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mpegaudiodecheader.h
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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 {
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 */
54 
55 /* useful helper to get MPEG audio stream info. Return -1 if error in
56  header, otherwise the coded frame size in bytes */
57 int ff_mpa_decode_header(uint32_t head, int *sample_rate,
58  int *channels, int *frame_size, int *bitrate, enum AVCodecID *codec_id);
59 
60 /* fast header check for resync */
61 static inline int ff_mpa_check_header(uint32_t header){
62  /* header */
63  if ((header & 0xffe00000) != 0xffe00000)
64  return -1;
65  /* layer check */
66  if ((header & (3<<17)) == 0)
67  return -1;
68  /* bit rate */
69  if ((header & (0xf<<12)) == 0xf<<12)
70  return -1;
71  /* frequency */
72  if ((header & (3<<10)) == 3<<10)
73  return -1;
74  return 0;
75 }
76 
77 #endif /* AVCODEC_MPEGAUDIODECHEADER_H */
const char * s
Definition: avisynth_c.h:768
channels
Definition: aptx.c:30
static const uint8_t header[24]
Definition: sdr2.c:67
AVCodecID
Identify the syntax and semantics of the bitstream.
Definition: avcodec.h:214
static int ff_mpa_check_header(uint32_t header)
enum AVCodecID codec_id
Definition: vaapi_decode.c:236
sample_rate
int frame_size
Definition: mxfenc.c:1896
Libavcodec external API header.
#define MPA_DECODE_HEADER
int ff_mpa_decode_header(uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bitrate, enum AVCodecID *codec_id)
int avpriv_mpegaudio_decode_header(MPADecodeHeader *s, uint32_t header)