Microsoft DirectX 9.0

IAMExtDevice Interface

The IAMExtDevice interface enables an application to control an external device, such as a VCR, through the filter graph.

This interface controls basic device functions. Several other interfaces exist for controlling more specific functionality in a device:


The DV camcorder driver, MSDV, requires some additional constants that are defined in the header file Xprtdefs.h.

Hardware Requirements

To control an external VCR, certain hardware requirements are recommended. VCRs with an RS-422 serial interface require a special serial port card or an external RS-232-to-RS-422 adapter. In addition, for best performance, your computer should have a serial port card built with a 16550 high-performance UART (Universal Asynchronous Receiver/Transmitter) to sustain higher baud rates, such as 38.4 baud.

In addition to the methods inherited from IUnknown, the IAMExtDevice interface exposes the following methods.

Method Description
GetCapability Retrieves the capabilities of the device.
get_ExternalDeviceID Retrieves the model number of the device.
get_ExternalDeviceVersion Retrieves the version number of the device's operating software.
put_DevicePort Specifies the communication port to which the device is connected.
get_DevicePower Retrieves the device's power mode.
put_DevicePower Sets the device's power mode.
Calibrate Calibrates the device's transport mechanism.
get_DevicePort Retrieves the communication port to which the device is connected.


For Windows Driver Model (WDM) devices, the WDM Video Capture Filter automatically exposes this interface if the WDM driver supports the PROPSETID_EXT_DEVICE property set. For more information, see the DirectX DDK documenation.