interesting !
BTW: what kind of buffersizes did you use ?
single threaded, multi threaded app ?
with how much data did you prefill the DAC ?
eg. you open the card in fullduplex, stop it
prefill the DAC (write() ) with num frags x fragsize
bytes, and then begin the cycle
while(1)
{
read() fragment from soundcard
write() fragment to soundcard
}
the theoretical latency should be exactly
num_frags x fragsize
I was wondering how the latency measured externally
differed from this theoretical value.
did you use analog IO ?
let us know
Benno.
On Sat, 29 Jul 2000, Gary Scavone wrote:
> Hi David,
>
> This is not exactly along the same lines as your previous email, but I
> did an audio i/o latency test a few weeks ago here at CCRMA for the
> Midiman Delta 1010 card (8 channels analog i/o plus S/PDIF). I had a
> scope hooked up to both the input and the output of the card and used
> a square-wave generator for input (patched through the scope). I
> wrote a simple STK program that read in a buffer of data and
> immediately read it out. At 22 KHz, I was able to get down to about
> 18 ms i/o delay. At 44.1 KHz, however, I got it down to about 10 ms.
> I was, of course, using the ALSA driver. I tried doing some
> FIFO_SCHED priority stuff, but that didn't really affect the latency
> (I didn't expect it would).
>
> *******************************************************
> * Gary Scavone *
> * Center for Computer Research in Music & Acoustics *
> * Stanford University *
> * [EMAIL PROTECTED] *
> * http://www-ccrma.stanford.edu/~gary/ *
> *******************************************************
