Modularize intrabc motion vector costs in AV1_COMP

This CL groups intrabc motion vector cost related
variables from AV1_COMP into a new structure
IntraBCMVCosts and adds documentation for the same.

Change-Id: I8ff96a024dcf4a56b3ff2655017e0daa24572306

av1/encoder/encoder.h

diff --git a/av1/encoder/encoder.h b/av1/encoder/encoder.h
index c0cac27..82d00cb 100644
--- a/av1/encoder/encoder.h
+++ b/av1/encoder/encoder.h
@@ -1268,9 +1268,9 @@
   int internal_altref_allowed;
   // A flag to indicate if intrabc is ever used in current frame.
   int intrabc_used;
-  int dv_cost[2][MV_VALS];
-  // TODO(huisu@google.com): we can update dv_joint_cost per SB.
-  int dv_joint_cost[MV_JOINTS];
+
+  // Tables to calculate IntraBC MV cost.
+  IntraBCMVCosts dv_costs;
 
   // Mark which ref frames can be skipped for encoding current frame druing RDO.
   int prune_ref_frame_mask;

av1/encoder/rd.c

diff --git a/av1/encoder/rd.c b/av1/encoder/rd.c
index 3d13cda..e48c771 100644
--- a/av1/encoder/rd.c
+++ b/av1/encoder/rd.c
@@ -605,8 +605,10 @@
   if (!cpi->sf.rt_sf.use_nonrd_pick_mode && frame_is_intra_only(cm) &&
       cm->features.allow_screen_content_tools &&
       !is_stat_generation_stage(cpi)) {
-    int *dvcost[2] = { &cpi->dv_cost[0][MV_MAX], &cpi->dv_cost[1][MV_MAX] };
-    av1_build_nmv_cost_table(cpi->dv_joint_cost, dvcost, &cm->fc->ndvc,
+    IntraBCMVCosts *const dv_costs = &cpi->dv_costs;
+    int *dvcost[2] = { &dv_costs->mv_component[0][MV_MAX],
+                       &dv_costs->mv_component[1][MV_MAX] };
+    av1_build_nmv_cost_table(dv_costs->joint_mv, dvcost, &cm->fc->ndvc,
                              MV_SUBPEL_NONE);
   }
 

av1/encoder/rd.h

diff --git a/av1/encoder/rd.h b/av1/encoder/rd.h
index 34fbe9b..1addbae 100644
--- a/av1/encoder/rd.h
+++ b/av1/encoder/rd.h
@@ -82,6 +82,20 @@
   double mc_saved_base, mc_count_base;
 } RD_OPT;
 
+typedef struct {
+  // Cost of transmitting the actual motion vector.
+  // mv_component[0][i] is the cost of motion vector with horizontal component
+  // (mv_row) equal to i - MV_MAX.
+  // mv_component[1][i] is the cost of motion vector with vertical component
+  // (mv_col) equal to i - MV_MAX.
+  int mv_component[2][MV_VALS];
+
+  // joint_mv[i] is the cost of transmitting joint mv(MV_JOINT_TYPE) of
+  // type i.
+  // TODO(huisu@google.com): we can update dv_joint_cost per SB.
+  int joint_mv[MV_JOINTS];
+} IntraBCMVCosts;
+
 static INLINE void av1_init_rd_stats(RD_STATS *rd_stats) {
 #if CONFIG_RD_DEBUG
   int plane;

av1/encoder/rdopt.c

diff --git a/av1/encoder/rdopt.c b/av1/encoder/rdopt.c
index 9f27786..02afcd1 100644
--- a/av1/encoder/rdopt.c
+++ b/av1/encoder/rdopt.c
@@ -2783,11 +2783,12 @@
     av1_enc_build_inter_predictor(cm, xd, mi_row, mi_col, NULL, bsize, 0,
                                   av1_num_planes(cm) - 1);
 
-    int *dvcost[2] = { (int *)&cpi->dv_cost[0][MV_MAX],
-                       (int *)&cpi->dv_cost[1][MV_MAX] };
+    const IntraBCMVCosts *const dv_costs = &cpi->dv_costs;
+    int *dvcost[2] = { (int *)&dv_costs->mv_component[0][MV_MAX],
+                       (int *)&dv_costs->mv_component[1][MV_MAX] };
     // TODO(aconverse@google.com): The full motion field defining discount
     // in MV_COST_WEIGHT is too large. Explore other values.
-    const int rate_mv = av1_mv_bit_cost(&dv, &dv_ref.as_mv, cpi->dv_joint_cost,
+    const int rate_mv = av1_mv_bit_cost(&dv, &dv_ref.as_mv, dv_costs->joint_mv,
                                         dvcost, MV_COST_WEIGHT_SUB);
     const int rate_mode = x->intrabc_cost[1];
     RD_STATS rd_stats_yuv, rd_stats_y, rd_stats_uv;