Microsoft DirectX 9.0

MSDV Driver

MSDV is the Microsoft® Windows® Driver Model (WDM) driver for DV camcorders. It is exposed to applications as the WDM Video Capture filter. MSDV supports a subset of the interfaces described on the filter's reference page. If a DV camcorder is available on the user's system, it appears in both the "Video Capture Sources" category (CLSID_VideoInputDeviceCategory) and the "WDM Streaming Rendering Devices" category (AM_KSCATEGORY_RENDER). The friendly name is "Microsoft DV Camera and VCR," or a localized equivalant. To add this filter to a filter graph, use the ICreateDevEnum interface. For more information, see Enumerating Devices and Filters.

MSDV exposes the IAMExtDevice, IAMExtTransport, and IAMTimecodeReader interfaces for controlling the camcorder.

MSDV has two output pins. One output pin delivers interleaved audio-video data, and the other delivers video data without audio. Only one output pin can be rendered at a time. It has one input pin, which transmits data from the computer to the camcorder. MSDV will not accept simultaneous input and output connections, because a camcorder cannot capture and transmit at the same time. For information about which DV formats are supported, see DV Video Subtypes.

Some tips on using MSDV:

The IGraphBuilder::Render method will not render an output pin on MSDV, because the Filter Graph Manager tries to connect the pin to MSDV's own input pin. Because MSDV rejects the connection, the method fails. Instead, use IGraphBuilder::Connect or ICaptureGraphBuilder2::RenderStream.
When a filter graph contains MSDV, MSDV should supply the reference clock for the graph. As of DirectX 8.0, the Filter Graph Manager will automatically choose MSDV as the reference clock. With earlier versions, you should call the IMediaFilter::SetSyncSource method on the Filter Graph Manager. For more information about clocks, see Time and Clocks in DirectShow.
Depending on the device, some methods in IAMExtDevice, IAMExtTransport, and IAMTimeCodeReader might return WIN32 error codes instead of HRESULT values. Possible error codes include the following:

Error Code	Description
ERROR_TIMEOUT	An external device command has timed out.
ERROR_REQ_NOT_ACCEP	The device did not accept this external device command.
ERROR_NOT_SUPPORTED	The device does not support this external device command.
ERROR_REQUEST_ABORTED	An external device command was aborted. Possbly the device was removed or a bus reset occurred.

Device Information

In Windows Millennium Edition and Windows XP, the DV filter's device moniker supports a "Description" property in addition to the "FriendlyName" property. This property returns a description of the device, taken from the INF file, which usually contains the brand name of the device. This property is not supported for all device models, however.

For more information about device monikers, see Using the System Device Enumerator.

Clock Times

The MSDV driver uses the 1394 bus clock that is contained in the 1394 data packets to derive the clock. It uses these values to time stamp the DV media samples. Because this source clock is not the computer system clock, the times will eventually drift from the computer system clock. As noted above, however, by default the Filter Graph Manager will select MSDV as the graph reference clock.

The IAMDroppedFrame interface reports the driver's current measure of dropped frames; this value may not be perfectly synchronized with the actual number of dropped frames at a given time. If frames are dropped, it indicates the system is not balanced (data production exceeds data consumption). For example, the user's hard disk may not be fast enough to support DV capture rates.

See Also