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mpegaudio_parser.c
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1 /*
2  * MPEG Audio parser
3  * Copyright (c) 2003 Fabrice Bellard
4  * Copyright (c) 2003 Michael Niedermayer
5  *
6  * This file is part of FFmpeg.
7  *
8  * FFmpeg is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU Lesser General Public
10  * License as published by the Free Software Foundation; either
11  * version 2.1 of the License, or (at your option) any later version.
12  *
13  * FFmpeg is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16  * Lesser General Public License for more details.
17  *
18  * You should have received a copy of the GNU Lesser General Public
19  * License along with FFmpeg; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21  */
22 
23 #include "parser.h"
24 #include "mpegaudiodecheader.h"
25 #include "libavutil/common.h"
26 #include "libavformat/apetag.h" // for APE tag.
27 #include "libavformat/id3v1.h" // for ID3v1_TAG_SIZE
28 
29 typedef struct MpegAudioParseContext {
32  uint32_t header;
36 
37 #define MPA_HEADER_SIZE 4
38 
39 /* header + layer + freq + lsf/mpeg25 */
40 #define SAME_HEADER_MASK \
41  (0xffe00000 | (3 << 17) | (3 << 10) | (3 << 19))
42 
44  AVCodecContext *avctx,
45  const uint8_t **poutbuf, int *poutbuf_size,
46  const uint8_t *buf, int buf_size)
47 {
49  ParseContext *pc = &s->pc;
50  uint32_t state= pc->state;
51  int i;
52  int next= END_NOT_FOUND;
53  int flush = !buf_size;
54 
55  for(i=0; i<buf_size; ){
56  if(s->frame_size){
57  int inc= FFMIN(buf_size - i, s->frame_size);
58  i += inc;
59  s->frame_size -= inc;
60  state = 0;
61 
62  if(!s->frame_size){
63  next= i;
64  break;
65  }
66  }else{
67  while(i<buf_size){
68  int ret, sr, channels, bit_rate, frame_size;
69  enum AVCodecID codec_id = avctx->codec_id;
70 
71  state= (state<<8) + buf[i++];
72 
73  ret = ff_mpa_decode_header(state, &sr, &channels, &frame_size, &bit_rate, &codec_id);
74  if (ret < 4) {
75  if (i > 4)
76  s->header_count = -2;
77  } else {
78  int header_threshold = avctx->codec_id != AV_CODEC_ID_NONE && avctx->codec_id != codec_id;
79  if((state&SAME_HEADER_MASK) != (s->header&SAME_HEADER_MASK) && s->header)
80  s->header_count= -3;
81  s->header= state;
82  s->header_count++;
83  s->frame_size = ret-4;
84 
85  if (s->header_count > header_threshold) {
86  avctx->sample_rate= sr;
87  avctx->channels = channels;
88  s1->duration = frame_size;
89  avctx->codec_id = codec_id;
90  if (s->no_bitrate || !avctx->bit_rate) {
91  s->no_bitrate = 1;
92  avctx->bit_rate += (bit_rate - avctx->bit_rate) / (s->header_count - header_threshold);
93  }
94  }
95 
97  s->frame_size = 0;
98  next = buf_size;
99  } else if (codec_id == AV_CODEC_ID_MP3ADU) {
101  "MP3ADU full parser");
102  return 0; /* parsers must not return error codes */
103  }
104 
105  break;
106  }
107  }
108  }
109  }
110 
111  pc->state= state;
112  if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
113  *poutbuf = NULL;
114  *poutbuf_size = 0;
115  return buf_size;
116  }
117 
118  if (flush && buf_size >= ID3v1_TAG_SIZE && memcmp(buf, "TAG", 3) == 0) {
119  *poutbuf = NULL;
120  *poutbuf_size = 0;
121  return next;
122  }
123 
124  if (flush && buf_size >= APE_TAG_FOOTER_BYTES && memcmp(buf, APE_TAG_PREAMBLE, 8) == 0) {
125  *poutbuf = NULL;
126  *poutbuf_size = 0;
127  return next;
128  }
129 
130  *poutbuf = buf;
131  *poutbuf_size = buf_size;
132  return next;
133 }
134 
135 
138  .priv_data_size = sizeof(MpegAudioParseContext),
139  .parser_parse = mpegaudio_parse,
140  .parser_close = ff_parse_close,
141 };
#define NULL
Definition: coverity.c:32
static void flush(AVCodecContext *avctx)
int64_t bit_rate
the average bitrate
Definition: avcodec.h:1570
channels
Definition: aptx.c:30
#define SAME_HEADER_MASK
int codec_ids[5]
Definition: avcodec.h:5202
int duration
Duration of the current frame.
Definition: avcodec.h:5156
uint8_t
static int mpegaudio_parse(AVCodecParserContext *s1, AVCodecContext *avctx, const uint8_t **poutbuf, int *poutbuf_size, const uint8_t *buf, int buf_size)
AVCodecID
Identify the syntax and semantics of the bitstream.
Definition: avcodec.h:215
int ff_combine_frame(ParseContext *pc, int next, const uint8_t **buf, int *buf_size)
Combine the (truncated) bitstream to a complete frame.
Definition: parser.c:319
preferred ID for decoding MPEG audio layer 1, 2 or 3
Definition: avcodec.h:552
#define APE_TAG_PREAMBLE
Definition: apetag.h:28
void ff_parse_close(AVCodecParserContext *s)
Definition: parser.c:397
#define FFMIN(a, b)
Definition: common.h:96
#define s(width, name)
Definition: cbs_vp9.c:257
enum AVCodecID codec_id
Definition: vaapi_decode.c:362
#define APE_TAG_FOOTER_BYTES
Definition: apetag.h:30
int frame_size
Definition: mxfenc.c:2117
enum AVCodecID codec_id
Definition: avcodec.h:1530
int sample_rate
samples per second
Definition: avcodec.h:2175
main external API structure.
Definition: avcodec.h:1520
void * buf
Definition: avisynth_c.h:690
uint32_t state
contains the last few bytes in MSB order
Definition: parser.h:33
AVCodecParser ff_mpegaudio_parser
#define s1
Definition: regdef.h:38
#define END_NOT_FOUND
Definition: parser.h:40
void avpriv_report_missing_feature(void *avc, const char *msg,...) av_printf_format(2
Log a generic warning message about a missing feature.
static struct @282 state
MPEG Audio header decoder.
common internal and external API header
#define PARSER_FLAG_COMPLETE_FRAMES
Definition: avcodec.h:5068
int ff_mpa_decode_header(uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bit_rate, enum AVCodecID *codec_id)
int channels
number of audio channels
Definition: avcodec.h:2176
#define ID3v1_TAG_SIZE
Definition: id3v1.h:27