Inside Macintosh: QuickTime Components /

Chapter 8 - Video Digitizer Components / Video Digitizer Components Reference

Video Digitizer Component Functions / Setting Video Destinations

VDSetPlayThruDestination

You can use the VDSetPlayThruDestination function in your application to establish the destination settings for a video digitizer component.

All video digitizer components must support this function.

pascal VideoDigitizerError VDSetPlayThruDestination
                               (VideoDigitizerComponent ci,
                                 PixMapHandle dest, 
                                 Rect *destRect, 
                                 MatrixRecord *m, RgnHandle mask);

ci

Specifies the video digitizer component for the request. Applications obtain this reference from the Component Manager's OpenComponent function.

dest

Contains a handle to the destination pixel map. This pixel map may be in the video frame buffer of the Macintosh computer, or it may specify an offscreen buffer.

The video digitizer component examines this pixel map to determine the display characteristics of the video destination, including the base address, row bytes, and pixel depth. If the digitizer component does not support these characteristics, it sets the return value to badDepth. If the digitizer component cannot accommodate the location of the destination pixel map, it sets the return value to noDMA.

If you are going to use multiple output buffers, be sure to include this buffer in the buffer list that you define with the VDSetupBuffers function, which is described on page 8-54. You may call
the VDSetupBuffers function before calling VDSetPlayThruDestination.

destRect

Contains a pointer to a rectangle that specifies the size and location of the video destination. This rectangle must be in the coordinate system of the destination pixel map specified by the dest parameter.

This is an optional parameter. Applications may specify a transformation matrix to control the placement and scaling of the video image in the destination pixel map. In this case, the destRect parameter is set to nil and the m parameter specifies the matrix.

If the destRect parameter is nil, you can determine the destination rectangle for simple matrices by calling the TransformRect function using the current digitizer rectangle and this matrix. For more information on TransformRect, see the chapter "Movie Toolbox" in Inside Macintosh: QuickTime.

m

Contains a pointer to a matrix structure containing the transformation matrix for the destination video image. To determine the capabilities of a video digitizer component, you can call the VDGetDigitizerInfo function, described on page 8-24, in your application.

This is an optional parameter. Applications may specify a destination rectangle to control the placement and scaling of the video image in the destination pixel map. In this case, the m parameter is set to nil and the destRect parameter specifies the destination rectangle.

mask

Contains a region handle that defines a mask. Applications can use masks to control clipping of the video into the destination rectangle. This mask region is defined in the destination coordinate space.

This is an optional parameter. Applications may use alpha channels or key colors to control video blending. If there is no mask, applications should set the mask parameter to nil.

DESCRIPTION

The application provides the desired settings as parameters to this function. Applications should verify that the video digitizer component can accommodate the settings by calling the VDPreflightDestination function, described in the next section.

Applications set the source digitizer rectangle by calling the VDSetDigitizerRect function, described on page 8-29.

RESULT CODES

noErr	0	No error
badDepth	-2207	Digitizer cannot accommodate pixel depth
noDMA	-2208	Digitizer cannot use DMA to this destination

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