| /* |
| * 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. |
| */ |
| |
| #ifndef AVCODEC_RANGECODER_H |
| #define AVCODEC_RANGECODER_H |
| |
| #include <stdint.h> |
| |
| #include "libavutil/common.h" |
| #include "libavutil/avassert.h" |
| |
| 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; |
| int overread; |
| #define MAX_OVERREAD 2 |
| } 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); |
| |
| /** |
| * Terminates the range coder |
| * @param version version 0 requires the decoder to know the data size in bytes |
| * version 1 needs about 1 bit more space but does not need to |
| * carry the size from encoder to decoder |
| */ |
| int ff_rac_terminate(RangeCoder *c, int version); |
| |
| /** |
| * Check if at the current position there is a valid looking termination |
| * @param version version 0 requires the decoder to know the data size in bytes |
| * version 1 needs about 1 bit more space but does not need to |
| * carry the size from encoder to decoder |
| * @returns negative AVERROR code on error or non negative. |
| */ |
| int ff_rac_check_termination(RangeCoder *c, int version); |
| |
| 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 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); |
| } |
| |
| static inline void put_rac(RangeCoder *c, uint8_t *const state, int bit) |
| { |
| int range1 = (c->range * (*state)) >> 8; |
| |
| 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]; |
| } |
| |
| 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++; |
| } else |
| c->overread ++; |
| } |
| } |
| |
| static inline int get_rac(RangeCoder *c, uint8_t *const state) |
| { |
| int range1 = (c->range * (*state)) >> 8; |
| |
| c->range -= range1; |
| 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; |
| } |
| } |
| |
| #endif /* AVCODEC_RANGECODER_H */ |