IDirectDrawVideo::UseScanLine

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Windows Embedded CE 6.0 R3

4/8/2010

This method determines whether the renderer should check the current scan line when drawing a video.

Syntax

HRESULT UseScanLine(
  long UseScanLine
);

Parameters

• UseScanLine
  Long integer value that specifies whether or not to use the scan line information. Set to OATRUE to use scan line information or OAFALSE to ignore it.

Return Value

Returns E_INVALIDARG if the argument is invalid or NOERROR otherwise.

Remarks

If you blit a video image to the screen while the monitor's scan line is scanning over a visible portion of the screen, the complete image will be a composite of the old and new images.

This composite is known as a torn video image.

You can avoid torn images by waiting until the previous image is complete before blitting the new image.

Some video cards can retrieve the scan line's current position; if this information is available, you can have DirectShow try to reduce tearing by waiting until the scan line is offscreen before blitting the new image.

Checking the scan line location increases load on the processor and can reduce the amount of video frames delivered to the screen.

If scan line information is available, DirectShow uses it by default.

If you want to save processing time at the expense of minor image degradation, set UseScanLine to OAFALSE.

Requirements