av1/encoder/interp_search.c

/*
 * Copyright (c) 2020, 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/pred_common.h"
#include "av1/encoder/interp_search.h"
#include "av1/encoder/model_rd.h"
#include "av1/encoder/rdopt_utils.h"
#include "av1/encoder/reconinter_enc.h"

// return mv_diff
static inline int is_interp_filter_good_match(
    const INTERPOLATION_FILTER_STATS *st, MB_MODE_INFO *const mi,
    int skip_level) {
  const int is_comp = has_second_ref(mi);
  int i;

  for (i = 0; i < 1 + is_comp; ++i) {
    if (st->ref_frames[i] != mi->ref_frame[i]) return INT_MAX;
  }

  if (skip_level == 1 && is_comp) {
    if (st->comp_type != mi->interinter_comp.type) return INT_MAX;
    if (st->compound_idx != mi->compound_idx) return INT_MAX;
  }

  int mv_diff = 0;
  for (i = 0; i < 1 + is_comp; ++i) {
    mv_diff += abs(st->mv[i].as_mv.row - mi->mv[i].as_mv.row) +
               abs(st->mv[i].as_mv.col - mi->mv[i].as_mv.col);
  }
  return mv_diff;
}

static inline int save_interp_filter_search_stat(
    MB_MODE_INFO *const mbmi, int64_t rd, unsigned int pred_sse,
    INTERPOLATION_FILTER_STATS *interp_filter_stats,
    int interp_filter_stats_idx) {
  if (interp_filter_stats_idx < MAX_INTERP_FILTER_STATS) {
    INTERPOLATION_FILTER_STATS stat = { mbmi->interp_filters,
                                        { mbmi->mv[0], mbmi->mv[1] },
                                        { mbmi->ref_frame[0],
                                          mbmi->ref_frame[1] },
                                        mbmi->interinter_comp.type,
                                        mbmi->compound_idx,
                                        rd,
                                        pred_sse };
    interp_filter_stats[interp_filter_stats_idx] = stat;
    interp_filter_stats_idx++;
  }
  return interp_filter_stats_idx;
}

static inline int find_interp_filter_in_stats(
    MB_MODE_INFO *const mbmi, INTERPOLATION_FILTER_STATS *interp_filter_stats,
    int interp_filter_stats_idx, int skip_level) {
  // [skip_levels][single or comp]
  const int thr[2][2] = { { 0, 0 }, { 3, 7 } };
  const int is_comp = has_second_ref(mbmi);

  // Find good enough match.
  // TODO(yunqing): Separate single-ref mode and comp mode stats for fast
  // search.
  int best = INT_MAX;
  int match = -1;
  for (int j = 0; j < interp_filter_stats_idx; ++j) {
    const INTERPOLATION_FILTER_STATS *st = &interp_filter_stats[j];
    const int mv_diff = is_interp_filter_good_match(st, mbmi, skip_level);
    // Exact match is found.
    if (mv_diff == 0) {
      match = j;
      break;
    } else if (mv_diff < best && mv_diff <= thr[skip_level - 1][is_comp]) {
      best = mv_diff;
      match = j;
    }
  }

  if (match != -1) {
    mbmi->interp_filters = interp_filter_stats[match].filters;
    return match;
  }
  return -1;  // no match result found
}

static int find_interp_filter_match(
    MB_MODE_INFO *const mbmi, const AV1_COMP *const cpi,
    const InterpFilter assign_filter, const int need_search,
    INTERPOLATION_FILTER_STATS *interp_filter_stats,
    int interp_filter_stats_idx) {
  int match_found_idx = -1;
  if (cpi->sf.interp_sf.use_interp_filter && need_search)
    match_found_idx = find_interp_filter_in_stats(
        mbmi, interp_filter_stats, interp_filter_stats_idx,
        cpi->sf.interp_sf.use_interp_filter);

  if (!need_search || match_found_idx == -1)
    set_default_interp_filters(mbmi, assign_filter);
  return match_found_idx;
}

static inline int get_switchable_rate(MACROBLOCK *const x,
                                      const int_interpfilters filters,
                                      const int ctx[2], int dual_filter) {
  const InterpFilter filter0 = filters.as_filters.y_filter;
  int inter_filter_cost =
      x->mode_costs.switchable_interp_costs[ctx[0]][filter0];
  if (dual_filter) {
    const InterpFilter filter1 = filters.as_filters.x_filter;
    inter_filter_cost += x->mode_costs.switchable_interp_costs[ctx[1]][filter1];
  }
  return SWITCHABLE_INTERP_RATE_FACTOR * inter_filter_cost;
}

// Build inter predictor and calculate model rd
// for a given plane.
static inline void interp_model_rd_eval(
    MACROBLOCK *const x, const AV1_COMP *const cpi, BLOCK_SIZE bsize,
    const BUFFER_SET *const orig_dst, int plane_from, int plane_to,
    RD_STATS *rd_stats, int is_skip_build_pred) {
  const AV1_COMMON *cm = &cpi->common;
  MACROBLOCKD *const xd = &x->e_mbd;
  RD_STATS tmp_rd_stats;
  av1_init_rd_stats(&tmp_rd_stats);

  // Skip inter predictor if the predictor is already available.
  if (!is_skip_build_pred) {
    const int mi_row = xd->mi_row;
    const int mi_col = xd->mi_col;
    av1_enc_build_inter_predictor(cm, xd, mi_row, mi_col, orig_dst, bsize,
                                  plane_from, plane_to);
  }

  model_rd_sb_fn[cpi->sf.rt_sf.use_simple_rd_model
                     ? MODELRD_LEGACY
                     : MODELRD_TYPE_INTERP_FILTER](
      cpi, bsize, x, xd, plane_from, plane_to, &tmp_rd_stats.rate,
      &tmp_rd_stats.dist, &tmp_rd_stats.skip_txfm, &tmp_rd_stats.sse, NULL,
      NULL, NULL);

  av1_merge_rd_stats(rd_stats, &tmp_rd_stats);
}

// calculate the rdcost of given interpolation_filter
static inline int64_t interpolation_filter_rd(
    MACROBLOCK *const x, const AV1_COMP *const cpi,
    const TileDataEnc *tile_data, BLOCK_SIZE bsize,
    const BUFFER_SET *const orig_dst, int64_t *const rd,
    RD_STATS *rd_stats_luma, RD_STATS *rd_stats, int *const switchable_rate,
    const BUFFER_SET *dst_bufs[2], int filter_idx, const int switchable_ctx[2],
    const int skip_pred) {
  const AV1_COMMON *cm = &cpi->common;
  const InterpSearchFlags *interp_search_flags = &cpi->interp_search_flags;
  const int num_planes = av1_num_planes(cm);
  MACROBLOCKD *const xd = &x->e_mbd;
  MB_MODE_INFO *const mbmi = xd->mi[0];
  RD_STATS this_rd_stats_luma, this_rd_stats;

  // Initialize rd_stats structures to default values.
  av1_init_rd_stats(&this_rd_stats_luma);
  this_rd_stats = *rd_stats_luma;
  const int_interpfilters last_best = mbmi->interp_filters;
  mbmi->interp_filters = filter_sets[filter_idx];
  const int tmp_rs =
      get_switchable_rate(x, mbmi->interp_filters, switchable_ctx,
                          cm->seq_params->enable_dual_filter);

  int64_t min_rd = RDCOST(x->rdmult, tmp_rs, 0);
  if (min_rd > *rd) {
    mbmi->interp_filters = last_best;
    return 0;
  }

  (void)tile_data;

  assert(skip_pred != 2);
  assert((rd_stats_luma->rate >= 0) && (rd_stats->rate >= 0));
  assert((rd_stats_luma->dist >= 0) && (rd_stats->dist >= 0));
  assert((rd_stats_luma->sse >= 0) && (rd_stats->sse >= 0));
  assert((rd_stats_luma->skip_txfm == 0) || (rd_stats_luma->skip_txfm == 1));
  assert((rd_stats->skip_txfm == 0) || (rd_stats->skip_txfm == 1));
  assert((skip_pred >= 0) &&
         (skip_pred <= interp_search_flags->default_interp_skip_flags));

  // When skip_txfm pred is equal to default_interp_skip_flags,
  // skip both luma and chroma MC.
  // For mono-chrome images:
  // num_planes = 1 and cpi->default_interp_skip_flags = 1,
  // skip_pred = 1: skip both luma and chroma
  // skip_pred = 0: Evaluate luma and as num_planes=1,
  // skip chroma evaluation
  int tmp_skip_pred =
      (skip_pred == interp_search_flags->default_interp_skip_flags)
          ? INTERP_SKIP_LUMA_SKIP_CHROMA
          : skip_pred;

  switch (tmp_skip_pred) {
    case INTERP_EVAL_LUMA_EVAL_CHROMA:
      // skip_pred = 0: Evaluate both luma and chroma.
      // Luma MC
      interp_model_rd_eval(x, cpi, bsize, orig_dst, AOM_PLANE_Y, AOM_PLANE_Y,
                           &this_rd_stats_luma, 0);
      this_rd_stats = this_rd_stats_luma;
#if CONFIG_COLLECT_RD_STATS == 3
      RD_STATS rd_stats_y;
      av1_pick_recursive_tx_size_type_yrd(cpi, x, &rd_stats_y, bsize,
                                          INT64_MAX);
      PrintPredictionUnitStats(cpi, tile_data, x, &rd_stats_y, bsize);
#endif  // CONFIG_COLLECT_RD_STATS == 3
      AOM_FALLTHROUGH_INTENDED;
    case INTERP_SKIP_LUMA_EVAL_CHROMA:
      // skip_pred = 1: skip luma evaluation (retain previous best luma stats)
      // and do chroma evaluation.
      for (int plane = 1; plane < num_planes; ++plane) {
        int64_t tmp_rd =
            RDCOST(x->rdmult, tmp_rs + this_rd_stats.rate, this_rd_stats.dist);
        if (tmp_rd >= *rd) {
          mbmi->interp_filters = last_best;
          return 0;
        }
        interp_model_rd_eval(x, cpi, bsize, orig_dst, plane, plane,
                             &this_rd_stats, 0);
      }
      break;
    case INTERP_SKIP_LUMA_SKIP_CHROMA:
      // both luma and chroma evaluation is skipped
      this_rd_stats = *rd_stats;
      break;
    case INTERP_EVAL_INVALID:
    default: assert(0); return 0;
  }
  int64_t tmp_rd =
      RDCOST(x->rdmult, tmp_rs + this_rd_stats.rate, this_rd_stats.dist);

  if (tmp_rd < *rd) {
    *rd = tmp_rd;
    *switchable_rate = tmp_rs;
    if (skip_pred != interp_search_flags->default_interp_skip_flags) {
      if (skip_pred == INTERP_EVAL_LUMA_EVAL_CHROMA) {
        // Overwrite the data as current filter is the best one
        *rd_stats_luma = this_rd_stats_luma;
        *rd_stats = this_rd_stats;
        // As luma MC data is computed, no need to recompute after the search
        x->recalc_luma_mc_data = 0;
      } else if (skip_pred == INTERP_SKIP_LUMA_EVAL_CHROMA) {
        // As luma MC data is not computed, update of luma data can be skipped
        *rd_stats = this_rd_stats;
        // As luma MC data is not recomputed and current filter is the best,
        // indicate the possibility of recomputing MC data
        // If current buffer contains valid MC data, toggle to indicate that
        // luma MC data needs to be recomputed
        x->recalc_luma_mc_data ^= 1;
      }
      swap_dst_buf(xd, dst_bufs, num_planes);
    }
    return 1;
  }
  mbmi->interp_filters = last_best;
  return 0;
}

static inline INTERP_PRED_TYPE is_pred_filter_search_allowed(
    const AV1_COMP *const cpi, MACROBLOCKD *xd, BLOCK_SIZE bsize,
    int_interpfilters *af, int_interpfilters *lf) {
  const AV1_COMMON *cm = &cpi->common;
  const MB_MODE_INFO *const above_mbmi = xd->above_mbmi;
  const MB_MODE_INFO *const left_mbmi = xd->left_mbmi;
  const int bsl = mi_size_wide_log2[bsize];
  int is_horiz_eq = 0, is_vert_eq = 0;

  if (above_mbmi && is_inter_block(above_mbmi))
    *af = above_mbmi->interp_filters;

  if (left_mbmi && is_inter_block(left_mbmi)) *lf = left_mbmi->interp_filters;

  if (af->as_filters.x_filter != INTERP_INVALID)
    is_horiz_eq = af->as_filters.x_filter == lf->as_filters.x_filter;
  if (af->as_filters.y_filter != INTERP_INVALID)
    is_vert_eq = af->as_filters.y_filter == lf->as_filters.y_filter;

  INTERP_PRED_TYPE pred_filter_type = (is_vert_eq << 1) + is_horiz_eq;
  const int mi_row = xd->mi_row;
  const int mi_col = xd->mi_col;
  int pred_filter_enable =
      cpi->sf.interp_sf.cb_pred_filter_search
          ? (((mi_row + mi_col) >> bsl) +
             get_chessboard_index(cm->current_frame.frame_number)) &
                0x1
          : 0;
  pred_filter_enable &= is_horiz_eq || is_vert_eq;
  // pred_filter_search = 0: pred_filter is disabled
  // pred_filter_search = 1: pred_filter is enabled and only horz pred matching
  // pred_filter_search = 2: pred_filter is enabled and only vert pred matching
  // pred_filter_search = 3: pred_filter is enabled and
  //                         both vert, horz pred matching
  return pred_filter_enable * pred_filter_type;
}

static DUAL_FILTER_TYPE find_best_interp_rd_facade(
    MACROBLOCK *const x, const AV1_COMP *const cpi,
    const TileDataEnc *tile_data, BLOCK_SIZE bsize,
    const BUFFER_SET *const orig_dst, int64_t *const rd, RD_STATS *rd_stats_y,
    RD_STATS *rd_stats, int *const switchable_rate,
    const BUFFER_SET *dst_bufs[2], const int switchable_ctx[2],
    const int skip_pred, uint16_t allow_interp_mask, int is_w4_or_h4) {
  int tmp_skip_pred = skip_pred;
  DUAL_FILTER_TYPE best_filt_type = REG_REG;

  // If no filter are set to be evaluated, return from function
  if (allow_interp_mask == 0x0) return best_filt_type;
  // For block width or height is 4, skip the pred evaluation of SHARP_SHARP
  tmp_skip_pred = is_w4_or_h4
                      ? cpi->interp_search_flags.default_interp_skip_flags
                      : skip_pred;

  // Loop over the all filter types and evaluate for only allowed filter types
  for (int filt_type = SHARP_SHARP; filt_type >= REG_REG; --filt_type) {
    const int is_filter_allowed =
        get_interp_filter_allowed_mask(allow_interp_mask, filt_type);
    if (is_filter_allowed)
      if (interpolation_filter_rd(x, cpi, tile_data, bsize, orig_dst, rd,
                                  rd_stats_y, rd_stats, switchable_rate,
                                  dst_bufs, filt_type, switchable_ctx,
                                  tmp_skip_pred))
        best_filt_type = filt_type;
    tmp_skip_pred = skip_pred;
  }
  return best_filt_type;
}

static inline void pred_dual_interp_filter_rd(
    MACROBLOCK *const x, const AV1_COMP *const cpi,
    const TileDataEnc *tile_data, BLOCK_SIZE bsize,
    const BUFFER_SET *const orig_dst, int64_t *const rd, RD_STATS *rd_stats_y,
    RD_STATS *rd_stats, int *const switchable_rate,
    const BUFFER_SET *dst_bufs[2], const int switchable_ctx[2],
    const int skip_pred, INTERP_PRED_TYPE pred_filt_type, int_interpfilters *af,
    int_interpfilters *lf) {
  (void)lf;
  assert(pred_filt_type > INTERP_HORZ_NEQ_VERT_NEQ);
  assert(pred_filt_type < INTERP_PRED_TYPE_ALL);
  uint16_t allowed_interp_mask = 0;

  if (pred_filt_type == INTERP_HORZ_EQ_VERT_NEQ) {
    // pred_filter_search = 1: Only horizontal filter is matching
    allowed_interp_mask =
        av1_interp_dual_filt_mask[pred_filt_type - 1][af->as_filters.x_filter];
  } else if (pred_filt_type == INTERP_HORZ_NEQ_VERT_EQ) {
    // pred_filter_search = 2: Only vertical filter is matching
    allowed_interp_mask =
        av1_interp_dual_filt_mask[pred_filt_type - 1][af->as_filters.y_filter];
  } else {
    // pred_filter_search = 3: Both horizontal and vertical filter are matching
    int filt_type =
        af->as_filters.x_filter + af->as_filters.y_filter * SWITCHABLE_FILTERS;
    set_interp_filter_allowed_mask(&allowed_interp_mask, filt_type);
  }
  // REG_REG is already been evaluated in the beginning
  reset_interp_filter_allowed_mask(&allowed_interp_mask, REG_REG);
  find_best_interp_rd_facade(x, cpi, tile_data, bsize, orig_dst, rd, rd_stats_y,
                             rd_stats, switchable_rate, dst_bufs,
                             switchable_ctx, skip_pred, allowed_interp_mask, 0);
}
// Evaluate dual filter type
// a) Using above, left block interp filter
// b) Find the best horizontal filter and
//    then evaluate corresponding vertical filters.
static inline void fast_dual_interp_filter_rd(
    MACROBLOCK *const x, const AV1_COMP *const cpi,
    const TileDataEnc *tile_data, BLOCK_SIZE bsize,
    const BUFFER_SET *const orig_dst, int64_t *const rd, RD_STATS *rd_stats_y,
    RD_STATS *rd_stats, int *const switchable_rate,
    const BUFFER_SET *dst_bufs[2], const int switchable_ctx[2],
    const int skip_hor, const int skip_ver) {
  const InterpSearchFlags *interp_search_flags = &cpi->interp_search_flags;
  MACROBLOCKD *const xd = &x->e_mbd;
  MB_MODE_INFO *const mbmi = xd->mi[0];
  INTERP_PRED_TYPE pred_filter_type = INTERP_HORZ_NEQ_VERT_NEQ;
  int_interpfilters af = av1_broadcast_interp_filter(INTERP_INVALID);
  int_interpfilters lf = af;

  if (!have_newmv_in_inter_mode(mbmi->mode)) {
    pred_filter_type = is_pred_filter_search_allowed(cpi, xd, bsize, &af, &lf);
  }

  if (pred_filter_type) {
    pred_dual_interp_filter_rd(x, cpi, tile_data, bsize, orig_dst, rd,
                               rd_stats_y, rd_stats, switchable_rate, dst_bufs,
                               switchable_ctx, (skip_hor & skip_ver),
                               pred_filter_type, &af, &lf);
  } else {
    const int bw = block_size_wide[bsize];
    const int bh = block_size_high[bsize];
    int best_dual_mode = 0;
    int skip_pred =
        bw <= 4 ? interp_search_flags->default_interp_skip_flags : skip_hor;
    // TODO(any): Make use of find_best_interp_rd_facade()
    // if speed impact is negligible
    for (int i = (SWITCHABLE_FILTERS - 1); i >= 1; --i) {
      if (interpolation_filter_rd(x, cpi, tile_data, bsize, orig_dst, rd,
                                  rd_stats_y, rd_stats, switchable_rate,
                                  dst_bufs, i, switchable_ctx, skip_pred)) {
        best_dual_mode = i;
      }
      skip_pred = skip_hor;
    }
    // From best of horizontal EIGHTTAP_REGULAR modes, check vertical modes
    skip_pred =
        bh <= 4 ? interp_search_flags->default_interp_skip_flags : skip_ver;
    for (int i = (best_dual_mode + (SWITCHABLE_FILTERS * 2));
         i >= (best_dual_mode + SWITCHABLE_FILTERS); i -= SWITCHABLE_FILTERS) {
      interpolation_filter_rd(x, cpi, tile_data, bsize, orig_dst, rd,
                              rd_stats_y, rd_stats, switchable_rate, dst_bufs,
                              i, switchable_ctx, skip_pred);
      skip_pred = skip_ver;
    }
  }
}

// Find the best interp filter if dual_interp_filter = 0
static inline void find_best_non_dual_interp_filter(
    MACROBLOCK *const x, const AV1_COMP *const cpi,
    const TileDataEnc *tile_data, BLOCK_SIZE bsize,
    const BUFFER_SET *const orig_dst, int64_t *const rd, RD_STATS *rd_stats_y,
    RD_STATS *rd_stats, int *const switchable_rate,
    const BUFFER_SET *dst_bufs[2], const int switchable_ctx[2],
    const int skip_ver, const int skip_hor) {
  const InterpSearchFlags *interp_search_flags = &cpi->interp_search_flags;
  int8_t i;
  MACROBLOCKD *const xd = &x->e_mbd;
  MB_MODE_INFO *const mbmi = xd->mi[0];

  uint16_t interp_filter_search_mask =
      interp_search_flags->interp_filter_search_mask;

  if (cpi->sf.interp_sf.adaptive_interp_filter_search == 2) {
    const FRAME_UPDATE_TYPE update_type =
        get_frame_update_type(&cpi->ppi->gf_group, cpi->gf_frame_index);
    const int ctx0 = av1_get_pred_context_switchable_interp(xd, 0);
    const int ctx1 = av1_get_pred_context_switchable_interp(xd, 1);
    int use_actual_frame_probs = 1;
    const int *switchable_interp_p0;
    const int *switchable_interp_p1;
#if CONFIG_FPMT_TEST
    use_actual_frame_probs =
        (cpi->ppi->fpmt_unit_test_cfg == PARALLEL_SIMULATION_ENCODE) ? 0 : 1;
    if (!use_actual_frame_probs) {
      switchable_interp_p0 = (int *)cpi->ppi->temp_frame_probs
                                 .switchable_interp_probs[update_type][ctx0];
      switchable_interp_p1 = (int *)cpi->ppi->temp_frame_probs
                                 .switchable_interp_probs[update_type][ctx1];
    }
#endif
    if (use_actual_frame_probs) {
      switchable_interp_p0 =
          cpi->ppi->frame_probs.switchable_interp_probs[update_type][ctx0];
      switchable_interp_p1 =
          cpi->ppi->frame_probs.switchable_interp_probs[update_type][ctx1];
    }
    static const int thr[7] = { 0, 8, 8, 8, 8, 0, 8 };
    const int thresh = thr[update_type];
    for (i = 0; i < SWITCHABLE_FILTERS; i++) {
      // For non-dual case, the 2 dir's prob should be identical.
      assert(switchable_interp_p0[i] == switchable_interp_p1[i]);
      if (switchable_interp_p0[i] < thresh &&
          switchable_interp_p1[i] < thresh) {
        DUAL_FILTER_TYPE filt_type = i + SWITCHABLE_FILTERS * i;
        reset_interp_filter_allowed_mask(&interp_filter_search_mask, filt_type);
      }
    }
  }

  // Regular filter evaluation should have been done and hence the same should
  // be the winner
  assert(x->e_mbd.mi[0]->interp_filters.as_int == filter_sets[0].as_int);
  if ((skip_hor & skip_ver) != interp_search_flags->default_interp_skip_flags) {
    INTERP_PRED_TYPE pred_filter_type = INTERP_HORZ_NEQ_VERT_NEQ;
    int_interpfilters af = av1_broadcast_interp_filter(INTERP_INVALID);
    int_interpfilters lf = af;

    pred_filter_type = is_pred_filter_search_allowed(cpi, xd, bsize, &af, &lf);
    if (pred_filter_type) {
      assert(af.as_filters.x_filter != INTERP_INVALID);
      int filter_idx = SWITCHABLE * af.as_filters.x_filter;
      // This assert tells that (filter_x == filter_y) for non-dual filter case
      assert(filter_sets[filter_idx].as_filters.x_filter ==
             filter_sets[filter_idx].as_filters.y_filter);
      if (cpi->sf.interp_sf.adaptive_interp_filter_search &&
          !(get_interp_filter_allowed_mask(interp_filter_search_mask,
                                           filter_idx))) {
        return;
      }
      if (filter_idx) {
        interpolation_filter_rd(x, cpi, tile_data, bsize, orig_dst, rd,
                                rd_stats_y, rd_stats, switchable_rate, dst_bufs,
                                filter_idx, switchable_ctx,
                                (skip_hor & skip_ver));
      }
      return;
    }
  }
  // Reuse regular filter's modeled rd data for sharp filter for following
  // cases
  // 1) When bsize is 4x4
  // 2) When block width is 4 (i.e. 4x8/4x16 blocks) and MV in vertical
  // direction is full-pel
  // 3) When block height is 4 (i.e. 8x4/16x4 blocks) and MV in horizontal
  // direction is full-pel
  // TODO(any): Optimize cases 2 and 3 further if luma MV in relavant direction
  // alone is full-pel

  if ((bsize == BLOCK_4X4) ||
      (block_size_wide[bsize] == 4 &&
       skip_ver == interp_search_flags->default_interp_skip_flags) ||
      (block_size_high[bsize] == 4 &&
       skip_hor == interp_search_flags->default_interp_skip_flags)) {
    int skip_pred = skip_hor & skip_ver;
    uint16_t allowed_interp_mask = 0;

    // REG_REG filter type is evaluated beforehand, hence skip it
    set_interp_filter_allowed_mask(&allowed_interp_mask, SHARP_SHARP);
    set_interp_filter_allowed_mask(&allowed_interp_mask, SMOOTH_SMOOTH);
    if (cpi->sf.interp_sf.adaptive_interp_filter_search)
      allowed_interp_mask &= interp_filter_search_mask;

    find_best_interp_rd_facade(x, cpi, tile_data, bsize, orig_dst, rd,
                               rd_stats_y, rd_stats, switchable_rate, dst_bufs,
                               switchable_ctx, skip_pred, allowed_interp_mask,
                               1);
  } else {
    int skip_pred = (skip_hor & skip_ver);
    for (i = (SWITCHABLE_FILTERS + 1); i < DUAL_FILTER_SET_SIZE;
         i += (SWITCHABLE_FILTERS + 1)) {
      // This assert tells that (filter_x == filter_y) for non-dual filter case
      assert(filter_sets[i].as_filters.x_filter ==
             filter_sets[i].as_filters.y_filter);
      if (cpi->sf.interp_sf.adaptive_interp_filter_search &&
          !(get_interp_filter_allowed_mask(interp_filter_search_mask, i))) {
        continue;
      }
      interpolation_filter_rd(x, cpi, tile_data, bsize, orig_dst, rd,
                              rd_stats_y, rd_stats, switchable_rate, dst_bufs,
                              i, switchable_ctx, skip_pred);
      // In first iteration, smooth filter is evaluated. If smooth filter
      // (which is less sharper) is the winner among regular and smooth filters,
      // sharp filter evaluation is skipped
      // TODO(any): Refine this gating based on modelled rd only (i.e., by not
      // accounting switchable filter rate)
      if (cpi->sf.interp_sf.skip_sharp_interp_filter_search &&
          skip_pred != interp_search_flags->default_interp_skip_flags) {
        if (mbmi->interp_filters.as_int == filter_sets[SMOOTH_SMOOTH].as_int)
          break;
      }
    }
  }
}

static inline void calc_interp_skip_pred_flag(MACROBLOCK *const x,
                                              const AV1_COMP *const cpi,
                                              int *skip_hor, int *skip_ver) {
  const AV1_COMMON *cm = &cpi->common;
  MACROBLOCKD *const xd = &x->e_mbd;
  MB_MODE_INFO *const mbmi = xd->mi[0];
  const int num_planes = av1_num_planes(cm);
  const int is_compound = has_second_ref(mbmi);
  assert(is_intrabc_block(mbmi) == 0);
  for (int ref = 0; ref < 1 + is_compound; ++ref) {
    const struct scale_factors *const sf =
        get_ref_scale_factors_const(cm, mbmi->ref_frame[ref]);
    // TODO(any): Refine skip flag calculation considering scaling
    if (av1_is_scaled(sf)) {
      *skip_hor = 0;
      *skip_ver = 0;
      break;
    }
    const MV mv = mbmi->mv[ref].as_mv;
    int skip_hor_plane = 0;
    int skip_ver_plane = 0;
    for (int plane_idx = 0; plane_idx < AOMMAX(1, (num_planes - 1));
         ++plane_idx) {
      struct macroblockd_plane *const pd = &xd->plane[plane_idx];
      const int bw = pd->width;
      const int bh = pd->height;
      const MV mv_q4 = clamp_mv_to_umv_border_sb(
          xd, &mv, bw, bh, pd->subsampling_x, pd->subsampling_y);
      const int sub_x = (mv_q4.col & SUBPEL_MASK) << SCALE_EXTRA_BITS;
      const int sub_y = (mv_q4.row & SUBPEL_MASK) << SCALE_EXTRA_BITS;
      skip_hor_plane |= ((sub_x == 0) << plane_idx);
      skip_ver_plane |= ((sub_y == 0) << plane_idx);
    }
    *skip_hor &= skip_hor_plane;
    *skip_ver &= skip_ver_plane;
    // It is not valid that "luma MV is sub-pel, whereas chroma MV is not"
    assert(*skip_hor != 2);
    assert(*skip_ver != 2);
  }
  // When compond prediction type is compound segment wedge, luma MC and chroma
  // MC need to go hand in hand as mask generated during luma MC is reuired for
  // chroma MC. If skip_hor = 0 and skip_ver = 1, mask used for chroma MC during
  // vertical filter decision may be incorrect as temporary MC evaluation
  // overwrites the mask. Make skip_ver as 0 for this case so that mask is
  // populated during luma MC
  if (is_compound && mbmi->compound_idx == 1 &&
      mbmi->interinter_comp.type == COMPOUND_DIFFWTD) {
    assert(mbmi->comp_group_idx == 1);
    if (*skip_hor == 0 && *skip_ver == 1) *skip_ver = 0;
  }
}

/*!\brief AV1 interpolation filter search
 *
 * \ingroup inter_mode_search
 *
 * \param[in]     cpi               Top-level encoder structure.
 * \param[in]     tile_data         Pointer to struct holding adaptive
 *                                  data/contexts/models for the tile during
 *                                  encoding.
 * \param[in]     x                 Pointer to struc holding all the data for
 *                                  the current macroblock.
 * \param[in]     bsize             Current block size.
 * \param[in]     tmp_dst           A temporary prediction buffer to hold a
 *                                  computed prediction.
 * \param[in,out] orig_dst          A prediction buffer to hold a computed
 *                                  prediction. This will eventually hold the
 *                                  final prediction, and the tmp_dst info will
 *                                  be copied here.
 * \param[in,out] rd                The RD cost associated with the selected
 *                                  interpolation filter parameters.
 * \param[in,out] switchable_rate   The rate associated with using a SWITCHABLE
 *                                  filter mode.
 * \param[in,out] skip_build_pred   Indicates whether or not to build the inter
 *                                  predictor. If this is 0, the inter predictor
 *                                  has already been built and thus we can avoid
 *                                  repeating computation.
 * \param[in]     args              HandleInterModeArgs struct holding
 *                                  miscellaneous arguments for inter mode
 *                                  search. See the documentation for this
 *                                  struct for a description of each member.
 * \param[in]     ref_best_rd       Best RD found so far for this block.
 *                                  It is used for early termination of this
 *                                  search if the RD exceeds this value.
 *
 * \return Returns INT64_MAX if the filter parameters are invalid and the
 * current motion mode being tested should be skipped. It returns 0 if the
 * parameter search is a success.
 */
int64_t av1_interpolation_filter_search(
    MACROBLOCK *const x, const AV1_COMP *const cpi,
    const TileDataEnc *tile_data, BLOCK_SIZE bsize,
    const BUFFER_SET *const tmp_dst, const BUFFER_SET *const orig_dst,
    int64_t *const rd, int *const switchable_rate, int *skip_build_pred,
    HandleInterModeArgs *args, int64_t ref_best_rd) {
  const AV1_COMMON *cm = &cpi->common;
  const InterpSearchFlags *interp_search_flags = &cpi->interp_search_flags;
  const int num_planes = av1_num_planes(cm);
  MACROBLOCKD *const xd = &x->e_mbd;
  MB_MODE_INFO *const mbmi = xd->mi[0];
  const int need_search = av1_is_interp_needed(xd);
  const int ref_frame = xd->mi[0]->ref_frame[0];
  RD_STATS rd_stats_luma, rd_stats;

  // Initialization of rd_stats structures with default values
  av1_init_rd_stats(&rd_stats_luma);
  av1_init_rd_stats(&rd_stats);

  int match_found_idx = -1;
  const InterpFilter assign_filter = cm->features.interp_filter;

  match_found_idx = find_interp_filter_match(
      mbmi, cpi, assign_filter, need_search, args->interp_filter_stats,
      args->interp_filter_stats_idx);

  if (match_found_idx != -1) {
    *rd = args->interp_filter_stats[match_found_idx].rd;
    x->pred_sse[ref_frame] =
        args->interp_filter_stats[match_found_idx].pred_sse;
    *skip_build_pred = 0;
    return 0;
  }

  int switchable_ctx[2];
  switchable_ctx[0] = av1_get_pred_context_switchable_interp(xd, 0);
  switchable_ctx[1] = av1_get_pred_context_switchable_interp(xd, 1);
  *switchable_rate =
      get_switchable_rate(x, mbmi->interp_filters, switchable_ctx,
                          cm->seq_params->enable_dual_filter);

  // Do MC evaluation for default filter_type.
  // Luma MC
  interp_model_rd_eval(x, cpi, bsize, orig_dst, AOM_PLANE_Y, AOM_PLANE_Y,
                       &rd_stats_luma, *skip_build_pred);

#if CONFIG_COLLECT_RD_STATS == 3
  RD_STATS rd_stats_y;
  av1_pick_recursive_tx_size_type_yrd(cpi, x, &rd_stats_y, bsize, INT64_MAX);
  PrintPredictionUnitStats(cpi, tile_data, x, &rd_stats_y, bsize);
#endif  // CONFIG_COLLECT_RD_STATS == 3
  // Chroma MC
  if (num_planes > 1) {
    interp_model_rd_eval(x, cpi, bsize, orig_dst, AOM_PLANE_U, AOM_PLANE_V,
                         &rd_stats, *skip_build_pred);
  }
  *skip_build_pred = 1;

  av1_merge_rd_stats(&rd_stats, &rd_stats_luma);

  assert(rd_stats.rate >= 0);

  *rd = RDCOST(x->rdmult, *switchable_rate + rd_stats.rate, rd_stats.dist);
  x->pred_sse[ref_frame] = (unsigned int)(rd_stats_luma.sse >> 4);

  if (assign_filter != SWITCHABLE || match_found_idx != -1) {
    return 0;
  }
  if (!need_search) {
    int_interpfilters filters = av1_broadcast_interp_filter(EIGHTTAP_REGULAR);
    assert(mbmi->interp_filters.as_int == filters.as_int);
    (void)filters;
    return 0;
  }
  if (args->modelled_rd != NULL) {
    if (has_second_ref(mbmi)) {
      const int ref_mv_idx = mbmi->ref_mv_idx;
      MV_REFERENCE_FRAME *refs = mbmi->ref_frame;
      const int mode0 = compound_ref0_mode(mbmi->mode);
      const int mode1 = compound_ref1_mode(mbmi->mode);
      const int64_t mrd = AOMMIN(args->modelled_rd[mode0][ref_mv_idx][refs[0]],
                                 args->modelled_rd[mode1][ref_mv_idx][refs[1]]);
      if ((*rd >> 1) > mrd && ref_best_rd < INT64_MAX) {
        return INT64_MAX;
      }
    }
  }

  x->recalc_luma_mc_data = 0;
  // skip_flag=xx (in binary form)
  // Setting 0th flag corresonds to skipping luma MC and setting 1st bt
  // corresponds to skipping chroma MC  skip_flag=0 corresponds to "Don't skip
  // luma and chroma MC"  Skip flag=1 corresponds to "Skip Luma MC only"
  // Skip_flag=2 is not a valid case
  // skip_flag=3 corresponds to "Skip both luma and chroma MC"
  int skip_hor = interp_search_flags->default_interp_skip_flags;
  int skip_ver = interp_search_flags->default_interp_skip_flags;
  calc_interp_skip_pred_flag(x, cpi, &skip_hor, &skip_ver);

  // do interp_filter search
  restore_dst_buf(xd, *tmp_dst, num_planes);
  const BUFFER_SET *dst_bufs[2] = { tmp_dst, orig_dst };
  // Evaluate dual interp filters
  if (cm->seq_params->enable_dual_filter) {
    if (cpi->sf.interp_sf.use_fast_interpolation_filter_search) {
      fast_dual_interp_filter_rd(x, cpi, tile_data, bsize, orig_dst, rd,
                                 &rd_stats_luma, &rd_stats, switchable_rate,
                                 dst_bufs, switchable_ctx, skip_hor, skip_ver);
    } else {
      // Use full interpolation filter search
      uint16_t allowed_interp_mask = ALLOW_ALL_INTERP_FILT_MASK;
      // REG_REG filter type is evaluated beforehand, so loop is repeated over
      // REG_SMOOTH to SHARP_SHARP for full interpolation filter search
      reset_interp_filter_allowed_mask(&allowed_interp_mask, REG_REG);
      find_best_interp_rd_facade(x, cpi, tile_data, bsize, orig_dst, rd,
                                 &rd_stats_luma, &rd_stats, switchable_rate,
                                 dst_bufs, switchable_ctx,
                                 (skip_hor & skip_ver), allowed_interp_mask, 0);
    }
  } else {
    // Evaluate non-dual interp filters
    find_best_non_dual_interp_filter(
        x, cpi, tile_data, bsize, orig_dst, rd, &rd_stats_luma, &rd_stats,
        switchable_rate, dst_bufs, switchable_ctx, skip_ver, skip_hor);
  }
  swap_dst_buf(xd, dst_bufs, num_planes);
  // Recompute final MC data if required
  if (x->recalc_luma_mc_data == 1) {
    // Recomputing final luma MC data is required only if the same was skipped
    // in either of the directions  Condition below is necessary, but not
    // sufficient
    assert((skip_hor == 1) || (skip_ver == 1));
    const int mi_row = xd->mi_row;
    const int mi_col = xd->mi_col;
    av1_enc_build_inter_predictor(cm, xd, mi_row, mi_col, orig_dst, bsize,
                                  AOM_PLANE_Y, AOM_PLANE_Y);
  }
  x->pred_sse[ref_frame] = (unsigned int)(rd_stats_luma.sse >> 4);

  // save search results
  if (cpi->sf.interp_sf.use_interp_filter) {
    assert(match_found_idx == -1);
    args->interp_filter_stats_idx = save_interp_filter_search_stat(
        mbmi, *rd, x->pred_sse[ref_frame], args->interp_filter_stats,
        args->interp_filter_stats_idx);
  }
  return 0;
}