Add init_scan_order()

init_scan_order will set non_zero_prob at every position in the block to
0.5 and then sort the non_zero_prob to get a zig zag scan order as
initialize scan order

Change-Id: I5cd9379b16e7a601e89783cc8a59355429a1f0c2

av1/common/entropymode.c

@@ -11,6 +11,7 @@
 
 #include "aom_mem/aom_mem.h"
 
+#include "av1/common/scan.h"
 #include "av1/common/onyxc_int.h"
 #include "av1/common/seg_common.h"
 
@@ -1169,6 +1170,10 @@ void av1_setup_past_independence(AV1_COMMON *cm) {
   av1_default_coef_probs(cm);
   init_mode_probs(cm->fc);
   av1_init_mv_probs(cm);
+#if CONFIG_ADAPT_SCAN
+  init_scan_order(cm);
+#endif
+
   cm->fc->initialized = 1;
 
   if (cm->frame_type == KEY_FRAME || cm->error_resilient_mode ||

av1/common/scan.c

@@ -950,4 +950,20 @@ void update_scan_order_facade(AV1_COMMON *cm, TX_SIZE tx_size,
   update_neighbors(tx_size, scan, iscan, nb);
 }
 
+void init_scan_order(AV1_COMMON *cm) {
+  TX_SIZE tx_size;
+  TX_TYPE tx_type;
+  for (tx_size = TX_4X4; tx_size < TX_SIZES; ++tx_size) {
+    for (tx_type = DCT_DCT; tx_type < TX_TYPES; ++tx_type) {
+      uint32_t *non_zero_prob = get_non_zero_prob(cm->fc, tx_size, tx_type);
+      int tx2d_size = get_tx2d_size(tx_size);
+      int i;
+      for (i = 0; i < tx2d_size; ++i) {
+        non_zero_prob[i] = (1 << 16) / 2;  // init non_zero_prob to 0.5
+      }
+      update_scan_order_facade(cm, tx_size, tx_type);
+    }
+  }
+}
+
 #endif

av1/common/scan.h

@@ -59,6 +59,7 @@ void update_scan_order(TX_SIZE tx_size, int16_t *sort_order, int16_t *scan,
 // neighbors[] accordingly.
 void update_neighbors(int tx_size, const int16_t *scan, const int16_t *iscan,
                       int16_t *neighbors);
+void init_scan_order(AV1_COMMON *cm);
 #endif
 
 static INLINE int get_coef_context(const int16_t *neighbors,