/*
* Entagged Audio Tag library
* Copyright (c) 2003-2005 Rapha�l Slinckx <raphael@slinckx.net>
* Copyright (c) 2004-2005 Christian Laireiter <liree@web.de>
*
* 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.ogg.util;
import entagged.audioformats.EncodingInfo;
import entagged.audioformats.exceptions.*;
import java.io.*;
public class OggInfoReader {
public EncodingInfo read( RandomAccessFile raf ) throws CannotReadException, IOException {
EncodingInfo info = new EncodingInfo();
long oldPos = 0;
//Reads the file encoding infos -----------------------------------
raf.seek( 0 );
double PCMSamplesNumber = -1;
raf.seek( raf.length()-2);
while(raf.getFilePointer() >= 4) {
if(raf.read()==0x53) {
raf.seek( raf.getFilePointer() - 4);
byte[] ogg = new byte[3];
raf.readFully(ogg);
if(ogg[0]==0x4F && ogg[1]==0x67 && ogg[2]==0x67) {
raf.seek( raf.getFilePointer() - 3);
oldPos = raf.getFilePointer();
raf.seek(raf.getFilePointer() + 26);
int pageSegments = raf.readByte()&0xFF; //Unsigned
raf.seek( oldPos );
byte[] b = new byte[27 + pageSegments];
raf.readFully( b );
OggPageHeader pageHeader = new OggPageHeader( b );
raf.seek(0);
PCMSamplesNumber = pageHeader.getAbsoluteGranulePosition();
break;
}
}
raf.seek( raf.getFilePointer() - 2);
}
if(PCMSamplesNumber == -1){
throw new CannotReadException("Error: Could not find the Ogg Setup block");
}
//Supposing 1st page = codec infos
// 2nd page = comment+decode info
//...Extracting 1st page
byte[] b = new byte[4];
oldPos = raf.getFilePointer();
raf.seek(26);
int pageSegments = raf.read()&0xFF; //Unsigned
raf.seek( oldPos );
b = new byte[27 + pageSegments];
raf.read( b );
OggPageHeader pageHeader = new OggPageHeader( b );
byte[] vorbisData = new byte[pageHeader.getPageLength()];
raf.read( vorbisData );
VorbisCodecHeader vorbisCodecHeader = new VorbisCodecHeader( vorbisData );
//Populates encodingInfo----------------------------------------------------
info.setPreciseLength( (float) (PCMSamplesNumber / vorbisCodecHeader.getSamplingRate()));
info.setChannelNumber( vorbisCodecHeader.getChannelNumber() );
info.setSamplingRate( vorbisCodecHeader.getSamplingRate() );
info.setEncodingType( vorbisCodecHeader.getEncodingType() );
info.setExtraEncodingInfos( "" );
if(vorbisCodecHeader.getNominalBitrate() != 0
&& vorbisCodecHeader.getMaxBitrate() == vorbisCodecHeader.getNominalBitrate()
&& vorbisCodecHeader.getMinBitrate() == vorbisCodecHeader.getNominalBitrate()) {
//CBR (in kbps)
info.setBitrate(vorbisCodecHeader.getNominalBitrate() / 1000);
info.setVbr(false);
}
else if(vorbisCodecHeader.getNominalBitrate() != 0
&& vorbisCodecHeader.getMaxBitrate() == 0
&& vorbisCodecHeader.getMinBitrate() == 0) {
//Average vbr (in kpbs)
info.setBitrate(vorbisCodecHeader.getNominalBitrate() / 1000);
info.setVbr(true);
}
else {
info.setBitrate( computeBitrate( info.getLength(), raf.length() ) );
info.setVbr(true);
}
return info;
}
private int computeBitrate( int length, long size ) {
return (int) ( ( size / 1000 ) * 8 / length );
}
}