FFmpeg
mpegaudiodecheader.h
Go to the documentation of this file.
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 
47 typedef struct 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 */
55 
56 /* useful helper to get MPEG audio stream info. Return -1 if error in
57  header, otherwise the coded frame size in bytes */
58 int 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 */
62 static 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 */
MPADecodeHeader
Definition: mpegaudiodecheader.h:47
sample_rate
sample_rate
Definition: ffmpeg_filter.c:156
codec_id.h
s
#define s(width, name)
Definition: cbs_vp9.c:257
frame_size
int frame_size
Definition: mxfenc.c:2207
channels
channels
Definition: aptx.h:33
codec_id
enum AVCodecID codec_id
Definition: vaapi_decode.c:369
AVCodecID
AVCodecID
Identify the syntax and semantics of the bitstream.
Definition: codec_id.h:47
ff_mpa_check_header
static int ff_mpa_check_header(uint32_t header)
Definition: mpegaudiodecheader.h:62
header
static const uint8_t header[24]
Definition: sdr2.c:67
MPA_DECODE_HEADER
#define MPA_DECODE_HEADER
Definition: mpegaudiodecheader.h:35
bitrate
int64_t bitrate
Definition: h264_levels.c:131
ff_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)
Definition: mpegaudiodecheader.c:120
xf
#define xf(width, name, var, range_min, range_max, subs,...)
Definition: cbs_av1.c:664
avpriv_mpegaudio_decode_header
int avpriv_mpegaudio_decode_header(MPADecodeHeader *s, uint32_t header)
Definition: mpegaudiodecheader.c:34