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Subject:Continuous USB input needed - Red, any ideas?
Posted by: Chienworks
Date:9/14/2004 1:09:30 PM

I just had a visit from the engineering department and they're trying to come up with some fast test procedures for some new USB-based telephone handsets we're prototyping. They've been using Sound Forge 7 to monitor the signal from these handsets in the lab and it works well, being able to check levels and see a real-time frequency response graph while playing generated sweeps.

The problem they have is that if they disconnect the handset to switch to testing another one, Sound Forge switches back to using Microsoft Sound Mapper for the input and they can't switch back to the USB port without quitting and restarting Sound Forge. While this is ok for testing a few models during the design stage it takes far too long to use as a test procedure while building the full prototype run. For that matter, when we go into production and have thousands each day this certainly won't work at all.

Is there any way to keep Sound Forge looking at the USB input when there is no device connected? They thought that maybe having an intelligent USB hub might do the job and we have one on order, but i'm not sure it will help since it's basically just a USB repeater and not a device on it's own.

We're pretty new to this USB stuff so we're not even sure what may be out there. Is there anyone else in this sort of business who knows of dedicated USB audio testing devices? Any leads would be appreciated. Thanks!

Subject:RE: Continuous USB input needed - Red, any ideas?
Reply by: Rednroll
Date:9/14/2004 2:45:11 PM

Ouch....Well I ran some tests to try this out. My work laptop, which I'm currently on has a USB hub, with a Sound Devices USBpre connected to it. Running the spectral analysis monitoring input with the USBpre selected, I unplugged it and it caused a hard crash in Sound Forge, where I had to do a hard reboot to get things back.

Here's what I did to get it to work though. I disabled my onboard Sound Card and set the USBpre as the default device in Windows Sound mapper. In Sound Forge I choose to then use the Microsoft Sound Mapper driver. Since the USBpre was the only available Sound Card, I figured Windows could not change the device to something else when I unplugged the USBpre. In Sound Forge, I ran SA monitoring input again, and then unplugged the USBpre. This time Sound Forge didn't crash. Then I plugged the USBpre back into the USB hub. When the device came back up, I just had to unclick the realtime monitor button and then click it again to re-enable realtime monitor and the SA started working again. Probably not ideal for production due to a couple extra mouse clicks.

I also tried this samething with another Spectral Analyzer software I have, which is Spectra by Sound Technologies. In Spectra it doesn't have a microsoft soundmapper selection. When Spectra was running and I unplugged the USBpre it caused Spectra to crash. If I ran Spectra and then pressed the stop button, followed by unplugging the USBpre and then reconnecting, then pressing run in Spectra it wouldn't crash and worked ok.

The better solution:
So now I tried these same steps in Sound Forge using the USBpre driver. Run SA with realtime input monitoring. Then you need to stop the Realtime monitoring. Unplug the USB device. Reconnect the next device. When the device becomes available re-enable the realtime monitoring button.

I haven't tried this without the USB hub, but I'm thinking it will have the same results with a hub or without one.

Subject:RE: Continuous USB input needed - Red, any ideas?
Reply by: Rednroll
Date:9/14/2004 4:28:09 PM

I think any of these solutions are probably less than Ideal for what you're trying to do. I'm thinking you probably want to just be able to plug in the telephone and have a production worker be able to tell if it's working properly without having to do any additional tasks of clicking buttons in the software, thus opening up other possibilities of mistakes..... You know the whole Japanese production method of "poka Yoke". What you might end up having to do is to have the software engineer develop a special windows driver that will register and unregister the device on the USB connection without the host software (ie Sound Forge) knowing it's been disconnected.

Subject:RE: Continuous USB input needed - Red, any ideas?
Reply by: Chienworks
Date:9/14/2004 7:08:58 PM

Thanks Red! Sounds very promising so far. I'll pass this on to our engineers in the morning and see if it works for them. I think it will be fine for our initial prototype run (maybe 250 handsets over 3 days). If the customers really like the product and start ordering 10,000 piece lots then we'll have the cash to go buy a real test stand (we found one to do exactly what we want for about $3000). For now a few extra clicks aren't going to be a problem.

Thanks again!

Subject:RE: Continuous USB input needed - Red, any ideas?
Reply by: musicvid10
Date:9/15/2004 8:37:03 PM

Chien,

Might try using Vegas as your monitoring app rather than SF -- you should be able to disconnect and reconnect the USB interface, no need to restart the app . . . . .

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