how to synchronise audio and video using xuggler

I am developing Screen Recorder with Audio using xuggler in java. I have successfully created video file and Audio file separately. now I wants to Synchronize those two file. I have tried using "ConcatenateAudioAndVideo.java", but when I run the file then it just produce 44bytes file. Can anyone tell me what is the problem? Thanks in advance.

I was also heaving the problem of Synchronize two file (audio and video). There were lots of tips to do this on Internet but not a complete code example. I solved it by writing the code using xuggler. Here is the code. If you have any question please do ask. I will help you, as much i can. This is the code:

import com.xuggle.mediatool.IMediaWriter;
import com.xuggle.mediatool.ToolFactory;
import com.xuggle.xuggler.IAudioSamples;
import com.xuggle.xuggler.ICodec;
import com.xuggle.xuggler.IContainer;
import com.xuggle.xuggler.IPacket;
import com.xuggle.xuggler.IStream;
import com.xuggle.xuggler.IStreamCoder;
import com.xuggle.xuggler.IVideoPicture;


 /**
 * This class is used to merge audio and video file.
 *
 * @author Arslaan Ejaz
 */
public class DecodeAndSaveAudioVideo {

 public static void main(String[] args)
  {

    String filenamevideo = "f:/testvidfol/video.mp4"; //this is the input file for video. you can change extension
    String filenameaudio = "f:/testvidfol/audio.wav"; //this is the input file for audio. you can change extension


    IMediaWriter mWriter = ToolFactory.makeWriter("f:/testvidfol/audiovideooutput.flv"); //output file

    IContainer containerVideo = IContainer.make();
    IContainer containerAudio = IContainer.make();

    if (containerVideo.open(filenamevideo, IContainer.Type.READ, null) < 0)
        throw new IllegalArgumentException("Cant find " + filenamevideo);

    if (containerAudio.open(filenameaudio, IContainer.Type.READ, null) < 0)
        throw new IllegalArgumentException("Cant find " + filenameaudio);

    int numStreamVideo = containerVideo.getNumStreams();
    int numStreamAudio = containerAudio.getNumStreams();

    System.out.println("Number of video streams: "+numStreamVideo + "\n" + "Number of audio streams: "+numStreamAudio );

int videostreamt = -1; //this is the video stream id
int audiostreamt = -1;

IStreamCoder  videocoder = null;

    for(int i=0; i<numStreamVideo; i++){
        IStream stream = containerVideo.getStream(i);
        IStreamCoder code = stream.getStreamCoder();

        if(code.getCodecType() == ICodec.Type.CODEC_TYPE_VIDEO)
        {
            videostreamt = i;
            videocoder = code;
            break;
        }

    }

    for(int i=0; i<numStreamAudio; i++){
        IStream stream = containerAudio.getStream(i);
        IStreamCoder code = stream.getStreamCoder();

        if(code.getCodecType() == ICodec.Type.CODEC_TYPE_AUDIO)
        {
            audiostreamt = i;
            break;
        }

    }

    if (videostreamt == -1) throw new RuntimeException("No video steam found");
    if (audiostreamt == -1) throw new RuntimeException("No audio steam found");

    if(videocoder.open()<0 ) throw new RuntimeException("Cant open video coder");
    IPacket packetvideo = IPacket.make();

    IStreamCoder audioCoder = containerAudio.getStream(audiostreamt).getStreamCoder();

    if(audioCoder.open()<0 ) throw new RuntimeException("Cant open audio coder");
    mWriter.addAudioStream(1, 1, audioCoder.getChannels(), audioCoder.getSampleRate());

    mWriter.addVideoStream(0, 0, videocoder.getWidth(), videocoder.getHeight());

    IPacket packetaudio = IPacket.make();

    while(containerVideo.readNextPacket(packetvideo) >= 0 ||
            containerAudio.readNextPacket(packetaudio) >= 0){

        if(packetvideo.getStreamIndex() == videostreamt){

            //video packet
            IVideoPicture picture = IVideoPicture.make(videocoder.getPixelType(),
                    videocoder.getWidth(),
                    videocoder.getHeight());
            int offset = 0;
            while (offset < packetvideo.getSize()){
                int bytesDecoded = videocoder.decodeVideo(picture, 
                        packetvideo, 
                        offset);
                if(bytesDecoded < 0) throw new RuntimeException("bytesDecoded not working");
                offset += bytesDecoded;

                if(picture.isComplete()){
                    System.out.println(picture.getPixelType());
                    mWriter.encodeVideo(0, picture);

                }
            }
        } 

        if(packetaudio.getStreamIndex() == audiostreamt){   
        //audio packet

            IAudioSamples samples = IAudioSamples.make(512, 
                    audioCoder.getChannels(),
                    IAudioSamples.Format.FMT_S32);  
            int offset = 0;
            while(offset<packetaudio.getSize())
            {
                int bytesDecodedaudio = audioCoder.decodeAudio(samples, 
                        packetaudio,
                        offset);
                if (bytesDecodedaudio < 0)
                    throw new RuntimeException("could not detect audio");
                offset += bytesDecodedaudio;

                if (samples.isComplete()){
                     mWriter.encodeAudio(1, samples);

        }
            }

    }

  }
}
}