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"

#define MVREF_NEIGHBOURS 8
static const int mv_ref_blocks[BLOCK_SIZE_TYPES][MVREF_NEIGHBOURS][2] = {
  // SB4X4
  {{0, -1}, {-1, 0}, {-1, -1}, {0, -2}, {-2, 0}, {-1, -2}, {-2, -1}, {-2, -2}},
  // SB4X8
  {{0, -1}, {-1, 0}, {-1, -1}, {0, -2}, {-2, 0}, {-1, -2}, {-2, -1}, {-2, -2}},
  // SB8X4
  {{0, -1}, {-1, 0}, {-1, -1}, {0, -2}, {-2, 0}, {-1, -2}, {-2, -1}, {-2, -2}},
  // SB8X8
  {{0, -1}, {-1, 0}, {-1, -1}, {0, -2}, {-2, 0}, {-1, -2}, {-2, -1}, {-2, -2}},
  // SB8X16
  {{-1, 0}, {0, -1}, {-1, 1}, {-1, -1}, {-2, 0}, {0, -2}, {-1, -2}, {-2, -1}},
  // SB16X8
  {{0, -1}, {-1, 0}, {1, -1}, {-1, -1}, {0, -2}, {-2, 0}, {-2, -1}, {-1, -2}},
  // SB16X16
  {{0, -1}, {-1, 0}, {1, -1}, {-1, 1}, {-1, -1}, {0, -3}, {-3, 0}, {-3, -3}},
  // SB16X32
  {{-1, 0}, {0, -1}, {-1, 2}, {-1, -1}, {1, -1}, {-3, 0}, {0, -3}, {-3, -3}},
  // SB32X16
  {{0, -1}, {-1, 0}, {2, -1}, {-1, -1}, {-1, 1}, {0, -3}, {-3, 0}, {-3, -3}},
  // SB32X32
  {{1, -1}, {-1, 1}, {2, -1}, {-1, 2}, {-1, -1}, {0, -3}, {-3, 0}, {-3, -3}},
  // SB32X64
  {{-1, 0}, {0, -1}, {-1, 4}, {2, -1}, {-1, -1}, {-3, 0}, {0, -3}, {-1, 2}},
  // SB64X32
  {{0, -1}, {-1, 0}, {4, -1}, {-1, 2}, {-1, -1}, {0, -3}, {-3, 0}, {2, -1}},
  // SB64X64
  {{3, -1}, {-1, 3}, {4, -1}, {-1, 4}, {-1, -1}, {0, -1}, {-1, 0}, {6, -1}}
};
// clamp_mv_ref
#define MV_BORDER (16 << 3) // Allow 16 pels in 1/8th pel units

static void clamp_mv_ref(const MACROBLOCKD *xd, int_mv *mv) {
  clamp_mv(&mv->as_mv, xd->mb_to_left_edge - MV_BORDER,
                       xd->mb_to_right_edge + MV_BORDER,
                       xd->mb_to_top_edge - MV_BORDER,
                       xd->mb_to_bottom_edge + MV_BORDER);
}

// Gets a candidate reference motion vector from the given mode info
// structure if one exists that matches the given reference frame.
static int get_matching_candidate(const MODE_INFO *candidate_mi,
                                  MV_REFERENCE_FRAME ref_frame,
                                  int_mv *c_mv, int block_idx) {
  if (ref_frame == candidate_mi->mbmi.ref_frame[0]) {
    if (block_idx >= 0 && candidate_mi->mbmi.sb_type < BLOCK_SIZE_SB8X8)
      c_mv->as_int = candidate_mi->bmi[block_idx].as_mv[0].as_int;
    else
      c_mv->as_int = candidate_mi->mbmi.mv[0].as_int;
  } else if (ref_frame == candidate_mi->mbmi.ref_frame[1]) {
    if (block_idx >= 0 && candidate_mi->mbmi.sb_type < BLOCK_SIZE_SB8X8)
      c_mv->as_int = candidate_mi->bmi[block_idx].as_mv[1].as_int;
    else
      c_mv->as_int = candidate_mi->mbmi.mv[1].as_int;
  } else {
    return 0;
  }

  return 1;
}

// Gets candidate reference motion vector(s) from the given mode info
// structure if they exists and do NOT match the given reference frame.
static void get_non_matching_candidates(const MODE_INFO *candidate_mi,
                                        MV_REFERENCE_FRAME ref_frame,
                                        MV_REFERENCE_FRAME *c_ref_frame,
                                        int_mv *c_mv,
                                        MV_REFERENCE_FRAME *c2_ref_frame,
                                        int_mv *c2_mv) {

  c_mv->as_int = 0;
  c2_mv->as_int = 0;
  *c_ref_frame = INTRA_FRAME;
  *c2_ref_frame = INTRA_FRAME;

  // If first candidate not valid neither will be.
  if (candidate_mi->mbmi.ref_frame[0] > INTRA_FRAME) {
    // First candidate
    if (candidate_mi->mbmi.ref_frame[0] != ref_frame) {
      *c_ref_frame = candidate_mi->mbmi.ref_frame[0];
      c_mv->as_int = candidate_mi->mbmi.mv[0].as_int;
    }

    // Second candidate
    if ((candidate_mi->mbmi.ref_frame[1] > INTRA_FRAME) &&
        (candidate_mi->mbmi.ref_frame[1] != ref_frame) &&
        (candidate_mi->mbmi.mv[1].as_int != candidate_mi->mbmi.mv[0].as_int)) {
      *c2_ref_frame = candidate_mi->mbmi.ref_frame[1];
      c2_mv->as_int = candidate_mi->mbmi.mv[1].as_int;
    }
  }
}


// Performs mv sign inversion if indicated by the reference frame combination.
static void scale_mv(MV_REFERENCE_FRAME this_ref_frame,
                     MV_REFERENCE_FRAME candidate_ref_frame,
                     int_mv *candidate_mv, int *ref_sign_bias) {

  // Sign inversion where appropriate.
  if (ref_sign_bias[candidate_ref_frame] != ref_sign_bias[this_ref_frame]) {
    candidate_mv->as_mv.row = -candidate_mv->as_mv.row;
    candidate_mv->as_mv.col = -candidate_mv->as_mv.col;
  }
}

// Add a candidate mv.
// Discard if it has already been seen.
static void add_candidate_mv(int_mv *mv_list,  int *mv_scores,
                             int *candidate_count, int_mv candidate_mv,
                             int weight) {
  if (*candidate_count == 0) {
    mv_list[0].as_int = candidate_mv.as_int;
    mv_scores[0] = weight;
    *candidate_count += 1;
  } else if ((*candidate_count == 1) &&
             (candidate_mv.as_int != mv_list[0].as_int)) {
    mv_list[1].as_int = candidate_mv.as_int;
    mv_scores[1] = weight;
    *candidate_count += 1;
  }
}

// This function searches the neighbourhood of a given MB/SB
// to try and find candidate reference vectors.
//
void vp9_find_mv_refs_idx(VP9_COMMON *cm, MACROBLOCKD *xd, MODE_INFO *here,
                          MODE_INFO *lf_here, MV_REFERENCE_FRAME ref_frame,
                          int_mv *mv_ref_list, int *ref_sign_bias,
                          int block_idx, int mi_row, int mi_col) {
  int i;
  MODE_INFO *candidate_mi;
  MB_MODE_INFO *mbmi = &here->mbmi;
  int_mv c_refmv;
  int_mv c2_refmv;
  MV_REFERENCE_FRAME c_ref_frame;
  MV_REFERENCE_FRAME c2_ref_frame;
  int candidate_scores[MAX_MV_REF_CANDIDATES] = { 0 };
  int refmv_count = 0;
  const int (*mv_ref_search)[2] = mv_ref_blocks[mbmi->sb_type];
  const int mi_stride = cm->mode_info_stride;
  int intra_count = 0;
  int zero_count = 0;
  int newmv_count = 0;
  int x_idx = 0, y_idx = 0;

  // Blank the reference vector lists and other local structures.
  vpx_memset(mv_ref_list, 0, sizeof(int_mv) * MAX_MV_REF_CANDIDATES);

  if (mbmi->sb_type < BLOCK_SIZE_SB8X8) {
    x_idx = block_idx & 1;
    y_idx = block_idx >> 1;
  }

  // We first scan for candidate vectors that match the current reference frame
  // Look at nearest neigbours
  for (i = 0; i < 2; ++i) {
    const int mi_search_col = mi_col + mv_ref_search[i][0];
    const int mi_search_row = mi_row + mv_ref_search[i][1];
    if ((mi_search_col >= cm->cur_tile_mi_col_start) &&
        (mi_search_col < cm->cur_tile_mi_col_end) &&
        (mi_search_row >= 0) && (mi_search_row < cm->mi_rows)) {
      int b;

      candidate_mi = here + mv_ref_search[i][0] +
                     mi_stride * mv_ref_search[i][1];

      if (block_idx >= 0) {
        if (mv_ref_search[i][0])
          b = 1 + y_idx * 2;
        else
          b = 2 + x_idx;
      } else {
        b = -1;
      }
      if (get_matching_candidate(candidate_mi, ref_frame, &c_refmv, b))
        add_candidate_mv(mv_ref_list, candidate_scores, &refmv_count, c_refmv,
                         16);

      // Count number of neihgbours coded intra and zeromv
      intra_count += is_intra_mode(candidate_mi->mbmi.mode);
      zero_count += (candidate_mi->mbmi.mode == ZEROMV);
      newmv_count += (candidate_mi->mbmi.mode >= NEWMV);
    }
  }

  // More distant neigbours
  for (i = 2; (i < MVREF_NEIGHBOURS) &&
              (refmv_count < MAX_MV_REF_CANDIDATES); ++i) {
    const int mi_search_col = mi_col + mv_ref_search[i][0];
    const int mi_search_row = mi_row + mv_ref_search[i][1];
    if (mi_search_col >= cm->cur_tile_mi_col_start &&
        mi_search_col < cm->cur_tile_mi_col_end &&
        mi_search_row >= 0 &&
        mi_search_row < cm->mi_rows) {
      candidate_mi = here + mv_ref_search[i][0] +
                     mi_stride * mv_ref_search[i][1];

      if (get_matching_candidate(candidate_mi, ref_frame, &c_refmv, -1))
        add_candidate_mv(mv_ref_list, candidate_scores, &refmv_count, c_refmv,
                         16);
    }
  }

  // Look in the last frame if it exists
  if (lf_here && (refmv_count < MAX_MV_REF_CANDIDATES)) {
    candidate_mi = lf_here;
    if (get_matching_candidate(candidate_mi, ref_frame, &c_refmv, -1))
      add_candidate_mv(mv_ref_list, candidate_scores, &refmv_count, c_refmv,
                       16);
  }

  // If we have not found enough candidates consider ones where the
  // reference frame does not match. Break out when we have
  // MAX_MV_REF_CANDIDATES candidates.
  // Look first at spatial neighbours
  for (i = 0; (i < MVREF_NEIGHBOURS) &&
              (refmv_count < MAX_MV_REF_CANDIDATES); ++i) {
    const int mi_search_col = mi_col + mv_ref_search[i][0];
    const int mi_search_row = mi_row + mv_ref_search[i][1];
    if (mi_search_col >= cm->cur_tile_mi_col_start &&
        mi_search_col < cm->cur_tile_mi_col_end &&
        mi_search_row >= 0 &&
        mi_search_row < cm->mi_rows) {
      candidate_mi = here + mv_ref_search[i][0] +
                     mi_stride * mv_ref_search[i][1];

      get_non_matching_candidates(candidate_mi, ref_frame,
                                  &c_ref_frame, &c_refmv,
                                  &c2_ref_frame, &c2_refmv);

      if (c_ref_frame != INTRA_FRAME) {
        scale_mv(ref_frame, c_ref_frame, &c_refmv, ref_sign_bias);
        add_candidate_mv(mv_ref_list, candidate_scores,
                         &refmv_count, c_refmv, 1);
      }

      if (c2_ref_frame != INTRA_FRAME) {
        scale_mv(ref_frame, c2_ref_frame, &c2_refmv, ref_sign_bias);
        add_candidate_mv(mv_ref_list, candidate_scores,
                         &refmv_count, c2_refmv, 1);
      }
    }
  }

  // Look at the last frame if it exists
  if (lf_here && (refmv_count < MAX_MV_REF_CANDIDATES)) {
    candidate_mi = lf_here;
    get_non_matching_candidates(candidate_mi, ref_frame,
                                &c_ref_frame, &c_refmv,
                                &c2_ref_frame, &c2_refmv);

    if (c_ref_frame != INTRA_FRAME) {
      scale_mv(ref_frame, c_ref_frame, &c_refmv, ref_sign_bias);
      add_candidate_mv(mv_ref_list, candidate_scores,
                       &refmv_count, c_refmv, 1);
    }

    if (c2_ref_frame != INTRA_FRAME) {
      scale_mv(ref_frame, c2_ref_frame, &c2_refmv, ref_sign_bias);
      add_candidate_mv(mv_ref_list, candidate_scores,
                       &refmv_count, c2_refmv, 1);
    }
  }

  if (!intra_count) {
    if (!newmv_count) {
      // 0 = both zero mv
      // 1 = one zero mv + one a predicted mv
      // 2 = two predicted mvs
      mbmi->mb_mode_context[ref_frame] = 2 - zero_count;
    } else {
      // 3 = one predicted/zero and one new mv
      // 4 = two new mvs
      mbmi->mb_mode_context[ref_frame] = 2 + newmv_count;
    }
  } else {
    // 5 = one intra neighbour + x
    // 6 = two intra neighbours
    mbmi->mb_mode_context[ref_frame] = 4 + intra_count;
  }

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