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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 "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 | ||
46 | typedef 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 */ | |
53 | int 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 */ | |
57 | int avpriv_mpa_decode_header(AVCodecContext *avctx, uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bitrate); | |
58 | ||
59 | int avpriv_mpa_decode_header2(uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bitrate, enum AVCodecID *codec_id); | |
60 | ||
61 | /* fast header check for resync */ | |
62 | static inline int ff_mpa_check_header(uint32_t header){ | |
63 | /* header */ | |
64 | if ((header & 0xffe00000) != 0xffe00000) | |
65 | return -1; | |
66 | /* layer check */ | |
67 | if ((header & (3<<17)) == 0) | |
68 | return -1; | |
69 | /* bit rate */ | |
70 | if ((header & (0xf<<12)) == 0xf<<12) | |
71 | return -1; | |
72 | /* frequency */ | |
73 | if ((header & (3<<10)) == 3<<10) | |
74 | return -1; | |
75 | return 0; | |
76 | } | |
77 | ||
78 | #endif /* AVCODEC_MPEGAUDIODECHEADER_H */ |