entdec.h (2945B)
1 /* 2 * Copyright (c) 2001-2016, Alliance for Open Media. All rights reserved. 3 * 4 * This source code is subject to the terms of the BSD 2 Clause License and 5 * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License 6 * was not distributed with this source code in the LICENSE file, you can 7 * obtain it at www.aomedia.org/license/software. If the Alliance for Open 8 * Media Patent License 1.0 was not distributed with this source code in the 9 * PATENTS file, you can obtain it at www.aomedia.org/license/patent. 10 */ 11 12 #ifndef AOM_AOM_DSP_ENTDEC_H_ 13 #define AOM_AOM_DSP_ENTDEC_H_ 14 #include <limits.h> 15 #include "aom_dsp/entcode.h" 16 17 #ifdef __cplusplus 18 extern "C" { 19 #endif 20 21 typedef struct od_ec_dec od_ec_dec; 22 23 #if defined(OD_ACCOUNTING) && OD_ACCOUNTING 24 #define OD_ACC_STR , char *acc_str 25 #define od_ec_dec_bits(dec, ftb, str) od_ec_dec_bits_(dec, ftb, str) 26 #else 27 #define OD_ACC_STR 28 #define od_ec_dec_bits(dec, ftb, str) od_ec_dec_bits_(dec, ftb) 29 #endif 30 31 /*The entropy decoder context.*/ 32 struct od_ec_dec { 33 /*The start of the current input buffer.*/ 34 const unsigned char *buf; 35 /*An offset used to keep track of tell after reaching the end of the stream. 36 This is constant throughout most of the decoding process, but becomes 37 important once we hit the end of the buffer and stop incrementing bptr 38 (and instead pretend cnt has lots of bits).*/ 39 int32_t tell_offs; 40 /*The end of the current input buffer.*/ 41 const unsigned char *end; 42 /*The read pointer for the entropy-coded bits.*/ 43 const unsigned char *bptr; 44 /*The difference between the high end of the current range, (low + rng), and 45 the coded value, minus 1. 46 This stores up to OD_EC_WINDOW_SIZE bits of that difference, but the 47 decoder only uses the top 16 bits of the window to decode the next symbol. 48 As we shift up during renormalization, if we don't have enough bits left in 49 the window to fill the top 16, we'll read in more bits of the coded 50 value.*/ 51 od_ec_window dif; 52 /*The number of values in the current range.*/ 53 uint16_t rng; 54 /*The number of bits of data in the current value.*/ 55 int16_t cnt; 56 }; 57 58 /*See entdec.c for further documentation.*/ 59 60 void od_ec_dec_init(od_ec_dec *dec, const unsigned char *buf, uint32_t storage) 61 OD_ARG_NONNULL(1) OD_ARG_NONNULL(2); 62 63 OD_WARN_UNUSED_RESULT int od_ec_decode_bool_q15(od_ec_dec *dec, unsigned f) 64 OD_ARG_NONNULL(1); 65 OD_WARN_UNUSED_RESULT int od_ec_decode_cdf_q15(od_ec_dec *dec, 66 const uint16_t *cdf, int nsyms) 67 OD_ARG_NONNULL(1) OD_ARG_NONNULL(2); 68 69 OD_WARN_UNUSED_RESULT uint32_t od_ec_dec_bits_(od_ec_dec *dec, unsigned ftb) 70 OD_ARG_NONNULL(1); 71 72 OD_WARN_UNUSED_RESULT int od_ec_dec_tell(const od_ec_dec *dec) 73 OD_ARG_NONNULL(1); 74 OD_WARN_UNUSED_RESULT uint32_t od_ec_dec_tell_frac(const od_ec_dec *dec) 75 OD_ARG_NONNULL(1); 76 77 #ifdef __cplusplus 78 } // extern "C" 79 #endif 80 81 #endif // AOM_AOM_DSP_ENTDEC_H_