mi, MV_REFERENCE_FRAME ref_frame,
                           int_mv *mv_ref_list, int block, int mi_row,
                           int mi_col, int16_t *mode_context) {
  int i, refmv_count = 0;
  int context_counter = 0;
  const int bw = block_size_wide[mi->mbmi.sb_type];
  const int bh = block_size_high[mi->mbmi.sb_type];
  const TileInfo *const tile = &xd->tile;
  POSITION mv_ref_search[2];
  const int num_8x8_blocks_wide = mi_size_wide[mi->mbmi.sb_type];
  const int num_8x8_blocks_high = mi_size_high[mi->mbmi.sb_type];

  mv_ref_search[0].row = num_8x8_blocks_high - 1;
  mv_ref_search[0].col = -1;
  mv_ref_search[1].row = -1;
  mv_ref_search[1].col = num_8x8_blocks_wide - 1;

  // Blank the reference vector list
  memset(mv_ref_list, 0, sizeof(*mv_ref_list) * MAX_MV_REF_CANDIDATES);

  // The nearest 2 blocks are examined only.
  // If the size < 8x8, we get the mv from the bmi substructure;
  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, cm, mv_ref)) {
      const MODE_INFO *const candidate_mi =
          xd->mi[mv_ref->col + mv_ref->row * xd->mi_stride];
      const MB_MODE_INFO *const candidate = &candidate_mi->mbmi;
#if CONFIG_INTRABC
      if (ref_frame == INTRA_FRAME && !is_intrabc_block(candidate)) continue;
#endif  // CONFIG_INTRABC
      // Keep counts for entropy encoding.
      context_counter += mode_2_counter[candidate->mode];

      if (candidate->ref_frame[0] == ref_frame) {
        ADD_MV_REF_LIST(get_sub_block_mv(candidate_mi, 0, mv_ref->col, block),
                        refmv_count, mv_ref_list, bw, bh, xd, Done);
      } else if (candidate->ref_frame[1] == ref_frame) {
        ADD_MV_REF_LIST(get_sub_block_mv(candidate_mi, 1, mv_ref->col, block),
                        refmv_count, mv_ref_list, bw, bh, xd, Done);
      }
    }
  }

Done:

  if (mode_context)
    mode_context[ref_frame] = counter_to_context[context_counter];
}

void av1_find_mv_refs(const AV1_COMMON *cm, const MACROBLOCKD *xd,
                      MODE_INFO *mi, MV_REFERENCE_FRAME ref_frame,
                      uint8_t *ref_mv_count, CANDIDATE_MV *ref_mv_stack,
                      int16_t *compound_mode_context, int_mv *mv_ref_list,
                      int mi_row, int mi_col, find_mv_refs_sync sync,
                      void *const data, int16_t *mode_context) {
  int_mv zeromv[2];
  BLOCK_SIZE bsize = mi->mbmi.sb_type;
  int idx, all_zero = 1;
  MV_REFERENCE_FRAME rf[2];

  av1_update_mv_context(cm, xd, mi, ref_frame, mv_ref_list, -1, mi_row, mi_col,
                        compound_mode_context);

  if (!CONFIG_INTRABC || ref_frame != INTRA_FRAME) {
    av1_set_ref_frame(rf, ref_frame);
    zeromv[0].as_int = gm_get_motion_vector(&cm->global_motion[rf[0]],
                                            cm->allow_high_precision_mv, bsize,
                                            mi_col, mi_row, 0
#if CONFIG_AMVR
                                            ,
                                            cm->cur_frame_force_integer_mv
#endif
                                            )
                           .as_int;
    zeromv[1].as_int = (rf[1] != NONE_FRAME)
                           ? gm_get_motion_vector(&cm->global_motion[rf[1]],
                                                  cm->allow_high_precision_mv,
                                                  bsize, mi_col, mi_row, 0
#if CONFIG_AMVR
                                                  ,
                                                  cm->cur_frame_force_integer_mv
#endif
                                                  )
                                 .as_int
                           : 0;
  } else {
    zeromv[0].as_int = zeromv[1].as_int = 0;
  }

  if (ref_frame <= ALTREF_FRAME)
    find_mv_refs_idx(cm, xd, mi, ref_frame, mv_ref_list, -1, mi_row, mi_col,
                     sync, data, mode_context, zeromv[0]);

  setup_ref_mv_list(cm, xd, ref_frame, ref_mv_count, ref_mv_stack, mv_ref_list,
#if USE_CUR_GM_REFMV
                    zeromv,
#endif  // USE_CUR_GM_REFMV
                    -1, mi_row, mi_col, mode_context);
  /* Note: If global motion is enabled, then we want to set the ALL_ZERO flag
     iff all of the MVs we could generate with NEARMV/NEARESTMV are equivalent
     to the global motion vector.
     Note: For the following to work properly, the encoder can't throw away
     any global motion models after calling this function, even if they are
     unused. Instead we rely on the recode loop: If any non-IDENTITY model
     is unused, the whole frame will be re-encoded without it.
     The problem is that, otherwise, we can end up in the following situation:
     * Encoder has a global motion model with nonzero translational part,
       and all candidate MVs are zero. So the ALL_ZERO flag is unset.
     * Encoder throws away global motion because it is never used.
     * Decoder sees that there is no global motion and all candidate MVs are
       zero, so sets the ALL_ZERO flag.
     * This leads to an encode/decode mismatch.
  */
  for (idx = 0; idx < AOMMIN(3, *ref_mv_count); ++idx) {
    if (ref_mv_stack[idx].this_mv.as_int != zeromv[0].as_int) all_zero = 0;
    if (ref_frame > ALTREF_FRAME)
      if (ref_mv_stack[idx].comp_mv.as_int != zeromv[1].as_int) all_zero = 0;
  }
  if (*ref_mv_count < 2 && ref_frame <= ALTREF_FRAME) {
    for (idx = 0; idx < MAX_MV_REF_CANDIDATES; ++idx)
      if (mv_ref_list[idx].as_int != zeromv[0].as_int) all_zero = 0;
  }

#if !CONFIG_OPT_REF_MV
  if (all_zero) mode_context[ref_frame] |= (1 << ALL_ZERO_FLAG_OFFSET);
#else
  (void)all_zero;
#endif
}

void av1_find_best_ref_mvs(int allow_hp, int_mv *mvlist, int_mv *nearest_mv,
                           int_mv *near_mv
#if CONFIG_AMVR
                           ,
                           int is_integer
#endif
                           ) {
  int i;
  // Make sure all the candidates are properly clamped etc
  for (i = 0; i < MAX_MV_REF_CANDIDATES; ++i) {
#if CONFIG_AMVR
    lower_mv_precision(&mvlist[i].as_mv, allow_hp, is_integer);
#else
    lower_mv_precision(&mvlist[i].as_mv, allow_hp);
#endif
  }
  *nearest_mv = mvlist[0];
  *near_mv = mvlist[1];
}

#if CONFIG_FRAME_MARKER
void av1_setup_frame_buf_refs(AV1_COMMON *cm) {
  cm->cur_frame->cur_frame_offset = cm->frame_offset;
  int alt_buf_idx = cm->frame_refs[ALTREF_FRAME - LAST_FRAME].idx;
  int lst_buf_idx = cm->frame_refs[LAST_FRAME - LAST_FRAME].idx;
  int gld_buf_idx = cm->frame_refs[GOLDEN_FRAME - LAST_FRAME].idx;

  int lst2_buf_idx = cm->frame_refs[LAST2_FRAME - LAST_FRAME].idx;
  int lst3_buf_idx = cm->frame_refs[LAST3_FRAME - LAST_FRAME].idx;
  int bwd_buf_idx = cm->frame_refs[BWDREF_FRAME - LAST_FRAME].idx;
  int alt2_buf_idx = cm->frame_refs[ALTREF2_FRAME - LAST_FRAME].idx;

  if (alt_buf_idx >= 0)
    cm->cur_frame->alt_frame_offset =
        cm->buffer_pool->frame_bufs[alt_buf_idx].cur_frame_offset;

  if (lst_buf_idx >= 0)
    cm->cur_frame->lst_frame_offset =
        cm->buffer_pool->frame_bufs[lst_buf_idx].cur_frame_offset;

  if (gld_buf_idx >= 0)
    cm->cur_frame->gld_frame_offset =
        cm->buffer_pool->frame_bufs[gld_buf_idx].cur_frame_offset;

  if (lst2_buf_idx >= 0)
    cm->cur_frame->lst2_frame_offset =
        cm->buffer_pool->frame_bufs[lst2_buf_idx].cur_frame_offset;

  if (lst3_buf_idx >= 0)
    cm->cur_frame->lst3_frame_offset =
        cm->buffer_pool->frame_bufs[lst3_buf_idx].cur_frame_offset;

  if (bwd_buf_idx >= 0)
    cm->cur_frame->bwd_frame_offset =
        cm->buffer_pool->frame_bufs[bwd_buf_idx].cur_frame_offset;

  if (alt2_buf_idx >= 0)
    cm->cur_frame->alt2_frame_offset =
        cm->buffer_pool->frame_bufs[alt2_buf_idx].cur_frame_offset;
}

#if CONFIG_FRAME_SIGN_BIAS
void av1_setup_frame_sign_bias(AV1_COMMON *cm) {
  MV_REFERENCE_FRAME ref_frame;
  for (ref_frame = LAST_FRAME; ref_frame <= ALTREF_FRAME; ++ref_frame) {
    const int buf_idx = cm->frame_refs[ref_frame - LAST_FRAME].idx;
    if (buf_idx != INVALID_IDX) {
      const int ref_frame_offset =
          cm->buffer_pool->frame_bufs[buf_idx].cur_frame_offset;
      cm->ref_frame_sign_bias[ref_frame] =
          (ref_frame_offset <= (int)cm->frame_offset) ? 0 : 1;
    } else {
      cm->ref_frame_sign_bias[ref_frame] = 0;
    }
  }
}
#endif  // CONFIG_FRAME_SIGN_BIAS
#endif  // CONFIG_FRAME_MARKER

#if CONFIG_MFMV || CONFIG_EXT_SKIP
// Although we assign 32 bit integers, all the values are strictly under 14
// bits.
static int div_mult[64] = {
  0,    16384, 8192, 5461, 4096, 3276, 2730, 2340, 2048, 1820, 1638, 1489, 1365,
  1260, 1170,  1092, 1024, 963,  910,  862,  819,  780,  744,  712,  682,  655,
  630,  606,   585,  564,  546,  528,  512,  496,  481,  468,  455,  442,  431,
  420,  409,   399,  390,  381,  372,  364,  356,  348,  341,  334,  327,  321,
  315,  309,   303,  297,  292,  287,  282,  277,  273,  268,  264,  260,
};

// TODO(jingning): Consider the use of lookup table for (num / den)
// altogether.
static void get_mv_projection(MV *output, MV ref, int num, int den) {
  output->row =
      (int16_t)(ROUND_POWER_OF_TWO_SIGNED(ref.row * num * div_mult[den], 14));
  output->col =
      (int16_t)(ROUND_POWER_OF_TWO_SIGNED(ref.col * num * div_mult[den], 14));
}
#endif  // CONFIG_MFMV || CONFIG_EXT_SKIP

#if CONFIG_MFMV
#define MAX_OFFSET_WIDTH 64
#define MAX_OFFSET_HEIGHT 0

static int get_block_position(AV1_COMMON *cm, int *mi_r, int *mi_c, int blk_row,
                              int blk_col, MV mv, int sign_bias) {
  const int base_blk_row = (blk_row >> 3) << 3;
  const int base_blk_col = (blk_col >> 3) << 3;

  const int row_offset = (mv.row >= 0) ? (mv.row >> (4 + MI_SIZE_LOG2))
                                       : -((-mv.row) >> (4 + MI_SIZE_LOG2));

  const int col_offset = (mv.col >= 0) ? (mv.col >> (4 + MI_SIZE_LOG2))
                                       : -((-mv.col) >> (4 + MI_SIZE_LOG2));

  int row = (sign_bias == 1) ? blk_row - row_offset : blk_row + row_offset;
  int col = (sign_bias == 1) ? blk_col - col_offset : blk_col + col_offset;

  if (row < 0 || row >= (cm->mi_rows >> 1) || col < 0 ||
      col >= (cm->mi_cols >> 1))
    return 0;

  if (row <= base_blk_row - (MAX_OFFSET_HEIGHT >> 3) ||
      row >= base_blk_row + 8 + (MAX_OFFSET_HEIGHT >> 3) ||
      col <= base_blk_col - (MAX_OFFSET_WIDTH >> 3) ||
      col >= base_blk_col + 8 + (MAX_OFFSET_WIDTH >> 3))
    return 0;

  *mi_r = row;
  *mi_c = col;

  return 1;
}

static int motion_field_projection(AV1_COMMON *cm, MV_REFERENCE_FRAME ref_frame,
                                   int ref_stamp, int dir) {
  TPL_MV_REF *tpl_mvs_base = cm->tpl_mvs;
  int cur_rf_index[TOTAL_REFS_PER_FRAME] = { 0 };
  int ref_rf_idx[TOTAL_REFS_PER_FRAME] = { 0 };
  int cur_offset[TOTAL_REFS_PER_FRAME] = { 0 };
  int ref_offset[TOTAL_REFS_PER_FRAME] = { 0 };

  (void)dir;

  int ref_frame_idx = cm->frame_refs[FWD_RF_OFFSET(ref_frame)].idx;
  if (ref_frame_idx < 0) return 0;

  int ref_frame_index =
      cm->buffer_pool->frame_bufs[ref_frame_idx].cur_frame_offset;
  int cur_frame_index = cm->cur_frame->cur_frame_offset;
  int ref_to_cur = ref_frame_index - cur_frame_index;

  ref_rf_idx[LAST_FRAME] =
      cm->buffer_pool->frame_bufs[ref_frame_idx].lst_frame_offset;
  ref_rf_idx[GOLDEN_FRAME] =
      cm->buffer_pool->frame_bufs[ref_frame_idx].gld_frame_offset;
  ref_rf_idx[LAST2_FRAME] =
      cm->buffer_pool->frame_bufs[ref_frame_idx].lst2_frame_offset;
  ref_rf_idx[LAST3_FRAME] =
      cm->buffer_pool->frame_bufs[ref_frame_idx].lst3_frame_offset;
  ref_rf_idx[BWDREF_FRAME] =
      cm->buffer_pool->frame_bufs[ref_frame_idx].bwd_frame_offset;
  ref_rf_idx[ALTREF2_FRAME] =
      cm->buffer_pool->frame_bufs[ref_frame_idx].alt2_frame_offset;
  ref_rf_idx[ALTREF_FRAME] =
      cm->buffer_pool->frame_bufs[ref_frame_idx].alt_frame_offset;

  for (MV_REFERENCE_FRAME rf = LAST_FRAME; rf <= INTER_REFS_PER_FRAME; ++rf) {
    int buf_idx = cm->frame_refs[FWD_RF_OFFSET(rf)].idx;
    if (buf_idx >= 0)
      cur_rf_index[rf] = cm->buffer_pool->frame_bufs[buf_idx].cur_frame_offset;
    cur_offset[rf] = cur_frame_index - cur_rf_index[rf];
    ref_offset[rf] = ref_frame_index - ref_rf_idx[rf];
  }

  if (dir == 1) {
    ref_to_cur = -ref_to_cur;
    for (MV_REFERENCE_FRAME rf = LAST_FRAME; rf <= INTER_REFS_PER_FRAME; ++rf) {
      cur_offset[rf] = -cur_offset[rf];
      ref_offset[rf] = -ref_offset[rf];
    }
  }

  if (dir == 2) ref_to_cur = -ref_to_cur;

  MV_REF *mv_ref_base = cm->buffer_pool->frame_bufs[ref_frame_idx].mvs;
  const int mvs_rows = (cm->mi_rows + 1) >> 1;
  const int mvs_cols = (cm->mi_cols + 1) >> 1;

  for (int blk_row = 0; blk_row < mvs_rows; ++blk_row) {
    for (int blk_col = 0; blk_col < mvs_cols; ++blk_col) {
      MV_REF *mv_ref = &mv_ref_base[blk_row * mvs_cols + blk_col];
      MV fwd_mv = mv_ref->mv[dir & 0x01].as_mv;

      const int ref_frame_offset = ref_offset[mv_ref->ref_frame[dir & 0x01]];

      if (mv_ref->ref_frame[dir & 0x01] > INTRA_FRAME) {
        int_mv this_mv;
        int mi_r, mi_c;

        get_mv_projection(&this_mv.as_mv, fwd_mv, ref_to_cur, ref_frame_offset);
        int pos_valid = get_block_position(cm, &mi_r, &mi_c, blk_row, blk_col,
                                           this_mv.as_mv, dir >> 1);
        if (pos_valid) {
          int mi_offset = mi_r * (cm->mi_stride >> 1) + mi_c;

          for (MV_REFERENCE_FRAME rf = ALTREF_FRAME; rf >= LAST_FRAME; --rf) {
            get_mv_projection(&this_mv.as_mv, fwd_mv, cur_offset[rf],
                              ref_frame_offset);
            tpl_mvs_base[mi_offset].mfmv[FWD_RF_OFFSET(rf)][ref_stamp].as_int =
                this_mv.as_int;
          }
        }
      }
    }
  }

  return 1;
}

void av1_setup_motion_field(AV1_COMMON *cm) {
  int cur_frame_index = cm->cur_frame->cur_frame_offset;
  int alt_frame_index = 0, gld_frame_index = 0;
  int bwd_frame_index = 0, alt2_frame_index = 0;

  TPL_MV_REF *tpl_mvs_base = cm->tpl_mvs;
  for (int ref_frame = 0; ref_frame < INTER_REFS_PER_FRAME; ++ref_frame) {
    int size = ((cm->mi_rows + MAX_MIB_SIZE) >> 1) * (cm->mi_stride >> 1);
    for (int idx = 0; idx < size; ++idx) {
      for (int i = 0; i < MFMV_STACK_SIZE; ++i)
        tpl_mvs_base[idx].mfmv[ref_frame][i].as_int = INVALID_MV;
    }
  }

  int gld_buf_idx = cm->frame_refs[GOLDEN_FRAME - LAST_FRAME].idx;
  int alt_buf_idx = cm->frame_refs[ALTREF_FRAME - LAST_FRAME].idx;
  int lst_buf_idx = cm->frame_refs[LAST_FRAME - LAST_FRAME].idx;
  int bwd_buf_idx = cm->frame_refs[BWDREF_FRAME - LAST_FRAME].idx;
  int alt2_buf_idx = cm->frame_refs[ALTREF2_FRAME - LAST_FRAME].idx;

  if (alt_buf_idx >= 0)
    alt_frame_index = cm->buffer_pool->frame_bufs[alt_buf_idx].cur_frame_offset;

  if (gld_buf_idx >= 0)
    gld_frame_index = cm->buffer_pool->frame_bufs[gld_buf_idx].cur_frame_offset;

  if (bwd_buf_idx >= 0)
    bwd_frame_index = cm->buffer_pool->frame_bufs[bwd_buf_idx].cur_frame_offset;

  if (alt2_buf_idx >= 0)
    alt2_frame_index =
        cm->buffer_pool->frame_bufs[alt2_buf_idx].cur_frame_offset;

  memset(cm->ref_frame_side, 0, sizeof(cm->ref_frame_side));
  for (int ref_frame = LAST_FRAME; ref_frame <= INTER_REFS_PER_FRAME;
       ++ref_frame) {
    int buf_idx = cm->frame_refs[ref_frame - LAST_FRAME].idx;
    int frame_index = -1;
    if (buf_idx >= 0)
      frame_index = cm->buffer_pool->frame_bufs[buf_idx].cur_frame_offset;
    if (frame_index > cur_frame_index)
      cm->ref_frame_side[ref_frame] = 1;
    else if (frame_index == cur_frame_index)
      cm->ref_frame_side[ref_frame] = -1;
  }

  int ref_stamp = MFMV_STACK_SIZE - 1;

  if (lst_buf_idx >= 0) {
    const int alt_frame_idx =
        cm->buffer_pool->frame_bufs[lst_buf_idx].alt_frame_offset;

    const int is_lst_overlay = (alt_frame_idx == gld_frame_index);
    if (!is_lst_overlay) motion_field_projection(cm, LAST_FRAME, ref_stamp, 1);

    --ref_stamp;
  }

  if (bwd_frame_index > cur_frame_index) {
    if (motion_field_projection(cm, BWDREF_FRAME, ref_stamp, 0)) --ref_stamp;
  }

  if (alt2_frame_index > cur_frame_index) {
    if (motion_field_projection(cm, ALTREF2_FRAME, ref_stamp, 0)) --ref_stamp;
  }

  if (alt_frame_index > cur_frame_index && ref_stamp >= 0)
    if (motion_field_projection(cm, ALTREF_FRAME, ref_stamp, 0)) --ref_stamp;
}
#endif  // CONFIG_MFMV

#if CONFIG_EXT_WARPED_MOTION
static INLINE void record_samples(MB_MODE_INFO *mbmi, int *pts, int *pts_inref,
                                  int *pts_mv, int global_offset_r,
                                  int global_offset_c, int row_offset,
                                  int sign_r, int col_offset, int sign_c) {
  int bw = block_size_wide[mbmi->sb_type];
  int bh = block_size_high[mbmi->sb_type];
  int cr_offset = row_offset * MI_SIZE + sign_r * AOMMAX(bh, MI_SIZE) / 2 - 1;
  int cc_offset = col_offset * MI_SIZE + sign_c * AOMMAX(bw, MI_SIZE) / 2 - 1;
  int x = cc_offset + global_offset_c;
  int y = cr_offset + global_offset_r;

  pts[0] = (x * 8);
  pts[1] = (y * 8);
  pts_inref[0] = (x * 8) + mbmi->mv[0].as_mv.col;
  pts_inref[1] = (y * 8) + mbmi->mv[0].as_mv.row;
  pts_mv[0] = mbmi->mv[0].as_mv.col;
  pts_mv[1] = mbmi->mv[0].as_mv.row;
}

// Only sort pts and pts_inref, and pts_mv is not sorted.
#define TRIM_THR 16
int sortSamples(int *pts_mv, MV *mv, int *pts, int *pts_inref, int len) {
  int pts_mvd[SAMPLES_ARRAY_SIZE] = { 0 };
  int i, j, k;
  int ret = len;
  assert(len <= SAMPLES_MAX);

  for (i = 0; i < len; ++i)
    pts_mvd[i] =
        abs(pts_mv[2 * i] - mv->col) + abs(pts_mv[2 * i + 1] - mv->row);

  // TODO(yunqingwang): len is capped at 8 after this. Thus, modify this to find
  // the best 8 samples instead of sorting all samples.
  for (i = 1; i <= len - 1; ++i) {
    for (j = 0; j < i; ++j) {
      if (pts_mvd[j] > pts_mvd[i]) {
        int temp, tempi, tempj, ptempi, ptempj;

        temp = pts_mvd[i];
        tempi = pts[2 * i];
        tempj = pts[2 * i + 1];
        ptempi = pts_inref[2 * i];
        ptempj = pts_inref[2 * i + 1];

        for (k = i; k > j; k--) {
          pts_mvd[k] = pts_mvd[k - 1];
          pts[2 * k] = pts[2 * (k - 1)];
          pts[2 * k + 1] = pts[2 * (k - 1) + 1];
          pts_inref[2 * k] = pts_inref[2 * (k - 1)];
          pts_inref[2 * k + 1] = pts_inref[2 * (k - 1) + 1];
        }

        pts_mvd[j] = temp;
        pts[2 * j] = tempi;
        pts[2 * j + 1] = tempj;
        pts_inref[2 * j] = ptempi;
        pts_inref[2 * j + 1] = ptempj;
        break;
      }
    }
  }
  len = AOMMIN(len, LEAST_SQUARES_SAMPLES_MAX);

  for (i = len - 1; i >= 1; i--) {
    if ((pts_mvd[i] - pts_mvd[i - 1]) >= TRIM_THR) ret = i;
  }

  return ret;
}

// Note: Samples returned are at 1/8-pel precision
int findSamples(const AV1_COMMON *cm, MACROBLOCKD *xd, int mi_row, int mi_col,
                int *pts, int *pts_inref, int *pts_mv, int *pts_wm) {
  MB_MODE_INFO *const mbmi0 = &(xd->mi[0]->mbmi);
  int ref_frame = mbmi0->ref_frame[0];
  int up_available = xd->up_available;
  int left_available = xd->left_available;
  int i, mi_step = 1, np = 0;
  int global_offset_c = mi_col * MI_SIZE;
  int global_offset_r = mi_row * MI_SIZE;

  const TileInfo *const tile = &xd->tile;
  int do_tl = 1;
  int do_tr = 1;

  // scan the nearest above rows
  if (up_available) {
    int mi_row_offset = -1;
    MODE_INFO *mi = xd->mi[mi_row_offset * xd->mi_stride];
    MB_MODE_INFO *mbmi = &mi->mbmi;
    uint8_t n8_w = mi_size_wide[mbmi->sb_type];

    if (xd->n8_w <= n8_w) {
      // Handle "current block width <= above block width" case.
      int col_offset = -mi_col % n8_w;

      if (col_offset < 0) do_tl = 0;
      if (col_offset + n8_w > xd->n8_w) do_tr = 0;

      if (mbmi->ref_frame[0] == ref_frame && mbmi->ref_frame[1] == NONE_FRAME) {
        record_samples(mbmi, pts, pts_inref, pts_mv, global_offset_r,
                       global_offset_c, 0, -1, col_offset, 1);
        pts_wm[0] = mi_row_offset * xd->mi_stride;
        pts_wm[1] = (mbmi->motion_mode == WARPED_CAUSAL)
                        ? (n8_w * mi_size_high[mbmi->sb_type])
                        : 0;
        pts_wm += 2;
        pts += 2;
        pts_inref += 2;
        pts_mv += 2;
        np++;
        if (np >= SAMPLES_MAX) return SAMPLES_MAX;
      }
    } else {
      // Handle "current block width > above block width" case.
      for (i = 0; i < AOMMIN(xd->n8_w, cm->mi_cols - mi_col); i += mi_step) {
        int mi_col_offset = i;
        mi = xd->mi[mi_col_offset + mi_row_offset * xd->mi_stride];
        mbmi = &mi->mbmi;
        n8_w = mi_size_wide[mbmi->sb_type];
        mi_step = AOMMIN(xd->n8_w, n8_w);

        if (mbmi->ref_frame[0] == ref_frame &&
            mbmi->ref_frame[1] == NONE_FRAME) {
          record_samples(mbmi, pts, pts_inref, pts_mv, global_offset_r,
                         global_offset_c, 0, -1, i, 1);
          pts_wm[0] = mi_col_offset + mi_row_offset * xd->mi_stride;
          pts_wm[1] = (mbmi->motion_mode == WARPED_CAUSAL)
                          ? (n8_w * mi_size_high[mbmi->sb_type])
                          : 0;
          pts_wm += 2;
          pts += 2;
          pts_inref += 2;
          pts_mv += 2;
          np++;
          if (np >= SAMPLES_MAX) return SAMPLES_MAX;
        }
      }
    }
  }
  assert(np <= SAMPLES_MAX);

  // scan the nearest left columns
  if (left_available) {
    int mi_col_offset = -1;

    MODE_INFO *mi = xd->mi[mi_col_offset];
    MB_MODE_INFO *mbmi = &mi->mbmi;
    uint8_t n8_h = mi_size_high[mbmi->sb_type];

    if (xd->n8_h <= n8_h) {
      // Handle "current block height <= above block height" case.
      int row_offset = -mi_row % n8_h;

      if (row_offset < 0) do_tl = 0;

      if (mbmi->ref_frame[0] == ref_frame && mbmi->ref_frame[1] == NONE_FRAME) {
        record_samples(mbmi, pts, pts_inref, pts_mv, global_offset_r,
                       global_offset_c, row_offset, 1, 0, -1);
        pts_wm[0] = mi_col_offset;
        pts_wm[1] = (mbmi->motion_mode == WARPED_CAUSAL)
                        ? (n8_h * mi_size_wide[mbmi->sb_type])
                        : 0;
        pts_wm += 2;
        pts += 2;
        pts_inref += 2;
        pts_mv += 2;
        np++;
        if (np >= SAMPLES_MAX) return SAMPLES_MAX;
      }
    } else {
      // Handle "current block height > above block height" case.
      for (i = 0; i < AOMMIN(xd->n8_h, cm->mi_rows - mi_row); i += mi_step) {
        int mi_row_offset = i;
        mi = xd->mi[mi_col_offset + mi_row_offset * xd->mi_stride];
        mbmi = &mi->mbmi;
        n8_h = mi_size_high[mbmi->sb_type];
        mi_step = AOMMIN(xd->n8_h, n8_h);

        if (mbmi->ref_frame[0] == ref_frame &&
            mbmi->ref_frame[1] == NONE_FRAME) {
          record_samples(mbmi, pts, pts_inref, pts_mv, global_offset_r,
                         global_offset_c, i, 1, 0, -1);
          pts_wm[0] = mi_col_offset + mi_row_offset * xd->mi_stride;
          pts_wm[1] = (mbmi->motion_mode == WARPED_CAUSAL)
                          ? (n8_h * mi_size_wide[mbmi->sb_type])
                          : 0;
          pts_wm += 2;
          pts += 2;
          pts_inref += 2;
          pts_mv += 2;
          np++;
          if (np >= SAMPLES_MAX) return SAMPLES_MAX;
        }
      }
    }
  }
  assert(np <= SAMPLES_MAX);

  // Top-left block
  if (do_tl && left_available && up_available) {
    int mi_row_offset = -1;
    int mi_col_offset = -1;

    MODE_INFO *mi = xd->mi[mi_col_offset + mi_row_offset * xd->mi_stride];
    MB_MODE_INFO *mbmi = &mi->mbmi;

    if (mbmi->ref_frame[0] == ref_frame && mbmi->ref_frame[1] == NONE_FRAME) {
      record_samples(mbmi, pts, pts_inref, pts_mv, global_offset_r,
                     global_offset_c, 0, -1, 0, -1);
      pts_wm[0] = mi_col_offset + mi_row_offset * xd->mi_stride;
      pts_wm[1] =
          (mbmi->motion_mode == WARPED_CAUSAL)
              ? (mi_size_wide[mbmi->sb_type] * mi_size_high[mbmi->sb_type])
              : 0;
      pts_wm += 2;
      pts += 2;
      pts_inref += 2;
      pts_mv += 2;
      np++;
      if (np >= SAMPLES_MAX) return SAMPLES_MAX;
    }
  }
  assert(np <= SAMPLES_MAX);

  // Top-right block
  if (do_tr &&
      has_top_right(cm, xd, mi_row, mi_col, AOMMAX(xd->n8_w, xd->n8_h))) {
    POSITION trb_pos = { -1, xd->n8_w };

    if (is_inside(tile, mi_col, mi_row, cm->mi_rows, cm, &trb_pos)) {
      int mi_row_offset = -1;
      int mi_col_offset = xd->n8_w;

      MODE_INFO *mi = xd->mi[mi_col_offset + mi_row_offset * xd->mi_stride];
      MB_MODE_INFO *mbmi = &mi->mbmi;

      if (mbmi->ref_frame[0] == ref_frame && mbmi->ref_frame[1] == NONE_FRAME) {
        record_samples(mbmi, pts, pts_inref, pts_mv, global_offset_r,
                       global_offset_c, 0, -1, xd->n8_w, 1);
        pts_wm[0] = mi_col_offset + mi_row_offset * xd->mi_stride;
        pts_wm[1] =
            (mbmi->motion_mode == WARPED_CAUSAL)
                ? (mi_size_wide[mbmi->sb_type] * mi_size_high[mbmi->sb_type])
                : 0;
        np++;
        if (np >= SAMPLES_MAX) return SAMPLES_MAX;
      }
    }
  }
  assert(np <= SAMPLES_MAX);

  return np;
}
#else
void calc_projection_samples(MB_MODE_INFO *const mbmi, int x, int y,
                             int *pts_inref) {
  pts_inref[0] = (x * 8) + mbmi->mv[0].as_mv.col;
  pts_inref[1] = (y * 8) + mbmi->mv[0].as_mv.row;
}

// Note: Samples returned are at 1/8-pel precision
int findSamples(const AV1_COMMON *cm, MACROBLOCKD *xd, int mi_row, int mi_col,
                int *pts, int *pts_inref) {
  MB_MODE_INFO *const mbmi0 = &(xd->mi[0]->mbmi);
  int ref_frame = mbmi0->ref_frame[0];
  int up_available = xd->up_available;
  int left_available = xd->left_available;
  int i, mi_step, np = 0;
  int global_offset_c = mi_col * MI_SIZE;
  int global_offset_r = mi_row * MI_SIZE;

  // scan the above row
  if (up_available) {
    for (i = 0; i < AOMMIN(xd->n8_w, cm->mi_cols - mi_col); i += mi_step) {
      int mi_row_offset = -1;
      int mi_col_offset = i;

      MODE_INFO *mi = xd->mi[mi_col_offset + mi_row_offset * xd->mi_stride];
      MB_MODE_INFO *mbmi = &mi->mbmi;

      mi_step = AOMMIN(xd->n8_w, mi_size_wide[mbmi->sb_type]);

      if (mbmi->ref_frame[0] == ref_frame && mbmi->ref_frame[1] == NONE_FRAME) {
        int bw = block_size_wide[mbmi->sb_type];
        int bh = block_size_high[mbmi->sb_type];
        int cr_offset = -AOMMAX(bh, MI_SIZE) / 2 - 1;
        int cc_offset = i * MI_SIZE + AOMMAX(bw, MI_SIZE) / 2 - 1;
        int x = cc_offset + global_offset_c;
        int y = cr_offset + global_offset_r;

        pts[0] = (x * 8);
        pts[1] = (y * 8);
        calc_projection_samples(mbmi, x, y, pts_inref);
        pts += 2;
        pts_inref += 2;
        np++;
        if (np >= LEAST_SQUARES_SAMPLES_MAX) return LEAST_SQUARES_SAMPLES_MAX;
      }
    }
  }
  assert(2 * np <= SAMPLES_ARRAY_SIZE);

  // scan the left column
  if (left_available) {
    for (i = 0; i < AOMMIN(xd->n8_h, cm->mi_rows - mi_row); i += mi_step) {
      int mi_row_offset = i;
      int mi_col_offset = -1;

      MODE_INFO *mi = xd->mi[mi_col_offset + mi_row_offset * xd->mi_stride];
      MB_MODE_INFO *mbmi = &mi->mbmi;

      mi_step = AOMMIN(xd->n8_h, mi_size_high[mbmi->sb_type]);

      if (mbmi->ref_frame[0] == ref_frame && mbmi->ref_frame[1] == NONE_FRAME) {
        int bw = block_size_wide[mbmi->sb_type];
        int bh = block_size_high[mbmi->sb_type];
        int cr_offset = i * MI_SIZE + AOMMAX(bh, MI_SIZE) / 2 - 1;
        int cc_offset = -AOMMAX(bw, MI_SIZE) / 2 - 1;
        int x = cc_offset + global_offset_c;
        int y = cr_offset + global_offset_r;

        pts[0] = (x * 8);
        pts[1] = (y * 8);
        calc_projection_samples(mbmi, x, y, pts_inref);
        pts += 2;
        pts_inref += 2;
        np++;
        if (np >= LEAST_SQUARES_SAMPLES_MAX) return LEAST_SQUARES_SAMPLES_MAX;
      }
    }
  }
  assert(2 * np <= SAMPLES_ARRAY_SIZE);

  if (left_available && up_available) {
    int mi_row_offset = -1;
    int mi_col_offset = -1;

    MODE_INFO *mi = xd->mi[mi_col_offset + mi_row_offset * xd->mi_stride];
    MB_MODE_INFO *mbmi = &mi->mbmi;

    if (mbmi->ref_frame[0] == ref_frame && mbmi->ref_frame[1] == NONE_FRAME) {
      int bw = block_size_wide[mbmi->sb_type];
      int bh = block_size_high[mbmi->sb_type];
      int cr_offset = -AOMMAX(bh, MI_SIZE) / 2 - 1;
      int cc_offset = -AOMMAX(bw, MI_SIZE) / 2 - 1;
      int x = cc_offset + global_offset_c;
      int y = cr_offset + global_offset_r;

      pts[0] = (x * 8);
      pts[1] = (y * 8);
      calc_projection_samples(mbmi, x, y, pts_inref);
      np++;
    }
  }
  assert(2 * np <= SAMPLES_ARRAY_SIZE);

  return np;
}
#endif  // CONFIG_EXT_WARPED_MOTION

#if CONFIG_EXT_SKIP
void av1_setup_skip_mode_allowed(AV1_COMMON *const cm) {
  cm->is_skip_mode_allowed = 0;
  cm->ref_frame_idx_0 = cm->ref_frame_idx_1 = INVALID_IDX;

  if (cm->frame_type == KEY_FRAME || cm->intra_only) return;

  RefCntBuffer *const frame_bufs = cm->buffer_pool->frame_bufs;
  const int cur_frame_offset = cm->frame_offset;
  int ref_frame_offset[2] = { -1, INT_MAX };
  int ref_idx[2] = { INVALID_IDX, INVALID_IDX };
  int ref_buf_idx[2] = { INVALID_IDX, INVALID_IDX };

  // Identify the nearest forward and backward references
  for (int i = 0; i < INTER_REFS_PER_FRAME; ++i) {
    const int buf_idx = cm->frame_refs[i].idx;
    if (buf_idx == INVALID_IDX) continue;

    const int ref_offset = frame_bufs[buf_idx].cur_frame_offset;
    if (ref_offset < cur_frame_offset) {
      // Forward reference
      if (ref_offset > ref_frame_offset[0]) {
        ref_frame_offset[0] = ref_offset;
        ref_idx[0] = i;
        ref_buf_idx[0] = buf_idx;
      }
    } else if (ref_offset > cur_frame_offset) {
      // Backward reference
      if (ref_offset < ref_frame_offset[1]) {
        ref_frame_offset[1] = ref_offset;
        ref_idx[1] = i;
        ref_buf_idx[1] = buf_idx;
      }
    }
  }

  // Flag is set when and only when both forward and backward references
  // are available and their distance is no greater than 3, i.e. as
  // opposed to the current frame position, the reference distance pair are
  // either: (1, 1), (1, 2), or (2, 1).
  if (ref_idx[0] != INVALID_IDX && ref_idx[1] != INVALID_IDX) {
    const int cur_to_fwd = cm->frame_offset - ref_frame_offset[0];
    const int cur_to_bwd = ref_frame_offset[1] - cm->frame_offset;
#if 0
    if ((ref_frame_offset[1] - ref_frame_offset[0]) <= 3)
#endif  // 0
    if (abs(cur_to_fwd - cur_to_bwd) <= 1) {
      cm->is_skip_mode_allowed = 1;
      cm->ref_frame_idx_0 = ref_idx[0];
      cm->ref_frame_idx_1 = ref_idx[1];
    }
  }

  // Set up the temporal mv candidates for skip mode.
  cm->tpl_frame_ref0_idx = INVALID_IDX;
  if (cm->is_skip_mode_allowed && cm->use_ref_frame_mvs) {
    const int tpl_ref1_buf_idx = ref_buf_idx[1];
    const int tpl_ref1_ref_offsets[INTER_REFS_PER_FRAME] = {
      frame_bufs[tpl_ref1_buf_idx].lst_frame_offset,
      frame_bufs[tpl_ref1_buf_idx].lst2_frame_offset,
      frame_bufs[tpl_ref1_buf_idx].lst3_frame_offset,
      frame_bufs[tpl_ref1_buf_idx].gld_frame_offset,
      frame_bufs[tpl_ref1_buf_idx].bwd_frame_offset,
      frame_bufs[tpl_ref1_buf_idx].alt2_frame_offset,
      frame_bufs[tpl_ref1_buf_idx].alt_frame_offset
    };

    for (int i = 0; i < INTER_REFS_PER_FRAME; ++i) {
      if (tpl_ref1_ref_offsets[i] == ref_frame_offset[0]) {
        cm->tpl_frame_ref0_idx = i;
        break;
      }
    }
  }
}

// Identify mvs for skip mode in the following order:
// (1) Search the spatial two neighboring blocks (left/top);
// (2) Search the temporal neighboring blocks;
// (3) Consider NEAREST_NEARESTMV.

#define SKIP_MODE_MV_LISTS 3
#define SPATIAL_CANDIDATES 2
#define TEMPORAL_CANDIDATES 2
#define TOTAL_CANDIDATES (SPATIAL_CANDIDATES + TEMPORAL_CANDIDATES)

void av1_setup_skip_mode_mvs(const AV1_COMMON *cm, const MACROBLOCKD *xd,
                             MB_MODE_INFO *mbmi, int mi_row, int mi_col,
                             const int_mv nearest_mv[2], find_mv_refs_sync sync,
                             void *const data) {
#if 0
  const int sb_mi_size = mi_size_wide[cm->sb_size];
#endif  // 0
  const TileInfo *const tile = &xd->tile;
  int i;

  const MV_REFERENCE_FRAME skip_mode_refs[2] = {
    LAST_FRAME + cm->ref_frame_idx_0, LAST_FRAME + cm->ref_frame_idx_1
  };
  const int8_t ref_frame_types[SKIP_MODE_MV_LISTS] = {
    skip_mode_refs[0], skip_mode_refs[1], av1_ref_frame_type(skip_mode_refs)
  };
  int_mv mv_list[SKIP_MODE_MV_LISTS][TOTAL_CANDIDATES][2];
  int mv_list_count[SKIP_MODE_MV_LISTS] = { 0 };

  const BLOCK_SIZE bsize = mbmi->sb_type;
  const int bw = block_size_wide[AOMMAX(bsize, BLOCK_8X8)];
  const int bh = block_size_high[AOMMAX(bsize, BLOCK_8X8)];
  const int num_8x8_blocks_wide = num_8x8_blocks_wide_lookup[bsize];
  const int num_8x8_blocks_high = num_8x8_blocks_high_lookup[bsize];

  // === Search mv candidate(s) over spatial neighboring blocks.
  POSITION mv_search_pos_cur[SPATIAL_CANDIDATES];
  mv_search_pos_cur[0].row = num_8x8_blocks_high - 1;  // LEFT
  mv_search_pos_cur[0].col = -1;
  mv_search_pos_cur[1].row = -1;  // TOP
  mv_search_pos_cur[1].col = num_8x8_blocks_wide - 1;

  MB_MODE_INFO *candidate_mbmi[SPATIAL_CANDIDATES] = { NULL };
  for (i = 0; i < SPATIAL_CANDIDATES; ++i) {
    const POSITION *const mv_pos = &mv_search_pos_cur[i];
    if (is_inside(tile, mi_col, mi_row, cm->mi_rows, cm, mv_pos)) {
      candidate_mbmi[i] =
          !xd->mi[mv_pos->col + mv_pos->row * xd->mi_stride]
              ? NULL
              : &(xd->mi[mv_pos->col + mv_pos->row * xd->mi_stride]->mbmi);
#if 0
      if (candidate_mbmi[i] == NULL) continue;
      // TODO(zoeliu): To investigate whether following sanity check is needed.
      if ((mi_row & (sb_mi_size - 1)) + mv_pos->row >= sb_mi_size ||
          (mi_col & (sb_mi_size - 1)) + mv_pos->col >= sb_mi_size)
        continue;
#endif  // 0
    }
  }

  // First scan on the spatial neighbors, considering both reference frames
  // matched for compound mode.
  for (i = 0; i < SPATIAL_CANDIDATES; ++i) {
    if (candidate_mbmi[i]) {
      if (has_second_ref(candidate_mbmi[i])) {  // comp
        if (av1_ref_frame_type(candidate_mbmi[i]->ref_frame) ==
            ref_frame_types[2])
          SKIP_MODE_MV_LIST_ADD(candidate_mbmi[i]->mv, mv_list, mv_list_count,
                                2, bw, bh, xd);
      } else {  // single
        if (candidate_mbmi[i]->ref_frame[0] == ref_frame_types[0])
          SKIP_MODE_MV_LIST_ADD(candidate_mbmi[i]->mv, mv_list, mv_list_count,
                                0, bw, bh, xd);
        else if (candidate_mbmi[i]->ref_frame[0] == ref_frame_types[1])
          SKIP_MODE_MV_LIST_ADD(candidate_mbmi[i]->mv, mv_list, mv_list_count,
                                1, bw, bh, xd);
      }
    }
  }

  // Re-scan mv candidate(s) over spatial neighboring blocks of compound mode,
  // with only one reference frame matching the skip mode.
  for (i = 0; i < SPATIAL_CANDIDATES; ++i) {
    if (candidate_mbmi[i] && has_second_ref(candidate_mbmi[i])) {  // comp
      if (candidate_mbmi[i]->ref_frame[0] == ref_frame_types[0] ||
          candidate_mbmi[i]->ref_frame[1] == ref_frame_types[1]) {
        const int rf_idx =
            (candidate_mbmi[i]->ref_frame[1] == ref_frame_types[1]);
        const int_mv rf_mv[2] = { candidate_mbmi[i]->mv[rf_idx],
                                  candidate_mbmi[i]->mv[1 - rf_idx] };

        SKIP_MODE_MV_LIST_ADD(rf_mv, mv_list, mv_list_count, rf_idx, bw, bh,
                              xd);
      }
    }
  }

// TODO(hkuang): Remove this sync after fixing pthread_cond_broadcast
// on windows platform. The sync here is unncessary if use_perv_frame_mvs
// is 0. But after removing it, there will be hang in the unit test on windows
// due to several threads waiting for a thread's signal.
#if defined(_WIN32) && !HAVE_PTHREAD_H
  if (cm->frame_parallel_decode && sync != NULL) sync(data, mi_row);
#endif

  // === Search mv candidate(s) over temporal neighboring blocks.
  if (cm->tpl_frame_ref0_idx != INVALID_IDX) {
    // Synchronize here for frame parallel decode if sync function is provided.
    if (cm->frame_parallel_decode && sync != NULL) {
      sync(data, mi_row);
    }

    POSITION mv_search_pos_tpl[TEMPORAL_CANDIDATES];
    mv_search_pos_tpl[0].row = num_8x8_blocks_high - 1;  // current
    mv_search_pos_tpl[0].col = num_8x8_blocks_wide - 1;
    mv_search_pos_tpl[1].row = num_8x8_blocks_high;  // bottom-right
    mv_search_pos_tpl[1].col = num_8x8_blocks_wide;

    const int mvs_rows = (cm->mi_rows + 1) >> 1;
    const int mvs_cols = (cm->mi_cols + 1) >> 1;

    RefCntBuffer *const frame_bufs = cm->buffer_pool->frame_bufs;

    const int tpl_ref0_buf_idx = cm->frame_refs[cm->ref_frame_idx_0].idx;
    const int tpl_ref0_offset = frame_bufs[tpl_ref0_buf_idx].cur_frame_offset;
    const int tpl_ref1_buf_idx = cm->frame_refs[cm->ref_frame_idx_1].idx;
    const int tpl_ref1_offset = frame_bufs[tpl_ref1_buf_idx].cur_frame_offset;

    MV_REF *const tpl_mvs_base = frame_bufs[tpl_ref1_buf_idx].mvs;

    for (i = 0; i < TEMPORAL_CANDIDATES; ++i) {
      const POSITION *const mv_pos = &mv_search_pos_tpl[i];
      const int tpl_mvs_row = (mi_row + mv_pos->row + 1) >> 1;
      const int tpl_mvs_col = (mi_col + mv_pos->col + 1) >> 1;

      if (tpl_mvs_row >= 0 && tpl_mvs_row < mvs_rows && tpl_mvs_col >= 0 &&
          tpl_mvs_col < mvs_cols) {
        MV_REF *mv_ref = &tpl_mvs_base[tpl_mvs_row * mvs_cols + tpl_mvs_col];
        MV_REFERENCE_FRAME tpl_frame_rf[2] = { mv_ref->ref_frame[0],
                                               mv_ref->ref_frame[1] };

        // Check whether the temporal candidate block has its reference frame 0
        // point to the same forward reference most recent to the current frame.
        if (tpl_frame_rf[0] <= INTRA_FRAME ||
            FWD_RF_OFFSET(tpl_frame_rf[0]) != cm->tpl_frame_ref0_idx)
          continue;

        // Scale the temporal candiate mv of the same forward reference frame
        // for the current frame.
        const int cur_to_ref0 = AOMMAX(1, cm->frame_offset - tpl_ref0_offset);
        const int ref1_to_ref0 = AOMMAX(1, tpl_ref1_offset - tpl_ref0_offset);

        MV tpl_frame_mv[2] = { mv_ref->mv[0].as_mv, mv_ref->mv[1].as_mv };
        int_mv candidate_mv;
        get_mv_projection(&candidate_mv.as_mv, tpl_frame_mv[0], cur_to_ref0,
                          ref1_to_ref0);

        const int_mv tpl_mv[2] = { candidate_mv, mv_ref->mv[1] };
        SKIP_MODE_MV_LIST_ADD(tpl_mv, mv_list, mv_list_count, 0, bw, bh, xd);
      }
    }
  }

  // === Finalize the mv/ref selection for the current block of skip mode.
  // TODO(zoeliu): Several items to consider for possibly improving the coding
  // performance further:
  // (1) Consider more spatial / temporal neighboring blocks;
  // (2) Signal the selection to differentiate between single or compoud mode;
  // (3) May allow the use of the most recent forward reference of the temporal
  //     neighboring block.
  if (mv_list_count[2] > 0) {  // comp
    mbmi->ref_frame[0] = cm->ref_frame_idx_0 + LAST_FRAME;
    mbmi->ref_frame[1] = cm->ref_frame_idx_1 + LAST_FRAME;
    mbmi->mv[0].as_int = mv_list[2][0][0].as_int;
    mbmi->mv[1].as_int = mv_list[2][0][1].as_int;
  } else if (mv_list_count[0] > 0) {  // single - forward
    mbmi->ref_frame[0] = cm->ref_frame_idx_0 + LAST_FRAME;
    mbmi->ref_frame[1] = -1;
    mbmi->mv[0].as_int = mv_list[0][0][0].as_int;
  } else if (mv_list_count[1] > 0) {  // single - backward
    mbmi->ref_frame[0] = cm->ref_frame_idx_1 + LAST_FRAME;
    mbmi->ref_frame[1] = -1;
    mbmi->mv[0].as_int = mv_list[1][0][0].as_int;
  } else {
    mbmi->ref_frame[0] = cm->ref_frame_idx_0 + LAST_FRAME;
    mbmi->ref_frame[1] = cm->ref_frame_idx_1 + LAST_FRAME;
    mbmi->mv[0].as_int = nearest_mv[0].as_int;
    mbmi->mv[1].as_int = nearest_mv[1].as_int;
  }
}
#endif  // CONFIG_EXT_SKIP