IAMExtDevice interface (strmif.h)

[The feature associated with this page, DirectShow, is a legacy feature. It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation. Those features have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer, IMFMediaEngine and Audio/Video Capture in Media Foundation instead of DirectShow, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

The IAMExtDevice interface controls an external device, such as a DV camera or video tape recoder (VTR).

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


The IAMExtDevice interface inherits from the IUnknown interface. IAMExtDevice also has these types of members:


The IAMExtDevice interface has these methods.


The Calibrate method calibrates an external device's transport mechanism.

The get_DevicePort method retrieves the communication port to which the external device is connected.

The get_DevicePower method retrieves the external device's power mode.

The get_ExternalDeviceID method retrieves the model number of the external device.

The get_ExternalDeviceVersion retrieves the version number of the external device's operating software.

The GetCapability method retrieves the capabilities of the external device.

The put_DevicePort method assigns the communication port to which the external device is connected.

The put_DevicePower method assigns the external device's power mode to either on, off, or standby.


The DV device drivers require some additional constants that are defined in the header file Xprtdefs.h.

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 Windows Driver Kit (WDK) documentation.

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.


Requirement Value
Minimum supported client Windows 2000 Professional [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Target Platform Windows
Header strmif.h (include Dshow.h)

See also