Inside Macintosh: QuickTime Components /

Chapter 4 - Image Compressor Components / Image Compressor Components Reference

Functions / Indirect Functions

CDPreCompress

Your component receives the CDPreCompress request before compressing an image or a band of an image. The Image Compression Manager also calls this function when processing a sequence. In that case, the Image Compression Manager calls this function whenever the parameters governing the sequence operation have changed substantially. Your component indicates whether it can perform the requested compression operation.

pascal ComponentResult CDPreCompress 
                                    (CodecCompressParams *params);

params

Contains a pointer to a compression parameters structure. The Image Compression Manager places the appropriate parameter information in that structure. See "The Compression Parameters Structure" beginning on page 4-40 for details.

DESCRIPTION

Your component should return a 0 result code to indicate that it can handle the request. In addition, your component indicates any limitations on its capabilities in a compressor capability structure (see "The Compressor Capability Structure" beginning on page 4-35 for details). Your component should return a result code of codecConditionError if it cannot field the compression request.

Only compressors receive this request.

RESULT CODES

noErr	0	No error
paramErr	-50	Invalid parameter specified
codecConditionErr	-8972	Component cannot perform requested operation

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