[wdmaudiodev] Real Time Processing

  • From: Pieterjan Demarcke <pieterjan.demarcke@xxxxxxxxx>
  • To: wdmaudiodev@xxxxxxxxxxxxx
  • Date: Wed, 2 Mar 2005 23:19:55 +0100


in search of information about audio drivers i came across this
discussion group. I have a specific problem and i don't know what's
exactly possible, because i don't have the expertise. The situation is
as follows: for an engineering project i have to write software that
controls a self-made analog device. The controlled variable is the
output of -let's say- a sensor which is, with the help of some
electronics, connected to the sound card line-in. That signal must
then be rescaled and fed back to the line-out for controlling purposes
(btw. we have to use WinXP). This problem has to be solved this way,
as we can't make use of a microprocessor. My question to you is now:
how exactly can i get as less as latency as possible, so that the
delay between input and output is minimal? I already 'studied' the WDM
driver architecture and the best solution i have found so far is the
directks example on this site. But i am convinced it could be even
faster. I don't need any buffering as the processing must happen in
real time, sample by sample: the next sample of the signal should be
taken AFTER the previous one has finished processing and was already
sent back to the external device. I also need an interface to a
program in user mode which stores the original sample in a file. I
don't need the soundcard to do anything else so I thought the best
solution was to replace the vendor driver by my own, but as I don't
know how i should start with that, I'm also open to other ideas. A
certain latency between input and output is allowed, let's say max 5
ms. Is this possible and if so, what is the best way to approach this
problem? Any suggestions are welcome. Anyway thank you for your time,
I really appreciate it.

with kind regards,
Pieterjan Demarcke

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