Fix bipred and temporal MVP

- Fixes two errors in calculating the POC for the reference frame for
  temporal candidate MV scaling.
- Fixes using the MV for the wrong direction when the temporal MV
  predictor block uses bi-prediction.

Fixes #160.

src/inter.c

@@ -992,17 +992,31 @@ static bool add_temporal_candidate(const encoder_state_t *state,
     return false;
   }
 
-  int cand_list = colocated->inter.mv_dir & (1 << reflist) ? reflist : !reflist;
+  // When there are reference pictures from the future (POC > current POC)
+  // in L0 or L1, the primary list for the colocated PU is the inverse of
+  // collocated_from_l0_flag. Otherwise it is equal to reflist.
+  //
+  // In Kvazaar, the L1 list is only used for future pictures and the slice
+  // type is set to KVZ_SLICE_B if and only if L1 is used. Therefore we can
+  // simply check the slice type here. Kvazaar always sets
+  // collocated_from_l0_flag so the list is L1 for B-slices.
+  int col_list = state->frame->slicetype == KVZ_SLICE_P ? reflist : 1;
+
+  if ((colocated->inter.mv_dir & (col_list + 1)) == 0) {
+    // Use the other list if the colocated PU does not have a MV for the
+    // primary list.
+    col_list = 1 - col_list;
+  }
 
-  mv_out[0] = colocated->inter.mv[cand_list][0];
-  mv_out[1] = colocated->inter.mv[cand_list][1];
+  mv_out[0] = colocated->inter.mv[col_list][0];
+  mv_out[1] = colocated->inter.mv[col_list][1];
   apply_mv_scaling_pocs(
     state->frame->poc,
     state->frame->ref->pocs[current_ref],
     state->frame->ref->pocs[colocated_ref],
     state->frame->ref->images[colocated_ref]->ref_pocs[
       state->frame->ref->ref_LXs[colocated_ref]
-        [cand_list][colocated->inter.mv_ref[cand_list]]],
+        [col_list][colocated->inter.mv_ref[col_list]]],
     mv_out
   );
 
@@ -1124,7 +1138,8 @@ static void get_mv_cand_from_candidates(const encoder_state_t * const state,
                                              state->frame->ref_LX[reflist][cur_cu->inter.mv_ref[reflist]],
                                              (h != NULL) ? h : c3,
                                              reflist,
-                                             mv_cand[candidates])) {
+                                             mv_cand[candidates]))
+  {
     candidates++;
   }
 
@@ -1252,16 +1267,14 @@ static bool add_merge_candidate(const cu_info_t *cand,
  * \param use_b1    true, if candidate b1 can be used
  * \param mv_cand   Returns the merge candidates.
  * \param lcu       lcu containing the block
- * \param ref_idx   current reference index (used only by TMVP)
  * \return          number of merge candidates
  */
 uint8_t kvz_inter_get_merge_cand(const encoder_state_t * const state,
                                  int32_t x, int32_t y,
                                  int32_t width, int32_t height,
                                  bool use_a1, bool use_b1,
                                  inter_merge_cand_t mv_cand[MRG_MAX_NUM_CANDS],
-                                 lcu_t *lcu,
-                                 uint8_t ref_idx)
+                                 lcu_t *lcu)
 {
   uint8_t candidates = 0;
   int8_t zero_idx = 0;
@@ -1306,7 +1319,9 @@ uint8_t kvz_inter_get_merge_cand(const encoder_state_t * const state,
         (merge_cand.h != NULL) ? merge_cand.h : merge_cand.c3;
 
       if (add_temporal_candidate(state,
-                                 ref_idx,
+                                 // Reference index 0 is always used for
+                                 // the temporal merge candidate.
+                                 state->frame->ref_LX[reflist][0],
                                  temporal_cand,
                                  reflist,
                                  mv_cand[candidates].mv[reflist])) {

src/inter.h

@@ -85,6 +85,5 @@ uint8_t kvz_inter_get_merge_cand(const encoder_state_t * const state,
                                  int32_t width, int32_t height,
                                  bool use_a1, bool use_b1,
                                  inter_merge_cand_t mv_cand[MRG_MAX_NUM_CANDS],
-                                 lcu_t *lcu,
-                                 uint8_t ref_idx);
+                                 lcu_t *lcu);
 #endif

src/search_inter.c

@@ -1303,35 +1303,20 @@ static void search_pu_inter(encoder_state_t * const state,
   };
 
   // Search for merge mode candidates
-  if (!cfg->tmvp_enable) {
-    info.num_merge_cand = kvz_inter_get_merge_cand(
-        state,
-        x, y,
-        width, height,
-        merge_a1, merge_b1,
-        info.merge_cand,
-        lcu,
-        0
-    );
-  }
+  info.num_merge_cand = kvz_inter_get_merge_cand(
+      state,
+      x, y,
+      width, height,
+      merge_a1, merge_b1,
+      info.merge_cand,
+      lcu
+  );
 
   // Default to candidate 0
   CU_SET_MV_CAND(cur_cu, 0, 0);
   CU_SET_MV_CAND(cur_cu, 1, 0);
 
   for (int ref_idx = 0; ref_idx < state->frame->ref->used_size; ref_idx++) {
-    if (cfg->tmvp_enable) {
-      // Get list of candidates, TMVP required MV scaling for each reference
-      info.num_merge_cand = kvz_inter_get_merge_cand(
-          state,
-          x, y,
-          width, height,
-          merge_a1, merge_b1,
-          info.merge_cand,
-          lcu,
-          ref_idx
-      );
-    }
     info.ref_idx = ref_idx;
     info.ref = state->frame->ref->images[ref_idx];