System commands are interpreted directly by the Media Device Manager (MDM), and are not passed to the MCDs. The following table lists the system commands that are supported by MDM.
┌─────────────────────────┬───────────────────────────────────┐ │Command │Description │ ├─────────────────────────┼───────────────────────────────────┤ │MCI_ACQUIREDEVICE │Acquires use of the physical │ │ │resources for the device. │ ├─────────────────────────┼───────────────────────────────────┤ │MCI_CONNECTION │Returns information about the │ │ │device context connections. │ ├─────────────────────────┼───────────────────────────────────┤ │MCI_CONNECTORINFO │Returns information about the │ │ │connectors on a device. │ ├─────────────────────────┼───────────────────────────────────┤ │MCI_DEFAULTCONNECTION │Makes, breaks, or queries a default│ │ │connection. │ ├─────────────────────────┼───────────────────────────────────┤ │MCI_GROUP │Provides control over multiple │ │ │devices with a single command. │ ├─────────────────────────┼───────────────────────────────────┤ │MCI_MASTERAUDIO │Queries the current audio settings │ │ │when the driver is first opened. │ │ │This command is also used as a │ │ │basic command to later adjust the │ │ │master audio. │ ├─────────────────────────┼───────────────────────────────────┤ │MCI_SYSINFO │Obtains information about devices │ │ │installed in the system. │ ├─────────────────────────┼───────────────────────────────────┤ │MCI_RELEASEDEVICE │Releases exclusive use of the │ │ │physical resources for the devices.│ └─────────────────────────┴───────────────────────────────────┘