Video capture to mjpeg over udp

Question

I'm trying to build a simple video sender and receiver by doing the following:
read video frames from the camera
convert each image from the camera to motion JPEG
deliver them via UDP to the receiver where they are rendered
As this is my 1st try using JMF and working with image processing, I did the usual scouring of forum entries and Google searches on JMF and put together the following 1st attempt (client):
            Vector videoDeviceList = CaptureDeviceManager.getDeviceList(new VideoFormat("yuv"));
            CaptureDeviceInfo vdi = null;
            if(videoDeviceList.size() > 0)
                vdi = (CaptureDeviceInfo)videoDeviceList.firstElement();
        Format outputFormats[] = new Format[] { new VideoFormat(VideoFormat.MJPG) };
        ContentDescriptor outputType = new ContentDescriptor(ContentDescriptor.RAW);
        //FileTypeDescriptor outputType = new FileTypeDescriptor(FileTypeDescriptor.MPEG);
        ProcessorModel pm = new ProcessorModel(vdi.getLocator(), outputFormats, outputType);
            Processor p = Manager.createRealizedProcessor(pm);
            DataSource src = p.getDataOutput();
        // the next line throws a ClassCastException (due to the selected ContentDescriptor?)
            PullBufferDataSource pullsrc = (PullBufferDataSource)src;
            PullBufferStream[] streams = pullsrc.getStreams();
            PullBufferStream stream = streams[0];
            Buffer buffer = new Buffer();
            DatagramSocket cs = new DatagramSocket(9876, InetAddress.getByName("localhost"));
            while(!stream.endOfStream()) {
                stream.read(buffer);
                Object data = buffer.getData();
                if(data instanceof byte[]) {
                    byte[] sendData = (byte[])data;
                    cs.send(new DatagramPacket(sendData, sendData.length));
                else
                    System.out.println(data.getClass());
            }My code fails with a "java.lang.ClassCastException: com.sun.media.multiplexer.RawBufferMux$RawBufferDataSource."
I get why, but given that the correct DataSource is an inner class, I'm guessing that this is not the right approach.
Do I need to create a custom DataSource or DataSink to accomplish my goal for the client? By the way, what roles do a DataSource and DataSink play in JMF? Any feedback/leads would be greatly appreciated.
JR

Answer 1

Ok, I've updated my code to use a PushBufferDataSource instead and that worked. But the overall problem of streaming the video remains.
The following code works and writes an image to disk.
            PushBufferDataSource pullsrc = (PushBufferDataSource)src;
            PushBufferStream[] streams = pullsrc.getStreams();
            PushBufferStream stream = streams[0];
            Buffer buffer = new Buffer();
            p.start();
            while(!stream.endOfStream()) {
                stream.read(buffer);
                Object data = buffer.getData();
                int sendDataLength = buffer.getLength();
                if(data instanceof byte[]) {
                    byte[] sendData = (byte[])data;
                    FileOutputStream outs = new FileOutputStream("test.jpg");
                    outs.write(sendData);
                    outs.close();
                else
                    System.out.println(data.getClass());
            System.out.println("end of stream");The following code does not work (output follows code):
            PushBufferDataSource pullsrc = (PushBufferDataSource)src;
            PushBufferStream[] streams = pullsrc.getStreams();
            PushBufferStream stream = streams[0];
            Buffer buffer = new Buffer();
            cs = new DatagramSocket();
            p.start();
            System.out.println("about to read stream");
            while(!stream.endOfStream()) {
                System.out.println("about to read buffer");
                stream.read(buffer);
                System.out.println("read buffer");
                Object data = buffer.getData();
                int sendDataLength = buffer.getLength();
                System.out.println("got data");
                if(data instanceof byte[]) {
                    byte[] sendData = (byte[])data;
                    System.out.println("about to send data, length = " + sendData.length);
                    System.out.println("or is it length = " + sendDataLength);
                    ByteArrayOutputStream bos = new ByteArrayOutputStream();
                    DataOutputStream dos = new DataOutputStream(bos);
                    dos.writeInt(sendData.length);
                    dos.flush();
                    byte[] sendDataSize = bos.toByteArray();
                    cs.send(new DatagramPacket(sendDataSize, sendDataSize.length, InetAddress.getByName("localhost"), 9876));
                    for(int i = 0; i < sendData.length; ) {
                        int sendLength = sendData.length - i < 1024 ? sendData.length - i : 1024;
                        System.out.println("about send partial data, i = " + i + ", length = " + sendLength + ", upto = " + (i+sendLength));
*cs.send(new DatagramPacket(sendData, i, i + sendLength, InetAddress.getByName("localhost"), 9876));*
                        System.out.println("sent partial data");
                        i += sendLength;
                    System.out.println("sent whole data");
                else
                    System.out.println(data.getClass());
            System.out.println("end of stream");
about to read stream
about to read buffer
read buffer
got data
about to send data, length = 76032
or is it length = 2183
about send partial data, i = 0, length = 1024, upto = 1024
sent partial data
about send partial data, i = 1024, length = 1024, upto = 2048
sent partial data
about send partial data, i = 2048, length = 1024, upto = 3072
sent partial data
about send partial data, i = 37888, length = 1024, upto = 38912
java.lang.IllegalArgumentException: illegal length or offset
    at java.net.DatagramPacket.setData(Unknown Source)
    at java.net.DatagramPacket.<init>(Unknown Source)
    at VideoSender.main(VideoSender.java:102)The line throwing the exception has been highlighted in bold above.
DatagramPacket.<init> is passed a buffer of length = 76032, an offset of 37888 and a length of 1024, so why the Exception?
One thing I notice is that ((byte[]) Buffer.getData()).length is the actual file size that resulted from running the 1st code snippet. On the other hand, buffer.getLength() = 2183 which is seemingly random to me. Am I experiencing some race condition on the Buffer's underlying data object? How can I stream each image over the network?
Thanks.