/* * MP3 demuxer * Copyright (c) 2003 Fabrice Bellard * * This file is part of Libav. * * Libav is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * Libav is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with Libav; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ #include "libavutil/avstring.h" #include "libavutil/intreadwrite.h" #include "libavutil/crc.h" #include "libavutil/dict.h" #include "libavutil/mathematics.h" #include "avformat.h" #include "internal.h" #include "avio_internal.h" #include "id3v2.h" #include "id3v1.h" #include "replaygain.h" #include "libavcodec/avcodec.h" #include "libavcodec/mpegaudiodecheader.h" #define XING_FLAG_FRAMES 0x01 #define XING_FLAG_SIZE 0x02 #define XING_FLAG_TOC 0x04 #define XING_FLAC_QSCALE 0x08 #define XING_TOC_COUNT 100 typedef struct MP3DecContext { int xing_toc; unsigned frames; /* Total number of frames in file */ unsigned size; /* Total number of bytes in the stream */ int is_cbr; } MP3DecContext; /* mp3 read */ static int mp3_read_probe(AVProbeData *p) { int max_frames, first_frames = 0; int frames, ret; uint32_t header; uint8_t *buf, *buf0, *buf2, *end; buf0 = p->buf; end = p->buf + p->buf_size - sizeof(uint32_t); while(buf0 < end && !*buf0) buf0++; max_frames = 0; buf = buf0; for(; buf < end; buf= buf2+1) { buf2 = buf; for(frames = 0; buf2 < end; frames++) { MPADecodeHeader h; header = AV_RB32(buf2); ret = avpriv_mpegaudio_decode_header(&h, header); if (ret != 0) break; buf2 += h.frame_size; } max_frames = FFMAX(max_frames, frames); if(buf == buf0) first_frames= frames; } // keep this in sync with ac3 probe, both need to avoid // issues with MPEG-files! if (first_frames >= 10) return AVPROBE_SCORE_EXTENSION + 5; if (first_frames >= 4) return AVPROBE_SCORE_EXTENSION + 1; if (max_frames) { int pes = 0, i; unsigned int code = -1; #define VIDEO_ID 0x000001e0 #define AUDIO_ID 0x000001c0 /* do a search for mpegps headers to be able to properly bias * towards mpegps if we detect this stream as both. */ for (i = 0; i<p->buf_size; i++) { code = (code << 8) + p->buf[i]; if ((code & 0xffffff00) == 0x100) { if ((code & 0x1f0) == VIDEO_ID) pes++; else if((code & 0x1e0) == AUDIO_ID) pes++; } } if (pes) max_frames = (max_frames + pes - 1) / pes; } if (max_frames > 500) return AVPROBE_SCORE_EXTENSION; else if (max_frames >= 4) return AVPROBE_SCORE_EXTENSION / 2; else if (max_frames >= 1) return 1; else return 0; //mpegps_mp3_unrecognized_format.mpg has max_frames=3 } static void read_xing_toc(AVFormatContext *s, int64_t filesize, int64_t duration) { int i; MP3DecContext *mp3 = s->priv_data; if (!filesize && !(filesize = avio_size(s->pb))) { av_log(s, AV_LOG_WARNING, "Cannot determine file size, skipping TOC table.\n"); return; } for (i = 0; i < XING_TOC_COUNT; i++) { uint8_t b = avio_r8(s->pb); av_add_index_entry(s->streams[0], av_rescale(b, filesize, 256), av_rescale(i, duration, XING_TOC_COUNT), 0, 0, AVINDEX_KEYFRAME); } mp3->xing_toc = 1; } static void mp3_parse_info_tag(AVFormatContext *s, AVStream *st, MPADecodeHeader *c, uint32_t spf) { #define LAST_BITS(k, n) ((k) & ((1 << (n)) - 1)) #define MIDDLE_BITS(k, m, n) LAST_BITS((k) >> (m), ((n) - (m))) uint16_t crc; uint32_t v, delays; char version[10]; uint32_t peak = 0; int32_t r_gain = INT32_MIN, a_gain = INT32_MIN; MP3DecContext *mp3 = s->priv_data; static const int64_t xing_offtbl[2][2] = { { 32, 17 }, { 17, 9 } }; /* Check for Xing / Info tag */ avio_skip(s->pb, xing_offtbl[c->lsf == 1][c->nb_channels == 1]); v = avio_rb32(s->pb); mp3->is_cbr = v == MKBETAG('I', 'n', 'f', 'o'); if (v != MKBETAG('X', 'i', 'n', 'g') && !mp3->is_cbr) return; v = avio_rb32(s->pb); if (v & XING_FLAG_FRAMES) mp3->frames = avio_rb32(s->pb); if (v & XING_FLAG_SIZE) mp3->size = avio_rb32(s->pb); if (v & XING_FLAG_TOC && mp3->frames) read_xing_toc(s, mp3->size, av_rescale_q(mp3->frames, (AVRational){spf, c->sample_rate}, st->time_base)); /* VBR quality */ if (v & XING_FLAC_QSCALE) avio_rb32(s->pb); /* Encoder short version string */ memset(version, 0, sizeof(version)); avio_read(s->pb, version, 9); /* Info Tag revision + VBR method */ avio_r8(s->pb); /* Lowpass filter value */ avio_r8(s->pb); /* ReplayGain peak */ v = avio_rb32(s->pb); peak = av_rescale(v, 100000, 1 << 23); /* Radio ReplayGain */ v = avio_rb16(s->pb); if (MIDDLE_BITS(v, 13, 15) == 1) { r_gain = MIDDLE_BITS(v, 0, 8) * 10000; if (v & (1 << 9)) r_gain *= -1; } /* Audiophile ReplayGain */ v = avio_rb16(s->pb); if (MIDDLE_BITS(v, 13, 15) == 2) { a_gain = MIDDLE_BITS(v, 0, 8) * 10000; if (v & (1 << 9)) a_gain *= -1; } /* Encoding flags + ATH Type */ avio_r8(s->pb); /* if ABR {specified bitrate} else {minimal bitrate} */ avio_r8(s->pb); /* Encoder delays */ delays = avio_rb24(s->pb); st->codecpar->initial_padding = delays >> 12; st->codecpar->trailing_padding = delays & ((1 << 12) - 1); /* Misc */ avio_r8(s->pb); /* MP3 gain */ avio_r8(s->pb); /* Preset and surround info */ avio_rb16(s->pb); /* Music length */ avio_rb32(s->pb); /* Music CRC */ avio_rb16(s->pb); /* Info Tag CRC */ crc = ffio_get_checksum(s->pb); v = avio_rb16(s->pb); if (v == crc) { ff_replaygain_export_raw(st, r_gain, peak, a_gain, 0); av_dict_set(&st->metadata, "encoder", version, 0); } } static void mp3_parse_vbri_tag(AVFormatContext *s, AVStream *st, int64_t base) { uint32_t v; MP3DecContext *mp3 = s->priv_data; /* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */ avio_seek(s->pb, base + 4 + 32, SEEK_SET); v = avio_rb32(s->pb); if (v == MKBETAG('V', 'B', 'R', 'I')) { /* Check tag version */ if (avio_rb16(s->pb) == 1) { /* skip delay and quality */ avio_skip(s->pb, 4); mp3->size = avio_rb32(s->pb); mp3->frames = avio_rb32(s->pb); } } } /** * Try to find Xing/Info/VBRI tags and compute duration from info therein */ static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base) { uint32_t v, spf; MPADecodeHeader c; int vbrtag_size = 0; MP3DecContext *mp3 = s->priv_data; int ret; ffio_init_checksum(s->pb, ff_crcA001_update, 0); v = avio_rb32(s->pb); ret = avpriv_mpegaudio_decode_header(&c, v); if (ret < 0) return ret; else if (ret == 0) vbrtag_size = c.frame_size; if(c.layer != 3) return -1; spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */ mp3->frames = 0; mp3->size = 0; mp3_parse_info_tag(s, st, &c, spf); mp3_parse_vbri_tag(s, st, base); if (!mp3->frames && !mp3->size) return -1; /* Skip the vbr tag frame */ avio_seek(s->pb, base + vbrtag_size, SEEK_SET); if (mp3->frames) st->duration = av_rescale_q(mp3->frames, (AVRational){spf, c.sample_rate}, st->time_base); if (mp3->size && mp3->frames && !mp3->is_cbr) st->codecpar->bit_rate = av_rescale(mp3->size, 8 * c.sample_rate, mp3->frames * (int64_t)spf); return 0; } static int mp3_read_header(AVFormatContext *s) { AVStream *st; int64_t off; int ret; st = avformat_new_stream(s, NULL); if (!st) return AVERROR(ENOMEM); st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO; st->codecpar->codec_id = AV_CODEC_ID_MP3; st->need_parsing = AVSTREAM_PARSE_FULL; st->start_time = 0; // lcm of all mp3 sample rates avpriv_set_pts_info(st, 64, 1, 14112000); off = avio_tell(s->pb); if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX)) ff_id3v1_read(s); if (mp3_parse_vbr_tags(s, st, off) < 0) avio_seek(s->pb, off, SEEK_SET); ret = ff_replaygain_export(st, s->metadata); if (ret < 0) return ret; /* the parameters will be extracted from the compressed bitstream */ return 0; } #define MP3_PACKET_SIZE 1024 static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt) { int ret; ret = av_get_packet(s->pb, pkt, MP3_PACKET_SIZE); if (ret < 0) return ret; pkt->stream_index = 0; if (ret > ID3v1_TAG_SIZE && memcmp(&pkt->data[ret - ID3v1_TAG_SIZE], "TAG", 3) == 0) ret -= ID3v1_TAG_SIZE; /* note: we need to modify the packet size here to handle the last packet */ pkt->size = ret; return ret; } #define SEEK_PACKETS 4 #define SEEK_WINDOW (SEEK_PACKETS * MP3_PACKET_SIZE) /* The toc entry can position to the wrong byte offset, try to pick * the closest frame by probing the data in a window of 4 packets. */ static int check(AVIOContext *pb, int64_t pos, int64_t *out_pos) { MPADecodeHeader mh = { 0 }; int i; uint32_t header; int64_t off = 0; for (i = 0; i < SEEK_PACKETS; i++) { off = avio_seek(pb, pos + mh.frame_size, SEEK_SET); if (off < 0) break; header = avio_rb32(pb); if (avpriv_mpegaudio_decode_header(&mh, header)) break; out_pos[i] = off; } return i; } static int reposition(AVFormatContext *s, int64_t pos) { int ret, best_valid = -1; int64_t p, best_pos = -1; for (p = FFMAX(pos - SEEK_WINDOW / 2, 0); p < pos + SEEK_WINDOW / 2; p++) { int64_t out_pos[SEEK_PACKETS]; ret = check(s->pb, p, out_pos); if (best_valid < ret) { int i; for (i = 0; i < ret; i++) { if (llabs(best_pos - pos) > llabs(out_pos[i] - pos)) { best_pos = out_pos[i]; best_valid = ret; } } if (best_pos == pos && best_valid == SEEK_PACKETS) break; } } if (best_valid <= 0) return AVERROR(ENOSYS); p = avio_seek(s->pb, best_pos, SEEK_SET); if (p < 0) return p; return 0; } static int mp3_seek(AVFormatContext *s, int stream_index, int64_t timestamp, int flags) { MP3DecContext *mp3 = s->priv_data; AVIndexEntry *ie; AVStream *st = s->streams[0]; int64_t ret = av_index_search_timestamp(st, timestamp, flags); if (!mp3->xing_toc) return AVERROR(ENOSYS); if (ret < 0) return ret; ie = &st->index_entries[ret]; ret = reposition(s, ie->pos); if (ret < 0) return ret; ff_update_cur_dts(s, st, ie->timestamp); return 0; } AVInputFormat ff_mp3_demuxer = { .name = "mp3", .long_name = NULL_IF_CONFIG_SMALL("MP2/3 (MPEG audio layer 2/3)"), .read_probe = mp3_read_probe, .read_header = mp3_read_header, .read_packet = mp3_read_packet, .read_seek = mp3_seek, .priv_data_size = sizeof(MP3DecContext), .flags = AVFMT_GENERIC_INDEX, .extensions = "mp2,mp3,m2a,mpa", /* XXX: use probe */ };