Libav 0.7.1
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00001 /* 00002 * MP3 demuxer 00003 * Copyright (c) 2003 Fabrice Bellard 00004 * 00005 * This file is part of Libav. 00006 * 00007 * Libav is free software; you can redistribute it and/or 00008 * modify it under the terms of the GNU Lesser General Public 00009 * License as published by the Free Software Foundation; either 00010 * version 2.1 of the License, or (at your option) any later version. 00011 * 00012 * Libav is distributed in the hope that it will be useful, 00013 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 00015 * Lesser General Public License for more details. 00016 * 00017 * You should have received a copy of the GNU Lesser General Public 00018 * License along with Libav; if not, write to the Free Software 00019 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 00020 */ 00021 00022 #include "libavutil/avstring.h" 00023 #include "libavutil/intreadwrite.h" 00024 #include "libavutil/dict.h" 00025 #include "avformat.h" 00026 #include "id3v2.h" 00027 #include "id3v1.h" 00028 #include "libavcodec/mpegaudiodecheader.h" 00029 00030 /* mp3 read */ 00031 00032 static int mp3_read_probe(AVProbeData *p) 00033 { 00034 int max_frames, first_frames = 0; 00035 int fsize, frames, sample_rate; 00036 uint32_t header; 00037 uint8_t *buf, *buf0, *buf2, *end; 00038 AVCodecContext avctx; 00039 00040 buf0 = p->buf; 00041 end = p->buf + p->buf_size - sizeof(uint32_t); 00042 while(buf0 < end && !*buf0) 00043 buf0++; 00044 00045 max_frames = 0; 00046 buf = buf0; 00047 00048 for(; buf < end; buf= buf2+1) { 00049 buf2 = buf; 00050 00051 for(frames = 0; buf2 < end; frames++) { 00052 header = AV_RB32(buf2); 00053 fsize = ff_mpa_decode_header(&avctx, header, &sample_rate, &sample_rate, &sample_rate, &sample_rate); 00054 if(fsize < 0) 00055 break; 00056 buf2 += fsize; 00057 } 00058 max_frames = FFMAX(max_frames, frames); 00059 if(buf == buf0) 00060 first_frames= frames; 00061 } 00062 // keep this in sync with ac3 probe, both need to avoid 00063 // issues with MPEG-files! 00064 if (first_frames>=4) return AVPROBE_SCORE_MAX/2+1; 00065 else if(max_frames>500)return AVPROBE_SCORE_MAX/2; 00066 else if(max_frames>=4) return AVPROBE_SCORE_MAX/4; 00067 else if(max_frames>=1) return 1; 00068 else return 0; 00069 //mpegps_mp3_unrecognized_format.mpg has max_frames=3 00070 } 00071 00075 static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base) 00076 { 00077 uint32_t v, spf; 00078 unsigned frames = 0; /* Total number of frames in file */ 00079 unsigned size = 0; /* Total number of bytes in the stream */ 00080 const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}}; 00081 MPADecodeHeader c; 00082 int vbrtag_size = 0; 00083 00084 v = avio_rb32(s->pb); 00085 if(ff_mpa_check_header(v) < 0) 00086 return -1; 00087 00088 if (ff_mpegaudio_decode_header(&c, v) == 0) 00089 vbrtag_size = c.frame_size; 00090 if(c.layer != 3) 00091 return -1; 00092 00093 /* Check for Xing / Info tag */ 00094 avio_skip(s->pb, xing_offtbl[c.lsf == 1][c.nb_channels == 1]); 00095 v = avio_rb32(s->pb); 00096 if(v == MKBETAG('X', 'i', 'n', 'g') || v == MKBETAG('I', 'n', 'f', 'o')) { 00097 v = avio_rb32(s->pb); 00098 if(v & 0x1) 00099 frames = avio_rb32(s->pb); 00100 if(v & 0x2) 00101 size = avio_rb32(s->pb); 00102 } 00103 00104 /* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */ 00105 avio_seek(s->pb, base + 4 + 32, SEEK_SET); 00106 v = avio_rb32(s->pb); 00107 if(v == MKBETAG('V', 'B', 'R', 'I')) { 00108 /* Check tag version */ 00109 if(avio_rb16(s->pb) == 1) { 00110 /* skip delay and quality */ 00111 avio_skip(s->pb, 4); 00112 frames = avio_rb32(s->pb); 00113 size = avio_rb32(s->pb); 00114 } 00115 } 00116 00117 if(!frames && !size) 00118 return -1; 00119 00120 /* Skip the vbr tag frame */ 00121 avio_seek(s->pb, base + vbrtag_size, SEEK_SET); 00122 00123 spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */ 00124 if(frames) 00125 st->duration = av_rescale_q(frames, (AVRational){spf, c.sample_rate}, 00126 st->time_base); 00127 if(size && frames) 00128 st->codec->bit_rate = av_rescale(size, 8 * c.sample_rate, frames * (int64_t)spf); 00129 00130 return 0; 00131 } 00132 00133 static int mp3_read_header(AVFormatContext *s, 00134 AVFormatParameters *ap) 00135 { 00136 AVStream *st; 00137 int64_t off; 00138 00139 st = av_new_stream(s, 0); 00140 if (!st) 00141 return AVERROR(ENOMEM); 00142 00143 st->codec->codec_type = AVMEDIA_TYPE_AUDIO; 00144 st->codec->codec_id = CODEC_ID_MP3; 00145 st->need_parsing = AVSTREAM_PARSE_FULL; 00146 st->start_time = 0; 00147 00148 // lcm of all mp3 sample rates 00149 av_set_pts_info(st, 64, 1, 14112000); 00150 00151 off = avio_tell(s->pb); 00152 00153 if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX)) 00154 ff_id3v1_read(s); 00155 00156 if (mp3_parse_vbr_tags(s, st, off) < 0) 00157 avio_seek(s->pb, off, SEEK_SET); 00158 00159 /* the parameters will be extracted from the compressed bitstream */ 00160 return 0; 00161 } 00162 00163 #define MP3_PACKET_SIZE 1024 00164 00165 static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt) 00166 { 00167 int ret, size; 00168 // AVStream *st = s->streams[0]; 00169 00170 size= MP3_PACKET_SIZE; 00171 00172 ret= av_get_packet(s->pb, pkt, size); 00173 00174 pkt->stream_index = 0; 00175 if (ret <= 0) { 00176 return AVERROR(EIO); 00177 } 00178 00179 if (ret > ID3v1_TAG_SIZE && 00180 memcmp(&pkt->data[ret - ID3v1_TAG_SIZE], "TAG", 3) == 0) 00181 ret -= ID3v1_TAG_SIZE; 00182 00183 /* note: we need to modify the packet size here to handle the last 00184 packet */ 00185 pkt->size = ret; 00186 return ret; 00187 } 00188 00189 AVInputFormat ff_mp3_demuxer = { 00190 "mp3", 00191 NULL_IF_CONFIG_SMALL("MPEG audio layer 2/3"), 00192 0, 00193 mp3_read_probe, 00194 mp3_read_header, 00195 mp3_read_packet, 00196 .flags= AVFMT_GENERIC_INDEX, 00197 .extensions = "mp2,mp3,m2a", /* XXX: use probe */ 00198 };