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VideoProcessorSetStreamAlpha function

Sets the planar alpha for an input stream on the video processor.

Syntax


VOID APIENTRY* VideoProcessorSetStreamAlpha(
  _In_  D3D10DDI_HDEVICE hDevice,
  _In_  D3D11_1DDI_HVIDEOPROCESSOR hVideoProcessor,
  _In_  UINT StreamIndex,
  _In_  BOOL Enable,
  _In_  FLOAT Alpha
);

Parameters

hDevice [in]

A handle to the display device (graphics context).

hVideoProcessor [in]

A handle to the video processor object that was created through a call to the CreateVideoProcessor function.

StreamIndex [in]

The zero-based index of the input stream.

Enable [in]

If TRUE, alpha blending is to be enabled on the video processor.

Alpha [in]

A pointer to a FLOAT value that specifies the planar alpha value. The value can range from 0.0 (transparent) to 1.0 (opaque).

Note  If the Enable parameter is FALSE, this parameter is ignored.

Return value

This function does not return a value.

Remarks

By default, alpha blending is disabled.

For each pixel, the destination color value is computed as follows:

Cd = Cs * (As * Ap * Ae) + Cd * (1.0 - As * Ap * Ae)

where:

  • Cd = The color value of the destination pixel
  • Cs = The color value of the source pixel
  • As = The per-pixel source alpha
  • Ap = The planar alpha value
  • Ae = The palette-entry alpha value, or 1.0

Note  Palette-entry alpha values apply only to palettized color formats, and only when the device advertises support for the D3D11_1DDI_VIDEO_PROCESSOR_FEATURE_CAPS_ALPHA_PALETTE capability through the GetVideoProcessorCaps function. Otherwise, this factor equals 1.0.

The destination alpha value is computed according to the alpha fill mode. For more information, see VideoProcessorSetOutputAlphaFillMode

The driver reports its ability to support stereo alpha blending for an input stream in the D3D11_1DDI_VIDEO_PROCESSOR_CAPS structure that is returned through the GetVideoProcessorCaps function. If the driver supports the D3D11_1DDI_VIDEO_PROCESSOR_FEATURE_CAPS_ALPHA_STREAM capability, it can be enabled or disabled to produce stereo video frames.

Note  If the driver does not support the D3D11_1DDI_VIDEO_PROCESSOR_FEATURE_CAPS_STEREO capability, the Microsoft Direct3D runtime does not call the VideoProcessorSetStreamAlpha function.

Requirements

Minimum supported client

Windows 8

Minimum supported server

Windows Server 2012

Header

D3d10umddi.h (include D3d10umddi.h)

See also

CreateVideoProcessor
D3D11_1DDI_VIDEO_PROCESSOR_CAPS
GetVideoProcessorCaps
VideoProcessorSetOutputAlphaFillMode

 

 

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