[JMF] Cannot get device list

I have problem with my JMF code.
I cannot get device list. even if i try to do this

Code:

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CaptureDeviceManager.getDeviceList(null)

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it returns nothing "[]"

NB :
I try to get my device list in JMF Registry and it shows 2 Audio Device and 1 Video Device
I try to capture using JMStudio and it has no problem with it
my capture device supports RGBFormat and YUVFormat

can someone help me?
here is my code

Code:

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private void jalankanWebcam() {
        try {
            Vector deviceList = CaptureDeviceManager.getDeviceList(new RGBFormat());
            device = (CaptureDeviceInfo) deviceList.firstElement();
            ml = device.getLocator();
            player = Manager.createRealizedPlayer(ml);
            Format[] format = device.getFormats();                     
            FormatControl fc = (FormatControl)player.getControl("javax.media.control.FormatControl");
            fc.setFormat(format[0]);
            player.start();
            videoScreen = player.getVisualComponent();
            videoScreen.setBounds(0,0,600,480);
            this.add(videoScreen);
        } catch (Exception e) {
            System.out.println(e);
        }
    }

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Regrads,

Frans