/*
* 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.mpc.util;
import entagged.audioformats.EncodingInfo;
import entagged.audioformats.exceptions.*;
import java.io.*;
public class MpcInfoReader {
public EncodingInfo read( RandomAccessFile raf ) throws CannotReadException, IOException {
EncodingInfo info = new EncodingInfo();
//Begin info fetch-------------------------------------------
if ( raf.length()==0 ) {
//Empty File
System.err.println("Error: File empty");
throw new CannotReadException("File is empty");
}
raf.seek( 0 );
//MP+ Header string
byte[] b = new byte[3];
raf.read(b);
String mpc = new String(b);
if (!mpc.equals("MP+") && mpc.equals("ID3")) {
//TODO Do we have to do this ??
//we have an ID3v2 tag at the beginning
//We quickly jump to MPC data
raf.seek(6);
int tagSize = read_syncsafe_integer(raf);
raf.seek(tagSize+10);
//retry to read MPC stream
b = new byte[3];
raf.read(b);
mpc = new String(b);
if (!mpc.equals("MP+")) {
//We could definitely not go there
throw new CannotReadException("MP+ Header not found");
}
} else if (!mpc.equals("MP+")){
throw new CannotReadException("MP+ Header not found");
}
b = new byte[25];
raf.read(b);
MpcHeader mpcH = new MpcHeader(b);
//We only support v7 Stream format, so if it isn't v7, then returned values
//will be bogus, and the file will be ignored
double pcm = mpcH.getSamplesNumber();
// info.setLength( (int) ( pcm * 1152 / mpcH.getSamplingRate() ) );
info.setPreciseLength( (float) ( pcm * 1152 / mpcH.getSamplingRate() ) );
info.setChannelNumber( mpcH.getChannelNumber() );
info.setSamplingRate( mpcH.getSamplingRate() );
info.setEncodingType( mpcH.getEncodingType() );
info.setExtraEncodingInfos( mpcH.getEncoderInfo() );
info.setBitrate( computeBitrate( info.getLength(), raf.length() ) );
return info;
}
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;
}
private int computeBitrate( int length, long size ) {
return (int) ( ( size / 1000 ) * 8 / length );
}
}