libvpx: Pull from upstream

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"
 
 #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
+
+typedef enum {
+  BOTH_ZERO = 0,
+  ZERO_PLUS_PREDICTED = 1,
+  BOTH_PREDICTED = 2,
+  NEW_PLUS_NON_INTRA = 3,
+  BOTH_NEW = 4,
+  INTRA_PLUS_NON_INTRA = 5,
+  BOTH_INTRA = 6,
+  INVALID_CASE = 9
+} motion_vector_context;
+
+// This is used to figure out a context for the ref blocks. The code flattens
+// an array that would have 3 possible counts (0, 1 & 2) for 3 choices by
+// adding 9 for each intra block, 3 for each zero mv and 1 for each new
+// motion vector. This single number is then converted into a context
+// with a single lookup ( counter_to_context ).
+static const int mode_2_counter[MB_MODE_COUNT] = {
+  9,  // DC_PRED
+  9,  // V_PRED
+  9,  // H_PRED
+  9,  // D45_PRED
+  9,  // D135_PRED
+  9,  // D117_PRED
+  9,  // D153_PRED
+  9,  // D207_PRED
+  9,  // D63_PRED
+  9,  // TM_PRED
+  0,  // NEARESTMV
+  0,  // NEARMV
+  3,  // ZEROMV
+  1,  // NEWMV
+};
+
+// There are 3^3 different combinations of 3 counts that can be either 0,1 or
+// 2. However the actual count can never be greater than 2 so the highest
+// counter we need is 18. 9 is an invalid counter that's never used.
+static const int counter_to_context[19] = {
+  BOTH_PREDICTED,  // 0
+  NEW_PLUS_NON_INTRA,  // 1
+  BOTH_NEW,  // 2
+  ZERO_PLUS_PREDICTED,  // 3
+  NEW_PLUS_NON_INTRA,  // 4
+  INVALID_CASE,  // 5
+  BOTH_ZERO,  // 6
+  INVALID_CASE,  // 7
+  INVALID_CASE,  // 8
+  INTRA_PLUS_NON_INTRA,  // 9
+  INTRA_PLUS_NON_INTRA,  // 10
+  INVALID_CASE,  // 11
+  INTRA_PLUS_NON_INTRA,  // 12
+  INVALID_CASE,  // 13
+  INVALID_CASE,  // 14
+  INVALID_CASE,  // 15
+  INVALID_CASE,  // 16
+  INVALID_CASE,  // 17
+  BOTH_INTRA  // 18
+};
+
+static const MV mv_ref_blocks[BLOCK_SIZES][MVREF_NEIGHBOURS] = {
+  // 4X4
+  {{-1, 0}, {0, -1}, {-1, -1}, {-2, 0}, {0, -2}, {-2, -1}, {-1, -2}, {-2, -2}},
+  // 4X8
+  {{-1, 0}, {0, -1}, {-1, -1}, {-2, 0}, {0, -2}, {-2, -1}, {-1, -2}, {-2, -2}},
+  // 8X4
+  {{-1, 0}, {0, -1}, {-1, -1}, {-2, 0}, {0, -2}, {-2, -1}, {-1, -2}, {-2, -2}},
+  // 8X8
+  {{-1, 0}, {0, -1}, {-1, -1}, {-2, 0}, {0, -2}, {-2, -1}, {-1, -2}, {-2, -2}},
+  // 8X16
+  {{0, -1}, {-1, 0}, {1, -1}, {-1, -1}, {0, -2}, {-2, 0}, {-2, -1}, {-1, -2}},
+  // 16X8
   {{-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
+  // 16X16
+  {{-1, 0}, {0, -1}, {-1, 1}, {1, -1}, {-1, -1}, {-3, 0}, {0, -3}, {-3, -3}},
+  // 16X32
+  {{0, -1}, {-1, 0}, {2, -1}, {-1, -1}, {-1, 1}, {0, -3}, {-3, 0}, {-3, -3}},
+  // 32X16
   {{-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
+  // 32X32
+  {{-1, 1}, {1, -1}, {-1, 2}, {2, -1}, {-1, -1}, {-3, 0}, {0, -3}, {-3, -3}},
+  // 32X64
+  {{0, -1}, {-1, 0}, {4, -1}, {-1, 2}, {-1, -1}, {0, -3}, {-3, 0}, {2, -1}},
+  // 64X32
   {{-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}}
-};
+  // 64X64
+  {{-1, 3}, {3, -1}, {-1, 4}, {4, -1}, {-1, -1}, {-1, 0}, {0, -1}, {-1, 6}}
+};
+
+static const int idx_n_column_to_subblock[4][2] = {
+  {1, 2},
+  {1, 3},
+  {3, 2},
+  {3, 3}
+};
+
 // 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 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;
-    }
-  }
+static void clamp_mv_ref(MV *mv, const MACROBLOCKD *xd) {
+  clamp_mv(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);
+}
+
+// This function returns either the appropriate sub block or block's mv
+// on whether the block_size < 8x8 and we have check_sub_blocks set.
+static INLINE int_mv get_sub_block_mv(const MODE_INFO *candidate,
+                                      int check_sub_blocks, int which_mv,
+                                      int search_col, int block_idx) {
+  return check_sub_blocks && candidate->mbmi.sb_type < BLOCK_8X8
+          ? candidate->bmi[idx_n_column_to_subblock[block_idx][search_col == 0]]
+              .as_mv[which_mv]
+          : candidate->mbmi.mv[which_mv];
 }
 
 
 // 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) {
-
-  // 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;
-  }
+static INLINE int_mv scale_mv(const MB_MODE_INFO *mbmi, int ref,
+                              const MV_REFERENCE_FRAME this_ref_frame,
+                              const int *ref_sign_bias) {
+  int_mv mv = mbmi->mv[ref];
+  if (ref_sign_bias[mbmi->ref_frame[ref]] != ref_sign_bias[this_ref_frame]) {
+    mv.as_mv.row *= -1;
+    mv.as_mv.col *= -1;
+  }
+  return mv;
+}
+
+// This macro is used to add a motion vector mv_ref list if it isn't
+// already in the list.  If it's the second motion vector it will also
+// skip all additional processing and jump to done!
+#define ADD_MV_REF_LIST(MV) \
+  do { \
+    if (refmv_count) { \
+      if ((MV).as_int != mv_ref_list[0].as_int) { \
+        mv_ref_list[refmv_count] = (MV); \
+        goto Done; \
+      } \
+    } else { \
+      mv_ref_list[refmv_count++] = (MV); \
+    } \
+  } while (0)
+
+// If either reference frame is different, not INTRA, and they
+// are different from each other scale and add the mv to our list.
+#define IF_DIFF_REF_FRAME_ADD_MV(CANDIDATE) \
+  do { \
+    if ((CANDIDATE)->ref_frame[0] != ref_frame) \
+      ADD_MV_REF_LIST(scale_mv((CANDIDATE), 0, ref_frame, ref_sign_bias)); \
+    if ((CANDIDATE)->ref_frame[1] != ref_frame && \
+        has_second_ref(CANDIDATE) && \
+        (CANDIDATE)->mv[1].as_int != (CANDIDATE)->mv[0].as_int) \
+      ADD_MV_REF_LIST(scale_mv((CANDIDATE), 1, ref_frame, ref_sign_bias)); \
+  } while (0)
+
+
+// Checks that the given mi_row, mi_col and search point
+// are inside the borders of the tile.
+static INLINE int is_inside(const VP9_COMMON *cm, int mi_col, int mi_row,
+                            const MV *mv) {
+  return !(mi_row + mv->row < 0 ||
+           mi_col + mv->col < cm->cur_tile_mi_col_start ||
+           mi_row + mv->row >= cm->mi_rows ||
+           mi_col + mv->col >= cm->cur_tile_mi_col_end);
 }
 
 // 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 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] = { 0 };
-  int refmv_count = 0;
-  const int (*mv_ref_search)[2] = mv_ref_blocks[mbmi->sb_type];
-  const int mi_col = get_mi_col(xd);
-  const int mi_row = get_mi_row(xd);
-  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
+void vp9_find_mv_refs_idx(const VP9_COMMON *cm, const MACROBLOCKD *xd,
+                          MODE_INFO *mi, const MODE_INFO *prev_mi,
+                          MV_REFERENCE_FRAME ref_frame,
+                          int_mv *mv_ref_list,
+                          int block_idx,
+                          int mi_row, int mi_col) {
+  const int *ref_sign_bias = cm->ref_frame_sign_bias;
+  int i, refmv_count = 0;
+  const MV *const mv_ref_search = mv_ref_blocks[mi->mbmi.sb_type];
+  const MB_MODE_INFO *const prev_mbmi = prev_mi ? &prev_mi->mbmi : NULL;
+  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 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] +
-                     (mv_ref_search[i][1] * xd->mode_info_stride);
-
-      if (block_idx >= 0) {
-        if (mv_ref_search[i][0])
-          b = 1 + y_idx * 2;
-        else
-          b = 2 + x_idx;
+    const MV *const mv_ref = &mv_ref_search[i];
+    if (is_inside(cm, mi_col, mi_row, mv_ref)) {
+      const int check_sub_blocks = block_idx >= 0;
+      const MODE_INFO *const candidate_mi = &mi[mv_ref->col + mv_ref->row
+                                                * xd->mode_info_stride];
+      const MB_MODE_INFO *const candidate = &candidate_mi->mbmi;
+      // Keep counts for entropy encoding.
+      context_counter += mode_2_counter[candidate->mode];
+
+      // Check if the candidate comes from the same reference frame.
+      if (candidate->ref_frame[0] == ref_frame) {
+        ADD_MV_REF_LIST(get_sub_block_mv(candidate_mi, check_sub_blocks, 0,
+                                         mv_ref->col, block_idx));
+        different_ref_found = candidate->ref_frame[1] != ref_frame;
       } 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 += (candidate_mi->mbmi.mode < NEARESTMV);
-      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] +
-                     (mv_ref_search[i][1] * xd->mode_info_stride);
-
-      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 (candidate->ref_frame[1] == ref_frame)
+          // Add second motion vector if it has the same ref_frame.
+          ADD_MV_REF_LIST(get_sub_block_mv(candidate_mi, check_sub_blocks, 1,
+                                           mv_ref->col, block_idx));
+        different_ref_found = 1;
       }
     }
   }
 
-  // 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] +
-                     (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);
+  // 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 MV *const mv_ref = &mv_ref_search[i];
+    if (is_inside(cm, mi_col, mi_row, mv_ref)) {
+      const MB_MODE_INFO *const candidate = &mi[mv_ref->col + mv_ref->row
+                                                * xd->mode_info_stride].mbmi;
+
+      if (candidate->ref_frame[0] == ref_frame) {
+        ADD_MV_REF_LIST(candidate->mv[0]);
+        different_ref_found = candidate->ref_frame[1] != ref_frame;
+      } else {
+        if (candidate->ref_frame[1] == ref_frame)
+          ADD_MV_REF_LIST(candidate->mv[1]);
+        different_ref_found = 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);
+  // 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 MV *mv_ref = &mv_ref_search[i];
+      if (is_inside(cm, mi_col, mi_row, mv_ref)) {
+        const MB_MODE_INFO *const candidate = &mi[mv_ref->col + mv_ref->row
+                                                  * xd->mode_info_stride].mbmi;
+
+        // If the candidate is INTRA we don't want to consider its mv.
+        if (is_inter_block(candidate))
+          IF_DIFF_REF_FRAME_ADD_MV(candidate);
+      }
     }
-
-    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);
-    }
-  }
-
-  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;
-  }
+  }
+
+  // Since we still don't have a candidate we'll try the last frame.
+  if (prev_mbmi && is_inter_block(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(xd, &mv_ref_list[i]);
-  }
-}
+  for (i = 0; i < MAX_MV_REF_CANDIDATES; ++i)
+    clamp_mv_ref(&mv_ref_list[i].as_mv, xd);
+}