1/*
2 * MPEG Audio header decoder
3 * Copyright (c) 2001, 2002 Fabrice Bellard
4 *
5 * This file is part of FFmpeg.
6 *
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.
11 *
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.
16 *
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
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 <stdint.h>
31#include "codec_id.h"
32
33#define MP3_MASK 0xFFFE0CCF
34
35#define MPA_DECODE_HEADER \
36    int frame_size; \
37    int error_protection; \
38    int layer; \
39    int sample_rate; \
40    int sample_rate_index; /* between 0 and 8 */ \
41    int bit_rate; \
42    int nb_channels; \
43    int mode; \
44    int mode_ext; \
45    int lsf;
46
47typedef struct MPADecodeHeader {
48  MPA_DECODE_HEADER
49} MPADecodeHeader;
50
51/* header decoding. MUST check the header before because no
52   consistency check is done there. Return 1 if free format found and
53   that the frame size must be computed externally */
54int avpriv_mpegaudio_decode_header(MPADecodeHeader *s, uint32_t header);
55
56/* useful helper to get MPEG audio stream info. Return -1 if error in
57   header, otherwise the coded frame size in bytes */
58int ff_mpa_decode_header(uint32_t head, int *sample_rate,
59                         int *channels, int *frame_size, int *bitrate, enum AVCodecID *codec_id);
60
61/* fast header check for resync */
62static inline int ff_mpa_check_header(uint32_t header){
63    /* header */
64    if ((header & 0xffe00000) != 0xffe00000)
65        return -1;
66    /* version check */
67    if ((header & (3<<19)) == 1<<19)
68        return -1;
69    /* layer check */
70    if ((header & (3<<17)) == 0)
71        return -1;
72    /* bit rate */
73    if ((header & (0xf<<12)) == 0xf<<12)
74        return -1;
75    /* frequency */
76    if ((header & (3<<10)) == 3<<10)
77        return -1;
78    return 0;
79}
80
81#endif /* AVCODEC_MPEGAUDIODECHEADER_H */
82