1/* 2 * FLAC common code 3 * Copyright (c) 2009 Justin Ruggles 4 * 5 * This file is part of Libav. 6 * 7 * Libav is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU Lesser General Public 9 * License as published by the Free Software Foundation; either 10 * version 2.1 of the License, or (at your option) any later version. 11 * 12 * Libav is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 15 * Lesser General Public License for more details. 16 * 17 * You should have received a copy of the GNU Lesser General Public 18 * License along with Libav; if not, write to the Free Software 19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 20 */ 21 22#include "libavutil/crc.h" 23#include "flac.h" 24#include "flacdata.h" 25 26static const int8_t sample_size_table[] = { 0, 8, 12, 0, 16, 20, 24, 0 }; 27 28static int64_t get_utf8(GetBitContext *gb) 29{ 30 int64_t val; 31 GET_UTF8(val, get_bits(gb, 8), return -1;) 32 return val; 33} 34 35int ff_flac_decode_frame_header(AVCodecContext *avctx, GetBitContext *gb, 36 FLACFrameInfo *fi, int log_level_offset) 37{ 38 int bs_code, sr_code, bps_code; 39 40 /* frame sync code */ 41 if ((get_bits(gb, 15) & 0x7FFF) != 0x7FFC) { 42 av_log(avctx, AV_LOG_ERROR + log_level_offset, "invalid sync code\n"); 43 return -1; 44 } 45 46 /* variable block size stream code */ 47 fi->is_var_size = get_bits1(gb); 48 49 /* block size and sample rate codes */ 50 bs_code = get_bits(gb, 4); 51 sr_code = get_bits(gb, 4); 52 53 /* channels and decorrelation */ 54 fi->ch_mode = get_bits(gb, 4); 55 if (fi->ch_mode < FLAC_MAX_CHANNELS) { 56 fi->channels = fi->ch_mode + 1; 57 fi->ch_mode = FLAC_CHMODE_INDEPENDENT; 58 } else if (fi->ch_mode <= FLAC_CHMODE_MID_SIDE) { 59 fi->channels = 2; 60 } else { 61 av_log(avctx, AV_LOG_ERROR + log_level_offset, 62 "invalid channel mode: %d\n", fi->ch_mode); 63 return -1; 64 } 65 66 /* bits per sample */ 67 bps_code = get_bits(gb, 3); 68 if (bps_code == 3 || bps_code == 7) { 69 av_log(avctx, AV_LOG_ERROR + log_level_offset, 70 "invalid sample size code (%d)\n", 71 bps_code); 72 return -1; 73 } 74 fi->bps = sample_size_table[bps_code]; 75 76 /* reserved bit */ 77 if (get_bits1(gb)) { 78 av_log(avctx, AV_LOG_ERROR + log_level_offset, 79 "broken stream, invalid padding\n"); 80 return -1; 81 } 82 83 /* sample or frame count */ 84 fi->frame_or_sample_num = get_utf8(gb); 85 if (fi->frame_or_sample_num < 0) { 86 av_log(avctx, AV_LOG_ERROR + log_level_offset, 87 "sample/frame number invalid; utf8 fscked\n"); 88 return -1; 89 } 90 91 /* blocksize */ 92 if (bs_code == 0) { 93 av_log(avctx, AV_LOG_ERROR + log_level_offset, 94 "reserved blocksize code: 0\n"); 95 return -1; 96 } else if (bs_code == 6) { 97 fi->blocksize = get_bits(gb, 8) + 1; 98 } else if (bs_code == 7) { 99 fi->blocksize = get_bits(gb, 16) + 1; 100 } else { 101 fi->blocksize = ff_flac_blocksize_table[bs_code]; 102 } 103 104 /* sample rate */ 105 if (sr_code < 12) { 106 fi->samplerate = ff_flac_sample_rate_table[sr_code]; 107 } else if (sr_code == 12) { 108 fi->samplerate = get_bits(gb, 8) * 1000; 109 } else if (sr_code == 13) { 110 fi->samplerate = get_bits(gb, 16); 111 } else if (sr_code == 14) { 112 fi->samplerate = get_bits(gb, 16) * 10; 113 } else { 114 av_log(avctx, AV_LOG_ERROR + log_level_offset, 115 "illegal sample rate code %d\n", 116 sr_code); 117 return -1; 118 } 119 120 /* header CRC-8 check */ 121 skip_bits(gb, 8); 122 if (av_crc(av_crc_get_table(AV_CRC_8_ATM), 0, gb->buffer, 123 get_bits_count(gb)/8)) { 124 av_log(avctx, AV_LOG_ERROR + log_level_offset, 125 "header crc mismatch\n"); 126 return -1; 127 } 128 129 return 0; 130} 131 132int ff_flac_get_max_frame_size(int blocksize, int ch, int bps) 133{ 134 /* Technically, there is no limit to FLAC frame size, but an encoder 135 should not write a frame that is larger than if verbatim encoding mode 136 were to be used. */ 137 138 int count; 139 140 count = 16; /* frame header */ 141 count += ch * ((7+bps+7)/8); /* subframe headers */ 142 if (ch == 2) { 143 /* for stereo, need to account for using decorrelation */ 144 count += (( 2*bps+1) * blocksize + 7) / 8; 145 } else { 146 count += ( ch*bps * blocksize + 7) / 8; 147 } 148 count += 2; /* frame footer */ 149 150 return count; 151} 152