vpx/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"

#define MVREF_NEIGHBOURS 8

static int b_mv_ref_search[MVREF_NEIGHBOURS][2] = {
  {0, -1}, {-1, 0}, {-1, -1}, {0, -2},
  {-2, 0}, {-1, -2}, {-2, -1}, {-2, -2}
};

static int mb_mv_ref_search[MVREF_NEIGHBOURS][2] = {
    {0, -1}, {-1, 0}, {-1, -1}, {0, -3},
    {-3, 0}, {-1, -3}, {-3, -1}, {-3, -3}
};

static int sb_mv_ref_search[MVREF_NEIGHBOURS][2] = {
    {0, -1}, {-1, 0}, {2, -1}, {-1, 2},
    {-1, -1}, {0, -3}, {-3, 0}, {-1, -3}
};

static int sb64_mv_ref_search[MVREF_NEIGHBOURS][2] = {
    {0, -1}, {-1, 0}, {2, -1}, {-1,  2},
    {4, -1}, {-1, 4}, {6, -1}, {-1, -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) {
  mv->as_mv.col = clamp(mv->as_mv.col, xd->mb_to_left_edge - MV_BORDER,
                                       xd->mb_to_right_edge + MV_BORDER);
  mv->as_mv.row = clamp(mv->as_mv.row, xd->mb_to_top_edge - MV_BORDER,
                                       xd->mb_to_bottom_edge + MV_BORDER);
}

// Gets a candidate refenence 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) {
  if (ref_frame == candidate_mi->mbmi.ref_frame) {
    c_mv->as_int = candidate_mi->mbmi.mv[0].as_int;
  } else if (ref_frame == candidate_mi->mbmi.second_ref_frame) {
    c_mv->as_int = candidate_mi->mbmi.mv[1].as_int;
  } else {
    return 0;
  }

  return 1;
}

// Gets candidate refenence 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 > INTRA_FRAME) {
    // First candidate
    if (candidate_mi->mbmi.ref_frame != ref_frame) {
      *c_ref_frame = candidate_mi->mbmi.ref_frame;
      c_mv->as_int = candidate_mi->mbmi.mv[0].as_int;
    }

    // Second candidate
    if ((candidate_mi->mbmi.second_ref_frame > INTRA_FRAME) &&
        (candidate_mi->mbmi.second_ref_frame != ref_frame) &&
        (candidate_mi->mbmi.mv[1].as_int != candidate_mi->mbmi.mv[0].as_int)) {
      *c2_ref_frame = candidate_mi->mbmi.second_ref_frame;
      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(MACROBLOCKD *xd, MV_REFERENCE_FRAME this_ref_frame,
                     MV_REFERENCE_FRAME candidate_ref_frame,
                     int_mv *candidate_mv, int *ref_sign_bias) {
  // int frame_distances[MAX_REF_FRAMES];
  // int last_distance = 1;
  // int gf_distance = xd->frames_since_golden;
  // int arf_distance = xd->frames_till_alt_ref_frame;

  // 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;
  }

  /*
  // Scale based on frame distance if the reference frames not the same.
  frame_distances[INTRA_FRAME] = 1;   // should never be used
  frame_distances[LAST_FRAME] = 1;
  frame_distances[GOLDEN_FRAME] =
    (xd->frames_since_golden) ? xd->frames_si nce_golden : 1;
  frame_distances[ALTREF_FRAME] =
    (xd->frames_till_alt_ref_frame) ? xd->frames_till_alt_ref_frame : 1;

  if (frame_distances[this_ref_frame] &&
      frame_distances[candidate_ref_frame]) {
    candidate_mv->as_mv.row =
      (short)(((int)(candidate_mv->as_mv.row) *
               frame_distances[this_ref_frame]) /
              frame_distances[candidate_ref_frame]);

    candidate_mv->as_mv.col =
      (short)(((int)(candidate_mv->as_mv.col) *
               frame_distances[this_ref_frame]) /
              frame_distances[candidate_ref_frame]);
  }
  */
}

// 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(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 i;
  MODE_INFO *candidate_mi;
  MB_MODE_INFO * mbmi = &xd->mode_info_context->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];
  int refmv_count = 0;
  int split_count = 0;
  int (*mv_ref_search)[2];
  const int mi_col = get_mi_col(xd);
  // Blank the reference vector lists and other local structures.
  vpx_memset(mv_ref_list, 0, sizeof(int_mv) * MAX_MV_REF_CANDIDATES);
  vpx_memset(candidate_scores, 0, sizeof(candidate_scores));

  if (mbmi->sb_type == BLOCK_SIZE_SB64X64) {
    mv_ref_search = sb64_mv_ref_search;
  } else if (mbmi->sb_type >= BLOCK_SIZE_SB32X32) {
    mv_ref_search = sb_mv_ref_search;
  } else if (mbmi->sb_type >= BLOCK_SIZE_MB16X16) {
    mv_ref_search = mb_mv_ref_search;
  } else {
    mv_ref_search = b_mv_ref_search;
  }

  // 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];

    if ((mi_search_col >= cm->cur_tile_mi_col_start) &&
        (mi_search_col < cm->cur_tile_mi_col_end) &&
        ((mv_ref_search[i][1] << 6) >= xd->mb_to_top_edge)) {

      candidate_mi = here + mv_ref_search[i][0] +
                     (mv_ref_search[i][1] * xd->mode_info_stride);

      if (get_matching_candidate(candidate_mi, ref_frame, &c_refmv)) {
        add_candidate_mv(mv_ref_list, candidate_scores,
                         &refmv_count, c_refmv, 16);
      }
      split_count += (candidate_mi->mbmi.mode == SPLITMV);
    }
  }

  // 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];

    if ((mi_search_col >= cm->cur_tile_mi_col_start) &&
        (mi_search_col < cm->cur_tile_mi_col_end) &&
        ((mv_ref_search[i][1] << 6) >= xd->mb_to_top_edge)) {
      candidate_mi = here + mv_ref_search[i][0] +
                     (mv_ref_search[i][1] * xd->mode_info_stride);

      if (get_matching_candidate(candidate_mi, ref_frame, &c_refmv)) {
        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)) {
      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];

    if ((mi_search_col >= cm->cur_tile_mi_col_start) &&
        (mi_search_col < cm->cur_tile_mi_col_end) &&
        ((mv_ref_search[i][1] << 6) >= xd->mb_to_top_edge)) {
      candidate_mi = here + mv_ref_search[i][0] +
                     (mv_ref_search[i][1] * xd->mode_info_stride);

      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(xd, 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(xd, 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(xd, 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(xd, ref_frame, c2_ref_frame, &c2_refmv, ref_sign_bias);
      add_candidate_mv(mv_ref_list, candidate_scores,
                       &refmv_count, c2_refmv, 1);
    }
  }

  // Define inter mode coding context.
  // 0,0 was best
  if (mv_ref_list[0].as_int == 0) {
    // 0,0 is only candidate
    if (refmv_count <= 1) {
      mbmi->mb_mode_context[ref_frame] = 0;
    // non zero candidates candidates available
    } else if (split_count == 0) {
      mbmi->mb_mode_context[ref_frame] = 1;
    } else {
      mbmi->mb_mode_context[ref_frame] = 2;
    }
  } else if (split_count == 0) {
    // Non zero best, No Split MV cases
    mbmi->mb_mode_context[ref_frame] = candidate_scores[0] >= 16 ? 3 : 4;
  } else {
    // Non zero best, some split mv
    mbmi->mb_mode_context[ref_frame] = candidate_scores[0] >= 16 ? 5 : 6;
  }

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