renormalize VP5/6/7/8 range coder without loop

Originally committed as revision 23915 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/Makefile

@@ -376,7 +376,7 @@ OBJS-$(CONFIG_VP5_DECODER)             += vp5.o vp56.o vp56data.o vp56dsp.o \
 OBJS-$(CONFIG_VP6_DECODER)             += vp6.o vp56.o vp56data.o vp56dsp.o \
                                           vp3dsp.o vp6dsp.o huffman.o
 OBJS-$(CONFIG_VP8_DECODER)             += vp8.o vp8dsp.o vp56.o vp56data.o \
-                                          h264pred.o
+                                          h264pred.o cabac.o
 OBJS-$(CONFIG_VQA_DECODER)             += vqavideo.o
 OBJS-$(CONFIG_WAVPACK_DECODER)         += wavpack.o
 OBJS-$(CONFIG_WMAPRO_DECODER)          += wmaprodec.o wma.o

libavcodec/vp56.h

@@ -28,6 +28,7 @@
 #include "dsputil.h"
 #include "get_bits.h"
 #include "bytestream.h"
+#include "cabac.h"
 #include "vp56dsp.h"
 
 typedef struct vp56_context VP56Context;
@@ -195,6 +196,7 @@ static inline int vp56_rac_get_prob(VP56RangeCoder *c, uint8_t prob)
     unsigned int low = 1 + (((c->high - 1) * prob) >> 8);
     unsigned int low_shift = low << 8;
     int bit = c->code_word >= low_shift;
+    int shift;
 
     if (bit) {
         c->high -= low;
@@ -204,13 +206,13 @@ static inline int vp56_rac_get_prob(VP56RangeCoder *c, uint8_t prob)
     }
 
     /* normalize */
-    while (c->high < 128) {
-        c->high <<= 1;
-        c->code_word <<= 1;
-        if (--c->bits == 0 && c->buffer < c->end) {
-            c->bits = 8;
-            c->code_word |= *c->buffer++;
-        }
+    shift = ff_h264_norm_shift[c->high] - 1;
+    c->high      <<= shift;
+    c->code_word <<= shift;
+    c->bits       -= shift;
+    if(c->bits <= 0 && c->buffer < c->end) {
+        c->code_word |= *c->buffer++ << -c->bits;
+        c->bits += 8;
     }
     return bit;
 }