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get_vlc() optimization 

Originally committed as revision 735 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2002-07-10 17:32:59 +00:00
parent 82dd7d0dec
commit cceabc8656
2 changed files with 39 additions and 49 deletions
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2
libavcodec/common.c
View File

@ -286,7 +286,7 @@ static int build_table(VLC *vlc, int table_nb_bits,
return -1;
/* note: realloc has been done, so reload tables */
table = &vlc->table[table_index];
table[i][0] = index; //code
table[i][0] = index - table_index; //code
}
}
return table_index;

86
libavcodec/common.h
View File

@ -732,64 +732,54 @@ int init_vlc(VLC *vlc, int nb_bits, int nb_codes,
const void *codes, int codes_wrap, int codes_size);
void free_vlc(VLC *vlc);
//note table will be trashed (pointer increased)
#define GET_VLC(code, name, gb, table, bits, max_depth)\
{\
int n, index, nb_bits;\
\
index= SHOW_UBITS(name, gb, bits);\
code = table[index][0];\
n = table[index][1];\
\
if(max_depth > 1 && n < 0){\
LAST_SKIP_BITS(name, gb, bits)\
UPDATE_CACHE(name, gb)\
\
nb_bits = -n;\
table += code;\
\
index= SHOW_UBITS(name, gb, nb_bits);\
code = table[index][0];\
n = table[index][1];\
if(max_depth > 2 && n < 0){\
LAST_SKIP_BITS(name, gb, nb_bits)\
UPDATE_CACHE(name, gb)\
\
nb_bits = -n;\
table += code;\
\
index= SHOW_UBITS(name, gb, nb_bits);\
code = table[index][0];\
n = table[index][1];\
}\
}\
SKIP_BITS(name, gb, n)\
}
static inline int get_vlc(GetBitContext *s, VLC *vlc)
{
int code, n, nb_bits, index;
VLC_TYPE (*table)[2];
int code;
VLC_TYPE (*table)[2]= vlc->table;
OPEN_READER(re, s)
UPDATE_CACHE(re, s)
nb_bits = vlc->bits;
table = vlc->table;
GET_VLC(code, re, s, table, vlc->bits, 3)
#ifdef FAST_GET_FIRST_VLC
index= SHOW_UBITS(re, s, nb_bits);
code = table[index][0];
n = table[index][1];
if (n > 0) {
/* most common case (90%)*/
LAST_SKIP_BITS(re, s, n)
CLOSE_READER(re, s)
return code;
} else if (n == 0) {
return -1;
} else {
LAST_SKIP_BITS(re, s, nb_bits)
UPDATE_CACHE(re, s) //this isnt needed but its faster if its here
nb_bits = -n;
table = vlc->table + code;
}
#endif
for(;;) {
index= SHOW_UBITS(re, s, nb_bits);
code = table[index][0];
n = table[index][1];
if (n > 0) {
/* most common case */
SKIP_BITS(re, s, n)
#ifdef STATS
st_bit_counts[st_current_index] += n;
#endif
break;
} else if (n == 0) {
return -1;
} else {
LAST_SKIP_BITS(re, s, nb_bits)
UPDATE_CACHE(re, s)
#ifdef STATS
st_bit_counts[st_current_index] += nb_bits;
#endif
nb_bits = -n;
table = vlc->table + code;
}
}
CLOSE_READER(re, s)
return code;
}
/* define it to include statistics code (useful only for optimizing
codec efficiency */
//#define STATS