1/*
2 * MPEG Audio header decoder
3 * Copyright (c) 2001, 2002 Fabrice Bellard
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/**
23 * @file
24 * MPEG Audio header decoder.
25 */
26
27#ifndef AVCODEC_MPEGAUDIODECHEADER_H
28#define AVCODEC_MPEGAUDIODECHEADER_H
29
30#include "avcodec.h"
31
32#define MP3_MASK 0xFFFE0CCF
33
34#define MPA_DECODE_HEADER \
35    int frame_size; \
36    int error_protection; \
37    int layer; \
38    int sample_rate; \
39    int sample_rate_index; /* between 0 and 8 */ \
40    int bit_rate; \
41    int nb_channels; \
42    int mode; \
43    int mode_ext; \
44    int lsf;
45
46typedef struct MPADecodeHeader {
47  MPA_DECODE_HEADER
48} MPADecodeHeader;
49
50/* header decoding. MUST check the header before because no
51   consistency check is done there. Return 1 if free format found and
52   that the frame size must be computed externally */
53int avpriv_mpegaudio_decode_header(MPADecodeHeader *s, uint32_t header);
54
55/* useful helper to get mpeg audio stream infos. Return -1 if error in
56   header, otherwise the coded frame size in bytes */
57int avpriv_mpa_decode_header(AVCodecContext *avctx, uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bitrate);
58
59/* fast header check for resync */
60static inline int ff_mpa_check_header(uint32_t header){
61    /* header */
62    if ((header & 0xffe00000) != 0xffe00000)
63        return -1;
64    /* layer check */
65    if ((header & (3<<17)) == 0)
66        return -1;
67    /* bit rate */
68    if ((header & (0xf<<12)) == 0xf<<12)
69        return -1;
70    /* frequency */
71    if ((header & (3<<10)) == 3<<10)
72        return -1;
73    return 0;
74}
75
76#endif /* AVCODEC_MPEGAUDIODECHEADER_H */
77