92 строки
3.2 KiB
C
92 строки
3.2 KiB
C
/*
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* Copyright (c) 2001-2016, Alliance for Open Media. All rights reserved
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*
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* This source code is subject to the terms of the BSD 2 Clause License and
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* the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
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* was not distributed with this source code in the LICENSE file, you can
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* obtain it at www.aomedia.org/license/software. If the Alliance for Open
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* Media Patent License 1.0 was not distributed with this source code in the
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* PATENTS file, you can obtain it at www.aomedia.org/license/patent.
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*/
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#if !defined(_entdec_H)
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#define _entdec_H (1)
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#include <limits.h>
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#include "aom_dsp/entcode.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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typedef struct od_ec_dec od_ec_dec;
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#if defined(OD_ACCOUNTING) && OD_ACCOUNTING
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#define OD_ACC_STR , char *acc_str
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#define od_ec_dec_bits(dec, ftb, str) od_ec_dec_bits_(dec, ftb, str)
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#else
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#define OD_ACC_STR
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#define od_ec_dec_bits(dec, ftb, str) od_ec_dec_bits_(dec, ftb)
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#endif
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/*The entropy decoder context.*/
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struct od_ec_dec {
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/*The start of the current input buffer.*/
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const unsigned char *buf;
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/*The read pointer for the raw bits.*/
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const unsigned char *eptr;
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/*Bits that will be read from/written at the end.*/
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od_ec_window end_window;
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/*Number of valid bits in end_window.*/
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int nend_bits;
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/*An offset used to keep track of tell after reaching the end of the stream.
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This is constant throughout most of the decoding process, but becomes
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important once we hit the end of the buffer and stop incrementing pointers
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(and instead pretend cnt/nend_bits have lots of bits).*/
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int32_t tell_offs;
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/*The end of the current input buffer.*/
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const unsigned char *end;
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/*The read pointer for the entropy-coded bits.*/
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const unsigned char *bptr;
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/*The difference between the coded value and the low end of the current
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range.
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{EC_SMALLMUL} The difference between the high end of the current range,
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(low + rng), and the coded value, minus 1.
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This stores up to OD_EC_WINDOW_SIZE bits of that difference, but the
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decoder only uses the top 16 bits of the window to decode the next symbol.
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As we shift up during renormalization, if we don't have enough bits left in
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the window to fill the top 16, we'll read in more bits of the coded
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value.*/
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od_ec_window dif;
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/*The number of values in the current range.*/
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uint16_t rng;
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/*The number of bits of data in the current value.*/
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int16_t cnt;
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/*Nonzero if an error occurred.*/
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int error;
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};
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/*See entdec.c for further documentation.*/
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void od_ec_dec_init(od_ec_dec *dec, const unsigned char *buf, uint32_t storage)
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OD_ARG_NONNULL(1) OD_ARG_NONNULL(2);
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OD_WARN_UNUSED_RESULT int od_ec_decode_bool_q15(od_ec_dec *dec, unsigned f)
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OD_ARG_NONNULL(1);
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OD_WARN_UNUSED_RESULT int od_ec_decode_cdf_q15(od_ec_dec *dec,
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const uint16_t *cdf, int nsyms)
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OD_ARG_NONNULL(1) OD_ARG_NONNULL(2);
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OD_WARN_UNUSED_RESULT uint32_t od_ec_dec_bits_(od_ec_dec *dec, unsigned ftb)
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OD_ARG_NONNULL(1);
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OD_WARN_UNUSED_RESULT int od_ec_dec_tell(const od_ec_dec *dec)
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OD_ARG_NONNULL(1);
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OD_WARN_UNUSED_RESULT uint32_t od_ec_dec_tell_frac(const od_ec_dec *dec)
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OD_ARG_NONNULL(1);
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#ifdef __cplusplus
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} // extern "C"
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#endif
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#endif
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