i have the sony audio mastering suite, and when choosing the capture device i get the option for MIC-IN, LINE-IN, RCA-IN, AND ASIO COMPAT. DEVICE. it says asio is preferred, but what is it?

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Mac G5 workstation with 4 gigs of ram, 4x250 gig drives in raid 5. High availability cluster server running centos for a server. 2xCanon GL2 cameras.

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