September 14, 2007 7:46 PM

/*
 * Copyright (C) 2006 Astrient Labs, LLC Licensed under the Apache License,
 * Version 2.0 (the "License"); you may not use this file except in compliance 
 * with the License. You may obtain a copy of the License at 
 * 
 *    http://www.apache.org/licenses/LICENSE-2.0 
 * 
 * Unless required by applicable law or agreed to in writing, software 
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the 
 * License for the specific language governing permissions and limitations under
 * the License.
 * 
 * Astrient Labs, LLC 
 * www.astrientlabs.com 
 * rashid@astrientlabs.com
 * Rashid Mayes 2005
 */
package com.astrientlabs.audio;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;

import javax.sound.midi.InvalidMidiDataException;
import javax.sound.midi.MidiFileFormat;
import javax.sound.midi.MidiSystem;
import javax.sound.midi.Sequence;
import javax.sound.midi.Track;

public class MidiConverter
{
    public static boolean isType1(byte[] data) throws InvalidMidiDataException, IOException
    {
        return isType1(new ByteArrayInputStream(data));
    }

    public static boolean isType1(InputStream is) throws InvalidMidiDataException, IOException
    {
        MidiFileFormat format = MidiSystem.getMidiFileFormat(is);
        return (format.getType() == 1);
    }

    public static byte[] convertToType(byte[] data, int maxTracks) throws InvalidMidiDataException, IOException
    {
        return convertToType0(new ByteArrayInputStream(data), maxTracks);
    }

    public static byte[] convertToType0(InputStream is, int maxTracks) throws InvalidMidiDataException, IOException
    {
        Sequence sequence = MidiSystem.getSequence(is);

        Track[] tracks = sequence.getTracks();
        Track first = tracks[0];
        Track track;

        for (int i = 1; i  tracks.length; i++)
        {
            track = tracks[i];
            if (i  maxTracks)
                for (int j = 0, stop = track.size(); j  stop; first.add(track.get(j++)))
                    ;
            sequence.deleteTrack(track);
        }

        ByteArrayOutputStream os = new ByteArrayOutputStream(1024);
        MidiSystem.write(sequence, 0, os);

        return os.toByteArray();
    }

    public static void main(String[] args)
    {
        try
        {
            RandomAccessFile raf = new RandomAccessFile(new File("G:/in.mid"), "r");
            byte[] data = new byte[(int) raf.length()];
            raf.readFully(data);

            ByteArrayInputStream bais = new ByteArrayInputStream(data);

            if (isType1(bais))
            {
                bais.reset();
                data = convertToType0(bais, 8);

                FileOutputStream fos = new FileOutputStream(new File("g:out.mid"));
                fos.write(data);
                fos.close(); // finally:)
            }
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
        System.exit(0);
    }
}