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Chapter 3 - Image Compression Manager / Image Compression Manager Reference

Image Compression Manager Functions / Changing Sequence-Compression Parameters

GetCSequencePrevBuffer

The GetCSequencePrevBuffer function determines the location of the previous image buffer allocated by the compressor.

pascal OSErr GetCSequencePrevBuffer (ImageSequence seqID,
                                     GWorldPtr *gworld);

seqID

Contains the unique sequence identifier that was returned by the CompressSequenceBegin function (described on page 3-100).

gworld

Contains a pointer to a field to receive a pointer to the structure of type GWorld that describes the graphics world for the image buffer. If the compressor has allocated an offscreen image buffer, the compressor returns an appropriate pointer to the graphics world (of type GWorldPtr) in the field referred to by this parameter. If the compressor has not allocated a buffer, the function returns an error result code.

You should not dispose of this graphics world--the returned pointer refers to a buffer that the Image Compression Manager is using.

DESCRIPTION

If you do not specify a previous image buffer with the prev parameter to the CompressSequenceBegin function, the compressor allocates an offscreen graphics world for you. Your program can obtain access to the pixel map in that graphics world by calling this function.

Note that the GetCSequencePrevBuffer function only returns information about buffers that were allocated by the compressor. You cannot use this function to determine the location of a buffer you have provided.

RESULT CODES

noErr	0	No error
paramErr	-50	Invalid parameter specified