source/libvpx/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 neighbourhood 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,
                             const TileInfo *const tile,
                             MODE_INFO *mi, MV_REFERENCE_FRAME ref_frame,
                             int_mv *mv_ref_list,
                             int block, int mi_row, int mi_col) {
  const int *ref_sign_bias = cm->ref_frame_sign_bias;
  int i, refmv_count = 0;
  const MODE_INFO *prev_mi = cm->coding_use_prev_mi && cm->prev_mi
        ? cm->prev_mi_grid_visible[mi_row * xd->mi_stride + mi_col]
        : NULL;
  const MB_MODE_INFO *const prev_mbmi = prev_mi ? &prev_mi->mbmi : NULL;


  const POSITION *const mv_ref_search = mv_ref_blocks[mi->mbmi.sb_type];

  int different_ref_found = 0;
  int context_counter = 0;

  // Blank the reference vector list
  vpx_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];
      const MB_MODE_INFO *const candidate = &candidate_mi->mbmi;
      // 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));
      else if (candidate->ref_frame[1] == ref_frame)
        ADD_MV_REF_LIST(get_sub_block_mv(candidate_mi, 1, mv_ref->col, block));
    }
  }

  // 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 MB_MODE_INFO *const candidate = &xd->mi[mv_ref->col + mv_ref->row *
                                                    xd->mi_stride]->mbmi;
      different_ref_found = 1;

      if (candidate->ref_frame[0] == ref_frame)
        ADD_MV_REF_LIST(candidate->mv[0]);
      else if (candidate->ref_frame[1] == ref_frame)
        ADD_MV_REF_LIST(candidate->mv[1]);
    }
  }

  // Check the last frame's mode and mv info.
  if (prev_mbmi) {
    if (prev_mbmi->ref_frame[0] == ref_frame)
      ADD_MV_REF_LIST(prev_mbmi->mv[0]);
    else if (prev_mbmi->ref_frame[1] == ref_frame)
      ADD_MV_REF_LIST(prev_mbmi->mv[1]);
  }

  // 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 MB_MODE_INFO *const candidate = &xd->mi[mv_ref->col + mv_ref->row
                                              * xd->mi_stride]->mbmi;

        // If the candidate is INTRA we don't want to consider its mv.
        IF_DIFF_REF_FRAME_ADD_MV(candidate);
      }
    }
  }

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

 Done:

  mi->mbmi.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,
                                    const TileInfo *const tile,
                                    MODE_INFO *mi, MV_REFERENCE_FRAME ref_frame,
                                    int_mv *mv_ref_list,
                                    int mi_row, int mi_col) {
  find_mv_refs_idx(cm, xd, tile, mi, ref_frame, mv_ref_list, -1,
                   mi_row, mi_col);
}

static void lower_mv_precision(MV *mv, int allow_hp) {
  const int use_hp = allow_hp && vp9_use_mv_hp(mv);
  if (!use_hp) {
    if (mv->row & 1)
      mv->row += (mv->row > 0 ? -1 : 1);
    if (mv->col & 1)
      mv->col += (mv->col > 0 ? -1 : 1);
  }
}


void vp9_find_best_ref_mvs(MACROBLOCKD *xd, int allow_hp,
                           int_mv *mvlist, int_mv *nearest, int_mv *near) {
  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 = mvlist[0];
  *near = mvlist[1];
}

void vp9_append_sub8x8_mvs_for_idx(VP9_COMMON *cm, MACROBLOCKD *xd,
                                   const TileInfo *const tile,
                                   int block, int ref, int mi_row, int mi_col,
                                   int_mv *nearest, int_mv *near) {
  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, tile, mi, mi->mbmi.ref_frame[ref], mv_list, block,
                   mi_row, mi_col);

  near->as_int = 0;
  switch (block) {
    case 0:
      nearest->as_int = mv_list[0].as_int;
      near->as_int = mv_list[1].as_int;
      break;
    case 1:
    case 2:
      nearest->as_int = bmi[0].as_mv[ref].as_int;
      for (n = 0; n < MAX_MV_REF_CANDIDATES; ++n)
        if (nearest->as_int != mv_list[n].as_int) {
          near->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->as_int = bmi[2].as_mv[ref].as_int;
      for (n = 0; n < 2 + MAX_MV_REF_CANDIDATES; ++n)
        if (nearest->as_int != candidates[n].as_int) {
          near->as_int = candidates[n].as_int;
          break;
        }
      break;
    }
    default:
      assert("Invalid block index.");
  }
}