Inside Macintosh: QuickTime Components /

Chapter 8 - Video Digitizer Components / Video Digitizer Components Reference

Video Digitizer Component Functions / Controlling Digitization

VDGetDataRate

The VDGetDataRate function allows an application to retrieve information that describes the performance capabilities of a video digitizer.

pascal VideoDigitizerError VDGetDataRate 
                                    (VideoDigitizerComponent ci, 
                                     long *milliSecPerFrame, 
                                     Fixed *framesPerSecond, 
                                     long *bytesPerSecond);

ci

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

milliSecPerFrame

Contains a pointer to a long integer. The video digitizer returns a value that indicates the number of milliseconds of synchronous overhead involved in digitizing a single frame. This value includes the average delay incurred between the time when the digitizer requests a frame from its associated device, and the time at which the device delivers the frame.

framesPerSecond

Contains a pointer to a fixed value. The video digitizer supplies the maximum rate at which it can capture video. Note that this value may differ from the rate that the application set with the VDSetFrameRate function, described in the previous section.

bytesPerSecond

Contains a pointer to a long integer. Video digitizers that can return compressed image data return a value that indicates the approximate number of bytes per second that the digitizer is generating compressed data, given the current compression settings and frame rate settings.

RESULT CODES

noErr	0	No error
digiUnimpErr	-2201	Function not supported