MMProgRef - Subsystem Messages

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Multimedia Programming Reference
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The **MCIDRV** commands provide subsystem communication between MDM (Media Device Manager) and the MCDs (Media Control Drivers). The current set of MCIDRV commands provide for device resource management.

The MCIDRV_SAVE and MCIDRV_RESTORE messages allow MDM to manage devices that support multiple device contexts either concurrently or serially. The MCIDRV_CHANGERESOURCE message allows MCDs to change the resource consumed by a device context as required. MCIDRV_CHANGERESOURCE is sent from an MCD to MDM. A device context is made active when the MCD receives an MCIDRV_RESTORE from MDM. An MCI_OPEN command is not complete (the device is not active) until MDM has sent the MCD an MCIDRV_RESTORE. Similarly, when MDM sends an MCD the MCIDRV_SAVE command, the MCD will make the device context inactive. These commands provide multiple device contexts the ability to share one device.

Message Description

MCIDRV_CHANGERESOURCE: Changes the class or resource units assigned to the given device context.
MCIDRV_RESTORE: Restores state of an inactive device context.
MCIDRV_SAVE: Saves state of a device context.