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 "internal.h"
28#include "id3v2.h"
29#include "id3v1.h"
30#include "libavcodec/mpegaudiodecheader.h"
31
32/* mp3 read */
33
34static int mp3_read_probe(AVProbeData *p)
35{
36    int max_frames, first_frames = 0;
37    int fsize, frames, sample_rate;
38    uint32_t header;
39    uint8_t *buf, *buf0, *buf2, *end;
40    AVCodecContext avctx;
41
42    buf0 = p->buf;
43    end = p->buf + p->buf_size - sizeof(uint32_t);
44    while(buf0 < end && !*buf0)
45        buf0++;
46
47    max_frames = 0;
48    buf = buf0;
49
50    for(; buf < end; buf= buf2+1) {
51        buf2 = buf;
52
53        for(frames = 0; buf2 < end; frames++) {
54            header = AV_RB32(buf2);
55            fsize = avpriv_mpa_decode_header(&avctx, header, &sample_rate, &sample_rate, &sample_rate, &sample_rate);
56            if(fsize < 0)
57                break;
58            buf2 += fsize;
59        }
60        max_frames = FFMAX(max_frames, frames);
61        if(buf == buf0)
62            first_frames= frames;
63    }
64    // keep this in sync with ac3 probe, both need to avoid
65    // issues with MPEG-files!
66    if   (first_frames>=4) return AVPROBE_SCORE_MAX/2+1;
67    else if(max_frames>500)return AVPROBE_SCORE_MAX/2;
68    else if(max_frames>=4) return AVPROBE_SCORE_MAX/4;
69    else if(max_frames>=1) return 1;
70    else                   return 0;
71//mpegps_mp3_unrecognized_format.mpg has max_frames=3
72}
73
74/**
75 * Try to find Xing/Info/VBRI tags and compute duration from info therein
76 */
77static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
78{
79    uint32_t v, spf;
80    unsigned frames = 0; /* Total number of frames in file */
81    unsigned size = 0; /* Total number of bytes in the stream */
82    const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};
83    MPADecodeHeader c;
84    int vbrtag_size = 0;
85
86    v = avio_rb32(s->pb);
87    if(ff_mpa_check_header(v) < 0)
88      return -1;
89
90    if (avpriv_mpegaudio_decode_header(&c, v) == 0)
91        vbrtag_size = c.frame_size;
92    if(c.layer != 3)
93        return -1;
94
95    /* Check for Xing / Info tag */
96    avio_skip(s->pb, xing_offtbl[c.lsf == 1][c.nb_channels == 1]);
97    v = avio_rb32(s->pb);
98    if(v == MKBETAG('X', 'i', 'n', 'g') || v == MKBETAG('I', 'n', 'f', 'o')) {
99        v = avio_rb32(s->pb);
100        if(v & 0x1)
101            frames = avio_rb32(s->pb);
102        if(v & 0x2)
103            size = avio_rb32(s->pb);
104    }
105
106    /* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */
107    avio_seek(s->pb, base + 4 + 32, SEEK_SET);
108    v = avio_rb32(s->pb);
109    if(v == MKBETAG('V', 'B', 'R', 'I')) {
110        /* Check tag version */
111        if(avio_rb16(s->pb) == 1) {
112            /* skip delay and quality */
113            avio_skip(s->pb, 4);
114            frames = avio_rb32(s->pb);
115            size = avio_rb32(s->pb);
116        }
117    }
118
119    if(!frames && !size)
120        return -1;
121
122    /* Skip the vbr tag frame */
123    avio_seek(s->pb, base + vbrtag_size, SEEK_SET);
124
125    spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
126    if(frames)
127        st->duration = av_rescale_q(frames, (AVRational){spf, c.sample_rate},
128                                    st->time_base);
129    if(size && frames)
130        st->codec->bit_rate = av_rescale(size, 8 * c.sample_rate, frames * (int64_t)spf);
131
132    return 0;
133}
134
135static int mp3_read_header(AVFormatContext *s,
136                           AVFormatParameters *ap)
137{
138    AVStream *st;
139    int64_t off;
140
141    st = avformat_new_stream(s, NULL);
142    if (!st)
143        return AVERROR(ENOMEM);
144
145    st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
146    st->codec->codec_id = CODEC_ID_MP3;
147    st->need_parsing = AVSTREAM_PARSE_FULL;
148    st->start_time = 0;
149
150    // lcm of all mp3 sample rates
151    avpriv_set_pts_info(st, 64, 1, 14112000);
152
153    off = avio_tell(s->pb);
154
155    if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
156        ff_id3v1_read(s);
157
158    if (mp3_parse_vbr_tags(s, st, off) < 0)
159        avio_seek(s->pb, off, SEEK_SET);
160
161    /* the parameters will be extracted from the compressed bitstream */
162    return 0;
163}
164
165#define MP3_PACKET_SIZE 1024
166
167static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)
168{
169    int ret, size;
170    //    AVStream *st = s->streams[0];
171
172    size= MP3_PACKET_SIZE;
173
174    ret= av_get_packet(s->pb, pkt, size);
175
176    pkt->stream_index = 0;
177    if (ret <= 0) {
178        return AVERROR(EIO);
179    }
180
181    if (ret > ID3v1_TAG_SIZE &&
182        memcmp(&pkt->data[ret - ID3v1_TAG_SIZE], "TAG", 3) == 0)
183        ret -= ID3v1_TAG_SIZE;
184
185    /* note: we need to modify the packet size here to handle the last
186       packet */
187    pkt->size = ret;
188    return ret;
189}
190
191AVInputFormat ff_mp3_demuxer = {
192    .name           = "mp3",
193    .long_name      = NULL_IF_CONFIG_SMALL("MPEG audio layer 2/3"),
194    .read_probe     = mp3_read_probe,
195    .read_header    = mp3_read_header,
196    .read_packet    = mp3_read_packet,
197    .flags= AVFMT_GENERIC_INDEX,
198    .extensions = "mp2,mp3,m2a", /* XXX: use probe */
199};
200