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198 lines
5.5 KiB
198 lines
5.5 KiB
/* |
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* MP3 demuxer |
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* Copyright (c) 2003 Fabrice Bellard |
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* |
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* This file is part of Libav. |
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* |
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* Libav is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* Libav is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with Libav; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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#include "libavutil/avstring.h" |
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#include "libavutil/intreadwrite.h" |
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#include "libavutil/dict.h" |
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#include "avformat.h" |
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#include "id3v2.h" |
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#include "id3v1.h" |
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#include "libavcodec/mpegaudiodecheader.h" |
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/* mp3 read */ |
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static int mp3_read_probe(AVProbeData *p) |
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{ |
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int max_frames, first_frames = 0; |
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int fsize, frames, sample_rate; |
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uint32_t header; |
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uint8_t *buf, *buf0, *buf2, *end; |
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AVCodecContext avctx; |
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buf0 = p->buf; |
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end = p->buf + p->buf_size - sizeof(uint32_t); |
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while(buf0 < end && !*buf0) |
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buf0++; |
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max_frames = 0; |
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buf = buf0; |
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for(; buf < end; buf= buf2+1) { |
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buf2 = buf; |
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for(frames = 0; buf2 < end; frames++) { |
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header = AV_RB32(buf2); |
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fsize = ff_mpa_decode_header(&avctx, header, &sample_rate, &sample_rate, &sample_rate, &sample_rate); |
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if(fsize < 0) |
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break; |
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buf2 += fsize; |
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} |
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max_frames = FFMAX(max_frames, frames); |
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if(buf == buf0) |
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first_frames= frames; |
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} |
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// keep this in sync with ac3 probe, both need to avoid |
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// issues with MPEG-files! |
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if (first_frames>=4) return AVPROBE_SCORE_MAX/2+1; |
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else if(max_frames>500)return AVPROBE_SCORE_MAX/2; |
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else if(max_frames>=4) return AVPROBE_SCORE_MAX/4; |
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else if(max_frames>=1) return 1; |
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else return 0; |
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//mpegps_mp3_unrecognized_format.mpg has max_frames=3 |
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} |
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/** |
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* Try to find Xing/Info/VBRI tags and compute duration from info therein |
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*/ |
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static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base) |
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{ |
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uint32_t v, spf; |
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unsigned frames = 0; /* Total number of frames in file */ |
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unsigned size = 0; /* Total number of bytes in the stream */ |
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const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}}; |
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MPADecodeHeader c; |
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int vbrtag_size = 0; |
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v = avio_rb32(s->pb); |
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if(ff_mpa_check_header(v) < 0) |
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return -1; |
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if (ff_mpegaudio_decode_header(&c, v) == 0) |
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vbrtag_size = c.frame_size; |
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if(c.layer != 3) |
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return -1; |
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/* Check for Xing / Info tag */ |
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avio_skip(s->pb, xing_offtbl[c.lsf == 1][c.nb_channels == 1]); |
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v = avio_rb32(s->pb); |
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if(v == MKBETAG('X', 'i', 'n', 'g') || v == MKBETAG('I', 'n', 'f', 'o')) { |
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v = avio_rb32(s->pb); |
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if(v & 0x1) |
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frames = avio_rb32(s->pb); |
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if(v & 0x2) |
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size = avio_rb32(s->pb); |
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} |
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/* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */ |
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avio_seek(s->pb, base + 4 + 32, SEEK_SET); |
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v = avio_rb32(s->pb); |
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if(v == MKBETAG('V', 'B', 'R', 'I')) { |
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/* Check tag version */ |
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if(avio_rb16(s->pb) == 1) { |
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/* skip delay and quality */ |
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avio_skip(s->pb, 4); |
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frames = avio_rb32(s->pb); |
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size = avio_rb32(s->pb); |
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} |
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} |
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if(!frames && !size) |
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return -1; |
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/* Skip the vbr tag frame */ |
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avio_seek(s->pb, base + vbrtag_size, SEEK_SET); |
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spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */ |
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if(frames) |
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st->duration = av_rescale_q(frames, (AVRational){spf, c.sample_rate}, |
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st->time_base); |
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if(size && frames) |
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st->codec->bit_rate = av_rescale(size, 8 * c.sample_rate, frames * (int64_t)spf); |
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return 0; |
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} |
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static int mp3_read_header(AVFormatContext *s, |
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AVFormatParameters *ap) |
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{ |
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AVStream *st; |
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int64_t off; |
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st = av_new_stream(s, 0); |
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if (!st) |
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return AVERROR(ENOMEM); |
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st->codec->codec_type = AVMEDIA_TYPE_AUDIO; |
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st->codec->codec_id = CODEC_ID_MP3; |
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st->need_parsing = AVSTREAM_PARSE_FULL; |
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st->start_time = 0; |
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// lcm of all mp3 sample rates |
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av_set_pts_info(st, 64, 1, 14112000); |
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off = avio_tell(s->pb); |
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if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX)) |
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ff_id3v1_read(s); |
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if (mp3_parse_vbr_tags(s, st, off) < 0) |
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avio_seek(s->pb, off, SEEK_SET); |
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/* the parameters will be extracted from the compressed bitstream */ |
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return 0; |
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} |
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#define MP3_PACKET_SIZE 1024 |
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static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt) |
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{ |
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int ret, size; |
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// AVStream *st = s->streams[0]; |
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size= MP3_PACKET_SIZE; |
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ret= av_get_packet(s->pb, pkt, size); |
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pkt->stream_index = 0; |
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if (ret <= 0) { |
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return AVERROR(EIO); |
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} |
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if (ret > ID3v1_TAG_SIZE && |
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memcmp(&pkt->data[ret - ID3v1_TAG_SIZE], "TAG", 3) == 0) |
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ret -= ID3v1_TAG_SIZE; |
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/* note: we need to modify the packet size here to handle the last |
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packet */ |
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pkt->size = ret; |
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return ret; |
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} |
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AVInputFormat ff_mp3_demuxer = { |
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"mp3", |
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NULL_IF_CONFIG_SMALL("MPEG audio layer 2/3"), |
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0, |
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mp3_read_probe, |
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mp3_read_header, |
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mp3_read_packet, |
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.flags= AVFMT_GENERIC_INDEX, |
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.extensions = "mp2,mp3,m2a", /* XXX: use probe */ |
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};
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