avcodec/lagarithrac: increase LUT from 256 to 1024 bytes

about 2 cycles (~1%) faster lag_get_rac()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/lagarithrac.c

@@ -45,9 +45,9 @@ void ff_lag_rac_init(lag_rac *l, GetBitContext *gb, int length)
 
     l->range        = 0x80;
     l->low          = *l->bytestream >> 1;
-    l->hash_shift   = FFMAX((int)l->scale - 8, 0);
+    l->hash_shift   = FFMAX((int)l->scale - 10, 0);
 
-    for (i = j = 0; i < 256; i++) {
+    for (i = j = 0; i < 1024; i++) {
         unsigned r = i << l->hash_shift;
         while (l->prob[j + 1] <= r)
             j++;

libavcodec/lagarithrac.h

@@ -48,7 +48,7 @@ typedef struct lag_rac {
     const uint8_t *bytestream_end;    /**< End position of input bytestream. */
 
     uint32_t prob[258];         /**< Table of cumulative probability for each symbol. */
-    uint8_t  range_hash[256];   /**< Hash table mapping upper byte to approximate symbol. */
+    uint8_t  range_hash[1024];   /**< Hash table mapping upper byte to approximate symbol. */
 } lag_rac;
 
 void ff_lag_rac_init(lag_rac *l, GetBitContext *gb, int length);