Dear Stephan, In fact, I set theConnectionInterface.Id =NULL, then what is the default value. According to what you say, as long as I update the position, the port class will send more valid data to me. Am I correct? Thanks Stephan Kappertz <stephan@xxxxxxxxxx> wrote: You should check the pins ConnectionInterface.Id when the pin is created. Most likely the ConnectionInterface is KSINTERFACE_STANDARD_LOOPED_STREAMING. This means that your driver receives just one valid circular buffer when playback starts. It is supposed to loop through this buffer until playback stops. The current DMA position that your driver reports will be used to update the portion of the circular buffer with new data that is currently NOT played. Stephan -----Ursprüngliche Nachricht----- Von: wdmaudiodev-bounce@xxxxxxxxxxxxx [mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] Im Auftrag von david lee Gesendet: Monday, October 11, 2004 11:35 AM An: wdmaudiodev@xxxxxxxxxxxxx Betreff: [wdmaudiodev] DirectSound and PowerDVD/WinDVD Strange behavior Dear all, When I use PowerDVD/WinDVD SPDIF pass through and select direct sound audio render, I always get a lot of zero data with a few valid data in the beginning of playback. Due to use driver to decode the AC3/DTS data, I am not sure how to handle these zero data. Any suggestion? (Treat them as data need to be decoded or as rubbish and discarded) BTW, if I select waveout audio render, All the data at the beginning are useful valid data,which I can decode. Thanks in advance David Yahoo! Mobile - Download the latest ringtones, games, and more! Yahoo! Mobile - Download the latest ringtones, games, and more!