Inside Macintosh: QuickTime Components /

Chapter 8 - Video Digitizer Components / Video Digitizer Components Reference

Video Digitizer Component Functions / Controlling Compressed Source Devices

VDSetCompressionOnOff

The VDSetCompressionOnOff function allows an application to start and stop compression by digitizers that can deliver either compressed or uncompressed image data.

pascal VideoDigitizerError VDSetCompressionOnOff 
                           (VideoDigitizerComponent ci, 
                            Boolean state);

ci

Identifies the application's connection to the video digitizer component. An application obtains this value from the Component Manager's OpenComponent function.

state

Contains a Boolean value that indicates whether to enable or
disable compression. Applications set this parameter to true to enable compression. Setting it to false disables compression.

DESCRIPTION

This is a required function for digitizers that are going to perform compression.
These digitizers have their digiOutDoesCompress capability flag set to 1 and their digiOutDoesCompressOnly flag set to 0. Digitizers that support this capability typically deliver uncompressed image data in addition to the compressed data stream; the uncompressed data is ready for display.

Digitizers that only provide compressed data have their digiOutDoesCompressOnly flag set to 1, rather than 0. These digitizers may either ignore this function or return a nonzero result code.

Applications must call this function before they call either VDSetCompression or VDCompressOneFrameAsync. This allows the video digitizer to prepare for the operation.

RESULT CODES

noErr	0	No error
digiUnimpErr	-2201	Function not supported

Main | Top of Section | What's New | Apple Computer, Inc. | Find It | Feedback | Help