Hi Hueng Pei, I searched the mailing list and luckily found that you have asked the question which is a similar problem I encounter now. May I know how did you solve the audio start & pause problem? I'd like to describe my problem here again: I have a webcam with a build-in microphone which is a USB Audio Class compliant device. The microphone supports 16KHz, 16Bit, Mono audio format only, this is a hardware limitation. The microphone works well with Microsoft driver, after loaded my upper filter audio driver, the audio device under WDM Streaming System Deviecs also works fine, but the one under Audio Capture Sources keeps Start and Pause again and again in GraphEdit, NetMeeting & MSN. There is no such problem in my own application, I bet it's my own application set to 16KHz, 16Bit, Mono audio format directly. In GraphEdit, the capture pin of device under WDM Streaming System Deviecs show the correct audio format, but the capture pin of device under Audio Capture Devices showed lots of audio format exclude the correct one, and it showed 44.1KHz, 16Bit, Stereo audio format after render capture pin. I guess it caused by the upper filter driver did not return a correct audio format list, but I do not know where to return the audio format to the device under Audio Capture Device. How could I fix it? Any suggestion would greatly appreciated, thanks in advance. Barry Gu