Inside Macintosh: QuickTime Components /

Chapter 5 - Sequence Grabber Components / Sequence Grabber Components Reference

Application-Defined Functions /

MyGrabCompleteFunction

The sequence grabber component calls your grab-complete function in order to determine whether the current frame-capture operation is complete. Once a frame has been completely captured, you can modify its contents to suit your needs. For example, you can overlay text onto the video image.

Your function must present the following interface:

pascal ComponentResult MyGrabCompleteFunction (SGChannel c,
                                                short bufferNum,
                                                Boolean *done,
                                                long refCon);

c

Specifies the reference that identifies the channel for this operation.

bufferNum

Identifies the buffer for this operation. You can obtain information about this buffer by calling the SGGetBufferInfo function, which is described on page 5-98.

done

Contains a pointer to a Boolean value. Your function sets this Boolean value to indicate whether the frame has been completely captured. Set the Boolean value to true if the capture is complete; set it to false if it is incomplete.

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 grab-complete function can use the sequence grabber
component's SGGrabFrameComplete function to support the
default behavior. SGGrabFrameComplete is described on page 5-100.

See Listing 5-6 on page 5-18 for a sample grab-complete function. This function draws the letters "QT" over each video frame in the sequence.

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