vpx_rac.h (3697B)
1 /* 2 * Copyright (C) 2006 Aurelien Jacobs <aurel@gnuage.org> 3 * 4 * This file is part of FFmpeg. 5 * 6 * FFmpeg is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU Lesser General Public 8 * License as published by the Free Software Foundation; either 9 * version 2.1 of the License, or (at your option) any later version. 10 * 11 * FFmpeg is distributed in the hope that it will be useful, 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 * Lesser General Public License for more details. 15 * 16 * You should have received a copy of the GNU Lesser General Public 17 * License along with FFmpeg; if not, write to the Free Software 18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 19 */ 20 21 /** 22 * @file 23 * Common VP5-VP9 range decoder stuff 24 */ 25 26 #ifndef AVCODEC_VPX_RAC_H 27 #define AVCODEC_VPX_RAC_H 28 29 #include <stdint.h> 30 31 #include "config.h" 32 #include "libavutil/attributes.h" 33 #include "bytestream.h" 34 35 typedef struct VPXRangeCoder { 36 int high; 37 int bits; /* stored negated (i.e. negative "bits" is a positive number of 38 bits left) in order to eliminate a negate in cache refilling */ 39 const uint8_t *buffer; 40 const uint8_t *end; 41 unsigned int code_word; 42 int end_reached; 43 } VPXRangeCoder; 44 45 extern const uint8_t ff_vpx_norm_shift[256]; 46 int ff_vpx_init_range_decoder(VPXRangeCoder *c, const uint8_t *buf, int buf_size); 47 48 /** 49 * returns 1 if the end of the stream has been reached, 0 otherwise. 50 */ 51 static av_always_inline int vpx_rac_is_end(VPXRangeCoder *c) 52 { 53 if (c->end <= c->buffer && c->bits >= 0) 54 c->end_reached ++; 55 return c->end_reached > 10; 56 } 57 58 static av_always_inline unsigned int vpx_rac_renorm(VPXRangeCoder *c) 59 { 60 int shift = ff_vpx_norm_shift[c->high]; 61 int bits = c->bits; 62 unsigned int code_word = c->code_word; 63 64 c->high <<= shift; 65 code_word <<= shift; 66 bits += shift; 67 if(bits >= 0 && c->buffer < c->end) { 68 code_word |= bytestream_get_be16(&c->buffer) << bits; 69 bits -= 16; 70 } 71 c->bits = bits; 72 return code_word; 73 } 74 75 #if ARCH_ARM 76 #include "arm/vpx_arith.h" 77 #elif ARCH_X86 78 #include "x86/vpx_arith.h" 79 #endif 80 81 #ifndef vpx_rac_get_prob 82 #define vpx_rac_get_prob vpx_rac_get_prob 83 static av_always_inline int vpx_rac_get_prob(VPXRangeCoder *c, uint8_t prob) 84 { 85 unsigned int code_word = vpx_rac_renorm(c); 86 unsigned int low = 1 + (((c->high - 1) * prob) >> 8); 87 unsigned int low_shift = low << 16; 88 int bit = code_word >= low_shift; 89 90 c->high = bit ? c->high - low : low; 91 c->code_word = bit ? code_word - low_shift : code_word; 92 93 return bit; 94 } 95 #endif 96 97 #ifndef vpx_rac_get_prob_branchy 98 // branchy variant, to be used where there's a branch based on the bit decoded 99 static av_always_inline int vpx_rac_get_prob_branchy(VPXRangeCoder *c, int prob) 100 { 101 unsigned long code_word = vpx_rac_renorm(c); 102 unsigned low = 1 + (((c->high - 1) * prob) >> 8); 103 unsigned low_shift = low << 16; 104 105 if (code_word >= low_shift) { 106 c->high -= low; 107 c->code_word = code_word - low_shift; 108 return 1; 109 } 110 111 c->high = low; 112 c->code_word = code_word; 113 return 0; 114 } 115 #endif 116 117 static av_always_inline int vpx_rac_get(VPXRangeCoder *c) 118 { 119 unsigned int code_word = vpx_rac_renorm(c); 120 /* equiprobable */ 121 int low = (c->high + 1) >> 1; 122 unsigned int low_shift = low << 16; 123 int bit = code_word >= low_shift; 124 if (bit) { 125 c->high -= low; 126 code_word -= low_shift; 127 } else { 128 c->high = low; 129 } 130 131 c->code_word = code_word; 132 return bit; 133 } 134 135 #endif /* AVCODEC_VPX_RAC_H */