This message is sent to release the exclusive use of physical device resources by a group or device instance.

ulParam1 (ULONG)

This parameter can contain the following flags:

MCI_NOTIFY

A notification message will be posted to the window specified in the hwndCallback parameter of the data structure pointed to by the pParam2 parameter. The notification will be posted when the action indicated by this message is completed or when an error occurs.
MCI_WAIT
Control is not to be returned until the action indicated by this message is completed or an error occurs.
MCI_RETURN_RESOURCE
This flag releases a device instance from the active state and makes the next available inactive device instance active. The device instance will not be made active again unless MCI_ACQUIREDEVICE is issued for this device instance, or no other application is using the device. If the instance is already inactive, the message is ignored.

pParam2 (PMCI_GENERIC_PARMS)

A pointer to the default media control interface parameter data structure.

rc (ULONG)

Return codes indicating success or type of failure:

MCIERR_SUCCESS

If the function succeeds, 0 is returned.
MCIERR_INVALID_DEVICE_ID
The device ID is not valid.
MCIERR_INVALID_FLAG
Flag (ulParam1) is invalid.
MCIERR_FLAGS_NOT_COMPATIBLE
Flags cannot be used together.

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