diff options
| -rw-r--r-- | liba52/bitstream.c | 8 | ||||
| -rw-r--r-- | liba52/bitstream.h | 33 |
2 files changed, 39 insertions, 2 deletions
diff --git a/liba52/bitstream.c b/liba52/bitstream.c index 0a48cab2c4..9c01de8ff7 100644 --- a/liba52/bitstream.c +++ b/liba52/bitstream.c @@ -31,7 +31,12 @@ #define BUFFER_SIZE 4096 +#ifdef ALT_BITSTREAM_READER +int indx=0; +uint32_t * buffer_start; +#else static uint32_t * buffer_start; +#endif uint32_t bits_left; uint32_t current_word; @@ -43,6 +48,9 @@ void bitstream_set_ptr (uint8_t * buf) align = (int)buf & 3; buffer_start = (uint32_t *) (buf - align); bits_left = 0; +#ifdef ALT_BITSTREAM_READER + indx=0; +#endif bitstream_get (align * 8); } diff --git a/liba52/bitstream.h b/liba52/bitstream.h index 0be249e1f2..0b7e31dcc9 100644 --- a/liba52/bitstream.h +++ b/liba52/bitstream.h @@ -21,6 +21,9 @@ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ +// alternative (faster) bitstram reader (reades upto 3 bytes over the end of the input) +#define ALT_BITSTREAM_READER + /* (stolen from the kernel) */ #ifdef WORDS_BIGENDIAN @@ -46,18 +49,33 @@ # endif #endif +#ifdef ALT_BITSTREAM_READER +extern uint32_t *buffer_start; +extern int indx; +#else extern uint32_t bits_left; extern uint32_t current_word; +#endif void bitstream_set_ptr (uint8_t * buf); uint32_t bitstream_get_bh(uint32_t num_bits); int32_t bitstream_get_bh_2(uint32_t num_bits); + static inline uint32_t -bitstream_get(uint32_t num_bits) +bitstream_get(uint32_t num_bits) // note num_bits is practically a constant due to inlineing { +#ifdef ALT_BITSTREAM_READER + uint32_t result= swab32( *(uint32_t *)(((uint8_t *)buffer_start)+(indx>>3)) ); + + result<<= (indx&0x07); + result>>= 32 - num_bits; + indx+= num_bits; + + return result; +#else uint32_t result; - + if(num_bits < bits_left) { result = (current_word << (32 - bits_left)) >> (32 - num_bits); bits_left -= num_bits; @@ -65,11 +83,21 @@ bitstream_get(uint32_t num_bits) } return bitstream_get_bh(num_bits); +#endif } static inline int32_t bitstream_get_2(uint32_t num_bits) { +#ifdef ALT_BITSTREAM_READER + int32_t result= swab32( *(uint32_t *)(((uint8_t *)buffer_start)+(indx>>3)) ); + + result<<= (indx&0x07); + result>>= 32 - num_bits; + indx+= num_bits; + + return result; +#else int32_t result; if(num_bits < bits_left) { @@ -79,4 +107,5 @@ bitstream_get_2(uint32_t num_bits) } return bitstream_get_bh_2(num_bits); +#endif } |