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