| Microsoft DirectX 8.1 (C++) |
This topic applies to Windows XP Home Edition and Windows XP Professional only.
The IVMRMixerBitmap interface is implemented by the VMR filter. Applications use this interface to pass to the VMR a Windows bitmap or DirectDraw surface that contains a static image that they want to blend with the currently playing video stream. You can pass images to the VMR as frequently as you like, but changing the image several times per second may impact the performance and smoothness of the video being rendered. The new image will be blended with the next and all subsequent video frames rendered by the VMR. Internally, the VMR uses its mixer component to perform the blending operation. Therefore the VMR must be configured correctly prior to commencing video playback. Even if only a single video stream is present, applications should call IVMRFilterConfig::SetNumberOfStreams with a value of “1” to cause the VMR to load the mixer and compositor. The image can contain embedded per pixel alpha information; this allows the image to contain regions that are transparent. Transparent areas can also be identified by a color key value. Changes in the image are only shown on the screen while the filter graph is running.
In addition to the methods inherited from IUnknown, the IVMRMixerBitmap interface exposes the following methods:
| IVMRMixerBitmap Methods | Description |
| GetAlphaBitmapParameters | Retrieves a copy of the current image and related blending parameters. |
| SetAlphaBitmap | Specifies a new bitmap image and the source location of the bitmap and how and where it should be rendered on the destination rectangle. |
| UpdateAlphaBitmapParameters | Changes the bitmap location, size and blending value. |