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Timing problems with USB sound cards

To: <>
Subject: Timing problems with USB sound cards
From: "Gillespie, Douglas" <>
Date: Tue, 10 May 2005 11:17:05 EDT
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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