By using Direct I/O in the US-800 driver, audio signals can be exchanged between applications that use different interfaces. Using this function, the following types of operations are possible.
Record the playback sound of a multimedia player into a DAW that uses ASIO.[/li]
Record the output of an ASIO DAW into a WDM application.[/li]
Send the US-800 input signal to a WDM application.[/li]
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This functionality is quite rare. I it find it useful, I can connect Windows output to a ASIO host and thus apply system wide audio processing. It also came in handy when I couldn't get my head around how to export mixdown of a session when I tried a sequencer, forgot which now...
Here's an incomplete list of interfaces that have this functionality:
ESI Maya44, U46, Duafire
Infrasonic Quartet
E-MU 0404, 1212m, 1820, 1616m
Tascam US 800
Keep in mind some are discontinued and native PCI support is quickly disappearing.
Feel free to comment and If I forgot an interface let me know.