aac_ac3_parser.c
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1 /*
2  * Common AAC and AC-3 parser
3  * Copyright (c) 2003 Fabrice Bellard
4  * Copyright (c) 2003 Michael Niedermayer
5  *
6  * This file is part of Libav.
7  *
8  * Libav 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  * Libav 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 Libav; 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 "aac_ac3_parser.h"
25 
27  AVCodecContext *avctx,
28  const uint8_t **poutbuf, int *poutbuf_size,
29  const uint8_t *buf, int buf_size)
30 {
32  ParseContext *pc = &s->pc;
33  int len, i;
34  int new_frame_start;
35 
36 get_next:
37  i=END_NOT_FOUND;
38  if(s->remaining_size <= buf_size){
39  if(s->remaining_size && !s->need_next_header){
40  i= s->remaining_size;
41  s->remaining_size = 0;
42  }else{ //we need a header first
43  len=0;
44  for(i=s->remaining_size; i<buf_size; i++){
45  s->state = (s->state<<8) + buf[i];
46  if((len=s->sync(s->state, s, &s->need_next_header, &new_frame_start)))
47  break;
48  }
49  if(len<=0){
50  i=END_NOT_FOUND;
51  }else{
52  s->state=0;
53  i-= s->header_size -1;
54  s->remaining_size = len;
55  if(!new_frame_start || pc->index+i<=0){
56  s->remaining_size += i;
57  goto get_next;
58  }
59  }
60  }
61  }
62 
63  if(ff_combine_frame(pc, i, &buf, &buf_size)<0){
64  s->remaining_size -= FFMIN(s->remaining_size, buf_size);
65  *poutbuf = NULL;
66  *poutbuf_size = 0;
67  return buf_size;
68  }
69 
70  *poutbuf = buf;
71  *poutbuf_size = buf_size;
72 
73  /* update codec info */
74  if(s->codec_id)
75  avctx->codec_id = s->codec_id;
76 
77  /* Due to backwards compatible HE-AAC the sample rate, channel count,
78  and total number of samples found in an AAC ADTS header are not
79  reliable. Bit rate is still accurate because the total frame duration in
80  seconds is still correct (as is the number of bits in the frame). */
81  if (avctx->codec_id != CODEC_ID_AAC) {
82  avctx->sample_rate = s->sample_rate;
83 
84  /* allow downmixing to stereo (or mono for AC-3) */
85  if(avctx->request_channels > 0 &&
86  avctx->request_channels < s->channels &&
87  (avctx->request_channels <= 2 ||
88  (avctx->request_channels == 1 &&
89  (avctx->codec_id == CODEC_ID_AC3 ||
90  avctx->codec_id == CODEC_ID_EAC3)))) {
91  avctx->channels = avctx->request_channels;
92  } else {
93  avctx->channels = s->channels;
94  avctx->channel_layout = s->channel_layout;
95  }
96  avctx->frame_size = s->samples;
97  avctx->audio_service_type = s->service_type;
98  }
99 
100  avctx->bit_rate = s->bit_rate;
101 
102  return i;
103 }
enum AVAudioServiceType audio_service_type
Type of service that the audio stream conveys.
Definition: avcodec.h:3141
int(* sync)(uint64_t state, struct AACAC3ParseContext *hdr_info, int *need_next_header, int *new_frame_start)
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:222
uint64_t channel_layout
Audio channel layout.
Definition: avcodec.h:2870
int bit_rate
the average bitrate
Definition: avcodec.h:1340
#define FFMIN(a, b)
Definition: common.h:55
enum CodecID codec_id
int frame_size
Samples per packet, initialized when calling 'init'.
Definition: avcodec.h:1470
NULL
Definition: eval.c:50
int sample_rate
samples per second
Definition: avcodec.h:1456
main external API structure.
Definition: avcodec.h:1329
#define s1
Definition: regdef.h:38
#define END_NOT_FOUND
Definition: parser.h:55
int ff_aac_ac3_parse(AVCodecParserContext *s1, AVCodecContext *avctx, const uint8_t **poutbuf, int *poutbuf_size, const uint8_t *buf, int buf_size)
int index
Definition: parser.h:30
int len
int channels
number of audio channels
Definition: avcodec.h:1457
enum CodecID codec_id
Definition: avcodec.h:1575