shift CABACContext.range right, this reduces the number of shifts needed in get_cabac() and is slightly faster on P3 (and should be much faster on P4 as the P4 except the more recent variants lacks an integer shifter and so shifts have ~10 times longer latency then simple operations like adds)

Originally committed as revision 6702 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 29 insertions, 6 deletions

diff --git a/libavcodec/cabac.c b/libavcodec/cabac.c
index 0cd5144801..91db6c33ea 100644
--- a/libavcodec/cabac.c
+++ b/libavcodec/cabac.c
@@ -51,7 +51,7 @@ static const uint8_t lps_range[64][4]= {
 };
 
 uint8_t ff_h264_mlps_state[4*64];
-uint8_t ff_h264_lps_range[2*65][4];
+uint8_t ff_h264_lps_range[4][2*64];
 uint8_t ff_h264_lps_state[2*64];
 uint8_t ff_h264_mps_state[2*64];
 
@@ -76,8 +76,8 @@ static const uint8_t lps_state[64]= {
  33,33,34,34,35,35,35,36,
  36,36,37,37,37,38,38,63,
 };
-
-const uint8_t ff_h264_norm_shift[128]= {
+#if 0
+const uint8_t ff_h264_norm_shift_old[128]= {
  7,6,5,5,4,4,4,4,3,3,3,3,3,3,3,3,
  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
  1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
@@ -87,6 +87,29 @@ const uint8_t ff_h264_norm_shift[128]= {
  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
 };
+#endif
+const uint8_t ff_h264_norm_shift[512]= {
+ 9,8,7,7,6,6,6,6,5,5,5,5,5,5,5,5,
+ 4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
+ 3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
+ 3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
+ 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
+ 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
+ 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
+ 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
+ 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
+ 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
+ 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
+ 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
+ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
+};
 
 /**
  *
@@ -121,7 +144,7 @@ void ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size){
     c->low =  (*c->bytestream++)<<10;
 #endif
     c->low+= ((*c->bytestream++)<<2) + 2;
-    c->range= 0x1FE<<(CABAC_BITS + 1);
+    c->range= 0x1FE;
 }
 
 void ff_init_cabac_states(CABACContext *c){
@@ -129,8 +152,8 @@ void ff_init_cabac_states(CABACContext *c){
 
     for(i=0; i<64; i++){
         for(j=0; j<4; j++){ //FIXME check if this is worth the 1 shift we save
-            ff_h264_lps_range[2*i+0][j+4]=
-            ff_h264_lps_range[2*i+1][j+4]= lps_range[i][j];
+            ff_h264_lps_range[j][2*i+0]=
+            ff_h264_lps_range[j][2*i+1]= lps_range[i][j];
         }
 
         ff_h264_mlps_state[128+2*i+0]=