vp9/common/vp9_mvref_common.c

/*
 *  Copyright (c) 2012 The WebM project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#include "vp9/common/vp9_mvref_common.h"

// This function searches the neighborhood of a given MB/SB
// to try and find candidate reference vectors.
static void find_mv_refs_idx(const VP9_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,
                             uint8_t *mode_context) {
  const int *ref_sign_bias = cm->ref_frame_sign_bias;
  int i, refmv_count = 0;
  const POSITION *const mv_ref_search = mv_ref_blocks[mi->sb_type];
  int different_ref_found = 0;
  int context_counter = 0;
  const MV_REF *const prev_frame_mvs = cm->use_prev_frame_mvs ?
      cm->prev_frame->mvs + mi_row * cm->mi_cols + mi_col : NULL;
  const TileInfo *const tile = &xd->tile;

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

  // 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, mv_ref)) {
      const MODE_INFO *const candidate_mi = xd->mi[mv_ref->col + mv_ref->row *
                                                   xd->mi_stride];
      // Keep counts for entropy encoding.
      context_counter += mode_2_counter[candidate_mi->mode];
      different_ref_found = 1;

      if (candidate_mi->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, Done);
      else if (candidate_mi->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, Done);
    }
  }

  // Check the rest of the neighbors in much the same way
  // as before except we don't need to keep track of sub blocks or
  // mode counts.
  for (; i < MVREF_NEIGHBOURS; ++i) {
    const POSITION *const mv_ref = &mv_ref_search[i];
    if (is_inside(tile, mi_col, mi_row, cm->mi_rows, mv_ref)) {
      const MODE_INFO *const candidate_mi =
          xd->mi[mv_ref->col + mv_ref->row * xd->mi_stride];
      different_ref_found = 1;

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

  // Check the last frame's mode and mv info.
  if (cm->use_prev_frame_mvs) {
    if (prev_frame_mvs->ref_frame[0] == ref_frame) {
      ADD_MV_REF_LIST(prev_frame_mvs->mv[0], refmv_count, mv_ref_list, Done);
    } else if (prev_frame_mvs->ref_frame[1] == ref_frame) {
      ADD_MV_REF_LIST(prev_frame_mvs->mv[1], refmv_count, mv_ref_list, Done);
    }
  }

  // Since we couldn't find 2 mvs from the same reference frame
  // go back through the neighbors and find motion vectors from
  // different reference frames.
  if (different_ref_found) {
    for (i = 0; i < MVREF_NEIGHBOURS; ++i) {
      const POSITION *mv_ref = &mv_ref_search[i];
      if (is_inside(tile, mi_col, mi_row, cm->mi_rows, mv_ref)) {
        const MODE_INFO *const candidate_mi =
            xd->mi[mv_ref->col + mv_ref->row * xd->mi_stride];

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

  // Since we still don't have a candidate we'll try the last frame.
  if (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, Done);
    }

    if (prev_frame_mvs->ref_frame[1] > INTRA_FRAME &&
        prev_frame_mvs->ref_frame[1] != ref_frame &&
        prev_frame_mvs->mv[1].as_int != prev_frame_mvs->mv[0].as_int) {
      int_mv mv = prev_frame_mvs->mv[1];
      if (ref_sign_bias[prev_frame_mvs->ref_frame[1]] !=
          ref_sign_bias[ref_frame]) {
        mv.as_mv.row *= -1;
        mv.as_mv.col *= -1;
      }
      ADD_MV_REF_LIST(mv, refmv_count, mv_ref_list, Done);
    }
  }

 Done:

  mode_context[ref_frame] = counter_to_context[context_counter];

  // Clamp vectors
  for (i = 0; i < MAX_MV_REF_CANDIDATES; ++i)
    clamp_mv_ref(&mv_ref_list[i].as_mv, xd);
}

void vp9_find_mv_refs(const VP9_COMMON *cm, const MACROBLOCKD *xd,
                      MODE_INFO *mi, MV_REFERENCE_FRAME ref_frame,
                      int_mv *mv_ref_list,
                      int mi_row, int mi_col,
                      uint8_t *mode_context) {
  find_mv_refs_idx(cm, xd, mi, ref_frame, mv_ref_list, -1,
                   mi_row, mi_col, mode_context);
}

void vp9_find_best_ref_mvs(MACROBLOCKD *xd, int allow_hp,
                           int_mv *mvlist, int_mv *nearest_mv,
                           int_mv *near_mv) {
  int i;
  // Make sure all the candidates are properly clamped etc
  for (i = 0; i < MAX_MV_REF_CANDIDATES; ++i) {
    lower_mv_precision(&mvlist[i].as_mv, allow_hp);
    clamp_mv2(&mvlist[i].as_mv, xd);
  }
  *nearest_mv = mvlist[0];
  *near_mv = mvlist[1];
}

void vp9_append_sub8x8_mvs_for_idx(VP9_COMMON *cm, MACROBLOCKD *xd,
                                   int block, int ref, int mi_row, int mi_col,
                                   int_mv *nearest_mv, int_mv *near_mv,
                                   uint8_t *mode_context) {
  int_mv mv_list[MAX_MV_REF_CANDIDATES];
  MODE_INFO *const mi = xd->mi[0];
  b_mode_info *bmi = mi->bmi;
  int n;

  assert(MAX_MV_REF_CANDIDATES == 2);

  find_mv_refs_idx(cm, xd, mi, mi->ref_frame[ref], mv_list, block,
                   mi_row, mi_col, mode_context);

  near_mv->as_int = 0;
  switch (block) {
    case 0:
      nearest_mv->as_int = mv_list[0].as_int;
      near_mv->as_int = mv_list[1].as_int;
      break;
    case 1:
    case 2:
      nearest_mv->as_int = bmi[0].as_mv[ref].as_int;
      for (n = 0; n < MAX_MV_REF_CANDIDATES; ++n)
        if (nearest_mv->as_int != mv_list[n].as_int) {
          near_mv->as_int = mv_list[n].as_int;
          break;
        }
      break;
    case 3: {
      int_mv candidates[2 + MAX_MV_REF_CANDIDATES];
      candidates[0] = bmi[1].as_mv[ref];
      candidates[1] = bmi[0].as_mv[ref];
      candidates[2] = mv_list[0];
      candidates[3] = mv_list[1];

      nearest_mv->as_int = bmi[2].as_mv[ref].as_int;
      for (n = 0; n < 2 + MAX_MV_REF_CANDIDATES; ++n)
        if (nearest_mv->as_int != candidates[n].as_int) {
          near_mv->as_int = candidates[n].as_int;
          break;
        }
      break;
    }
    default:
      assert(0 && "Invalid block index.");
  }
}