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"
27 #include "libavcodec/mpegaudiodecheader.h"
31 static int mp3_read_probe(AVProbeData *p)
33 int max_frames, first_frames = 0;
34 int fsize, frames, sample_rate;
36 uint8_t *buf, *buf0, *buf2, *end;
40 end = p->buf + p->buf_size - sizeof(uint32_t);
41 while(buf0 < end && !*buf0)
47 for(; buf < end; buf= buf2+1) {
50 for(frames = 0; buf2 < end; frames++) {
51 header = AV_RB32(buf2);
52 fsize = ff_mpa_decode_header(&avctx, header, &sample_rate, &sample_rate, &sample_rate, &sample_rate);
57 max_frames = FFMAX(max_frames, frames);
61 // keep this in sync with ac3 probe, both need to avoid
62 // issues with MPEG-files!
63 if (first_frames>=4) return AVPROBE_SCORE_MAX/2+1;
64 else if(max_frames>500)return AVPROBE_SCORE_MAX/2;
65 else if(max_frames>=4) return AVPROBE_SCORE_MAX/4;
66 else if(max_frames>=1) return 1;
68 //mpegps_mp3_unrecognized_format.mpg has max_frames=3
72 * Try to find Xing/Info/VBRI tags and compute duration from info therein
74 static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
77 unsigned frames = 0; /* Total number of frames in file */
78 unsigned size = 0; /* Total number of bytes in the stream */
79 const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};
84 if(ff_mpa_check_header(v) < 0)
87 if (ff_mpegaudio_decode_header(&c, v) == 0)
88 vbrtag_size = c.frame_size;
92 /* Check for Xing / Info tag */
93 url_fseek(s->pb, xing_offtbl[c.lsf == 1][c.nb_channels == 1], SEEK_CUR);
95 if(v == MKBETAG('X', 'i', 'n', 'g') || v == MKBETAG('I', 'n', 'f', 'o')) {
98 frames = get_be32(s->pb);
100 size = get_be32(s->pb);
103 /* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */
104 url_fseek(s->pb, base + 4 + 32, SEEK_SET);
106 if(v == MKBETAG('V', 'B', 'R', 'I')) {
107 /* Check tag version */
108 if(get_be16(s->pb) == 1) {
109 /* skip delay and quality */
110 url_fseek(s->pb, 4, SEEK_CUR);
111 frames = get_be32(s->pb);
112 size = get_be32(s->pb);
119 /* Skip the vbr tag frame */
120 url_fseek(s->pb, base + vbrtag_size, SEEK_SET);
122 spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
124 st->duration = av_rescale_q(frames, (AVRational){spf, c.sample_rate},
127 st->codec->bit_rate = av_rescale(size, 8 * c.sample_rate, frames * (int64_t)spf);
132 static int mp3_read_header(AVFormatContext *s,
133 AVFormatParameters *ap)
138 st = av_new_stream(s, 0);
140 return AVERROR(ENOMEM);
142 st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
143 st->codec->codec_id = CODEC_ID_MP3;
144 st->need_parsing = AVSTREAM_PARSE_FULL;
147 // lcm of all mp3 sample rates
148 av_set_pts_info(st, 64, 1, 14112000);
150 off = url_ftell(s->pb);
152 if (!av_metadata_get(s->metadata, "", NULL, AV_METADATA_IGNORE_SUFFIX))
155 if (mp3_parse_vbr_tags(s, st, off) < 0)
156 url_fseek(s->pb, off, SEEK_SET);
158 /* the parameters will be extracted from the compressed bitstream */
162 #define MP3_PACKET_SIZE 1024
164 static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)
167 // AVStream *st = s->streams[0];
169 size= MP3_PACKET_SIZE;
171 ret= av_get_packet(s->pb, pkt, size);
173 pkt->stream_index = 0;
177 /* note: we need to modify the packet size here to handle the last
183 AVInputFormat mp3_demuxer = {
185 NULL_IF_CONFIG_SMALL("MPEG audio layer 2/3"),
190 .flags= AVFMT_GENERIC_INDEX,
191 .extensions = "mp2,mp3,m2a", /* XXX: use probe */