3 * Copyright (c) 2003 Fabrice Bellard
5 * This file is part of FFmpeg.
7 * FFmpeg 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 * FFmpeg 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 FFmpeg; 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"
40 static int mp3_read_probe(AVProbeData *p)
42 int max_frames, first_frames = 0;
43 int fsize, frames, sample_rate;
45 uint8_t *buf, *buf0, *buf2, *end;
49 end = p->buf + p->buf_size - sizeof(uint32_t);
50 while(buf0 < end && !*buf0)
56 for(; buf < end; buf= buf2+1) {
59 for(frames = 0; buf2 < end; frames++) {
60 header = AV_RB32(buf2);
61 fsize = avpriv_mpa_decode_header(&avctx, header, &sample_rate, &sample_rate, &sample_rate, &sample_rate);
66 max_frames = FFMAX(max_frames, frames);
70 // keep this in sync with ac3 probe, both need to avoid
71 // issues with MPEG-files!
72 if (first_frames>=4) return AVPROBE_SCORE_MAX/2+1;
73 else if(max_frames>200)return AVPROBE_SCORE_MAX/2;
74 else if(max_frames>=4) return AVPROBE_SCORE_MAX/4;
75 else if(ff_id3v2_match(buf0, ID3v2_DEFAULT_MAGIC) && 2*ff_id3v2_tag_len(buf0) >= p->buf_size)
76 return AVPROBE_SCORE_MAX/8;
77 else if(max_frames>=1) return 1;
79 //mpegps_mp3_unrecognized_format.mpg has max_frames=3
83 * Try to find Xing/Info/VBRI tags and compute duration from info therein
85 static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
87 MP3Context *mp3 = s->priv_data;
89 unsigned frames = 0; /* Total number of frames in file */
90 unsigned size = 0; /* Total number of bytes in the stream */
91 const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};
96 if(ff_mpa_check_header(v) < 0)
99 if (avpriv_mpegaudio_decode_header(&c, v) == 0)
100 vbrtag_size = c.frame_size;
104 /* Check for Xing / Info tag */
105 avio_skip(s->pb, xing_offtbl[c.lsf == 1][c.nb_channels == 1]);
106 v = avio_rb32(s->pb);
107 if(v == MKBETAG('X', 'i', 'n', 'g') || v == MKBETAG('I', 'n', 'f', 'o')) {
108 v = avio_rb32(s->pb);
110 frames = avio_rb32(s->pb);
112 size = avio_rb32(s->pb);
114 avio_skip(s->pb, 100);
118 v = avio_rb32(s->pb);
119 if(v == MKBETAG('L', 'A', 'M', 'E') || v == MKBETAG('L', 'a', 'v', 'f')) {
120 avio_skip(s->pb, 21-4);
122 mp3->start_pad = v>>12;
123 mp3-> end_pad = v&4095;
124 st->skip_samples = mp3->start_pad + 528 + 1;
125 av_log(s, AV_LOG_DEBUG, "pad %d %d\n", mp3->start_pad, mp3-> end_pad);
129 /* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */
130 avio_seek(s->pb, base + 4 + 32, SEEK_SET);
131 v = avio_rb32(s->pb);
132 if(v == MKBETAG('V', 'B', 'R', 'I')) {
133 /* Check tag version */
134 if(avio_rb16(s->pb) == 1) {
135 /* skip delay and quality */
137 size = avio_rb32(s->pb);
138 frames = avio_rb32(s->pb);
145 /* Skip the vbr tag frame */
146 avio_seek(s->pb, base + vbrtag_size, SEEK_SET);
148 spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
150 st->duration = av_rescale_q(frames, (AVRational){spf, c.sample_rate},
153 st->codec->bit_rate = av_rescale(size, 8 * c.sample_rate, frames * (int64_t)spf);
158 static int mp3_read_header(AVFormatContext *s)
160 MP3Context *mp3 = s->priv_data;
164 st = avformat_new_stream(s, NULL);
166 return AVERROR(ENOMEM);
168 st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
169 st->codec->codec_id = AV_CODEC_ID_MP3;
170 st->need_parsing = AVSTREAM_PARSE_FULL_RAW;
173 // lcm of all mp3 sample rates
174 avpriv_set_pts_info(st, 64, 1, 14112000);
177 off = avio_tell(s->pb);
179 if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
183 mp3->filesize = avio_size(s->pb);
185 if (mp3_parse_vbr_tags(s, st, off) < 0)
186 avio_seek(s->pb, off, SEEK_SET);
188 /* the parameters will be extracted from the compressed bitstream */
192 #define MP3_PACKET_SIZE 1024
194 static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)
196 MP3Context *mp3 = s->priv_data;
200 size= MP3_PACKET_SIZE;
201 pos = avio_tell(s->pb);
202 if(mp3->filesize > ID3v1_TAG_SIZE && pos < mp3->filesize)
203 size= FFMIN(size, mp3->filesize - pos);
205 ret= av_get_packet(s->pb, pkt, size);
212 pkt->flags &= ~AV_PKT_FLAG_CORRUPT;
213 pkt->stream_index = 0;
215 if (ret >= ID3v1_TAG_SIZE &&
216 memcmp(&pkt->data[ret - ID3v1_TAG_SIZE], "TAG", 3) == 0)
217 ret -= ID3v1_TAG_SIZE;
219 /* note: we need to modify the packet size here to handle the last
225 static int read_seek(AVFormatContext *s, int stream_index, int64_t timestamp, int flags)
227 MP3Context *mp3 = s->priv_data;
228 AVStream *st = s->streams[stream_index];
230 st->skip_samples = timestamp <= 0 ? mp3->start_pad + 528 + 1 : 0;
235 AVInputFormat ff_mp3_demuxer = {
237 .long_name = NULL_IF_CONFIG_SMALL("MP2/3 (MPEG audio layer 2/3)"),
238 .priv_data_size = sizeof(MP3Context),
239 .read_probe = mp3_read_probe,
240 .read_header = mp3_read_header,
241 .read_packet = mp3_read_packet,
242 .read_seek = read_seek,
243 .flags = AVFMT_GENERIC_INDEX,
244 .extensions = "mp2,mp3,m2a", /* XXX: use probe */