Kopete shows a device with 'black' output, 
trying to adjust brightness yields:
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Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
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[Thread debugging using libthread_db enabled]
[New Thread -1241381168 (LWP 25884)]
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[KCrash handler]
#6  0xb5a4cf25 in Kopete::AV::VideoInput::setBrightness ()
   from /usr/lib/libkopete_videodevice.so.0
#7  0xb5a4f686 in Kopete::AV::VideoDevice::setBrightness ()
   from /usr/lib/libkopete_videodevice.so.0
#8  0xb5a56674 in Kopete::AV::VideoDevicePool::setBrightness ()
   from /usr/lib/libkopete_videodevice.so.0
#9  0xb56f0c21 in AVDeviceConfig::slotBrightnessSliderChanged ()
   from /usr/lib/kde3/kcm_kopete_avdeviceconfig.so
#10 0xb56f1456 in AVDeviceConfig::qt_invoke ()
   from /usr/lib/kde3/kcm_kopete_avdeviceconfig.so
#11 0xb68be940 in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#12 0xb68bf12a in QObject::activate_signal () from /usr/lib/libqt-mt.so.3
#13 0xb6c69a21 in QSlider::valueChanged () from /usr/lib/libqt-mt.so.3
#14 0xb69fb20f in QSlider::valueChange () from /usr/lib/libqt-mt.so.3
#15 0xb69ee342 in QRangeControl::setValue () from /usr/lib/libqt-mt.so.3
#16 0xb69f9e83 in QSlider::setValue () from /usr/lib/libqt-mt.so.3
#17 0xb69faaae in QSlider::moveSlider () from /usr/lib/libqt-mt.so.3
#18 0xb69fb177 in QSlider::mouseMoveEvent () from /usr/lib/libqt-mt.so.3
#19 0xb68f556b in QWidget::event () from /usr/lib/libqt-mt.so.3
#20 0xb68559e8 in QApplication::internalNotify () from /usr/lib/libqt-mt.so.3
#21 0xb6857ba6 in QApplication::notify () from /usr/lib/libqt-mt.so.3
#22 0xb7019ce2 in KApplication::notify () from /usr/lib/libkdecore.so.4
#23 0xb67e825d in QApplication::sendSpontaneousEvent ()
   from /usr/lib/libqt-mt.so.3
#24 0xb67e6ec2 in QETWidget::translateMouseEvent ()
   from /usr/lib/libqt-mt.so.3
#25 0xb67e4fac in QApplication::x11ProcessEvent () from /usr/lib/libqt-mt.so.3
#26 0xb67fc180 in QEventLoop::processEvents () from /usr/lib/libqt-mt.so.3
#27 0xb68700be in QEventLoop::enterLoop () from /usr/lib/libqt-mt.so.3
#28 0xb686fece in QEventLoop::exec () from /usr/lib/libqt-mt.so.3
#29 0xb6857591 in QApplication::exec () from /usr/lib/libqt-mt.so.3
#30 0x0807feec in ?? ()
#31 0xbfad75b4 in ?? ()
#32 0xbfad75ac in ?? ()
#33 0xbfad75a4 in ?? ()
#34 0x00000000 in ?? ()