3 * Copyright (c) 2003 Fabrice Bellard
5 * This file is part of Libav.
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.
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.
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
22 #include "libavutil/avstring.h"
23 #include "libavutil/intreadwrite.h"
24 #include "libavutil/dict.h"
25 #include "libavutil/mathematics.h"
30 #include "libavcodec/mpegaudiodecheader.h"
34 static int mp3_read_probe(AVProbeData *p)
36 int max_frames, first_frames = 0;
37 int fsize, frames, sample_rate;
39 uint8_t *buf, *buf0, *buf2, *end;
43 end = p->buf + p->buf_size - sizeof(uint32_t);
44 while(buf0 < end && !*buf0)
50 for(; buf < end; buf= buf2+1) {
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);
60 max_frames = FFMAX(max_frames, frames);
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;
71 //mpegps_mp3_unrecognized_format.mpg has max_frames=3
75 * Try to find Xing/Info/VBRI tags and compute duration from info therein
77 static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
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}};
87 if(ff_mpa_check_header(v) < 0)
90 if (avpriv_mpegaudio_decode_header(&c, v) == 0)
91 vbrtag_size = c.frame_size;
95 /* Check for Xing / Info tag */
96 avio_skip(s->pb, xing_offtbl[c.lsf == 1][c.nb_channels == 1]);
98 if(v == MKBETAG('X', 'i', 'n', 'g') || v == MKBETAG('I', 'n', 'f', 'o')) {
101 frames = avio_rb32(s->pb);
103 size = avio_rb32(s->pb);
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 */
114 frames = avio_rb32(s->pb);
115 size = avio_rb32(s->pb);
122 /* Skip the vbr tag frame */
123 avio_seek(s->pb, base + vbrtag_size, SEEK_SET);
125 spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
127 st->duration = av_rescale_q(frames, (AVRational){spf, c.sample_rate},
130 st->codec->bit_rate = av_rescale(size, 8 * c.sample_rate, frames * (int64_t)spf);
135 static int mp3_read_header(AVFormatContext *s,
136 AVFormatParameters *ap)
141 st = avformat_new_stream(s, NULL);
143 return AVERROR(ENOMEM);
145 st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
146 st->codec->codec_id = CODEC_ID_MP3;
147 st->need_parsing = AVSTREAM_PARSE_FULL;
150 // lcm of all mp3 sample rates
151 avpriv_set_pts_info(st, 64, 1, 14112000);
153 off = avio_tell(s->pb);
155 if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
158 if (mp3_parse_vbr_tags(s, st, off) < 0)
159 avio_seek(s->pb, off, SEEK_SET);
161 /* the parameters will be extracted from the compressed bitstream */
165 #define MP3_PACKET_SIZE 1024
167 static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)
170 // AVStream *st = s->streams[0];
172 size= MP3_PACKET_SIZE;
174 ret= av_get_packet(s->pb, pkt, size);
176 pkt->stream_index = 0;
181 if (ret > ID3v1_TAG_SIZE &&
182 memcmp(&pkt->data[ret - ID3v1_TAG_SIZE], "TAG", 3) == 0)
183 ret -= ID3v1_TAG_SIZE;
185 /* note: we need to modify the packet size here to handle the last
191 AVInputFormat ff_mp3_demuxer = {
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 */