flac.c
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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 
26 static const int8_t sample_size_table[] = { 0, 8, 12, 0, 16, 20, 24, 0 };
27 
28 static 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 
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;
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);
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 
132 int 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 }