FFmpeg: libavcodec/mpegaudio_parser.c Source File

FFmpeg
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 
27 
28  typedef struct MpegAudioParseContext {
29   ParseContext pc;
30   int frame_size;
31   uint32_t header;
32   int header_count;
33   int no_bitrate;
34 } MpegAudioParseContext;
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 
42  static int mpegaudio_parse(AVCodecParserContext *s1,
43  AVCodecContext *avctx,
44  const uint8_t **poutbuf, int *poutbuf_size,
45  const uint8_t *buf, int buf_size)
46 {
47  MpegAudioParseContext *s = s1->priv_data;
48  ParseContext *pc = &s->pc;
49  uint32_t state= pc->state;
50  int i;
51  int next= END_NOT_FOUND;
52 
53  for(i=0; i<buf_size; ){
54  if(s->frame_size){
55  int inc= FFMIN(buf_size - i, s->frame_size);
56  i += inc;
57  s->frame_size -= inc;
58  state = 0;
59 
60  if(!s->frame_size){
61  next= i;
62  break;
63  }
64  }else{
65  while(i<buf_size){
66  int ret, sr, channels, bit_rate, frame_size;
67  enum AVCodecID codec_id = avctx->codec_id;
68 
69  state= (state<<8) + buf[i++];
70 
71  ret = avpriv_mpa_decode_header2(state, &sr, &channels, &frame_size, &bit_rate, &codec_id);
72  if (ret < 4) {
73  if (i > 4)
74  s->header_count = -2;
75  } else {
76  int header_threshold = avctx->codec_id != AV_CODEC_ID_NONE && avctx->codec_id != codec_id;
77  if((state&SAME_HEADER_MASK) != (s->header&SAME_HEADER_MASK) && s->header)
78  s->header_count= -3;
79  s->header= state;
80  s->header_count++;
81  s->frame_size = ret-4;
82 
83  if (s->header_count > header_threshold) {
84  avctx->sample_rate= sr;
85  avctx->channels = channels;
86  s1->duration = frame_size;
87  avctx->codec_id = codec_id;
88  if (s->no_bitrate || !avctx->bit_rate) {
89  s->no_bitrate = 1;
90  avctx->bit_rate += (bit_rate - avctx->bit_rate) / (s->header_count - header_threshold);
91  }
92  }
93 
94  if (s1->flags & PARSER_FLAG_COMPLETE_FRAMES) {
95  s->frame_size = 0;
96  next = buf_size;
97  } else if (codec_id == AV_CODEC_ID_MP3ADU) {
98  avpriv_report_missing_feature(avctx,
99  "MP3ADU full parser");
100  return AVERROR_PATCHWELCOME;
101  }
102 
103  break;
104  }
105  }
106  }
107  }
108 
109  pc->state= state;
110  if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
111  *poutbuf = NULL;
112  *poutbuf_size = 0;
113  return buf_size;
114  }
115 
116  *poutbuf = buf;
117  *poutbuf_size = buf_size;
118  return next;
119 }
120 
121 
122  AVCodecParser ff_mpegaudio_parser = {
123  .codec_ids = { AV_CODEC_ID_MP1, AV_CODEC_ID_MP2, AV_CODEC_ID_MP3, AV_CODEC_ID_MP3ADU },
124  .priv_data_size = sizeof(MpegAudioParseContext),
125  .parser_parse = mpegaudio_parse,
126  .parser_close = ff_parse_close,
127 };
NULL
#define NULL
Definition: coverity.c:32
s
const char * s
Definition: avisynth_c.h:631
AV_CODEC_ID_NONE
Definition: avcodec.h:103
SAME_HEADER_MASK
#define SAME_HEADER_MASK
Definition: mpegaudio_parser.c:39
AVCodecParser::codec_ids
int codec_ids[5]
Definition: avcodec.h:4426
AV_CODEC_ID_MP1
Definition: avcodec.h:465
AVCodecParserContext::duration
int duration
Duration of the current frame.
Definition: avcodec.h:4380
uint8_t
uint8_t
Definition: audio_convert.c:194
mpegaudio_parse
static int mpegaudio_parse(AVCodecParserContext *s1, AVCodecContext *avctx, const uint8_t **poutbuf, int *poutbuf_size, const uint8_t *buf, int buf_size)
Definition: mpegaudio_parser.c:42
AVCodecID
AVCodecID
Identify the syntax and semantics of the bitstream.
Definition: avcodec.h:102
ff_combine_frame
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
PARSER_FLAG_COMPLETE_FRAMES
#define PARSER_FLAG_COMPLETE_FRAMES
Definition: avcodec.h:4281
AV_CODEC_ID_MP3
preferred ID for decoding MPEG audio layer 1, 2 or 3
Definition: avcodec.h:421
AVCodecParserContext::priv_data
void * priv_data
Definition: avcodec.h:4248
codec_id
enum AVCodecID codec_id
Definition: mov_chan.c:433
ff_parse_close
void ff_parse_close(AVCodecParserContext *s)
Definition: parser.c:307
AVCodecContext::bit_rate
int bit_rate
the average bitrate
Definition: avcodec.h:1305
FFMIN
#define FFMIN(a, b)
Definition: common.h:66
ret
ret
Definition: avfilter.c:974
AV_CODEC_ID_MP3ADU
Definition: avcodec.h:433
AVERROR_PATCHWELCOME
#define AVERROR_PATCHWELCOME
Not yet implemented in FFmpeg, patches welcome.
Definition: error.h:62
avpriv_mpa_decode_header2
int avpriv_mpa_decode_header2(uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bit_rate, enum AVCodecID *codec_id)
Definition: mpegaudiodecheader.c:116
frame_size
int frame_size
Definition: mxfenc.c:1803
AVCodecContext::codec_id
enum AVCodecID codec_id
Definition: avcodec.h:1258
AVCodecContext::sample_rate
int sample_rate
samples per second
Definition: avcodec.h:1985
AVCodecContext
main external API structure.
Definition: avcodec.h:1241
buf
void * buf
Definition: avisynth_c.h:553
ParseContext::state
uint32_t state
contains the last few bytes in MSB order
Definition: parser.h:33
ff_mpegaudio_parser
AVCodecParser ff_mpegaudio_parser
Definition: mpegaudio_parser.c:122
s1
#define s1
Definition: regdef.h:38
AV_CODEC_ID_MP2
Definition: avcodec.h:420
END_NOT_FOUND
#define END_NOT_FOUND
Definition: parser.h:40
avpriv_report_missing_feature
void avpriv_report_missing_feature(void *avc, const char *msg,...) av_printf_format(2
Log a generic warning message about a missing feature.
state
static uint32_t state
Definition: trasher.c:27
mpegaudiodecheader.h
MPEG Audio header decoder.
common.h
common internal and external API header
AVCodecContext::channels
int channels
number of audio channels
Definition: avcodec.h:1986
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