0,0 → 1,147 |
/* |
* Range coder |
* Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at> |
* |
* This file is part of FFmpeg. |
* |
* FFmpeg 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 2.1 of the License, or (at your option) any later version. |
* |
* FFmpeg 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 FFmpeg; if not, write to the Free Software |
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
*/ |
|
/** |
* @file |
* Range coder. |
*/ |
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#ifndef AVCODEC_RANGECODER_H |
#define AVCODEC_RANGECODER_H |
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#include <stdint.h> |
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#include "libavutil/common.h" |
#include "libavutil/avassert.h" |
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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; |
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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); |
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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++; |
} |
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c->low = (c->low & 0xFF) << 8; |
c->range <<= 8; |
} |
} |
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static inline int get_rac_count(RangeCoder *c) |
{ |
int x = c->bytestream - c->bytestream_start + c->outstanding_count; |
if (c->outstanding_byte >= 0) |
x++; |
return 8 * x - av_log2(c->range); |
} |
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static inline void put_rac(RangeCoder *c, uint8_t *const state, int bit) |
{ |
int range1 = (c->range * (*state)) >> 8; |
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av_assert2(*state); |
av_assert2(range1 < c->range); |
av_assert2(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]; |
} |
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renorm_encoder(c); |
} |
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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++; |
} |
} |
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static inline int get_rac(RangeCoder *c, uint8_t *const state) |
{ |
int range1 = (c->range * (*state)) >> 8; |
int av_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; |
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c->low -= c->range & one_mask; |
c->range += (range1 - c->range) & one_mask; |
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*state = c->zero_state[(*state) + (256 & one_mask)]; |
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refill(c); |
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return one_mask & 1; |
#endif |
} |
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#endif /* AVCODEC_RANGECODER_H */ |