/* * 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; } 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 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++; } } 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; 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 } #endif /* AVCODEC_RANGECODER_H */