09494de13656b0287c68bb3f41185d44dfe53738
[libav.git] / libavformat / mp3dec.c
1 /*
2 * MP3 demuxer
3 * Copyright (c) 2003 Fabrice Bellard
4 *
5 * This file is part of Libav.
6 *
7 * Libav is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * Libav is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with Libav; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22 #include "libavutil/avstring.h"
23 #include "libavutil/intreadwrite.h"
24 #include "libavutil/dict.h"
25 #include "libavutil/mathematics.h"
26 #include "avformat.h"
27 #include "id3v2.h"
28 #include "id3v1.h"
29 #include "libavcodec/mpegaudiodecheader.h"
30
31 /* mp3 read */
32
33 static int mp3_read_probe(AVProbeData *p)
34 {
35 int max_frames, first_frames = 0;
36 int fsize, frames, sample_rate;
37 uint32_t header;
38 uint8_t *buf, *buf0, *buf2, *end;
39 AVCodecContext avctx;
40
41 buf0 = p->buf;
42 end = p->buf + p->buf_size - sizeof(uint32_t);
43 while(buf0 < end && !*buf0)
44 buf0++;
45
46 max_frames = 0;
47 buf = buf0;
48
49 for(; buf < end; buf= buf2+1) {
50 buf2 = buf;
51
52 for(frames = 0; buf2 < end; frames++) {
53 header = AV_RB32(buf2);
54 fsize = ff_mpa_decode_header(&avctx, header, &sample_rate, &sample_rate, &sample_rate, &sample_rate);
55 if(fsize < 0)
56 break;
57 buf2 += fsize;
58 }
59 max_frames = FFMAX(max_frames, frames);
60 if(buf == buf0)
61 first_frames= frames;
62 }
63 // keep this in sync with ac3 probe, both need to avoid
64 // issues with MPEG-files!
65 if (first_frames>=4) return AVPROBE_SCORE_MAX/2+1;
66 else if(max_frames>500)return AVPROBE_SCORE_MAX/2;
67 else if(max_frames>=4) return AVPROBE_SCORE_MAX/4;
68 else if(max_frames>=1) return 1;
69 else return 0;
70 //mpegps_mp3_unrecognized_format.mpg has max_frames=3
71 }
72
73 /**
74 * Try to find Xing/Info/VBRI tags and compute duration from info therein
75 */
76 static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
77 {
78 uint32_t v, spf;
79 unsigned frames = 0; /* Total number of frames in file */
80 unsigned size = 0; /* Total number of bytes in the stream */
81 const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};
82 MPADecodeHeader c;
83 int vbrtag_size = 0;
84
85 v = avio_rb32(s->pb);
86 if(ff_mpa_check_header(v) < 0)
87 return -1;
88
89 if (ff_mpegaudio_decode_header(&c, v) == 0)
90 vbrtag_size = c.frame_size;
91 if(c.layer != 3)
92 return -1;
93
94 /* Check for Xing / Info tag */
95 avio_skip(s->pb, xing_offtbl[c.lsf == 1][c.nb_channels == 1]);
96 v = avio_rb32(s->pb);
97 if(v == MKBETAG('X', 'i', 'n', 'g') || v == MKBETAG('I', 'n', 'f', 'o')) {
98 v = avio_rb32(s->pb);
99 if(v & 0x1)
100 frames = avio_rb32(s->pb);
101 if(v & 0x2)
102 size = avio_rb32(s->pb);
103 }
104
105 /* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */
106 avio_seek(s->pb, base + 4 + 32, SEEK_SET);
107 v = avio_rb32(s->pb);
108 if(v == MKBETAG('V', 'B', 'R', 'I')) {
109 /* Check tag version */
110 if(avio_rb16(s->pb) == 1) {
111 /* skip delay and quality */
112 avio_skip(s->pb, 4);
113 frames = avio_rb32(s->pb);
114 size = avio_rb32(s->pb);
115 }
116 }
117
118 if(!frames && !size)
119 return -1;
120
121 /* Skip the vbr tag frame */
122 avio_seek(s->pb, base + vbrtag_size, SEEK_SET);
123
124 spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
125 if(frames)
126 st->duration = av_rescale_q(frames, (AVRational){spf, c.sample_rate},
127 st->time_base);
128 if(size && frames)
129 st->codec->bit_rate = av_rescale(size, 8 * c.sample_rate, frames * (int64_t)spf);
130
131 return 0;
132 }
133
134 static int mp3_read_header(AVFormatContext *s,
135 AVFormatParameters *ap)
136 {
137 AVStream *st;
138 int64_t off;
139
140 st = avformat_new_stream(s, NULL);
141 if (!st)
142 return AVERROR(ENOMEM);
143
144 st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
145 st->codec->codec_id = CODEC_ID_MP3;
146 st->need_parsing = AVSTREAM_PARSE_FULL;
147 st->start_time = 0;
148
149 // lcm of all mp3 sample rates
150 av_set_pts_info(st, 64, 1, 14112000);
151
152 off = avio_tell(s->pb);
153
154 if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
155 ff_id3v1_read(s);
156
157 if (mp3_parse_vbr_tags(s, st, off) < 0)
158 avio_seek(s->pb, off, SEEK_SET);
159
160 /* the parameters will be extracted from the compressed bitstream */
161 return 0;
162 }
163
164 #define MP3_PACKET_SIZE 1024
165
166 static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)
167 {
168 int ret, size;
169 // AVStream *st = s->streams[0];
170
171 size= MP3_PACKET_SIZE;
172
173 ret= av_get_packet(s->pb, pkt, size);
174
175 pkt->stream_index = 0;
176 if (ret <= 0) {
177 return AVERROR(EIO);
178 }
179
180 if (ret > ID3v1_TAG_SIZE &&
181 memcmp(&pkt->data[ret - ID3v1_TAG_SIZE], "TAG", 3) == 0)
182 ret -= ID3v1_TAG_SIZE;
183
184 /* note: we need to modify the packet size here to handle the last
185 packet */
186 pkt->size = ret;
187 return ret;
188 }
189
190 AVInputFormat ff_mp3_demuxer = {
191 .name = "mp3",
192 .long_name = NULL_IF_CONFIG_SMALL("MPEG audio layer 2/3"),
193 .read_probe = mp3_read_probe,
194 .read_header = mp3_read_header,
195 .read_packet = mp3_read_packet,
196 .flags= AVFMT_GENERIC_INDEX,
197 .extensions = "mp2,mp3,m2a", /* XXX: use probe */
198 };