Configuration Functions for Video Channel Components
Video channel components provide a number of functions that allow the sequence grabber to configure the channel's video characteristics. This section describes these video channel configuration functions, which the sequence grabber component uses only with video channels.The
SGSetChannelBoundsfunction allows the sequence grabber to set the display boundary rectangle for a video channel. TheSGGetChannelBoundsfunction determines a channel's boundary rectangle.The sequence grabber component uses the
SGGetSrcVideoBoundsfunction to determine the coordinates of the source video boundary rectangle. This rectangle defines the size of the source video image being captured by a video channel. TheSGSetVideoRectfunction specifies a part of the source video boundary rectangle to be captured by the channel. TheSGGetVideoRectfunction retrieves this active source video rectangle.Typically, video channel components use the Image Compression Manager to
compress the video data they capture. The sequence grabber component can control many aspects of this image-compression process. TheSGSetVideoCompressorTypefunction specifies the type of image compressor to use. The sequence grabber
can determine the type of image compressor currently in use by calling theSGGetVideoCompressorTypefunction. The sequence grabber component can specify a particular image compressor and set many image-compression parameters by calling theSGSetVideoCompressorfunction. The sequence grabber component can determine which image compressor is being used and its parameter settings by calling theSGGetVideoCompressorfunction.Video channel components typically work with a video digitizer component (see the chapter "Video Digitizer Components" in this book for a complete description of video digitizer components). Sequence grabber components provide functions that allow an application to work with a channel's video digitizer component. Video channel components, in turn, must provide support for these functions. The sequence
grabber component uses theSGGetVideoDigitizerComponentfunction to determine which video digitizer component is supplying data to your video
channel component. The sequence grabber component sets a channel's video digitizer component by calling theSGSetVideoDigitizerComponentfunction. If an application changes any video digitizer settings by calling the video digitizer component directly, the sequence grabber component informs your video channel component by calling theSGVideoDigitizerChangedfunction.Some video source data may contain unacceptable levels of visual noise or artifacts. One technique for removing this noise is to capture the image and then reduce it in size. During the size reduction process, the noise can be filtered out. Some video channel components may provide functions that allow the sequence grabber component to filter the input video data. The
SGSetCompressBufferfunction sets a filter buffer for a video channel. TheSGGetCompressBufferfunction returns information about your filter buffer.The sequence grabber can work with a video channel's frame rate by calling the
SGSetFrameRateandSGGetFrameRatefunctions. The sequence grabber can control whether your channel uses an offscreen buffer by calling yourSGSetUseScreenBufferandSGGetUseScreenBufferfunctions.Your
SGAlignChannelRectfunction allows the sequence grabber to determine a channel's optimum screen position.
Subtopics
- SGSetChannelBounds
- SGGetChannelBounds
- SGGetSrcVideoBounds
- SGSetVideoRect
- SGGetVideoRect
- SGSetVideoCompressorType
- SGGetVideoCompressorType
- SGSetVideoCompressor
- SGGetVideoCompressor
- SGSetVideoDigitizerComponent
- SGGetVideoDigitizerComponent
- SGVideoDigitizerChanged
- SGSetCompressBuffer
- SGGetCompressBuffer
- SGSetFrameRate
- SGGetFrameRate
- SGSetUseScreenBuffer
- SGGetUseScreenBuffer
- SGAlignChannelRect
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