Overlay Mixer (Windows CE 5.0)

Windows CE 5.0
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The Overlay Mixer filter is a video renderer that is designed specifically for broadcast video streams with Line21 closed captioning. The Overlay Mixer filter supports video port extensions (VPEs), which enable it to work with hardware MPEG-2 decoders that send data directly to the graphics card rather than over the PCI bus.

The Overlay Mixer filter can be used in other scenarios where you have multiple input streams, but it does not perform any actual mixing or alpha blending of the overlaid graphics. For all other rendering scenarios, the video renderer filter is the preferred renderer.

Both renderers make use of Microsoft DirectDraw® and overlay surfaces on the graphics card when these are available. The only difference is that the Overlay Mixer filter requires an overlay surface, whereas the Video Renderer filter can use other means of rendering video if an overlay surface is not available.

The Overlay Mixer filter uses destination color keying to mix video surfaces with overlays. It blits the color key and the subtitle or Line21 data to the primary surface and sends the video to the overlay surface. The graphics card then composites the two surfaces into its frame buffer.

The following table shows the filter properties.

Filter propertyDescription
Filter InterfacesIBaseFilter, IMediaPosition, IMediaSeeking, IQualProp
Input Pin Media TypesMajor Type: MEDIATYPE_Video subtypes:
  • MEDIASUBTYPE_Overlay (pin 0 only)
  • DirectDraw YUV formats: MEDIASUBTYPE_YUVxx (pin 0 only)
  • DirectDraw Video Acceleration formats: MEDIASUBTYPE_DVAxxx (pin 0 only)
  • DirectDraw RGB formats: MEDIASUBTYPE_RGBxx (all input pins)
    Format Type: Format_VIDEOINFO, Format_VIDEOINFO2
Input Pin InterfacesIMemInputPin, IOverlay (pin 0 only), IPin, IQualityControl, IVPNotify
Output Pin Media TypesMEDIATYPE_Video, MEDIASUBTYPE_Overlay
Output Pin InterfacesIPin, IQualityControl
Filter CLSIDCLSID_OverlayMixer
Filter CategoryCLSID_LegacyAmFilterCategory

See Also

Supported DirectShow Filters

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