Add MIN_TX_SIZE definition

Change-Id: I399d601d40827ac383a6687cbeaec59e9a9c63e4

vp10/common/enums.h

@@ -139,6 +139,8 @@ typedef uint8_t TX_SIZE;
 
 #define MAX_TX_SIZE_LOG2  5
 #define MAX_TX_SIZE       (1 << MAX_TX_SIZE_LOG2)
+#define MIN_TX_SIZE_LOG2  2
+#define MIN_TX_SIZE       (1 << MIN_TX_SIZE_LOG2)
 #define MAX_TX_SQUARE     (MAX_TX_SIZE * MAX_TX_SIZE)
 
 // Number of maxium size transform blocks in the maximum size superblock
@@ -146,6 +148,8 @@ typedef uint8_t TX_SIZE;
   ((MAX_SB_SIZE_LOG2 - MAX_TX_SIZE_LOG2) * 2)
 #define MAX_TX_BLOCKS_IN_MAX_SB (1 << MAX_TX_BLOCKS_IN_MAX_SB_LOG2)
 
+#define MAX_NUM_TXB  (1 << (MAX_SB_SIZE_LOG2 - MIN_TX_SIZE_LOG2))
+
 // frame transform mode
 typedef enum {
   ONLY_4X4            = 0,        // only 4x4 transform used