Inside Macintosh: QuickTime Components /

Chapter 5 - Sequence Grabber Components / Sequence Grabber Components Reference

Application-Defined Functions /

MyDisplayCompressFunction

The sequence grabber calls your display-compress function when it is working with a video digitizer component that supports compressed source data. Your display-compress function is responsible for decompressing and displaying a compressed image.

pascal ComponentResult MyDisplayCompressFunction (SGChannel c,
                                    Ptr dataPtr,                        
                                    ImageDescriptionHandle desc, 
                                    MatrixRecord *mp, 
                                    RgnHandle clipRgn, 
                                    long refCon);

c

Identifies the channel for this operation. The sequence grabber provides this value to your display-compress function.

dataPtr

Contains a pointer to the compressed image data.

desc

Specifies a handle to the image description structure to use for the decompression operation. See the chapter "Image Compression Manager" in Inside Macintosh: QuickTime for more information about this data structure.

mp

Contains a pointer to a matrix structure. This matrix structure contains the transformation matrix to use when displaying the image. If there is no matrix for the operation, this parameter is set to nil.

clipRgn

Contains a handle to the clipping region for the destination image.
This region is defined in the destination coordinate system. Apply the clipping region after the transformation matrix. If there is no clipping region, this parameter is set to nil.

refCon

Contains a reference constant value. You can set this value by calling the SGSetChannelRefCon function, which is described on page 5-64.

RESULT CODE

cantDoThatInCurrentMode

-9402

Request invalid in current mode

SEE ALSO

Your display-compress function may use the sequence grabber's SGDisplayCompress function to support the default behavior. SGDisplayCompress is discussed beginning on page 5-106.

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