sound generator application crashes

[kevinm]

I'm generating 90-degree phase offset sinusoids with noise on two sound card outputs (each card has stereo out for in-phase and quadrature output). I'm generating 4 sinusoids per soundcard and my user interface provides control over frequency and amplitude for the 8 complex sinusoids (16 real) as well as the noise amplitude. I'm using 4 "Noise and Tones Waveform" vi's to generate the tones and noise for four outputs (left and right channel on the 2 sound cards). I'm running at a 44.1kHz sample rate and the "Noise and Tones Waveform" vi is set for a block size of 4096 samples. The Sound Output (SO_xxxx) vi's are used for sound card output and I've configured the # of buffers from 2 to about 8.

I need to be able to adjust all the t
one parameters while the tones are playing.

My problem is that, after the application has been running for 15 minutes or so, the sound output stops. I can still move the sliders and other user controls on the front panel and the diplayed numbers change, but I cannot halt the vi using the usual method using a button the change the while condition to false inside my main while loop.

My Dell PC has a 1.8MHz P4 with 512MB of RAM and I'm using 2 Creative Labs Sound Blaster Audigy PCI soundcards.

Thanks!

[Arek]

kevinm,

Have you tried to reduce the application to generate only one channel simple waveform at a time ? What is the long term behaviour of such reduced vi ?

Arkadiusz Roszczewski
National Instruments

[kevinm]

I reduced the application to a single stereo channel (left and right channel for a single sound card), for a total of 8 sinusoids using 2 "Tones and Noise Waveform" vi's. It has been running for about 4 hours with no problems.

Thanks,

Kevin

[kevinm]

Not so fast ... after another hour, the sound output bacame "choppy" -- pulsing about 4-5 times per second. Task Manager shows CPU Usage at 13% and Memory Usage at ~ 352000K.

If I switch between applications (using Alt-Tab), the output stops momentarily. When I opened Outlook, the output stopped, then began pulsing at a slower rate, and the rate climed to ~ 4-5 pulses per second.

Sounds like some sort of realtime deadline was missed and wasn't recovered cleanly. I wouldn't mind if the output stopped momentarily if I start up a big application, but for it to go into this persistent pulsing behavior with no way to recover is unacceptable.

[Arek]

kevinm,

Do you generate a waveform in every step of the loop or only when parameters (eg. frequency) have to be changed ? Could you send a fragment of your code which can reproduce the problem.

Arkadiusz Roszczewski
National Instruments

[kevinm]

I've attached the reduced version of the application.

How would I change it so that the waveforms are only generated on parameter changes?

[Arek]

kevinm,

I have reproduced this behaviour with your reduced application. The problem has been reported for investigation. I will inform you about the status or the solution on Tuesday 20.

Arkadiusz Roszczewski
National Instruments

[Arek]

kevinm,

It seems that the problem can be caused by SO Wait.vi and its interactions with the sound driver. Detailed description of this behaviour has been sent to our R&D department for further investigation.
Thank you for your feedback.

Arkadiusz Roszczewski
National Instruments

[kevinm]

Is anyone working on this issue? When could I expect an answer? Thanks!

[Arek]

kevinm,

The issue has been reported and confirmed. Our R&D department is looking into it and will work on a solution for the future release of LabVIEW.

Arkadiusz Roszczewski
National Instruments