text: 
  /*
   *  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 <limits.h>
  
  #include "vp9/common/vp9_common.h"
  #include "vp9/common/vp9_pred_common.h"
  #include "vp9/common/vp9_seg_common.h"
  
  static INLINE const MB_MODE_INFO *get_mbmi(const MODE_INFO *const mi) {
    return (mi != NULL) ? &mi->mbmi : NULL;
  }
  
  // Returns a context number for the given MB prediction signal
  int vp9_get_pred_context_switchable_interp(const MACROBLOCKD *xd) {
    // Note:
    // The mode info data structure has a one element border above and to the
    // left of the entries correpsonding to real macroblocks.
    // The prediction flags in these dummy entries are initialised to 0.
    const MB_MODE_INFO *const left_mbmi = get_mbmi(get_left_mi(xd));
    const int left_type = left_mbmi != NULL && is_inter_block(left_mbmi) ?
                             left_mbmi->interp_filter : SWITCHABLE_FILTERS;
    const MB_MODE_INFO *const above_mbmi = get_mbmi(get_above_mi(xd));
    const int above_type = above_mbmi != NULL && is_inter_block(above_mbmi) ?
                               above_mbmi->interp_filter : SWITCHABLE_FILTERS;
  
    if (left_type == above_type)
      return left_type;
    else if (left_type == SWITCHABLE_FILTERS && above_type != SWITCHABLE_FILTERS)
      return above_type;
    else if (left_type != SWITCHABLE_FILTERS && above_type == SWITCHABLE_FILTERS)
      return left_type;
    else
      return SWITCHABLE_FILTERS;
  }
  
  // The mode info data structure has a one element border above and to the
  // left of the entries corresponding to real macroblocks.
  // The prediction flags in these dummy entries are initialized to 0.
  // 0 - inter/inter, inter/--, --/inter, --/--
  // 1 - intra/inter, inter/intra
  // 2 - intra/--, --/intra
  // 3 - intra/intra
  int vp9_get_intra_inter_context(const MACROBLOCKD *xd) {
    const MB_MODE_INFO *const above_mbmi = get_mbmi(get_above_mi(xd));
    const MB_MODE_INFO *const left_mbmi = get_mbmi(get_left_mi(xd));
    const int has_above = above_mbmi != NULL;
    const int has_left = left_mbmi != NULL;
  
    if (has_above && has_left) {  // both edges available
      const int above_intra = !is_inter_block(above_mbmi);
      const int left_intra = !is_inter_block(left_mbmi);
      return left_intra && above_intra ? 3
                                       : left_intra || above_intra;
    } else if (has_above || has_left) {  // one edge available
      return 2 * !is_inter_block(has_above ? above_mbmi : left_mbmi);
    } else {
      return 0;
    }
  }
  
  int vp9_get_reference_mode_context(const VP9_COMMON *cm,
                                     const MACROBLOCKD *xd) {
    int ctx;
    const MB_MODE_INFO *const above_mbmi = get_mbmi(get_above_mi(xd));
    const MB_MODE_INFO *const left_mbmi = get_mbmi(get_left_mi(xd));
    const int has_above = above_mbmi != NULL;
    const int has_left = left_mbmi != NULL;
    // Note:
    // The mode info data structure has a one element border above and to the
    // left of the entries correpsonding to real macroblocks.
    // The prediction flags in these dummy entries are initialised to 0.
    if (has_above && has_left) {  // both edges available
      if (!has_second_ref(above_mbmi) && !has_second_ref(left_mbmi))
        // neither edge uses comp pred (0/1)
        ctx = (above_mbmi->ref_frame[0] == cm->comp_fixed_ref) ^
              (left_mbmi->ref_frame[0] == cm->comp_fixed_ref);
      else if (!has_second_ref(above_mbmi))
        // one of two edges uses comp pred (2/3)
        ctx = 2 + (above_mbmi->ref_frame[0] == cm->comp_fixed_ref ||
                   !is_inter_block(above_mbmi));
      else if (!has_second_ref(left_mbmi))
        // one of two edges uses comp pred (2/3)
        ctx = 2 + (left_mbmi->ref_frame[0] == cm->comp_fixed_ref ||
                   !is_inter_block(left_mbmi));
      else  // both edges use comp pred (4)
        ctx = 4;
    } else if (has_above || has_left) {  // one edge available
      const MB_MODE_INFO *edge_mbmi = has_above ? above_mbmi : left_mbmi;
  
      if (!has_second_ref(edge_mbmi))
        // edge does not use comp pred (0/1)
        ctx = edge_mbmi->ref_frame[0] == cm->comp_fixed_ref;
      else
        // edge uses comp pred (3)
        ctx = 3;
    } else {  // no edges available (1)
      ctx = 1;
    }
    assert(ctx >= 0 && ctx < COMP_INTER_CONTEXTS);
    return ctx;
  }
  
  // Returns a context number for the given MB prediction signal
  int vp9_get_pred_context_comp_ref_p(const VP9_COMMON *cm,
                                      const MACROBLOCKD *xd) {
    int pred_context;
    const MB_MODE_INFO *const above_mbmi = get_mbmi(get_above_mi(xd));
    const MB_MODE_INFO *const left_mbmi = get_mbmi(get_left_mi(xd));
    const int above_in_image = above_mbmi != NULL;
    const int left_in_image = left_mbmi != NULL;
  
    // Note:
    // The mode info data structure has a one element border above and to the
    // left of the entries correpsonding to real macroblocks.
    // The prediction flags in these dummy entries are initialised to 0.
    const int fix_ref_idx = cm->ref_frame_sign_bias[cm->comp_fixed_ref];
    const int var_ref_idx = !fix_ref_idx;
  
    if (above_in_image && left_in_image) {  // both edges available
      const int above_intra = !is_inter_block(above_mbmi);
      const int left_intra = !is_inter_block(left_mbmi);
  
      if (above_intra && left_intra) {  // intra/intra (2)
        pred_context = 2;
      } else if (above_intra || left_intra) {  // intra/inter
        const MB_MODE_INFO *edge_mbmi = above_intra ? left_mbmi : above_mbmi;
  
        if (!has_second_ref(edge_mbmi))  // single pred (1/3)
          pred_context = 1 + 2 * (edge_mbmi->ref_frame[0] != cm->comp_var_ref[1]);
        else  // comp pred (1/3)
          pred_context = 1 + 2 * (edge_mbmi->ref_frame[var_ref_idx]
                                      != cm->comp_var_ref[1]);
      } else {  // inter/inter
        const int l_sg = !has_second_ref(left_mbmi);
        const int a_sg = !has_second_ref(above_mbmi);
        const MV_REFERENCE_FRAME vrfa = a_sg ? above_mbmi->ref_frame[0]
                                             : above_mbmi->ref_frame[var_ref_idx];
        const MV_REFERENCE_FRAME vrfl = l_sg ? left_mbmi->ref_frame[0]
                                             : left_mbmi->ref_frame[var_ref_idx];
  
        if (vrfa == vrfl && cm->comp_var_ref[1] == vrfa) {
          pred_context = 0;
        } else if (l_sg && a_sg) {  // single/single
          if ((vrfa == cm->comp_fixed_ref && vrfl == cm->comp_var_ref[0]) ||
              (vrfl == cm->comp_fixed_ref && vrfa == cm->comp_var_ref[0]))
            pred_context = 4;
          else if (vrfa == vrfl)
            pred_context = 3;
          else
            pred_context = 1;
        } else if (l_sg || a_sg) {  // single/comp
          const MV_REFERENCE_FRAME vrfc = l_sg ? vrfa : vrfl;
          const MV_REFERENCE_FRAME rfs = a_sg ? vrfa : vrfl;
          if (vrfc == cm->comp_var_ref[1] && rfs != cm->comp_var_ref[1])
            pred_context = 1;
          else if (rfs == cm->comp_var_ref[1] && vrfc != cm->comp_var_ref[1])
            pred_context = 2;
          else
            pred_context = 4;
        } else if (vrfa == vrfl) {  // comp/comp
          pred_context = 4;
        } else {
          pred_context = 2;
        }
      }
    } else if (above_in_image || left_in_image) {  // one edge available
      const MB_MODE_INFO *edge_mbmi = above_in_image ? above_mbmi : left_mbmi;
  
      if (!is_inter_block(edge_mbmi)) {
        pred_context = 2;
      } else {
        if (has_second_ref(edge_mbmi))
          pred_context = 4 * (edge_mbmi->ref_frame[var_ref_idx]
                                != cm->comp_var_ref[1]);
        else
          pred_context = 3 * (edge_mbmi->ref_frame[0] != cm->comp_var_ref[1]);
      }
    } else {  // no edges available (2)
      pred_context = 2;
    }
    assert(pred_context >= 0 && pred_context < REF_CONTEXTS);
  
    return pred_context;
  }
  
  int vp9_get_pred_context_single_ref_p1(const MACROBLOCKD *xd) {
    int pred_context;
    const MB_MODE_INFO *const above_mbmi = get_mbmi(get_above_mi(xd));
    const MB_MODE_INFO *const left_mbmi = get_mbmi(get_left_mi(xd));
    const int has_above = above_mbmi != NULL;
    const int has_left = left_mbmi != NULL;
    // Note:
    // The mode info data structure has a one element border above and to the
    // left of the entries correpsonding to real macroblocks.
    // The prediction flags in these dummy entries are initialised to 0.
    if (has_above && has_left) {  // both edges available
      const int above_intra = !is_inter_block(above_mbmi);
      const int left_intra = !is_inter_block(left_mbmi);
  
      if (above_intra && left_intra) {  // intra/intra
        pred_context = 2;
      } else if (above_intra || left_intra) {  // intra/inter or inter/intra
        const MB_MODE_INFO *edge_mbmi = above_intra ? left_mbmi : above_mbmi;
        if (!has_second_ref(edge_mbmi))
          pred_context = 4 * (edge_mbmi->ref_frame[0] == LAST_FRAME);
        else
          pred_context = 1 + (edge_mbmi->ref_frame[0] == LAST_FRAME ||
                              edge_mbmi->ref_frame[1] == LAST_FRAME);
      } else {  // inter/inter
        const int above_has_second = has_second_ref(above_mbmi);
        const int left_has_second = has_second_ref(left_mbmi);
        const MV_REFERENCE_FRAME above0 = above_mbmi->ref_frame[0];
        const MV_REFERENCE_FRAME above1 = above_mbmi->ref_frame[1];
        const MV_REFERENCE_FRAME left0 = left_mbmi->ref_frame[0];
        const MV_REFERENCE_FRAME left1 = left_mbmi->ref_frame[1];
  
        if (above_has_second && left_has_second) {
          pred_context = 1 + (above0 == LAST_FRAME || above1 == LAST_FRAME ||
                              left0 == LAST_FRAME || left1 == LAST_FRAME);
        } else if (above_has_second || left_has_second) {
          const MV_REFERENCE_FRAME rfs = !above_has_second ? above0 : left0;
          const MV_REFERENCE_FRAME crf1 = above_has_second ? above0 : left0;
          const MV_REFERENCE_FRAME crf2 = above_has_second ? above1 : left1;
  
          if (rfs == LAST_FRAME)
            pred_context = 3 + (crf1 == LAST_FRAME || crf2 == LAST_FRAME);
          else
            pred_context = (crf1 == LAST_FRAME || crf2 == LAST_FRAME);
        } else {
          pred_context = 2 * (above0 == LAST_FRAME) + 2 * (left0 == LAST_FRAME);
        }
      }
    } else if (has_above || has_left) {  // one edge available
      const MB_MODE_INFO *edge_mbmi = has_above ? above_mbmi : left_mbmi;
      if (!is_inter_block(edge_mbmi)) {  // intra
        pred_context = 2;
      } else {  // inter
        if (!has_second_ref(edge_mbmi))
          pred_context = 4 * (edge_mbmi->ref_frame[0] == LAST_FRAME);
        else
          pred_context = 1 + (edge_mbmi->ref_frame[0] == LAST_FRAME ||
                              edge_mbmi->ref_frame[1] == LAST_FRAME);
      }
    } else {  // no edges available
      pred_context = 2;
    }
  
    assert(pred_context >= 0 && pred_context < REF_CONTEXTS);
    return pred_context;
  }
  
  int vp9_get_pred_context_single_ref_p2(const MACROBLOCKD *xd) {
    int pred_context;
    const MB_MODE_INFO *const above_mbmi = get_mbmi(get_above_mi(xd));
    const MB_MODE_INFO *const left_mbmi = get_mbmi(get_left_mi(xd));
    const int has_above = above_mbmi != NULL;
    const int has_left = left_mbmi != NULL;
  
    // Note:
    // The mode info data structure has a one element border above and to the
    // left of the entries correpsonding to real macroblocks.
    // The prediction flags in these dummy entries are initialised to 0.
    if (has_above && has_left) {  // both edges available
      const int above_intra = !is_inter_block(above_mbmi);
      const int left_intra = !is_inter_block(left_mbmi);
  
      if (above_intra && left_intra) {  // intra/intra
        pred_context = 2;
      } else if (above_intra || left_intra) {  // intra/inter or inter/intra
        const MB_MODE_INFO *edge_mbmi = above_intra ? left_mbmi : above_mbmi;
        if (!has_second_ref(edge_mbmi)) {
          if (edge_mbmi->ref_frame[0] == LAST_FRAME)
            pred_context = 3;
          else
            pred_context = 4 * (edge_mbmi->ref_frame[0] == GOLDEN_FRAME);
        } else {
          pred_context = 1 + 2 * (edge_mbmi->ref_frame[0] == GOLDEN_FRAME ||
                                  edge_mbmi->ref_frame[1] == GOLDEN_FRAME);
        }
      } else {  // inter/inter
        const int above_has_second = has_second_ref(above_mbmi);
        const int left_has_second = has_second_ref(left_mbmi);
        const MV_REFERENCE_FRAME above0 = above_mbmi->ref_frame[0];
        const MV_REFERENCE_FRAME above1 = above_mbmi->ref_frame[1];
        const MV_REFERENCE_FRAME left0 = left_mbmi->ref_frame[0];
        const MV_REFERENCE_FRAME left1 = left_mbmi->ref_frame[1];
  
        if (above_has_second && left_has_second) {
          if (above0 == left0 && above1 == left1)
            pred_context = 3 * (above0 == GOLDEN_FRAME ||
                                above1 == GOLDEN_FRAME ||
                                left0 == GOLDEN_FRAME ||
                                left1 == GOLDEN_FRAME);
          else
            pred_context = 2;
        } else if (above_has_second || left_has_second) {
          const MV_REFERENCE_FRAME rfs = !above_has_second ? above0 : left0;
          const MV_REFERENCE_FRAME crf1 = above_has_second ? above0 : left0;
          const MV_REFERENCE_FRAME crf2 = above_has_second ? above1 : left1;
  
          if (rfs == GOLDEN_FRAME)
            pred_context = 3 + (crf1 == GOLDEN_FRAME || crf2 == GOLDEN_FRAME);
          else if (rfs == ALTREF_FRAME)
            pred_context = crf1 == GOLDEN_FRAME || crf2 == GOLDEN_FRAME;
          else
            pred_context = 1 + 2 * (crf1 == GOLDEN_FRAME || crf2 == GOLDEN_FRAME);
        } else {
          if (above0 == LAST_FRAME && left0 == LAST_FRAME) {
            pred_context = 3;
          } else if (above0 == LAST_FRAME || left0 == LAST_FRAME) {
            const MV_REFERENCE_FRAME edge0 = (above0 == LAST_FRAME) ? left0
                                                                    : above0;
            pred_context = 4 * (edge0 == GOLDEN_FRAME);
          } else {
            pred_context = 2 * (above0 == GOLDEN_FRAME) +
                               2 * (left0 == GOLDEN_FRAME);
          }
        }
      }
    } else if (has_above || has_left) {  // one edge available
      const MB_MODE_INFO *edge_mbmi = has_above ? above_mbmi : left_mbmi;
  
      if (!is_inter_block(edge_mbmi) ||
          (edge_mbmi->ref_frame[0] == LAST_FRAME && !has_second_ref(edge_mbmi)))
        pred_context = 2;
      else if (!has_second_ref(edge_mbmi))
        pred_context = 4 * (edge_mbmi->ref_frame[0] == GOLDEN_FRAME);
      else
        pred_context = 3 * (edge_mbmi->ref_frame[0] == GOLDEN_FRAME ||
                            edge_mbmi->ref_frame[1] == GOLDEN_FRAME);
    } else {  // no edges available (2)
      pred_context = 2;
    }
    assert(pred_context >= 0 && pred_context < REF_CONTEXTS);
    return pred_context;
  }
  // Returns a context number for the given MB prediction signal
  // The mode info data structure has a one element border above and to the
  // left of the entries corresponding to real blocks.
  // The prediction flags in these dummy entries are initialized to 0.
  int vp9_get_tx_size_context(const MACROBLOCKD *xd) {
    const int max_tx_size = max_txsize_lookup[xd->mi[0]->mbmi.sb_type];
    const MB_MODE_INFO *const above_mbmi = get_mbmi(get_above_mi(xd));
    const MB_MODE_INFO *const left_mbmi = get_mbmi(get_left_mi(xd));
    const int has_above = above_mbmi != NULL;
    const int has_left = left_mbmi != NULL;
    int above_ctx = (has_above && !above_mbmi->skip) ? (int)above_mbmi->tx_size
                                                     : max_tx_size;
    int left_ctx = (has_left && !left_mbmi->skip) ? (int)left_mbmi->tx_size
                                                  : max_tx_size;
    if (!has_left)
      left_ctx = above_ctx;
  
    if (!has_above)
      above_ctx = left_ctx;
  
    return (above_ctx + left_ctx) > max_tx_size;
  }
  
  int vp9_get_segment_id(VP9_COMMON *cm, const uint8_t *segment_ids,
                         BLOCK_SIZE bsize, int mi_row, int mi_col) {
    const int mi_offset = mi_row * cm->mi_cols + mi_col;
    const int bw = num_8x8_blocks_wide_lookup[bsize];
    const int bh = num_8x8_blocks_high_lookup[bsize];
    const int xmis = MIN(cm->mi_cols - mi_col, bw);
    const int ymis = MIN(cm->mi_rows - mi_row, bh);
    int x, y, segment_id = INT_MAX;
  
    for (y = 0; y < ymis; y++)
      for (x = 0; x < xmis; x++)
        segment_id = MIN(segment_id,
                         segment_ids[mi_offset + y * cm->mi_cols + x]);
  
    assert(segment_id >= 0 && segment_id < MAX_SEGMENTS);
    return segment_id;
  }
  