% mlquery SYSTEM: linux1 active UST: (default software UST source) DEVICES: Software DV_MMX Codec  OSS audio device 
This output indicates that there are two installed devices:
A software DV transcoder
An audio I/O device (which in this case is built using the Linux OSS driver)
Other options to mlquery allow you to gather more information about the installed devices. See the mlquery(1ml) man page for more information.