mirror of
https://github.com/FFmpeg/FFmpeg.git
synced 2024-12-23 12:43:46 +02:00
126 lines
3.4 KiB
C
126 lines
3.4 KiB
C
/*
|
|
* Range coder
|
|
* Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
|
|
*
|
|
* This library is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU Lesser General Public
|
|
* License as published by the Free Software Foundation; either
|
|
* version 2 of the License, or (at your option) any later version.
|
|
*
|
|
* This library is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
* Lesser General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU Lesser General Public
|
|
* License along with this library; if not, write to the Free Software
|
|
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|
|
*
|
|
*/
|
|
|
|
/**
|
|
* @file rangecoder.h
|
|
* Range coder.
|
|
*/
|
|
|
|
typedef struct RangeCoder{
|
|
int low;
|
|
int range;
|
|
int outstanding_count;
|
|
int outstanding_byte;
|
|
uint8_t zero_state[256];
|
|
uint8_t one_state[256];
|
|
uint8_t *bytestream_start;
|
|
uint8_t *bytestream;
|
|
uint8_t *bytestream_end;
|
|
}RangeCoder;
|
|
|
|
void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size);
|
|
void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf, int buf_size);
|
|
int ff_rac_terminate(RangeCoder *c);
|
|
void ff_build_rac_states(RangeCoder *c, int factor, int max_p);
|
|
|
|
static inline void renorm_encoder(RangeCoder *c){
|
|
//FIXME optimize
|
|
while(c->range < 0x100){
|
|
if(c->outstanding_byte < 0){
|
|
c->outstanding_byte= c->low>>8;
|
|
}else if(c->low <= 0xFF00){
|
|
*c->bytestream++ = c->outstanding_byte;
|
|
for(;c->outstanding_count; c->outstanding_count--)
|
|
*c->bytestream++ = 0xFF;
|
|
c->outstanding_byte= c->low>>8;
|
|
}else if(c->low >= 0x10000){
|
|
*c->bytestream++ = c->outstanding_byte + 1;
|
|
for(;c->outstanding_count; c->outstanding_count--)
|
|
*c->bytestream++ = 0x00;
|
|
c->outstanding_byte= (c->low>>8) & 0xFF;
|
|
}else{
|
|
c->outstanding_count++;
|
|
}
|
|
|
|
c->low = (c->low & 0xFF)<<8;
|
|
c->range <<= 8;
|
|
}
|
|
}
|
|
|
|
static inline void put_rac(RangeCoder *c, uint8_t * const state, int bit){
|
|
int range1= (c->range * (*state)) >> 8;
|
|
|
|
assert(*state);
|
|
assert(range1 < c->range);
|
|
assert(range1 > 0);
|
|
if(!bit){
|
|
c->range -= range1;
|
|
*state= c->zero_state[*state];
|
|
}else{
|
|
c->low += c->range - range1;
|
|
c->range = range1;
|
|
*state= c->one_state[*state];
|
|
}
|
|
|
|
renorm_encoder(c);
|
|
}
|
|
|
|
static inline void refill(RangeCoder *c){
|
|
if(c->range < 0x100){
|
|
c->range <<= 8;
|
|
c->low <<= 8;
|
|
if(c->bytestream < c->bytestream_end)
|
|
c->low+= c->bytestream[0];
|
|
c->bytestream++;
|
|
}
|
|
}
|
|
|
|
static inline int get_rac(RangeCoder *c, uint8_t * const state){
|
|
int range1= (c->range * (*state)) >> 8;
|
|
int attribute_unused one_mask;
|
|
|
|
c->range -= range1;
|
|
#if 1
|
|
if(c->low < c->range){
|
|
*state= c->zero_state[*state];
|
|
refill(c);
|
|
return 0;
|
|
}else{
|
|
c->low -= c->range;
|
|
*state= c->one_state[*state];
|
|
c->range = range1;
|
|
refill(c);
|
|
return 1;
|
|
}
|
|
#else
|
|
one_mask= (c->range - c->low-1)>>31;
|
|
|
|
c->low -= c->range & one_mask;
|
|
c->range += (range1 - c->range) & one_mask;
|
|
|
|
*state= c->zero_state[(*state) + (256&one_mask)];
|
|
|
|
refill(c);
|
|
|
|
return one_mask&1;
|
|
#endif
|
|
}
|
|
|