Inside Macintosh: QuickTime Components /

Chapter 5 - Sequence Grabber Components / Sequence Grabber Components Reference

Application-Defined Functions /

MyTransferFrameFunction

The sequence grabber component calls your transfer-frame function in order to move a video frame from the capture buffer into the channel's filter buffer.

Your transfer-frame function must support the following interface:

pascal ComponentResult MyTransferFrameFunction (SGChannel c, 
                                             short bufferNum,
                                             MatrixRecord *mp,
                                             RgnHandle clipRgn,
                                             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.

mp

Contains a pointer to a transformation matrix for the transfer operation. 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 applying 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.

DESCRIPTION

The sequence grabber component calls this function only when you are filtering the video data. By filtering the video data through a filter buffer, you can eliminate some visual artifacts that result from noisy input video sources. Your application sets a filter buffer by calling the SGSetCompressBuffer function, which is described on page 5-84.

If you are using a grab-complete function to determine when frames have been grabbed, you should also implement a grab-compress-complete function (described in the next section). Otherwise, the channel will decompress the specified image before calling your grab-complete function, which will result in significantly lower performance. For details on grab-complete functions, see page 5-108.

RESULT CODE

cantDoThatInCurrentMode

-9402

Request invalid in current mode

SEE ALSO

Your transfer-frame function can use the sequence grabber
component's SGTransferFrameForCompress function to support
the default behavior--SGTransferFrameForCompress is described
on page 5-104.

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