[wdmaudiodev] Re: DMA mode?

  • From: Tim Roberts <timr@xxxxxxxxx>
  • To: wdmaudiodev@xxxxxxxxxxxxx
  • Date: Tue, 11 Aug 2009 17:45:19 -0700

Pallavi Joshi wrote:
> Yup, I meant reducing the latency! Thanks so much for replying. This
> is easy then :)
> The main issue that I am facing is that I overwrite the playback
> buffer with new data before my previous data has finished playing.
> This is what MSDN documentation says about asynchronous IO:
> "Do not deallocate or modify the OVERLAPPED structure or the data
> buffer until all asynchronous IO has been completed."
> Due to this, I get missing data in my audio stream. Do you have any
> suggestions?

I'm not sure, you have a lot of concepts mixed up here.  Which playback
buffer are you overwriting?  Is it the application buffer that is being
handed to your ASIO driver?  Is it the kernel streaming buffers you are
handing to usbaudio.sys through IOCTL_KS_WRITE?

The advice is good: you can't start reusing a buffer until you know the
guy beneath you is finished with it, but the exact definition of
"finished with it" depends on which level you're at.

Tim Roberts, timr@xxxxxxxxx
Providenza & Boekelheide, Inc.


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