1/*
2 * MPEG Audio 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 "mpegaudiodecheader.h"
25
26
27typedef struct MpegAudioParseContext {
28    ParseContext pc;
29    int frame_size;
30    uint32_t header;
31    int header_count;
32} MpegAudioParseContext;
33
34#define MPA_HEADER_SIZE 4
35
36/* header + layer + bitrate + freq + lsf/mpeg25 */
37#define SAME_HEADER_MASK \
38   (0xffe00000 | (3 << 17) | (3 << 10) | (3 << 19))
39
40static int mpegaudio_parse(AVCodecParserContext *s1,
41                           AVCodecContext *avctx,
42                           const uint8_t **poutbuf, int *poutbuf_size,
43                           const uint8_t *buf, int buf_size)
44{
45    MpegAudioParseContext *s = s1->priv_data;
46    ParseContext *pc = &s->pc;
47    uint32_t state= pc->state;
48    int i;
49    int next= END_NOT_FOUND;
50
51    for(i=0; i<buf_size; ){
52        if(s->frame_size){
53            int inc= FFMIN(buf_size - i, s->frame_size);
54            i += inc;
55            s->frame_size -= inc;
56
57            if(!s->frame_size){
58                next= i;
59                break;
60            }
61        }else{
62            while(i<buf_size){
63                int ret, sr, channels, bit_rate, frame_size;
64
65                state= (state<<8) + buf[i++];
66
67                ret = avpriv_mpa_decode_header(avctx, state, &sr, &channels, &frame_size, &bit_rate);
68                if (ret < 4) {
69                    s->header_count= -2;
70                } else {
71                    if((state&SAME_HEADER_MASK) != (s->header&SAME_HEADER_MASK) && s->header)
72                        s->header_count= -3;
73                    s->header= state;
74                    s->header_count++;
75                    s->frame_size = ret-4;
76
77                    if(s->header_count > 1){
78                        avctx->sample_rate= sr;
79                        avctx->channels   = channels;
80                        avctx->frame_size = frame_size;
81                        avctx->bit_rate   = bit_rate;
82                    }
83                    break;
84                }
85            }
86        }
87    }
88
89    pc->state= state;
90    if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
91        *poutbuf = NULL;
92        *poutbuf_size = 0;
93        return buf_size;
94    }
95
96    *poutbuf = buf;
97    *poutbuf_size = buf_size;
98    return next;
99}
100
101
102AVCodecParser ff_mpegaudio_parser = {
103    .codec_ids      = { CODEC_ID_MP1, CODEC_ID_MP2, CODEC_ID_MP3 },
104    .priv_data_size = sizeof(MpegAudioParseContext),
105    .parser_parse   = mpegaudio_parse,
106    .parser_close   = ff_parse_close,
107};
108