Doug and list,
I've experienced the same problem with the Edirol UA-5. However, I haven't
noticed it with the UA-25, which is a newer simplified version of the UA-5.
Doug is correct that the problems with using a USB device, particularly
USB1.1 device, are data buffering and computer processing load. The UA-5
and UA-20 have known buffering problems and, as Doug suspected, when the
computer is busy with other processes, some of the USB data stream spills
into oblivion instead of being held by the interface unit. The solution is
to make sure your computer is not running too many processes when also being
used as a data acquisition device. It's best to us a Pentium chip with
hyperthreading technology. In addition, the Edirol and TASCAM instruction
manuals described the optimal computer configuration to use for making sound
recordings. This involves such things as setting priorities for background
operations.
Happy recording,
Joe
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Joseph R. Olson
Cetacean Research Technology
PO Box 70186
Seattle, WA 98127
TEL: 206-297-1310
877-824-5432 (outside the Seattle local calling area)
FAX: 206-784-0557
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www.cetaceanresearch.com
Cetacean Research Technology is a strategic partner of Sound Technology,
Inc. Spectra Group - Signal Analysis Division
> -----Original Message-----
> From:
> On Behalf Of Gillespie,
> Douglas
> Sent: Tuesday, 10 May 2005 8:17 AM
> To:
> Subject: Timing problems with USB sound cards
>
> I've had a couple of problems with the number of samples delivered
> from USB sound cards - the number of samples I get in my recordings is
> not always equal to the sample rate times the number of seconds I
> record for. This causes problems when I need to know the exact time of
> events which are not at the beginning of a file.
>
> This has happened with a Creative Labs Extigy and also with an Edirol
> UA20.
> The problem is intermittent and possibly associated with running far
> too many other processes on my computer at the same time. I suspect
> that the USB buffer is too small and when the PC can't keep up, it
> just skips samples rather than reporting an error.
>
> This message is partly a warning to anyone else using USB sound cards
> to make recordings where absolute timing of events is critical and
> partly a request to see if anyone knows any more about this problem
> and how to avoid it. I've never experienced it with PCI sound cards.
>
> Yours,
>
> Douglas Gillespie.
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