[wdmaudiodev] Re: DMA mode?

  • From: Pallavi Joshi <pallavi.v.joshi@xxxxxxxxx>
  • To: wdmaudiodev@xxxxxxxxxxxxx
  • Date: Tue, 11 Aug 2009 17:35:22 -0700

Hi Tim,

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?

Thanks,
Pallavi




On Tue, Aug 11, 2009 at 4:49 PM, Tim Roberts <timr@xxxxxxxxx> wrote:

> Pallavi Joshi wrote:
> >
> > I am developing an ASIO driver using kernel streaming. To increase the
> > audio latency, ...
>
> Do you mean "decrease" the audio latency?  ;)
>
> > ...I want to use DMA (Direct Memory Access) for communication between
> > my device and my ASIO driver. In my ASIO driver, I am using the
> > DeviceIoControl function with IOCTL_KS_READ_STREAM and
> > IOCTL_KS_WRITE_STREAM as the control codes for reading/writing data
> > from my USB audio device. Thus, I need to figure out a way which can
> > operate my USB audio device in the DMA mode. Note that I am using
> > kernel streaming pins here, thus there might be a way of telling the
> > kernel streaming filter to operate in the DMA mode. I haven't been
> > able to figure out how to do that though.
>
> All USB transactions use DMA.  It's required by the USB host controller
> specifications.
>
> --
> Tim Roberts, timr@xxxxxxxxx
> Providenza & Boekelheide, Inc.
>
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-- 
Pallavi Joshi
(480)-280-2017

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