[CFL] Compute prediction block DC_PRED as double

The prediction block level DC_PRED is stored and computed as double
instead of int.

Change-Id: I22766c102a7b62d4b5e7621438185808cc0ea8f4

av1/common/cfl.c

@@ -47,7 +47,7 @@ void cfl_dc_pred(MACROBLOCKD *xd, BLOCK_SIZE plane_bsize, TX_SIZE tx_size) {
                                : tx_size_high[tx_size];
 
   // Number of pixel on the top and left borders.
-  const int num_pel = block_width + block_height;
+  const double num_pel = block_width + block_height;
 
   int sum_u = 0;
   int sum_v = 0;
@@ -83,8 +83,8 @@ void cfl_dc_pred(MACROBLOCKD *xd, BLOCK_SIZE plane_bsize, TX_SIZE tx_size) {
     sum_v += block_height * 129;
   }
 
-  xd->cfl->dc_pred[CFL_PRED_U] = (sum_u + (num_pel >> 1)) / num_pel;
-  xd->cfl->dc_pred[CFL_PRED_V] = (sum_v + (num_pel >> 1)) / num_pel;
+  xd->cfl->dc_pred[CFL_PRED_U] = sum_u / num_pel;
+  xd->cfl->dc_pred[CFL_PRED_V] = sum_v / num_pel;
 }
 
 double cfl_ind_to_alpha(const MB_MODE_INFO *const mbmi,
@@ -100,7 +100,7 @@ double cfl_ind_to_alpha(const MB_MODE_INFO *const mbmi,
 
 // Predict the current transform block using CfL.
 void cfl_predict_block(const CFL_CTX *cfl, uint8_t *dst, int dst_stride,
-                       int row, int col, TX_SIZE tx_size, int dc_pred,
+                       int row, int col, TX_SIZE tx_size, double dc_pred,
                        double alpha) {
   const int width = tx_size_wide[tx_size];
   const int height = tx_size_high[tx_size];

av1/common/cfl.h

@@ -37,7 +37,7 @@ typedef struct {
   int subsampling_x, subsampling_y;
 
   // CfL Performs its own block level DC_PRED for each chromatic plane
-  int dc_pred[CFL_PRED_PLANES];
+  double dc_pred[CFL_PRED_PLANES];
 
   // Count the number of TX blocks in a predicted block to know when you are at
   // the last one, so you can check for skips.
@@ -61,7 +61,7 @@ void cfl_dc_pred(MACROBLOCKD *xd, BLOCK_SIZE plane_bsize, TX_SIZE tx_size);
 double cfl_ind_to_alpha(const MB_MODE_INFO *mbmi, CFL_PRED_TYPE pred_type);
 
 void cfl_predict_block(const CFL_CTX *cfl, uint8_t *dst, int dst_stride,
-                       int row, int col, TX_SIZE tx_size, int dc_pred,
+                       int row, int col, TX_SIZE tx_size, double dc_pred,
                        double alpha);
 
 void cfl_store(CFL_CTX *cfl, const uint8_t *input, int input_stride, int row,