PsychPortAudio long latencies

1
I've been trying to use PsychPortAudio a bit, and checking timing (with windows XP). I sent out a TTL pulse via a I/O card and then call PsychPortAudio to play a sound, and send both signals into an oscilloscope to check timing. When I do it with the InitializePsychSound set to needing low latency, the sound itself starts repeating in a weird way and basically crashes matlab. If I don't use the flag to use low latency, I get about a 500 ms latency between the TTL pulse and the sound, which a pretty substantial variance (~50 ms). When I use matlab's built-in sound function, that latency goes down to about 50 ms with less than 10 ms variance.

So, looking at InitializePsychSound, I see that better drivers or a better sound card can fix this. Any particular suggestions on a cheap solution? I really don't need anything that special, latencies on the order of Windows built-in sound function would be OK, although I'd like to do better.

Thanks for any help!
2
--- In psychtoolbox@yahoogroups.com, "matadasm" <matadasm@...> wrote:
>
> I've been trying to use PsychPortAudio a bit, and checking timing (with windows XP). I sent out a TTL pulse via a I/O card and then call PsychPortAudio to play a sound, and send both signals into an oscilloscope to check timing. When I do it with the InitializePsychSound set to needing low latency, the sound itself starts repeating in a weird way and basically crashes matlab. If I don't use the flag to use low latency, I get about a 500 ms latency between the TTL pulse and the sound, which a pretty substantial variance (~50 ms). When I use matlab's built-in sound function, that latency goes down to about 50 ms with less than 10 ms variance.
>
> So, looking at InitializePsychSound, I see that better drivers or a better sound card can fix this. Any particular suggestions on a cheap solution? I really don't need anything that special, latencies on the order of Windows built-in sound function would be OK, although I'd like to do better.
>

Installing Linux would be one way to (usually) get much better performance out of cheap soundcards or built-in chips -- at least with nowadays very common HDA onboard sound chips.

For Windows, any ASIO card should work pretty well. The Hardware->PsychPOrtAudio section of our Wiki has some test results with a few cards. If in doubt, a M-Audio Delta 1010-LT has not ever disappointed us, which is why we pick it in the lab as the default choice whenever we need high timing precision, low-latency, or multi-channel. I don't know its current prize, but probably in the low 100 Euros range. Doesn't mean that dozens of other cards wouldn't work as well.

-mario


> Thanks for any help!
>