[wdmaudiodev] Re: Record Buffer Issue
- From: Tim Roberts <timr@xxxxxxxxx>
- To: wdmaudiodev@xxxxxxxxxxxxx
- Date: Thu, 16 Sep 2004 09:09:50 -0700
David A. Hoatson wrote:
For recording, eight 64-byte buffers are passed in regardless of
sample rate. At 48kHz stereo, this means each buffer represents
~0.66ms, which is just at the limit of what gives acceptable
performance from faster machines. At 192kHz, the port driver still
only gives eight 64-byte buffers, so now that same buffer only
represents 0.166ms for stereo, or only 1 sample period for 16 channel
interleaved 32-bit (which my device can do)! This means the PC is not
able to respond to each interrupt fast enough and audio breakup will
occur in only 1.3ms (192kHz/Stereo). This essentially means that
recording through the port class driver is not possible at higher
sample rates/higher channel counts. I should mention that I am using
Windows XP SP2.
So far I have found nothing that allows my driver to control the size
or number of buffers that are passed in from the upper level driver.
Does anyone have a solution to this problem? I'm sure there is
something very basic that I am missing...
Although it might be too late for your driver, you can attenuate many
problems like this by using a DMA common buffer instead of letting KS do
the locking and unlocking. The cost of the extra copy is trivial on
modern computers.
--
- Tim Roberts, timr@xxxxxxxxx
Providenza & Boekelheide, Inc.
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