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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/id3v1.h" // for ID3v1_TAG_SIZE
27 
28 typedef struct MpegAudioParseContext {
31  uint32_t header;
35 
36 #define MPA_HEADER_SIZE 4
37 
38 /* header + layer + bitrate + freq + lsf/mpeg25 */
39 #define SAME_HEADER_MASK \
40  (0xffe00000 | (3 << 17) | (3 << 10) | (3 << 19))
41 
43  AVCodecContext *avctx,
44  const uint8_t **poutbuf, int *poutbuf_size,
45  const uint8_t *buf, int buf_size)
46 {
48  ParseContext *pc = &s->pc;
49  uint32_t state= pc->state;
50  int i;
51  int next= END_NOT_FOUND;
52  int flush = !buf_size;
53 
54  for(i=0; i<buf_size; ){
55  if(s->frame_size){
56  int inc= FFMIN(buf_size - i, s->frame_size);
57  i += inc;
58  s->frame_size -= inc;
59  state = 0;
60 
61  if(!s->frame_size){
62  next= i;
63  break;
64  }
65  }else{
66  while(i<buf_size){
67  int ret, sr, channels, bit_rate, frame_size;
68  enum AVCodecID codec_id = avctx->codec_id;
69 
70  state= (state<<8) + buf[i++];
71 
72  ret = avpriv_mpa_decode_header2(state, &sr, &channels, &frame_size, &bit_rate, &codec_id);
73  if (ret < 4) {
74  if (i > 4)
75  s->header_count = -2;
76  } else {
77  int header_threshold = avctx->codec_id != AV_CODEC_ID_NONE && avctx->codec_id != codec_id;
78  if((state&SAME_HEADER_MASK) != (s->header&SAME_HEADER_MASK) && s->header)
79  s->header_count= -3;
80  s->header= state;
81  s->header_count++;
82  s->frame_size = ret-4;
83 
84  if (s->header_count > header_threshold) {
85  avctx->sample_rate= sr;
86  avctx->channels = channels;
87  s1->duration = frame_size;
88  avctx->codec_id = codec_id;
89  if (s->no_bitrate || !avctx->bit_rate) {
90  s->no_bitrate = 1;
91  avctx->bit_rate += (bit_rate - avctx->bit_rate) / (s->header_count - header_threshold);
92  }
93  }
94 
96  s->frame_size = 0;
97  next = buf_size;
98  } else if (codec_id == AV_CODEC_ID_MP3ADU) {
100  "MP3ADU full parser");
101  return AVERROR_PATCHWELCOME;
102  }
103 
104  break;
105  }
106  }
107  }
108  }
109 
110  pc->state= state;
111  if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
112  *poutbuf = NULL;
113  *poutbuf_size = 0;
114  return buf_size;
115  }
116 
117  if (flush && buf_size >= ID3v1_TAG_SIZE && memcmp(buf, "TAG", 3) == 0) {
118  *poutbuf = NULL;
119  *poutbuf_size = 0;
120  return next;
121  }
122 
123  *poutbuf = buf;
124  *poutbuf_size = buf_size;
125  return next;
126 }
127 
128 
131  .priv_data_size = sizeof(MpegAudioParseContext),
132  .parser_parse = mpegaudio_parse,
133  .parser_close = ff_parse_close,
134 };
#define NULL
Definition: coverity.c:32
const char * s
Definition: avisynth_c.h:631
static void flush(AVCodecContext *avctx)
#define SAME_HEADER_MASK
int codec_ids[5]
Definition: avcodec.h:4718
int duration
Duration of the current frame.
Definition: avcodec.h:4672
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:102
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:231
#define PARSER_FLAG_COMPLETE_FRAMES
Definition: avcodec.h:4573
preferred ID for decoding MPEG audio layer 1, 2 or 3
Definition: avcodec.h:425
enum AVCodecID codec_id
Definition: mov_chan.c:433
void ff_parse_close(AVCodecParserContext *s)
Definition: parser.c:307
int bit_rate
the average bitrate
Definition: avcodec.h:1566
#define FFMIN(a, b)
Definition: common.h:66
ret
Definition: avfilter.c:974
static struct @197 state
#define AVERROR_PATCHWELCOME
Not yet implemented in FFmpeg, patches welcome.
Definition: error.h:62
int avpriv_mpa_decode_header2(uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bit_rate, enum AVCodecID *codec_id)
int frame_size
Definition: mxfenc.c:1803
enum AVCodecID codec_id
Definition: avcodec.h:1518
int sample_rate
samples per second
Definition: avcodec.h:2261
main external API structure.
Definition: avcodec.h:1501
void * buf
Definition: avisynth_c.h:553
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.
MPEG Audio header decoder.
common internal and external API header
int channels
number of audio channels
Definition: avcodec.h:2262
#define ID3v1_TAG_SIZE
Definition: id3v1.h:27