libavformat/mp3dec.c

   1 /*
   2  * MP3 demuxer
   3  * Copyright (c) 2003 Fabrice Bellard
   4  *
   5  * This file is part of Libav.
   6  *
   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.
  11  *
  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.
  16  *
  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
  20  */
  21
  22 #include "libavutil/avstring.h"
  23 #include "libavutil/intreadwrite.h"
  24 #include "libavutil/dict.h"
  25 #include "libavutil/mathematics.h"
  26 #include "avformat.h"
  27 #include "internal.h"
  28 #include "id3v2.h"
  29 #include "id3v1.h"
  30 #include "libavcodec/mpegaudiodecheader.h"
  31
  32 #define XING_FLAG_FRAMES 0x01
  33 #define XING_FLAG_SIZE   0x02
  34 #define XING_FLAG_TOC    0x04
  35
  36 #define XING_TOC_COUNT 100
  37
  38 typedef struct MP3DecContext {
  39     int xing_toc;
  40 } MP3DecContext;
  41
  42 /* mp3 read */
  43
  44 static int mp3_read_probe(AVProbeData *p)
  45 {
  46     int max_frames, first_frames = 0;
  47     int fsize, frames, sample_rate;
  48     uint32_t header;
  49     uint8_t *buf, *buf0, *buf2, *end;
  50     AVCodecContext avctx;
  51
  52     buf0 = p->buf;
  53     end = p->buf + p->buf_size - sizeof(uint32_t);
  54     while(buf0 < end && !*buf0)
  55         buf0++;
  56
  57     max_frames = 0;
  58     buf = buf0;
  59
  60     for(; buf < end; buf= buf2+1) {
  61         buf2 = buf;
  62
  63         for(frames = 0; buf2 < end; frames++) {
  64             header = AV_RB32(buf2);
  65             fsize = avpriv_mpa_decode_header(&avctx, header, &sample_rate, &sample_rate, &sample_rate, &sample_rate);
  66             if(fsize < 0)
  67                 break;
  68             buf2 += fsize;
  69         }
  70         max_frames = FFMAX(max_frames, frames);
  71         if(buf == buf0)
  72             first_frames= frames;
  73     }
  74     // keep this in sync with ac3 probe, both need to avoid
  75     // issues with MPEG-files!
  76     if (first_frames >= 4) return AVPROBE_SCORE_MAX / 2 + 1;
  77
  78     if (max_frames) {
  79         int pes = 0, i;
  80         unsigned int code = -1;
  81
  82 #define VIDEO_ID 0x000001e0
  83 #define AUDIO_ID 0x000001c0
  84         /* do a search for mpegps headers to be able to properly bias
  85          * towards mpegps if we detect this stream as both. */
  86         for (i = 0; i<p->buf_size; i++) {
  87             code = (code << 8) + p->buf[i];
  88             if ((code & 0xffffff00) == 0x100) {
  89                 if     ((code & 0x1f0) == VIDEO_ID) pes++;
  90                 else if((code & 0x1e0) == AUDIO_ID) pes++;
  91             }
  92         }
  93
  94         if (pes)
  95             max_frames = (max_frames + pes - 1) / pes;
  96     }
  97     if      (max_frames >  500) return AVPROBE_SCORE_MAX / 2;
  98     else if (max_frames >= 4)   return AVPROBE_SCORE_MAX / 4;
  99     else if (max_frames >= 1)   return 1;
 100     else                        return 0;
 101 //mpegps_mp3_unrecognized_format.mpg has max_frames=3
 102 }
 103
 104 static void read_xing_toc(AVFormatContext *s, int64_t filesize, int64_t duration)
 105 {
 106     int i;
 107     MP3DecContext *mp3 = s->priv_data;
 108
 109     if (!filesize &&
 110         !(filesize = avio_size(s->pb))) {
 111         av_log(s, AV_LOG_WARNING, "Cannot determine file size, skipping TOC table.\n");
 112         return;
 113     }
 114
 115     for (i = 0; i < XING_TOC_COUNT; i++) {
 116         uint8_t b = avio_r8(s->pb);
 117
 118         av_add_index_entry(s->streams[0],
 119                            av_rescale(b, filesize, 256),
 120                            av_rescale(i, duration, XING_TOC_COUNT),
 121                            0, 0, AVINDEX_KEYFRAME);
 122     }
 123     mp3->xing_toc = 1;
 124 }
 125
 126 /**
 127  * Try to find Xing/Info/VBRI tags and compute duration from info therein
 128  */
 129 static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
 130 {
 131     uint32_t v, spf;
 132     unsigned frames = 0; /* Total number of frames in file */
 133     unsigned size = 0; /* Total number of bytes in the stream */
 134     const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};
 135     MPADecodeHeader c;
 136     int vbrtag_size = 0;
 137     int is_cbr;
 138
 139     v = avio_rb32(s->pb);
 140     if(ff_mpa_check_header(v) < 0)
 141       return -1;
 142
 143     if (avpriv_mpegaudio_decode_header(&c, v) == 0)
 144         vbrtag_size = c.frame_size;
 145     if(c.layer != 3)
 146         return -1;
 147
 148     spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
 149
 150     /* Check for Xing / Info tag */
 151     avio_skip(s->pb, xing_offtbl[c.lsf == 1][c.nb_channels == 1]);
 152     v = avio_rb32(s->pb);
 153     is_cbr = v == MKBETAG('I', 'n', 'f', 'o');
 154     if (v == MKBETAG('X', 'i', 'n', 'g') || is_cbr) {
 155         v = avio_rb32(s->pb);
 156         if(v & XING_FLAG_FRAMES)
 157             frames = avio_rb32(s->pb);
 158         if(v & XING_FLAG_SIZE)
 159             size = avio_rb32(s->pb);
 160         if (v & XING_FLAG_TOC && frames)
 161             read_xing_toc(s, size, av_rescale_q(frames, (AVRational){spf, c.sample_rate},
 162                                     st->time_base));
 163     }
 164
 165     /* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */
 166     avio_seek(s->pb, base + 4 + 32, SEEK_SET);
 167     v = avio_rb32(s->pb);
 168     if(v == MKBETAG('V', 'B', 'R', 'I')) {
 169         /* Check tag version */
 170         if(avio_rb16(s->pb) == 1) {
 171             /* skip delay and quality */
 172             avio_skip(s->pb, 4);
 173             size = avio_rb32(s->pb);
 174             frames = avio_rb32(s->pb);
 175         }
 176     }
 177
 178     if(!frames && !size)
 179         return -1;
 180
 181     /* Skip the vbr tag frame */
 182     avio_seek(s->pb, base + vbrtag_size, SEEK_SET);
 183
 184     if(frames)
 185         st->duration = av_rescale_q(frames, (AVRational){spf, c.sample_rate},
 186                                     st->time_base);
 187     if (size && frames && !is_cbr)
 188         st->codec->bit_rate = av_rescale(size, 8 * c.sample_rate, frames * (int64_t)spf);
 189
 190     return 0;
 191 }
 192
 193 static int mp3_read_header(AVFormatContext *s)
 194 {
 195     AVStream *st;
 196     int64_t off;
 197
 198     st = avformat_new_stream(s, NULL);
 199     if (!st)
 200         return AVERROR(ENOMEM);
 201
 202     st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
 203     st->codec->codec_id = AV_CODEC_ID_MP3;
 204     st->need_parsing = AVSTREAM_PARSE_FULL;
 205     st->start_time = 0;
 206
 207     // lcm of all mp3 sample rates
 208     avpriv_set_pts_info(st, 64, 1, 14112000);
 209
 210     off = avio_tell(s->pb);
 211
 212     if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
 213         ff_id3v1_read(s);
 214
 215     if (mp3_parse_vbr_tags(s, st, off) < 0)
 216         avio_seek(s->pb, off, SEEK_SET);
 217
 218     /* the parameters will be extracted from the compressed bitstream */
 219     return 0;
 220 }
 221
 222 #define MP3_PACKET_SIZE 1024
 223
 224 static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)
 225 {
 226     int ret;
 227
 228     ret = av_get_packet(s->pb, pkt, MP3_PACKET_SIZE);
 229     if (ret < 0)
 230         return ret;
 231
 232     pkt->stream_index = 0;
 233
 234     if (ret > ID3v1_TAG_SIZE &&
 235         memcmp(&pkt->data[ret - ID3v1_TAG_SIZE], "TAG", 3) == 0)
 236         ret -= ID3v1_TAG_SIZE;
 237
 238     /* note: we need to modify the packet size here to handle the last
 239        packet */
 240     pkt->size = ret;
 241     return ret;
 242 }
 243
 244 static int mp3_seek(AVFormatContext *s, int stream_index, int64_t timestamp,
 245                     int flags)
 246 {
 247     MP3DecContext *mp3 = s->priv_data;
 248     AVIndexEntry *ie;
 249     AVStream *st = s->streams[0];
 250     int64_t ret  = av_index_search_timestamp(st, timestamp, flags);
 251     uint32_t header = 0;
 252
 253     if (!mp3->xing_toc)
 254         return AVERROR(ENOSYS);
 255
 256     if (ret < 0)
 257         return ret;
 258
 259     ie = &st->index_entries[ret];
 260     ret = avio_seek(s->pb, ie->pos, SEEK_SET);
 261     if (ret < 0)
 262         return ret;
 263
 264     while (!s->pb->eof_reached) {
 265         header = (header << 8) + avio_r8(s->pb);
 266         if (ff_mpa_check_header(header) >= 0) {
 267             ff_update_cur_dts(s, st, ie->timestamp);
 268             ret = avio_seek(s->pb, -4, SEEK_CUR);
 269             return (ret >= 0) ? 0 : ret;
 270         }
 271     }
 272
 273     return AVERROR_EOF;
 274 }
 275
 276 AVInputFormat ff_mp3_demuxer = {
 277     .name           = "mp3",
 278     .long_name      = NULL_IF_CONFIG_SMALL("MP2/3 (MPEG audio layer 2/3)"),
 279     .read_probe     = mp3_read_probe,
 280     .read_header    = mp3_read_header,
 281     .read_packet    = mp3_read_packet,
 282     .read_seek      = mp3_seek,
 283     .priv_data_size = sizeof(MP3DecContext),
 284     .flags          = AVFMT_GENERIC_INDEX,
 285     .extensions     = "mp2,mp3,m2a", /* XXX: use probe */
 286 };