Microsoft DirectX 9.0

IAMExtTransport Interface

The IAMExtTransport interface controls the transport on a VCR or camcorder. Applications can use this interface to play, record, or stop the transport; determine whether the transport contains media; and other transport-related functions. The implementation of this interface can vary, depending on the device. Some methods might return E_NOTIMPL if the device does not support them.

This interface also contains methods for non-linear editing through edit events and edit property sets. Currently, DirectShow does not provide any filters or drivers that implement this part of the interface.

Filter Developers: Implement this interface if you are writing a filter that controls an external device with a transport, such as a VCR. If you implement this interface, you should implement the IAMExtDevice interface as well.


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 to sustain higher baud rates, such as 38.4 baud.

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

Method Description
GetCapability Retrieves the general capabilities of an external transport.
put_MediaState Sets the current state of the media.
get_MediaState Retrieves the current state of the media.
put_LocalControl Sets the state of the device to local or remote control.
get_LocalControl Retrieves the state of the device.
GetStatus Determines the status of the transport.
GetTransportBasicParameters Retrieves the transport's basic parameter settings.
SetTransportBasicParameters Sets the transport's basic parameters.
GetTransportVideoParameters Retrieves the transport's video parameter settings.
SetTransportVideoParameters Sets the video parameters for the transport.
GetTransportAudioParameters Retrieves the transport's audio parameter settings.
SetTransportAudioParameters Sets audio parameter settings for the transport.
put_Mode Sets the movement of the transport to a new mode, such as play, stop, or record.
get_Mode Retrieves the mode of the transport.
put_Rate Sets the playback rate for variable-speed external devices.
get_Rate Retrieves the playback rate.
GetChase Retrieves the status of chase mode.
SetChase Enables or disables chase mode.
GetBump Retrieves status of bump mode.
SetBump Temporarily changes the speed of playback for synchronization of multiple external devices.
get_AntiClogControl Determines if the anti-headclog control is enabled or disabled.
put_AntiClogControl Enables or disables the transport's anti-headclog control.
GetEditPropertySet Retrieves the current state of an edit property set.
SetEditPropertySet Registers an edit property set that describes a group of edit properties.
GetEditProperty Retrieves individual parameters and values associated with a particular edit property set.
SetEditProperty Defines individual parameters and values associated with a particular edit property set.
get_EditStart Determines whether edit control is active.
put_EditStart Activates edit control.


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