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"
29 #include "libavcodec/mpegaudiodecheader.h"
33 static int mp3_read_probe(AVProbeData *p)
35 int max_frames, first_frames = 0;
36 int fsize, frames, sample_rate;
38 uint8_t *buf, *buf0, *buf2, *end;
42 end = p->buf + p->buf_size - sizeof(uint32_t);
43 while(buf0 < end && !*buf0)
49 for(; buf < end; buf= buf2+1) {
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);
59 max_frames = FFMAX(max_frames, frames);
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;
70 //mpegps_mp3_unrecognized_format.mpg has max_frames=3
74 * Try to find Xing/Info/VBRI tags and compute duration from info therein
76 static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
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}};
86 if(ff_mpa_check_header(v) < 0)
89 if (ff_mpegaudio_decode_header(&c, v) == 0)
90 vbrtag_size = c.frame_size;
94 /* Check for Xing / Info tag */
95 avio_skip(s->pb, xing_offtbl[c.lsf == 1][c.nb_channels == 1]);
97 if(v == MKBETAG('X', 'i', 'n', 'g') || v == MKBETAG('I', 'n', 'f', 'o')) {
100 frames = avio_rb32(s->pb);
102 size = avio_rb32(s->pb);
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 */
113 size = avio_rb32(s->pb);
114 frames = avio_rb32(s->pb);
121 /* Skip the vbr tag frame */
122 avio_seek(s->pb, base + vbrtag_size, SEEK_SET);
124 spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
126 st->duration = av_rescale_q(frames, (AVRational){spf, c.sample_rate},
129 st->codec->bit_rate = av_rescale(size, 8 * c.sample_rate, frames * (int64_t)spf);
134 static int mp3_read_header(AVFormatContext *s,
135 AVFormatParameters *ap)
140 st = av_new_stream(s, 0);
142 return AVERROR(ENOMEM);
144 st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
145 st->codec->codec_id = CODEC_ID_MP3;
146 st->need_parsing = AVSTREAM_PARSE_FULL;
149 // lcm of all mp3 sample rates
150 av_set_pts_info(st, 64, 1, 14112000);
152 off = avio_tell(s->pb);
154 if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
157 if (mp3_parse_vbr_tags(s, st, off) < 0)
158 avio_seek(s->pb, off, SEEK_SET);
160 /* the parameters will be extracted from the compressed bitstream */
164 #define MP3_PACKET_SIZE 1024
166 static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)
169 // AVStream *st = s->streams[0];
171 size= MP3_PACKET_SIZE;
173 ret= av_get_packet(s->pb, pkt, size);
175 pkt->stream_index = 0;
182 if (ret > ID3v1_TAG_SIZE &&
183 memcmp(&pkt->data[ret - ID3v1_TAG_SIZE], "TAG", 3) == 0)
184 ret -= ID3v1_TAG_SIZE;
186 /* note: we need to modify the packet size here to handle the last
192 AVInputFormat ff_mp3_demuxer = {
194 .long_name = NULL_IF_CONFIG_SMALL("MPEG audio layer 2/3"),
195 .read_probe = mp3_read_probe,
196 .read_header = mp3_read_header,
197 .read_packet = mp3_read_packet,
198 .flags= AVFMT_GENERIC_INDEX,
199 .extensions = "mp2,mp3,m2a", /* XXX: use probe */