3 * Copyright (c) 2009 Justin Ruggles
5 * This file is part of FFmpeg.
7 * FFmpeg 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.
12 * FFmpeg 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.
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22 #include "libavutil/crc.h"
26 static const int8_t sample_size_table[] = { 0, 8, 12, 0, 16, 20, 24, 0 };
28 static int64_t get_utf8(GetBitContext *gb)
31 GET_UTF8(val, get_bits(gb, 8), return -1;)
35 int ff_flac_decode_frame_header(AVCodecContext *avctx, GetBitContext *gb,
36 FLACFrameInfo *fi, int log_level_offset)
38 int bs_code, sr_code, bps_code;
41 if ((get_bits(gb, 15) & 0x7FFF) != 0x7FFC) {
42 av_log(avctx, AV_LOG_ERROR + log_level_offset, "invalid sync code\n");
46 /* variable block size stream code */
47 fi->is_var_size = get_bits1(gb);
49 /* block size and sample rate codes */
50 bs_code = get_bits(gb, 4);
51 sr_code = get_bits(gb, 4);
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) {
61 av_log(avctx, AV_LOG_ERROR + log_level_offset,
62 "invalid channel mode: %d\n", fi->ch_mode);
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",
74 fi->bps = sample_size_table[bps_code];
78 av_log(avctx, AV_LOG_ERROR + log_level_offset,
79 "broken stream, invalid padding\n");
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");
93 av_log(avctx, AV_LOG_ERROR + log_level_offset,
94 "reserved blocksize code: 0\n");
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;
101 fi->blocksize = ff_flac_blocksize_table[bs_code];
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;
114 av_log(avctx, AV_LOG_ERROR + log_level_offset,
115 "illegal sample rate code %d\n",
120 /* header CRC-8 check */
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");
132 int ff_flac_get_max_frame_size(int blocksize, int ch, int bps)
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
140 count = 16; /* frame header */
141 count += ch * ((7+bps+7)/8); /* subframe headers */
143 /* for stereo, need to account for using decorrelation */
144 count += (( 2*bps+1) * blocksize + 7) / 8;
146 count += ( ch*bps * blocksize + 7) / 8;
148 count += 2; /* frame footer */