yading@11: /*
yading@11:  * MP3 demuxer
yading@11:  * Copyright (c) 2003 Fabrice Bellard
yading@11:  *
yading@11:  * This file is part of FFmpeg.
yading@11:  *
yading@11:  * FFmpeg is free software; you can redistribute it and/or
yading@11:  * modify it under the terms of the GNU Lesser General Public
yading@11:  * License as published by the Free Software Foundation; either
yading@11:  * version 2.1 of the License, or (at your option) any later version.
yading@11:  *
yading@11:  * FFmpeg is distributed in the hope that it will be useful,
yading@11:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
yading@11:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
yading@11:  * Lesser General Public License for more details.
yading@11:  *
yading@11:  * You should have received a copy of the GNU Lesser General Public
yading@11:  * License along with FFmpeg; if not, write to the Free Software
yading@11:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
yading@11:  */
yading@11: 
yading@11: #include "libavutil/avstring.h"
yading@11: #include "libavutil/intreadwrite.h"
yading@11: #include "libavutil/dict.h"
yading@11: #include "libavutil/mathematics.h"
yading@11: #include "avformat.h"
yading@11: #include "internal.h"
yading@11: #include "id3v2.h"
yading@11: #include "id3v1.h"
yading@11: #include "libavcodec/mpegaudiodecheader.h"
yading@11: 
yading@11: #define XING_FLAG_FRAMES 0x01
yading@11: #define XING_FLAG_SIZE   0x02
yading@11: #define XING_FLAG_TOC    0x04
yading@11: 
yading@11: #define XING_TOC_COUNT 100
yading@11: 
yading@11: typedef struct {
yading@11:     int64_t filesize;
yading@11:     int xing_toc;
yading@11:     int start_pad;
yading@11:     int end_pad;
yading@11: } MP3DecContext;
yading@11: 
yading@11: /* mp3 read */
yading@11: 
yading@11: static int mp3_read_probe(AVProbeData *p)
yading@11: {
yading@11:     int max_frames, first_frames = 0;
yading@11:     int fsize, frames, sample_rate;
yading@11:     uint32_t header;
yading@11:     const uint8_t *buf, *buf0, *buf2, *end;
yading@11:     AVCodecContext avctx;
yading@11: 
yading@11:     buf0 = p->buf;
yading@11:     end = p->buf + p->buf_size - sizeof(uint32_t);
yading@11:     while(buf0 < end && !*buf0)
yading@11:         buf0++;
yading@11: 
yading@11:     max_frames = 0;
yading@11:     buf = buf0;
yading@11: 
yading@11:     for(; buf < end; buf= buf2+1) {
yading@11:         buf2 = buf;
yading@11: 
yading@11:         for(frames = 0; buf2 < end; frames++) {
yading@11:             header = AV_RB32(buf2);
yading@11:             fsize = avpriv_mpa_decode_header(&avctx, header, &sample_rate, &sample_rate, &sample_rate, &sample_rate);
yading@11:             if(fsize < 0)
yading@11:                 break;
yading@11:             buf2 += fsize;
yading@11:         }
yading@11:         max_frames = FFMAX(max_frames, frames);
yading@11:         if(buf == buf0)
yading@11:             first_frames= frames;
yading@11:     }
yading@11:     // keep this in sync with ac3 probe, both need to avoid
yading@11:     // issues with MPEG-files!
yading@11:     if   (first_frames>=4) return AVPROBE_SCORE_MAX/2+1;
yading@11:     else if(max_frames>200)return AVPROBE_SCORE_MAX/2;
yading@11:     else if(max_frames>=4) return AVPROBE_SCORE_MAX/4;
yading@11:     else if(ff_id3v2_match(buf0, ID3v2_DEFAULT_MAGIC) && 2*ff_id3v2_tag_len(buf0) >= p->buf_size)
yading@11:                            return AVPROBE_SCORE_MAX/8;
yading@11:     else if(max_frames>=1) return 1;
yading@11:     else                   return 0;
yading@11: //mpegps_mp3_unrecognized_format.mpg has max_frames=3
yading@11: }
yading@11: 
yading@11: static void read_xing_toc(AVFormatContext *s, int64_t filesize, int64_t duration)
yading@11: {
yading@11:     int i;
yading@11:     MP3DecContext *mp3 = s->priv_data;
yading@11: 
yading@11:     if (!filesize &&
yading@11:         !(filesize = avio_size(s->pb))) {
yading@11:         av_log(s, AV_LOG_WARNING, "Cannot determine file size, skipping TOC table.\n");
yading@11:         return;
yading@11:     }
yading@11: 
yading@11:     for (i = 0; i < XING_TOC_COUNT; i++) {
yading@11:         uint8_t b = avio_r8(s->pb);
yading@11: 
yading@11:         av_add_index_entry(s->streams[0],
yading@11:                            av_rescale(b, filesize, 256),
yading@11:                            av_rescale(i, duration, XING_TOC_COUNT),
yading@11:                            0, 0, AVINDEX_KEYFRAME);
yading@11:     }
yading@11:     mp3->xing_toc = 1;
yading@11: }
yading@11: 
yading@11: /**
yading@11:  * Try to find Xing/Info/VBRI tags and compute duration from info therein
yading@11:  */
yading@11: static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
yading@11: {
yading@11:     MP3DecContext *mp3 = s->priv_data;
yading@11:     uint32_t v, spf;
yading@11:     unsigned frames = 0; /* Total number of frames in file */
yading@11:     unsigned size = 0; /* Total number of bytes in the stream */
yading@11:     const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};
yading@11:     MPADecodeHeader c;
yading@11:     int vbrtag_size = 0;
yading@11:     int is_cbr;
yading@11: 
yading@11:     v = avio_rb32(s->pb);
yading@11:     if(ff_mpa_check_header(v) < 0)
yading@11:       return -1;
yading@11: 
yading@11:     if (avpriv_mpegaudio_decode_header(&c, v) == 0)
yading@11:         vbrtag_size = c.frame_size;
yading@11:     if(c.layer != 3)
yading@11:         return -1;
yading@11: 
yading@11:     spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
yading@11: 
yading@11:     /* Check for Xing / Info tag */
yading@11:     avio_skip(s->pb, xing_offtbl[c.lsf == 1][c.nb_channels == 1]);
yading@11:     v = avio_rb32(s->pb);
yading@11:     is_cbr = v == MKBETAG('I', 'n', 'f', 'o');
yading@11:     if (v == MKBETAG('X', 'i', 'n', 'g') || is_cbr) {
yading@11:         v = avio_rb32(s->pb);
yading@11:         if(v & XING_FLAG_FRAMES)
yading@11:             frames = avio_rb32(s->pb);
yading@11:         if(v & XING_FLAG_SIZE)
yading@11:             size = avio_rb32(s->pb);
yading@11:         if (v & XING_FLAG_TOC && frames)
yading@11:             read_xing_toc(s, size, av_rescale_q(frames, (AVRational){spf, c.sample_rate},
yading@11:                                     st->time_base));
yading@11:         if(v & 8)
yading@11:             avio_skip(s->pb, 4);
yading@11: 
yading@11:         v = avio_rb32(s->pb);
yading@11:         if(v == MKBETAG('L', 'A', 'M', 'E') || v == MKBETAG('L', 'a', 'v', 'f')) {
yading@11:             avio_skip(s->pb, 21-4);
yading@11:             v= avio_rb24(s->pb);
yading@11:             mp3->start_pad = v>>12;
yading@11:             mp3->  end_pad = v&4095;
yading@11:             st->skip_samples = mp3->start_pad + 528 + 1;
yading@11:             av_log(s, AV_LOG_DEBUG, "pad %d %d\n", mp3->start_pad, mp3->  end_pad);
yading@11:         }
yading@11:     }
yading@11: 
yading@11:     /* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */
yading@11:     avio_seek(s->pb, base + 4 + 32, SEEK_SET);
yading@11:     v = avio_rb32(s->pb);
yading@11:     if(v == MKBETAG('V', 'B', 'R', 'I')) {
yading@11:         /* Check tag version */
yading@11:         if(avio_rb16(s->pb) == 1) {
yading@11:             /* skip delay and quality */
yading@11:             avio_skip(s->pb, 4);
yading@11:             size = avio_rb32(s->pb);
yading@11:             frames = avio_rb32(s->pb);
yading@11:         }
yading@11:     }
yading@11: 
yading@11:     if(!frames && !size)
yading@11:         return -1;
yading@11: 
yading@11:     /* Skip the vbr tag frame */
yading@11:     avio_seek(s->pb, base + vbrtag_size, SEEK_SET);
yading@11: 
yading@11:     if(frames)
yading@11:         st->duration = av_rescale_q(frames, (AVRational){spf, c.sample_rate},
yading@11:                                     st->time_base);
yading@11:     if (size && frames && !is_cbr)
yading@11:         st->codec->bit_rate = av_rescale(size, 8 * c.sample_rate, frames * (int64_t)spf);
yading@11: 
yading@11:     return 0;
yading@11: }
yading@11: 
yading@11: static int mp3_read_header(AVFormatContext *s)
yading@11: {
yading@11:     MP3DecContext *mp3 = s->priv_data;
yading@11:     AVStream *st;
yading@11:     int64_t off;
yading@11: 
yading@11:     st = avformat_new_stream(s, NULL);
yading@11:     if (!st)
yading@11:         return AVERROR(ENOMEM);
yading@11: 
yading@11:     st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
yading@11:     st->codec->codec_id = AV_CODEC_ID_MP3;
yading@11:     st->need_parsing = AVSTREAM_PARSE_FULL_RAW;
yading@11:     st->start_time = 0;
yading@11: 
yading@11:     // lcm of all mp3 sample rates
yading@11:     avpriv_set_pts_info(st, 64, 1, 14112000);
yading@11: 
yading@11:     s->pb->maxsize = -1;
yading@11:     off = avio_tell(s->pb);
yading@11: 
yading@11:     if (!av_dict_get(s->metadata, "", NULL, AV_DICT_IGNORE_SUFFIX))
yading@11:         ff_id3v1_read(s);
yading@11: 
yading@11:     if(s->pb->seekable)
yading@11:         mp3->filesize = avio_size(s->pb);
yading@11: 
yading@11:     if (mp3_parse_vbr_tags(s, st, off) < 0)
yading@11:         avio_seek(s->pb, off, SEEK_SET);
yading@11: 
yading@11:     /* the parameters will be extracted from the compressed bitstream */
yading@11:     return 0;
yading@11: }
yading@11: 
yading@11: #define MP3_PACKET_SIZE 1024
yading@11: 
yading@11: static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)
yading@11: {
yading@11:     MP3DecContext *mp3 = s->priv_data;
yading@11:     int ret, size;
yading@11:     int64_t pos;
yading@11: 
yading@11:     size= MP3_PACKET_SIZE;
yading@11:     pos = avio_tell(s->pb);
yading@11:     if(mp3->filesize > ID3v1_TAG_SIZE && pos < mp3->filesize)
yading@11:         size= FFMIN(size, mp3->filesize - pos);
yading@11: 
yading@11:     ret= av_get_packet(s->pb, pkt, size);
yading@11:     if (ret <= 0) {
yading@11:         if(ret<0)
yading@11:             return ret;
yading@11:         return AVERROR_EOF;
yading@11:     }
yading@11: 
yading@11:     pkt->flags &= ~AV_PKT_FLAG_CORRUPT;
yading@11:     pkt->stream_index = 0;
yading@11: 
yading@11:     if (ret >= ID3v1_TAG_SIZE &&
yading@11:         memcmp(&pkt->data[ret - ID3v1_TAG_SIZE], "TAG", 3) == 0)
yading@11:         ret -= ID3v1_TAG_SIZE;
yading@11: 
yading@11:     /* note: we need to modify the packet size here to handle the last
yading@11:        packet */
yading@11:     pkt->size = ret;
yading@11:     return ret;
yading@11: }
yading@11: 
yading@11: static int check(AVFormatContext *s, int64_t pos)
yading@11: {
yading@11:     int64_t ret = avio_seek(s->pb, pos, SEEK_SET);
yading@11:     unsigned header;
yading@11:     MPADecodeHeader sd;
yading@11:     if (ret < 0)
yading@11:         return ret;
yading@11:     header = avio_rb32(s->pb);
yading@11:     if (ff_mpa_check_header(header) < 0)
yading@11:         return -1;
yading@11:     if (avpriv_mpegaudio_decode_header(&sd, header) == 1)
yading@11:         return -1;
yading@11:     return sd.frame_size;
yading@11: }
yading@11: 
yading@11: static int mp3_seek(AVFormatContext *s, int stream_index, int64_t timestamp,
yading@11:                     int flags)
yading@11: {
yading@11:     MP3DecContext *mp3 = s->priv_data;
yading@11:     AVIndexEntry *ie;
yading@11:     AVStream *st = s->streams[0];
yading@11:     int64_t ret  = av_index_search_timestamp(st, timestamp, flags);
yading@11:     int i, j;
yading@11: 
yading@11:     if (!mp3->xing_toc) {
yading@11:         st->skip_samples = timestamp <= 0 ? mp3->start_pad + 528 + 1 : 0;
yading@11: 
yading@11:         return -1;
yading@11:     }
yading@11: 
yading@11:     if (ret < 0)
yading@11:         return ret;
yading@11: 
yading@11:     ie = &st->index_entries[ret];
yading@11:     ret = avio_seek(s->pb, ie->pos, SEEK_SET);
yading@11:     if (ret < 0)
yading@11:         return ret;
yading@11: 
yading@11: #define MIN_VALID 3
yading@11:     for(i=0; i<4096; i++) {
yading@11:         int64_t pos = ie->pos + i;
yading@11:         for(j=0; j<MIN_VALID; j++) {
yading@11:             ret = check(s, pos);
yading@11:             if(ret < 0)
yading@11:                 break;
yading@11:             pos += ret;
yading@11:         }
yading@11:         if(j==MIN_VALID)
yading@11:             break;
yading@11:     }
yading@11:     if(j!=MIN_VALID)
yading@11:         i=0;
yading@11: 
yading@11:     ret = avio_seek(s->pb, ie->pos + i, SEEK_SET);
yading@11:     if (ret < 0)
yading@11:         return ret;
yading@11:     ff_update_cur_dts(s, st, ie->timestamp);
yading@11:     st->skip_samples = ie->timestamp <= 0 ? mp3->start_pad + 528 + 1 : 0;
yading@11:     return 0;
yading@11: }
yading@11: 
yading@11: AVInputFormat ff_mp3_demuxer = {
yading@11:     .name           = "mp3",
yading@11:     .long_name      = NULL_IF_CONFIG_SMALL("MP2/3 (MPEG audio layer 2/3)"),
yading@11:     .read_probe     = mp3_read_probe,
yading@11:     .read_header    = mp3_read_header,
yading@11:     .read_packet    = mp3_read_packet,
yading@11:     .read_seek      = mp3_seek,
yading@11:     .priv_data_size = sizeof(MP3DecContext),
yading@11:     .flags          = AVFMT_GENERIC_INDEX,
yading@11:     .extensions     = "mp2,mp3,m2a", /* XXX: use probe */
yading@11: };