Dear All: I have written an audio AVStream driver. It registers an audio capture filter into two different categories, Audio Capture Sources and WDM Streaming Capture Devices. The capture filter, which is in WDM Streaming Capture Devices folder, is workable well for any operations. However, when I use the corresponded filter within Audio Capture Sources, there is serious problem below: I can listen the sound from this filter, when I push the "play" button. But, when I push the "stop" button, the graphedit will be blocked!! The OnPinClose function cannot be called by directshow in my driver. Can you help me? Best Regards, H.P.