vpx/vp8/common/findnearmv.c

/*
 *  Copyright (c) 2010 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 "findnearmv.h"

const unsigned char vp8_mbsplit_offset[4][16] = {
  { 0,  8,  0,  0,  0,  0,  0,  0,  0,  0,   0,  0,  0,  0,  0,  0},
  { 0,  2,  0,  0,  0,  0,  0,  0,  0,  0,   0,  0,  0,  0,  0,  0},
  { 0,  2,  8, 10,  0,  0,  0,  0,  0,  0,   0,  0,  0,  0,  0,  0},
  { 0,  1,  2,  3,  4,  5,  6,  7,  8,  9,  10, 11, 12, 13, 14, 15}
};

/* Predict motion vectors using those from already-decoded nearby blocks.
   Note that we only consider one 4x4 subblock from each candidate 16x16
   macroblock.   */

void vp8_find_near_mvs
(
  MACROBLOCKD *xd,
  const MODE_INFO *here,
  const MODE_INFO *lf_here,
  int_mv *nearest,
  int_mv *nearby,
  int_mv *best_mv,
  int cnt[4],
  int refframe,
  int *ref_frame_sign_bias
) {
  const MODE_INFO *above = here - xd->mode_info_stride;
  const MODE_INFO *left = here - 1;
  const MODE_INFO *aboveleft = above - 1;
  const MODE_INFO *third = NULL;
  int_mv            near_mvs[4];
  int_mv           *mv = near_mvs;
  int             *cntx = cnt;
  enum {CNT_INTRA, CNT_NEAREST, CNT_NEAR, CNT_SPLITMV};

  /* Zero accumulators */
  mv[0].as_int = mv[1].as_int = mv[2].as_int = 0;
  cnt[0] = cnt[1] = cnt[2] = cnt[3] = 0;

  /* Process above */
  if (above->mbmi.ref_frame != INTRA_FRAME) {
    if (above->mbmi.mv.as_int) {
      (++mv)->as_int = above->mbmi.mv.as_int;
      mv_bias(ref_frame_sign_bias[above->mbmi.ref_frame],
              refframe, mv, ref_frame_sign_bias);
      ++cntx;
    }
    *cntx += 2;
  }

  /* Process left */
  if (left->mbmi.ref_frame != INTRA_FRAME) {
    if (left->mbmi.mv.as_int) {
      int_mv this_mv;
      this_mv.as_int = left->mbmi.mv.as_int;
      mv_bias(ref_frame_sign_bias[left->mbmi.ref_frame],
              refframe, &this_mv, ref_frame_sign_bias);

      if (this_mv.as_int != mv->as_int) {
        (++mv)->as_int = this_mv.as_int;
        ++cntx;
      }
      *cntx += 2;
    } else
      cnt[CNT_INTRA] += 2;
  }
  /* Process above left or the one from last frame */
  if (aboveleft->mbmi.ref_frame != INTRA_FRAME ||
      (lf_here->mbmi.ref_frame == LAST_FRAME && refframe == LAST_FRAME)) {
    if (aboveleft->mbmi.mv.as_int) {
      third = aboveleft;
    } else if (lf_here->mbmi.mv.as_int) {
      third = lf_here;
    }
    if (third) {
      int_mv this_mv;
      this_mv.as_int = third->mbmi.mv.as_int;
      mv_bias(ref_frame_sign_bias[third->mbmi.ref_frame],
              refframe, &this_mv, ref_frame_sign_bias);

      if (this_mv.as_int != mv->as_int) {
        (++mv)->as_int = this_mv.as_int;
        ++cntx;
      }
      *cntx += 1;
    } else
      cnt[CNT_INTRA] += 1;
  }

  /* If we have three distinct MV's ... */
  if (cnt[CNT_SPLITMV]) {
    /* See if the third MV can be merged with NEAREST */
    if (mv->as_int == near_mvs[CNT_NEAREST].as_int)
      cnt[CNT_NEAREST] += 1;
  }

  cnt[CNT_SPLITMV] = ((above->mbmi.mode == SPLITMV)
                      + (left->mbmi.mode == SPLITMV)) * 2
                     + (
                       lf_here->mbmi.mode == SPLITMV ||
                       aboveleft->mbmi.mode == SPLITMV);

  /* Swap near and nearest if necessary */
  if (cnt[CNT_NEAR] > cnt[CNT_NEAREST]) {
    int tmp;
    tmp = cnt[CNT_NEAREST];
    cnt[CNT_NEAREST] = cnt[CNT_NEAR];
    cnt[CNT_NEAR] = tmp;
    tmp = near_mvs[CNT_NEAREST].as_int;
    near_mvs[CNT_NEAREST].as_int = near_mvs[CNT_NEAR].as_int;
    near_mvs[CNT_NEAR].as_int = tmp;
  }

  /* Use near_mvs[0] to store the "best" MV */
  if (cnt[CNT_NEAREST] >= cnt[CNT_INTRA])
    near_mvs[CNT_INTRA] = near_mvs[CNT_NEAREST];

  /* Set up return values */
  best_mv->as_int = near_mvs[0].as_int;
  nearest->as_int = near_mvs[CNT_NEAREST].as_int;
  nearby->as_int = near_mvs[CNT_NEAR].as_int;

  /* Make sure that the 1/8th bits of the Mvs are zero if high_precision
   * is not being used, by truncating the last bit towards 0
   */
#if CONFIG_HIGH_PRECISION_MV
  if (!xd->allow_high_precision_mv) {
    if (best_mv->as_mv.row & 1)
      best_mv->as_mv.row += (best_mv->as_mv.row > 0 ? -1 : 1);
    if (best_mv->as_mv.col & 1)
      best_mv->as_mv.col += (best_mv->as_mv.col > 0 ? -1 : 1);
    if (nearest->as_mv.row & 1)
      nearest->as_mv.row += (nearest->as_mv.row > 0 ? -1 : 1);
    if (nearest->as_mv.col & 1)
      nearest->as_mv.col += (nearest->as_mv.col > 0 ? -1 : 1);
    if (nearby->as_mv.row & 1)
      nearby->as_mv.row += (nearby->as_mv.row > 0 ? -1 : 1);
    if (nearby->as_mv.col & 1)
      nearby->as_mv.col += (nearby->as_mv.col > 0 ? -1 : 1);
  }
#endif

  // TODO: move clamp outside findnearmv
  vp8_clamp_mv2(nearest, xd);
  vp8_clamp_mv2(nearby, xd);
  vp8_clamp_mv2(best_mv, xd);
}

vp8_prob *vp8_mv_ref_probs(VP8_COMMON *pc,
                           vp8_prob p[VP8_MVREFS - 1], const int near_mv_ref_ct[4]
                          ) {
  p[0] = pc->fc.vp8_mode_contexts [near_mv_ref_ct[0]] [0];
  p[1] = pc->fc.vp8_mode_contexts [near_mv_ref_ct[1]] [1];
  p[2] = pc->fc.vp8_mode_contexts [near_mv_ref_ct[2]] [2];
  p[3] = pc->fc.vp8_mode_contexts [near_mv_ref_ct[3]] [3];
  return p;
}