/*
* Entagged Audio Tag library
* Copyright (c) 2003-2005 Rapha�l Slinckx <raphael@slinckx.net>
*
* This library 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.
*
* This library 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 this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
package entagged.audioformats.mp3.util;
import entagged.audioformats.EncodingInfo;
import entagged.audioformats.exceptions.*;
import java.io.*;
public class Mp3InfoReader {
public EncodingInfo read( RandomAccessFile raf ) throws CannotReadException, IOException {
EncodingInfo encodingInfo = new EncodingInfo();
//Begin info fetch-------------------------------------------
if ( raf.length()==0 ) {
//Empty File
System.err.println("Error: File empty");
throw new CannotReadException("File is empty");
}
int id3TagSize = 0;
raf.seek( 0 );
// skip id3v2 tag, because there may be long pictures inside with
// slows reading and they can be not unsyncronized
byte[] bbb = new byte[3];
raf.read(bbb);
raf.seek(0);
String ID3 = new String(bbb);
if (ID3.equals("ID3")) {
raf.seek(6);
id3TagSize = read_syncsafe_integer(raf);
raf.seek(id3TagSize+10);
//System.err.println("TagSize: "+tagSize);
}
MPEGFrame firstFrame = null;
byte[] b = new byte[4];
raf.read(b);
// search for sync mark, but also for a right bitrate, samplerate and layer(that way you can
// read corrupted but playable files)
while ( !( (b[0]&0xFF)==0xFF && (b[1]&0xE0)==0xE0 && (b[1]&0x06)!=0 && (b[2]&0xF0)!=0xF0 && (b[2]&0x0C)!=0x0C ) && raf.getFilePointer() < raf.length()-4) {
//System.err.println(sync[0]+"|"+(sync[1]&0xE0)+"|"+((sync[1]&0xE0)==0xE0));
raf.seek( raf.getFilePointer() - 3);
//raf.read(sync);
raf.read(b);
}
//raf.seek( raf.getFilePointer() - 2 );
//System.err.println(raf.getFilePointer());
//raf.read( b );
firstFrame = new MPEGFrame( b );
//System.err.println(b[0]+"|"+b[1]+"|"+b[2]+"|"+b[3]);
//System.err.println("Frame at offset:"+new Long(raf.getFilePointer()-4)+firstFrame);
if ( firstFrame == null || !firstFrame.isValid() || firstFrame.getSamplingRate() == 0 ) {
//MP3File corrupted, no valid MPEG frames
//System.err.println("Error: could not synchronize to first mp3 frame");
throw new CannotReadException("Error: could not synchronize to first mp3 frame");
}
int firstFrameLength = firstFrame.getFrameLength();
//----------------------------------------------------------------------------
int skippedLength = 0;
if ( firstFrame.getMPEGVersion() == MPEGFrame.MPEG_VERSION_1 && firstFrame.getChannelMode() == MPEGFrame.CHANNEL_MODE_MONO ) {
raf.seek( raf.getFilePointer() + 17 );
skippedLength += 17;
}
else if ( firstFrame.getMPEGVersion() == MPEGFrame.MPEG_VERSION_1 ) {
raf.seek( raf.getFilePointer() + 32 );
skippedLength += 32;
}
else if ( firstFrame.getMPEGVersion() == MPEGFrame.MPEG_VERSION_2 && firstFrame.getChannelMode() == MPEGFrame.CHANNEL_MODE_MONO ) {
raf.seek( raf.getFilePointer() + 9 );
skippedLength += 9;
}
else if ( firstFrame.getMPEGVersion() == MPEGFrame.MPEG_VERSION_2 ) {
raf.seek( raf.getFilePointer() + 17 );
skippedLength += 17;
}
int optionalFrameLength = 0;
//System.err.println(mp3File);
//System.err.println(raf.getFilePointer());
byte[] xingPart1 = new byte[16];
raf.read( xingPart1 );
raf.seek( raf.getFilePointer() + 100 );
byte[] xingPart2 = new byte[4];
raf.read( xingPart2 );
VbrInfoFrame vbrInfoFrame = new XingMPEGFrame( xingPart1, xingPart2 );
if ( vbrInfoFrame.isValid() ) {
optionalFrameLength += 120;
byte[] lameHeader = new byte[36];
raf.read( lameHeader );
LameMPEGFrame currentLameFrame = new LameMPEGFrame( lameHeader );
if ( !currentLameFrame.isValid() )
raf.seek( raf.getFilePointer() - 36 ); //Skipping Lame frame reading
else
optionalFrameLength += 36; //Lame Frame read
raf.seek( raf.getFilePointer() + firstFrameLength - ( skippedLength + optionalFrameLength + 4 ) );
} else {
//Skipping Xing frame reading
raf.seek( raf.getFilePointer() - 120 - skippedLength + 32); //120 Xing bytes, unused skipped bytes then go to vbri location
// Try to read VBRI frame
byte[] vbriHeader = new byte[18];
raf.read( vbriHeader );
vbrInfoFrame = new VBRIMPEGFrame(vbriHeader);
raf.seek( raf.getFilePointer() - 18 - 4); //18 VBRI bytes and 4 mpeg info bytes
}
//----------------------------------------------------------------------------
//Length computation
double timePerFrame = ((double) firstFrame.getSampleNumber()) / firstFrame.getSamplingRate();
double lengthInSeconds;
if (vbrInfoFrame.isValid()) {
//Preffered Method: extracts time length with the Xing Header (vbr:Xing or cbr:Info) or VBRI****************
lengthInSeconds = ( timePerFrame * vbrInfoFrame.getFrameCount() );
encodingInfo.setVbr(vbrInfoFrame.isVbr());
int fs = vbrInfoFrame.getFileSize();
encodingInfo.setBitrate((int)( ( (fs==0 ? raf.length()-id3TagSize : fs) * 8 ) / ( timePerFrame * vbrInfoFrame.getFrameCount() * 1000 ) ));
}
else {
//Default Method: extracts time length using the file length and assuming CBR********************
int frameLength = firstFrame.getFrameLength();
if (frameLength==0)
throw new CannotReadException("Error while reading header(maybe file is corrupted, or missing first mpeg frame before xing header)");
lengthInSeconds = timePerFrame * ((raf.length()-id3TagSize) / frameLength);
encodingInfo.setVbr(false);
encodingInfo.setBitrate( firstFrame.getBitrate() );
}
//Populates encodingInfo----------------------------------------------------
encodingInfo.setPreciseLength ((float)lengthInSeconds );
encodingInfo.setChannelNumber( firstFrame.getChannelNumber() );
encodingInfo.setSamplingRate( firstFrame.getSamplingRate() );
encodingInfo.setEncodingType( firstFrame.MPEGVersionToString( firstFrame.getMPEGVersion() ) + " || " + firstFrame.layerToString( firstFrame.getLayerVersion() ) );
encodingInfo.setExtraEncodingInfos( "" );
return encodingInfo;
}
private int read_syncsafe_integer(RandomAccessFile raf)
throws IOException {
int value = 0;
value += (raf.read()& 0xFF) << 21;
value += (raf.read()& 0xFF) << 14;
value += (raf.read()& 0xFF) << 7;
value += (raf.read()& 0xFF);
return value;
}
}