av1/common/pred_common.c

/*
 * Copyright (c) 2021, Alliance for Open Media. All rights reserved
 *
 * This source code is subject to the terms of the BSD 3-Clause Clear License
 * and the Alliance for Open Media Patent License 1.0. If the BSD 3-Clause Clear
 * License was not distributed with this source code in the LICENSE file, you
 * can obtain it at aomedia.org/license/software-license/bsd-3-c-c/.  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
 * aomedia.org/license/patent-license/.
 */

#include "av1/common/common.h"
#include "av1/common/pred_common.h"
#include "av1/common/reconinter.h"
#include "av1/common/reconintra.h"
#include "av1/common/seg_common.h"

#if CONFIG_NEW_REF_SIGNALING
// Comparison function to sort reference frames in ascending score order
static int compare_score_data_asc(const void *a, const void *b) {
  if (((RefScoreData *)a)->score == ((RefScoreData *)b)->score) {
    return 0;
  } else if (((const RefScoreData *)a)->score >
             ((const RefScoreData *)b)->score) {
    return 1;
  } else {
    return -1;
  }
}

static void bubble_sort_ref_scores(RefScoreData *scores, int n_ranked) {
  for (int i = n_ranked - 1; i > 0; --i) {
    for (int j = 0; j < i; j++) {
      if (compare_score_data_asc(&scores[j], &scores[j + 1]) > 0) {
        RefScoreData score_temp = scores[j];
        scores[j] = scores[j + 1];
        scores[j + 1] = score_temp;
      }
    }
  }
}

// Checks to see if a particular reference frame is already in the reference
// frame map
static int is_in_ref_score(RefScoreData *map, int disp_order, int score,
                           int n_frames) {
  for (int i = 0; i < n_frames; i++) {
    if (disp_order == map[i].disp_order && score == map[i].score) return 1;
  }
  return 0;
}

// Only 7 out of 8 reference buffers will be used as reference frames. This
// function applies heuristics to determine which one to be left out.
static int get_unmapped_ref(RefScoreData *scores, int n_bufs) {
  if (n_bufs < INTER_REFS_PER_FRAME) return INVALID_IDX;

  int min_q = INT_MAX;
  int max_q = INT_MIN;
  for (int i = n_bufs - 1; i >= 0; i--) {
    min_q = AOMMIN(min_q, scores[i].base_qindex);
    max_q = AOMMAX(max_q, scores[i].base_qindex);
  }
  const int q_thresh = (max_q + min_q + 1) / 2;

  int unmapped_past_idx = INVALID_IDX;
  int unmapped_future_idx = INVALID_IDX;
  int max_past_score = 0;
  int max_future_score = 0;
  int n_past = 0;
  int n_future = 0;
  for (int i = 0; i < n_bufs; i++) {
    if (scores[i].base_qindex >= q_thresh) {
      int dist = scores[i].distance;
      if (dist > 0) {
        if (dist > max_past_score) {
          max_past_score = dist;
          unmapped_past_idx = i;
        }
        n_past++;
      } else if (dist < 0) {
        if (-dist > max_future_score) {
          max_future_score = -dist;
          unmapped_future_idx = i;
        }
        n_future++;
      }
    }
  }
  if (n_past > n_future) return unmapped_past_idx;
  if (n_past < n_future) return unmapped_future_idx;
  if (n_past == n_future && n_past > 0)
    return max_past_score >= max_future_score ? unmapped_past_idx
                                              : unmapped_future_idx;

  return INVALID_IDX;
}

// Obtain the lists of past/cur/future reference frames and their sizes.
void av1_get_past_future_cur_ref_lists(AV1_COMMON *cm, RefScoreData *scores) {
  int n_future = 0;
  int n_past = 0;
  int n_cur = 0;
  for (int i = 0; i < cm->ref_frames_info.num_total_refs; i++) {
    // If order hint is disabled, the scores and past/future information are
    // not available to the decoder. Assume all references are from the past.
    if (!cm->seq_params.order_hint_info.enable_order_hint ||
        scores[i].distance > 0) {
      cm->ref_frames_info.past_refs[n_past] = i;
      n_past++;
    } else if (scores[i].distance < 0) {
      cm->ref_frames_info.future_refs[n_future] = i;
      n_future++;
    } else {
      cm->ref_frames_info.cur_refs[n_cur] = i;
      n_cur++;
    }
  }
  cm->ref_frames_info.num_past_refs = n_past;
  cm->ref_frames_info.num_future_refs = n_future;
  cm->ref_frames_info.num_cur_refs = n_cur;
}

#define DIST_WEIGHT_BITS 6
#define DECAY_DIST_CAP 6

static const int temp_dist_score_lookup[7] = {
  0, 64, 96, 112, 120, 124, 126,
};

// Determine reference mapping by ranking the reference frames based on a
// score function.
void av1_get_ref_frames(AV1_COMMON *cm, int cur_frame_disp,
                        RefFrameMapPair *ref_frame_map_pairs) {
  RefScoreData scores[REF_FRAMES];
  memset(scores, 0, REF_FRAMES * sizeof(*scores));
  for (int i = 0; i < REF_FRAMES; i++) {
    scores[i].score = INT_MAX;
    cm->remapped_ref_idx[i] = INVALID_IDX;
  }
  int n_ranked = 0;

  // Give more weight to base_qindex if all references are from the past
  int max_disp = 0;
  for (int i = 0; i < REF_FRAMES; i++) {
    RefFrameMapPair cur_ref = ref_frame_map_pairs[i];
    if (cur_ref.disp_order == -1) continue;
    max_disp = AOMMAX(max_disp, cur_ref.disp_order);
  }

  // Compute a score for each reference buffer
  for (int i = 0; i < REF_FRAMES; i++) {
    // Get reference frame buffer
    RefFrameMapPair cur_ref = ref_frame_map_pairs[i];
    if (cur_ref.disp_order == -1) continue;
    const int ref_disp = cur_ref.disp_order;
    // In error resilient mode, ref mapping must be independent of the
    // base_qindex to ensure decoding independency
    const int ref_base_qindex = cur_ref.base_qindex;
    const int disp_diff = cur_frame_disp - ref_disp;
    int tdist = abs(disp_diff);
    const int score =
        max_disp > cur_frame_disp
            ? ((tdist << DIST_WEIGHT_BITS) + ref_base_qindex)
            : temp_dist_score_lookup[AOMMIN(tdist, DECAY_DIST_CAP)] +
                  AOMMAX(tdist - DECAY_DIST_CAP, 0) + ref_base_qindex;
    if (is_in_ref_score(scores, ref_disp, score, n_ranked)) continue;

    scores[n_ranked].index = i;
    scores[n_ranked].score = score;
    scores[n_ranked].distance = disp_diff;
    scores[n_ranked].disp_order = ref_disp;
    scores[n_ranked].base_qindex = ref_base_qindex;
    n_ranked++;
  }
  if (n_ranked > INTER_REFS_PER_FRAME) {
    const int unmapped_idx = get_unmapped_ref(scores, n_ranked);
    if (unmapped_idx != INVALID_IDX) scores[unmapped_idx].score = INT_MAX;
  }

  // Sort the references according to their score
  bubble_sort_ref_scores(scores, n_ranked);

  cm->ref_frames_info.num_total_refs =
      AOMMIN(n_ranked, cm->seq_params.max_reference_frames);
  for (int i = 0; i < cm->ref_frames_info.num_total_refs; i++) {
    cm->remapped_ref_idx[i] = scores[i].index;
    // The distance is not available to the decoder when order_hint is disabled.
    // In that case, set all distances to 1.
    cm->ref_frames_info.ref_frame_distance[i] =
        cm->seq_params.order_hint_info.enable_order_hint ? scores[i].distance
                                                         : 1;
  }

  // Fill in RefFramesInfo struct according to computed mapping
  av1_get_past_future_cur_ref_lists(cm, scores);

  if (n_ranked > INTER_REFS_PER_FRAME)
    cm->remapped_ref_idx[n_ranked - 1] = scores[n_ranked - 1].index;

  // Fill any slots that are empty (should only happen for the first 7 frames)
  for (int i = 0; i < REF_FRAMES; i++) {
    if (cm->remapped_ref_idx[i] == INVALID_IDX) cm->remapped_ref_idx[i] = 0;
  }
}
#else
/*!\cond */
// Struct to keep track of relevant reference frame data
typedef struct {
  int map_idx;
  int disp_order;
  int pyr_level;
  int used;
} RefBufMapData;
/*!\endcond */

// Comparison function to sort reference frames in ascending display order
static int compare_map_idx_pair_asc(const void *a, const void *b) {
  if (((RefBufMapData *)a)->disp_order == ((RefBufMapData *)b)->disp_order) {
    return 0;
  } else if (((const RefBufMapData *)a)->disp_order >
             ((const RefBufMapData *)b)->disp_order) {
    return 1;
  } else {
    return -1;
  }
}

// Checks to see if a particular reference frame is already in the reference
// frame map
static int is_in_ref_map(RefBufMapData *map, int disp_order, int n_frames) {
  for (int i = 0; i < n_frames; i++) {
    if (disp_order == map[i].disp_order) return 1;
  }
  return 0;
}

// Add a reference buffer index to a named reference slot
static void add_ref_to_slot(RefBufMapData *ref, int *const remapped_ref_idx,
                            int frame) {
  remapped_ref_idx[frame - LAST_FRAME] = ref->map_idx;
  ref->used = 1;
}

// Threshold dictating when we are allowed to start considering
// leaving lowest level frames unmapped
#define LOW_LEVEL_FRAMES_TR 5

// Find which reference buffer should be left out of the named mapping.
// This is because there are 8 reference buffers and only 7 named slots.
static void set_unmapped_ref(RefBufMapData *buffer_map, int n_bufs,
                             int n_min_level_refs, int min_level,
                             int cur_frame_disp) {
  int max_dist = 0;
  int unmapped_idx = -1;
  if (n_bufs <= ALTREF_FRAME) return;
  for (int i = 0; i < n_bufs; i++) {
    if (buffer_map[i].used) continue;
    if (buffer_map[i].pyr_level != min_level ||
        n_min_level_refs >= LOW_LEVEL_FRAMES_TR) {
      int dist = abs(cur_frame_disp - buffer_map[i].disp_order);
      if (dist > max_dist) {
        max_dist = dist;
        unmapped_idx = i;
      }
    }
  }
  assert(unmapped_idx >= 0 && "Unmapped reference not found");
  buffer_map[unmapped_idx].used = 1;
}

void av1_get_ref_frames(AV1_COMMON *const cm, int cur_frame_disp,
                        RefFrameMapPair *ref_frame_map_pairs) {
  int *const remapped_ref_idx = cm->remapped_ref_idx;

  int buf_map_idx = 0;

  // Initialize reference frame mappings
  for (int i = 0; i < REF_FRAMES; ++i) remapped_ref_idx[i] = INVALID_IDX;

  RefBufMapData buffer_map[REF_FRAMES];
  int n_bufs = 0;
  memset(buffer_map, 0, REF_FRAMES * sizeof(buffer_map[0]));
  int min_level = INT_MAX;
  int max_level = 0;

  // Go through current reference buffers and store display order, pyr level,
  // and map index.
  for (int map_idx = 0; map_idx < REF_FRAMES; map_idx++) {
    // Get reference frame buffer
    RefFrameMapPair ref_pair = ref_frame_map_pairs[map_idx];
    if (ref_pair.disp_order == -1) continue;
    const int frame_order = ref_pair.disp_order;
    // Avoid duplicates
    if (is_in_ref_map(buffer_map, frame_order, n_bufs)) continue;
    const int reference_frame_level = ref_pair.pyr_level;

    // Keep track of the lowest and highest levels that currently exist
    if (reference_frame_level < min_level) min_level = reference_frame_level;
    if (reference_frame_level > max_level) max_level = reference_frame_level;

    buffer_map[n_bufs].map_idx = map_idx;
    buffer_map[n_bufs].disp_order = frame_order;
    buffer_map[n_bufs].pyr_level = reference_frame_level;
    buffer_map[n_bufs].used = 0;
    n_bufs++;
  }

  // Sort frames in ascending display order
  qsort(buffer_map, n_bufs, sizeof(buffer_map[0]), compare_map_idx_pair_asc);

  int n_min_level_refs = 0;
  int n_past_high_level = 0;
  int closest_past_ref = -1;
  int golden_idx = -1;
  int altref_idx = -1;

  // Find the GOLDEN_FRAME and BWDREF_FRAME.
  // Also collect various stats about the reference frames for the remaining
  // mappings
  for (int i = n_bufs - 1; i >= 0; i--) {
    if (buffer_map[i].pyr_level == min_level) {
      // Keep track of the number of lowest level frames
      n_min_level_refs++;
      if (buffer_map[i].disp_order < cur_frame_disp && golden_idx == -1 &&
          remapped_ref_idx[GOLDEN_FRAME - LAST_FRAME] == INVALID_IDX) {
        // Save index for GOLDEN
        golden_idx = i;
      } else if (buffer_map[i].disp_order > cur_frame_disp &&
                 altref_idx == -1 &&
                 remapped_ref_idx[ALTREF_FRAME - LAST_FRAME] == INVALID_IDX) {
        // Save index for ALTREF
        altref_idx = i;
      }
    } else if (buffer_map[i].disp_order == cur_frame_disp) {
      // Map the BWDREF_FRAME if this is the show_existing_frame
      add_ref_to_slot(&buffer_map[i], remapped_ref_idx, BWDREF_FRAME);
    }

    // Keep track of the number of past frames that are not at the lowest level
    if (buffer_map[i].disp_order < cur_frame_disp &&
        buffer_map[i].pyr_level != min_level)
      n_past_high_level++;

    // Keep track of where the frames change from being past frames to future
    // frames
    if (buffer_map[i].disp_order < cur_frame_disp && closest_past_ref < 0)
      closest_past_ref = i;
  }

  // Do not map GOLDEN and ALTREF based on their pyramid level if all reference
  // frames have the same level
  if (n_min_level_refs <= n_bufs) {
    // Map the GOLDEN_FRAME
    if (golden_idx > -1)
      add_ref_to_slot(&buffer_map[golden_idx], remapped_ref_idx, GOLDEN_FRAME);
    // Map the ALTREF_FRAME
    if (altref_idx > -1)
      add_ref_to_slot(&buffer_map[altref_idx], remapped_ref_idx, ALTREF_FRAME);
  }

  // Find the buffer to be excluded from the mapping
  set_unmapped_ref(buffer_map, n_bufs, n_min_level_refs, min_level,
                   cur_frame_disp);

  // Place past frames in LAST_FRAME, LAST2_FRAME, and LAST3_FRAME
  for (int frame = LAST_FRAME; frame < GOLDEN_FRAME; frame++) {
    // Continue if the current ref slot is already full
    if (remapped_ref_idx[frame - LAST_FRAME] != INVALID_IDX) continue;
    // Find the next unmapped reference buffer
    // in decreasing ouptut oreder relative to current picture
    int next_buf_max = 0;
    int next_disp_order = INT_MIN;
    for (buf_map_idx = n_bufs - 1; buf_map_idx >= 0; buf_map_idx--) {
      if (!buffer_map[buf_map_idx].used &&
          buffer_map[buf_map_idx].disp_order < cur_frame_disp &&
          buffer_map[buf_map_idx].disp_order > next_disp_order) {
        next_disp_order = buffer_map[buf_map_idx].disp_order;
        next_buf_max = buf_map_idx;
      }
    }
    buf_map_idx = next_buf_max;
    if (buf_map_idx < 0) break;
    if (buffer_map[buf_map_idx].used) break;
    add_ref_to_slot(&buffer_map[buf_map_idx], remapped_ref_idx, frame);
  }

  // Place future frames (if there are any) in BWDREF_FRAME and ALTREF2_FRAME
  for (int frame = BWDREF_FRAME; frame < REF_FRAMES; frame++) {
    // Continue if the current ref slot is already full
    if (remapped_ref_idx[frame - LAST_FRAME] != INVALID_IDX) continue;
    // Find the next unmapped reference buffer
    // in increasing ouptut oreder relative to current picture
    int next_buf_max = 0;
    int next_disp_order = INT_MAX;
    for (buf_map_idx = n_bufs - 1; buf_map_idx >= 0; buf_map_idx--) {
      if (!buffer_map[buf_map_idx].used &&
          buffer_map[buf_map_idx].disp_order > cur_frame_disp &&
          buffer_map[buf_map_idx].disp_order < next_disp_order) {
        next_disp_order = buffer_map[buf_map_idx].disp_order;
        next_buf_max = buf_map_idx;
      }
    }
    buf_map_idx = next_buf_max;
    if (buf_map_idx < 0) break;
    if (buffer_map[buf_map_idx].used) break;
    add_ref_to_slot(&buffer_map[buf_map_idx], remapped_ref_idx, frame);
  }

  // Place remaining past frames
  buf_map_idx = closest_past_ref;
  for (int frame = LAST_FRAME; frame < REF_FRAMES; frame++) {
    // Continue if the current ref slot is already full
    if (remapped_ref_idx[frame - LAST_FRAME] != INVALID_IDX) continue;
    // Find the next unmapped reference buffer
    for (; buf_map_idx >= 0; buf_map_idx--) {
      if (!buffer_map[buf_map_idx].used) break;
    }
    if (buf_map_idx < 0) break;
    if (buffer_map[buf_map_idx].used) break;
    add_ref_to_slot(&buffer_map[buf_map_idx], remapped_ref_idx, frame);
  }

  // Place remaining future frames
  buf_map_idx = n_bufs - 1;
  for (int frame = ALTREF_FRAME; frame >= LAST_FRAME; frame--) {
    // Continue if the current ref slot is already full
    if (remapped_ref_idx[frame - LAST_FRAME] != INVALID_IDX) continue;
    // Find the next unmapped reference buffer
    for (; buf_map_idx > closest_past_ref; buf_map_idx--) {
      if (!buffer_map[buf_map_idx].used) break;
    }
    if (buf_map_idx < 0) break;
    if (buffer_map[buf_map_idx].used) break;
    add_ref_to_slot(&buffer_map[buf_map_idx], remapped_ref_idx, frame);
  }

  // Fill any slots that are empty (should only happen for the first 7 frames)
  for (int i = 0; i < REF_FRAMES; ++i)
    if (remapped_ref_idx[i] == INVALID_IDX) remapped_ref_idx[i] = 0;
}
#endif  // CONFIG_NEW_REF_SIGNALING

// Returns a context number for the given MB prediction signal
static InterpFilter get_ref_filter_type(const MB_MODE_INFO *ref_mbmi,
                                        const MACROBLOCKD *xd, int dir,
                                        MV_REFERENCE_FRAME ref_frame) {
  (void)xd;

  if (ref_mbmi->ref_frame[0] != ref_frame &&
      ref_mbmi->ref_frame[1] != ref_frame) {
    return SWITCHABLE_FILTERS;
  }
  (void)dir;
  return ref_mbmi->interp_fltr;
}

int av1_get_pred_context_switchable_interp(const MACROBLOCKD *xd, int dir) {
  const MB_MODE_INFO *const mbmi = xd->mi[0];
  const int ctx_offset =
      is_inter_ref_frame(mbmi->ref_frame[1]) * INTER_FILTER_COMP_OFFSET;
  assert(dir == 0 || dir == 1);
  const MV_REFERENCE_FRAME ref_frame = mbmi->ref_frame[0];
  // Note:
  // The mode info data structure has a one element border above and to the
  // left of the entries corresponding to real macroblocks.
  // The prediction flags in these dummy entries are initialized to 0.
  int filter_type_ctx = ctx_offset + (dir & 0x01) * INTER_FILTER_DIR_OFFSET;
  int left_type = SWITCHABLE_FILTERS;
  int above_type = SWITCHABLE_FILTERS;

  if (xd->left_available)
    left_type = get_ref_filter_type(xd->mi[-1], xd, dir, ref_frame);

  if (xd->up_available)
    above_type =
        get_ref_filter_type(xd->mi[-xd->mi_stride], xd, dir, ref_frame);

  if (left_type == above_type) {
    filter_type_ctx += left_type;
  } else if (left_type == SWITCHABLE_FILTERS) {
    assert(above_type != SWITCHABLE_FILTERS);
    filter_type_ctx += above_type;
  } else if (above_type == SWITCHABLE_FILTERS) {
    assert(left_type != SWITCHABLE_FILTERS);
    filter_type_ctx += left_type;
  } else {
    filter_type_ctx += SWITCHABLE_FILTERS;
  }

  return filter_type_ctx;
}

static void palette_add_to_cache(uint16_t *cache, int *n, uint16_t val) {
  // Do not add an already existing value
#if !CONFIG_INDEP_PALETTE_PARSING
  if (*n > 0 && val == cache[*n - 1]) return;
#endif  //! CONFIG_INDEP_PALETTE_PARSING

  cache[(*n)++] = val;
}

int av1_get_palette_cache(const MACROBLOCKD *const xd, int plane,
                          uint16_t *cache) {
  const int row = -xd->mb_to_top_edge >> 3;
  // Do not refer to above SB row when on SB boundary.
  const MB_MODE_INFO *const above_mi =
      (row % (1 << MIN_SB_SIZE_LOG2)) ? xd->above_mbmi : NULL;
  const MB_MODE_INFO *const left_mi = xd->left_mbmi;
  int above_n = 0, left_n = 0;
  if (above_mi) above_n = above_mi->palette_mode_info.palette_size[plane != 0];
  if (left_mi) left_n = left_mi->palette_mode_info.palette_size[plane != 0];
  if (above_n == 0 && left_n == 0) return 0;
  int above_idx = plane * PALETTE_MAX_SIZE;
  int left_idx = plane * PALETTE_MAX_SIZE;
  int n = 0;
  const uint16_t *above_colors =
      above_mi ? above_mi->palette_mode_info.palette_colors : NULL;
  const uint16_t *left_colors =
      left_mi ? left_mi->palette_mode_info.palette_colors : NULL;
  // Merge the sorted lists of base colors from above and left to get
  // combined sorted color cache.
  while (above_n > 0 && left_n > 0) {
    uint16_t v_above = above_colors[above_idx];
    uint16_t v_left = left_colors[left_idx];
#if CONFIG_INDEP_PALETTE_PARSING
    palette_add_to_cache(cache, &n, v_above);
    ++above_idx, --above_n;
    palette_add_to_cache(cache, &n, v_left);
    ++left_idx, --left_n;
#else
    if (v_left < v_above) {
      palette_add_to_cache(cache, &n, v_left);
      ++left_idx, --left_n;
    } else {
      palette_add_to_cache(cache, &n, v_above);
      ++above_idx, --above_n;
      if (v_left == v_above) ++left_idx, --left_n;
    }
#endif  // CONFIG_INDEP_PALETTE_PARSING
  }
  while (above_n-- > 0) {
    uint16_t val = above_colors[above_idx++];
    palette_add_to_cache(cache, &n, val);
  }
  while (left_n-- > 0) {
    uint16_t val = left_colors[left_idx++];
    palette_add_to_cache(cache, &n, val);
  }
  assert(n <= 2 * PALETTE_MAX_SIZE);
  return n;
}

// The mode info data structure has a one element border above and to the
// left of the entries corresponding to real macroblocks.
// The prediction flags in these dummy entries are initialized to 0.
// 0 - inter/inter, inter/--, --/inter, --/--
// 1 - intra/inter, inter/intra
// 2 - intra/--, --/intra
// 3 - intra/intra
int av1_get_intra_inter_context(const MACROBLOCKD *xd) {
  const MB_MODE_INFO *const above_mbmi = xd->above_mbmi;
  const MB_MODE_INFO *const left_mbmi = xd->left_mbmi;
  const int has_above = xd->up_available;
  const int has_left = xd->left_available;

  if (has_above && has_left) {  // both edges available
    const int above_intra = !is_inter_block(above_mbmi, xd->tree_type);
    const int left_intra = !is_inter_block(left_mbmi, xd->tree_type);
    return left_intra && above_intra ? 3 : left_intra || above_intra;
  } else if (has_above || has_left) {  // one edge available
    return 2 *
           !is_inter_block(has_above ? above_mbmi : left_mbmi, xd->tree_type);
  } else {
    return 0;
  }
}

#if CONFIG_NEW_REF_SIGNALING
#define IS_BACKWARD_REF_FRAME(ref_frame) \
  (get_dir_rank(cm, ref_frame, NULL) == 1)
#else
#define CHECK_BACKWARD_REFS(ref_frame) \
  (((ref_frame) >= BWDREF_FRAME) && ((ref_frame) <= ALTREF_FRAME))
#define IS_BACKWARD_REF_FRAME(ref_frame) CHECK_BACKWARD_REFS(ref_frame)
#endif  // CONFIG_NEW_REF_SIGNALING

int av1_get_reference_mode_context(const AV1_COMMON *cm,
                                   const MACROBLOCKD *xd) {
  (void)cm;
  int ctx;
  const MB_MODE_INFO *const above_mbmi = xd->above_mbmi;
  const MB_MODE_INFO *const left_mbmi = xd->left_mbmi;
  const int has_above = xd->up_available;
  const int has_left = xd->left_available;

  // Note:
  // The mode info data structure has a one element border above and to the
  // left of the entries corresponding to real macroblocks.
  // The prediction flags in these dummy entries are initialized to 0.
  if (has_above && has_left) {  // both edges available
    if (!has_second_ref(above_mbmi) && !has_second_ref(left_mbmi))
      // neither edge uses comp pred (0/1)
      ctx = IS_BACKWARD_REF_FRAME(above_mbmi->ref_frame[0]) ^
            IS_BACKWARD_REF_FRAME(left_mbmi->ref_frame[0]);
    else if (!has_second_ref(above_mbmi))
      // one of two edges uses comp pred (2/3)
      ctx = 2 + (IS_BACKWARD_REF_FRAME(above_mbmi->ref_frame[0]) ||
                 !is_inter_block(above_mbmi, xd->tree_type));
    else if (!has_second_ref(left_mbmi))
      // one of two edges uses comp pred (2/3)
      ctx = 2 + (IS_BACKWARD_REF_FRAME(left_mbmi->ref_frame[0]) ||
                 !is_inter_block(left_mbmi, xd->tree_type));
    else  // both edges use comp pred (4)
      ctx = 4;
  } else if (has_above || has_left) {  // one edge available
    const MB_MODE_INFO *edge_mbmi = has_above ? above_mbmi : left_mbmi;

    if (!has_second_ref(edge_mbmi))
      // edge does not use comp pred (0/1)
      ctx = IS_BACKWARD_REF_FRAME(edge_mbmi->ref_frame[0]);
    else
      // edge uses comp pred (3)
      ctx = 3;
  } else {  // no edges available (1)
    ctx = 1;
  }
  assert(ctx >= 0 && ctx < COMP_INTER_CONTEXTS);
  return ctx;
}

#if CONFIG_NEW_REF_SIGNALING
// The context for reference frame is defined by comparing A) the count of
// rank n references and B) the count of rank > n references in the neighboring
// blocks. Context will be 0 if A<B, 1 if A=B, and 2 if A>B.
int av1_get_ref_pred_context(const MACROBLOCKD *xd, MV_REFERENCE_FRAME ref,
                             int num_total_refs) {
  assert((ref + 1) < num_total_refs);
  const uint8_t *const ref_counts = &xd->neighbors_ref_counts[0];
  const int this_ref_count = ref_counts[ref];
  int next_refs_count = 0;

  for (int i = ref + 1; i < num_total_refs; i++) {
    next_refs_count += ref_counts[i];
  }

  const int pred_context = (this_ref_count == next_refs_count)
                               ? 1
                               : ((this_ref_count < next_refs_count) ? 0 : 2);

  assert(pred_context >= 0 && pred_context < REF_CONTEXTS);
  return pred_context;
}
#else
int av1_get_comp_reference_type_context(const MACROBLOCKD *xd) {
  int pred_context;
  const MB_MODE_INFO *const above_mbmi = xd->above_mbmi;
  const MB_MODE_INFO *const left_mbmi = xd->left_mbmi;
  const int above_in_image = xd->up_available;
  const int left_in_image = xd->left_available;

  if (above_in_image && left_in_image) {  // both edges available
    const int above_intra = !is_inter_block(above_mbmi, xd->tree_type);
    const int left_intra = !is_inter_block(left_mbmi, xd->tree_type);

    if (above_intra && left_intra) {  // intra/intra
      pred_context = 2;
    } else if (above_intra || left_intra) {  // intra/inter
      const MB_MODE_INFO *inter_mbmi = above_intra ? left_mbmi : above_mbmi;

      if (!has_second_ref(inter_mbmi))  // single pred
        pred_context = 2;
      else  // comp pred
        pred_context = 1 + 2 * has_uni_comp_refs(inter_mbmi);
    } else {  // inter/inter
      const int a_sg = !has_second_ref(above_mbmi);
      const int l_sg = !has_second_ref(left_mbmi);
      const MV_REFERENCE_FRAME frfa = above_mbmi->ref_frame[0];
      const MV_REFERENCE_FRAME frfl = left_mbmi->ref_frame[0];

      if (a_sg && l_sg) {  // single/single
        pred_context = 1 + 2 * (!(IS_BACKWARD_REF_FRAME(frfa) ^
                                  IS_BACKWARD_REF_FRAME(frfl)));
      } else if (l_sg || a_sg) {  // single/comp
        const int uni_rfc =
            a_sg ? has_uni_comp_refs(left_mbmi) : has_uni_comp_refs(above_mbmi);

        if (!uni_rfc)  // comp bidir
          pred_context = 1;
        else  // comp unidir
          pred_context = 3 + (!(IS_BACKWARD_REF_FRAME(frfa) ^
                                IS_BACKWARD_REF_FRAME(frfl)));
      } else {  // comp/comp
        const int a_uni_rfc = has_uni_comp_refs(above_mbmi);
        const int l_uni_rfc = has_uni_comp_refs(left_mbmi);

        if (!a_uni_rfc && !l_uni_rfc)  // bidir/bidir
          pred_context = 0;
        else if (!a_uni_rfc || !l_uni_rfc)  // unidir/bidir
          pred_context = 2;
        else  // unidir/unidir
          pred_context =
              3 + (!((frfa == BWDREF_FRAME) ^ (frfl == BWDREF_FRAME)));
      }
    }
  } else if (above_in_image || left_in_image) {  // one edge available
    const MB_MODE_INFO *edge_mbmi = above_in_image ? above_mbmi : left_mbmi;
    if (!is_inter_block(edge_mbmi, xd->tree_type)) {  // intra
      pred_context = 2;
    } else {                           // inter
      if (!has_second_ref(edge_mbmi))  // single pred
        pred_context = 2;
      else  // comp pred
        pred_context = 4 * has_uni_comp_refs(edge_mbmi);
    }
  } else {  // no edges available
    pred_context = 2;
  }

  assert(pred_context >= 0 && pred_context < COMP_REF_TYPE_CONTEXTS);
  return pred_context;
}

// Returns a context number for the given MB prediction signal
//
// Signal the uni-directional compound reference frame pair as either
// (BWDREF, ALTREF), or (LAST, LAST2) / (LAST, LAST3) / (LAST, GOLDEN),
// conditioning on the pair is known as uni-directional.
//
// 3 contexts: Voting is used to compare the count of forward references with
//             that of backward references from the spatial neighbors.
int av1_get_pred_context_uni_comp_ref_p(const MACROBLOCKD *xd) {
  const uint8_t *const ref_counts = &xd->neighbors_ref_counts[0];

  // Count of forward references (L, L2, L3, or G)
  const int frf_count = ref_counts[LAST_FRAME] + ref_counts[LAST2_FRAME] +
                        ref_counts[LAST3_FRAME] + ref_counts[GOLDEN_FRAME];
  // Count of backward references (B or A)
  const int brf_count = ref_counts[BWDREF_FRAME] + ref_counts[ALTREF2_FRAME] +
                        ref_counts[ALTREF_FRAME];

  const int pred_context =
      (frf_count == brf_count) ? 1 : ((frf_count < brf_count) ? 0 : 2);

  assert(pred_context >= 0 && pred_context < UNI_COMP_REF_CONTEXTS);
  return pred_context;
}

// Returns a context number for the given MB prediction signal
//
// Signal the uni-directional compound reference frame pair as
// either (LAST, LAST2), or (LAST, LAST3) / (LAST, GOLDEN),
// conditioning on the pair is known as one of the above three.
//
// 3 contexts: Voting is used to compare the count of LAST2_FRAME with the
//             total count of LAST3/GOLDEN from the spatial neighbors.
int av1_get_pred_context_uni_comp_ref_p1(const MACROBLOCKD *xd) {
  const uint8_t *const ref_counts = &xd->neighbors_ref_counts[0];

  // Count of LAST2
  const int last2_count = ref_counts[LAST2_FRAME];
  // Count of LAST3 or GOLDEN
  const int last3_or_gld_count =
      ref_counts[LAST3_FRAME] + ref_counts[GOLDEN_FRAME];

  const int pred_context = (last2_count == last3_or_gld_count)
                               ? 1
                               : ((last2_count < last3_or_gld_count) ? 0 : 2);

  assert(pred_context >= 0 && pred_context < UNI_COMP_REF_CONTEXTS);
  return pred_context;
}

// Returns a context number for the given MB prediction signal
//
// Signal the uni-directional compound reference frame pair as
// either (LAST, LAST3) or (LAST, GOLDEN),
// conditioning on the pair is known as one of the above two.
//
// 3 contexts: Voting is used to compare the count of LAST3_FRAME with the
//             total count of GOLDEN_FRAME from the spatial neighbors.
int av1_get_pred_context_uni_comp_ref_p2(const MACROBLOCKD *xd) {
  const uint8_t *const ref_counts = &xd->neighbors_ref_counts[0];

  // Count of LAST3
  const int last3_count = ref_counts[LAST3_FRAME];
  // Count of GOLDEN
  const int gld_count = ref_counts[GOLDEN_FRAME];

  const int pred_context =
      (last3_count == gld_count) ? 1 : ((last3_count < gld_count) ? 0 : 2);

  assert(pred_context >= 0 && pred_context < UNI_COMP_REF_CONTEXTS);
  return pred_context;
}

// == Common context functions for both comp and single ref ==
//
// Obtain contexts to signal a reference frame to be either LAST/LAST2 or
// LAST3/GOLDEN.
static int get_pred_context_ll2_or_l3gld(const MACROBLOCKD *xd) {
  const uint8_t *const ref_counts = &xd->neighbors_ref_counts[0];

  // Count of LAST + LAST2
  const int last_last2_count = ref_counts[LAST_FRAME] + ref_counts[LAST2_FRAME];
  // Count of LAST3 + GOLDEN
  const int last3_gld_count =
      ref_counts[LAST3_FRAME] + ref_counts[GOLDEN_FRAME];

  const int pred_context = (last_last2_count == last3_gld_count)
                               ? 1
                               : ((last_last2_count < last3_gld_count) ? 0 : 2);

  assert(pred_context >= 0 && pred_context < REF_CONTEXTS);
  return pred_context;
}

// Obtain contexts to signal a reference frame to be either LAST or LAST2.
static int get_pred_context_last_or_last2(const MACROBLOCKD *xd) {
  const uint8_t *const ref_counts = &xd->neighbors_ref_counts[0];

  // Count of LAST
  const int last_count = ref_counts[LAST_FRAME];
  // Count of LAST2
  const int last2_count = ref_counts[LAST2_FRAME];

  const int pred_context =
      (last_count == last2_count) ? 1 : ((last_count < last2_count) ? 0 : 2);

  assert(pred_context >= 0 && pred_context < REF_CONTEXTS);
  return pred_context;
}

// Obtain contexts to signal a reference frame to be either LAST3 or GOLDEN.
static int get_pred_context_last3_or_gld(const MACROBLOCKD *xd) {
  const uint8_t *const ref_counts = &xd->neighbors_ref_counts[0];

  // Count of LAST3
  const int last3_count = ref_counts[LAST3_FRAME];
  // Count of GOLDEN
  const int gld_count = ref_counts[GOLDEN_FRAME];

  const int pred_context =
      (last3_count == gld_count) ? 1 : ((last3_count < gld_count) ? 0 : 2);

  assert(pred_context >= 0 && pred_context < REF_CONTEXTS);
  return pred_context;
}

// Obtain contexts to signal a reference frame be either BWDREF/ALTREF2, or
// ALTREF.
static int get_pred_context_brfarf2_or_arf(const MACROBLOCKD *xd) {
  const uint8_t *const ref_counts = &xd->neighbors_ref_counts[0];

  // Counts of BWDREF, ALTREF2, or ALTREF frames (B, A2, or A)
  const int brfarf2_count =
      ref_counts[BWDREF_FRAME] + ref_counts[ALTREF2_FRAME];
  const int arf_count = ref_counts[ALTREF_FRAME];

  const int pred_context =
      (brfarf2_count == arf_count) ? 1 : ((brfarf2_count < arf_count) ? 0 : 2);

  assert(pred_context >= 0 && pred_context < REF_CONTEXTS);
  return pred_context;
}

// Obtain contexts to signal a reference frame be either BWDREF or ALTREF2.
static int get_pred_context_brf_or_arf2(const MACROBLOCKD *xd) {
  const uint8_t *const ref_counts = &xd->neighbors_ref_counts[0];

  // Count of BWDREF frames (B)
  const int brf_count = ref_counts[BWDREF_FRAME];
  // Count of ALTREF2 frames (A2)
  const int arf2_count = ref_counts[ALTREF2_FRAME];

  const int pred_context =
      (brf_count == arf2_count) ? 1 : ((brf_count < arf2_count) ? 0 : 2);

  assert(pred_context >= 0 && pred_context < REF_CONTEXTS);
  return pred_context;
}

// == Context functions for comp ref ==
//
// Returns a context number for the given MB prediction signal
// Signal the first reference frame for a compound mode be either
// GOLDEN/LAST3, or LAST/LAST2.
int av1_get_pred_context_comp_ref_p(const MACROBLOCKD *xd) {
  return get_pred_context_ll2_or_l3gld(xd);
}

// Returns a context number for the given MB prediction signal
// Signal the first reference frame for a compound mode be LAST,
// conditioning on that it is known either LAST/LAST2.
int av1_get_pred_context_comp_ref_p1(const MACROBLOCKD *xd) {
  return get_pred_context_last_or_last2(xd);
}

// Returns a context number for the given MB prediction signal
// Signal the first reference frame for a compound mode be GOLDEN,
// conditioning on that it is known either GOLDEN or LAST3.
int av1_get_pred_context_comp_ref_p2(const MACROBLOCKD *xd) {
  return get_pred_context_last3_or_gld(xd);
}

// Signal the 2nd reference frame for a compound mode be either
// ALTREF, or ALTREF2/BWDREF.
int av1_get_pred_context_comp_bwdref_p(const MACROBLOCKD *xd) {
  return get_pred_context_brfarf2_or_arf(xd);
}

// Signal the 2nd reference frame for a compound mode be either
// ALTREF2 or BWDREF.
int av1_get_pred_context_comp_bwdref_p1(const MACROBLOCKD *xd) {
  return get_pred_context_brf_or_arf2(xd);
}

// == Context functions for single ref ==
//
// For the bit to signal whether the single reference is a forward reference
// frame or a backward reference frame.
int av1_get_pred_context_single_ref_p1(const MACROBLOCKD *xd) {
  const uint8_t *const ref_counts = &xd->neighbors_ref_counts[0];

  // Count of forward reference frames
  const int fwd_count = ref_counts[LAST_FRAME] + ref_counts[LAST2_FRAME] +
                        ref_counts[LAST3_FRAME] + ref_counts[GOLDEN_FRAME];
  // Count of backward reference frames
  const int bwd_count = ref_counts[BWDREF_FRAME] + ref_counts[ALTREF2_FRAME] +
                        ref_counts[ALTREF_FRAME];

  const int pred_context =
      (fwd_count == bwd_count) ? 1 : ((fwd_count < bwd_count) ? 0 : 2);

  assert(pred_context >= 0 && pred_context < REF_CONTEXTS);
  return pred_context;
}

// For the bit to signal whether the single reference is ALTREF_FRAME or
// non-ALTREF backward reference frame, knowing that it shall be either of
// these 2 choices.
int av1_get_pred_context_single_ref_p2(const MACROBLOCKD *xd) {
  return get_pred_context_brfarf2_or_arf(xd);
}

// For the bit to signal whether the single reference is LAST3/GOLDEN or
// LAST2/LAST, knowing that it shall be either of these 2 choices.
int av1_get_pred_context_single_ref_p3(const MACROBLOCKD *xd) {
  return get_pred_context_ll2_or_l3gld(xd);
}

// For the bit to signal whether the single reference is LAST2_FRAME or
// LAST_FRAME, knowing that it shall be either of these 2 choices.
int av1_get_pred_context_single_ref_p4(const MACROBLOCKD *xd) {
  return get_pred_context_last_or_last2(xd);
}

// For the bit to signal whether the single reference is GOLDEN_FRAME or
// LAST3_FRAME, knowing that it shall be either of these 2 choices.
int av1_get_pred_context_single_ref_p5(const MACROBLOCKD *xd) {
  return get_pred_context_last3_or_gld(xd);
}

// For the bit to signal whether the single reference is ALTREF2_FRAME or
// BWDREF_FRAME, knowing that it shall be either of these 2 choices.
int av1_get_pred_context_single_ref_p6(const MACROBLOCKD *xd) {
  return get_pred_context_brf_or_arf2(xd);
}
#endif  // CONFIG_NEW_REF_SIGNALING