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Chapter 5 - Sequence Grabber Components / Sequence Grabber Components Reference

Sequence Grabber Component Functions

Working With Video Channels

Sequence grabber components provide a number of functions that allow you to configure the grabber's video channels. This section describes these configuration functions, which you can use only with video channels. You can determine whether a channel has a visual representation by calling the SGGetChannelInfo function, which is described on page 5-58. If you want to configure a sound channel, use the functions described in "Working With Sound Channels" beginning on page 5-88. If you want to configure general attributes of a channel, use the functions described in "Working With Channel Characteristics" beginning on page 5-55.

The SGGetSrcVideoBounds function allows you to determine the coordinates of the source video boundary rectangle. This rectangle defines the size of the source video image being captured by the video channel. You can use the SGSetVideoRect function to specify a part of the source video boundary rectangle to be captured by the channel. The SGGetVideoRect function allows you to determine the active source video rectangle.

Typically, the sequence grabber component uses the Image Compression Manager
to compress the video data it captures. You can control many aspects of this image- compression process. Use the SGSetVideoCompressorType function to specify the type of image compressor to use. You can determine the type of image compressor currently in use by calling the SGGetVideoCompressorType function. You can specify a particular image compressor and set many image-compression parameters by calling the SGSetVideoCompressor function. You can determine which image compressor is being used and its parameter settings by calling the SGGetVideoCompressor function.

The channel components that supply video data to a sequence grabber
component 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
you to work with a channel's video digitizer component. You can use the SGGetVideoDigitizerComponent function to determine which video digitizer component is supplying data to a specified channel component. You can set a channel's video digitizer by calling the SGSetVideoDigitizerComponent function. If you change any video digitizer settings by calling the video digitizer component directly, you should inform the sequence grabber component by calling the SGVideoDigitizerChanged function.

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. Sequence grabber components provide functions that allow you to filter the input video data.
The SGSetCompressBuffer function sets a filter buffer for a video channel. The SGGetCompressBuffer function returns information about your filter buffer.

You can work with a video channel's frame rate by calling the SGSetFrameRate and SGGetFrameRate functions. You can control whether a channel uses an offscreen buffer by calling the SGSetUseScreenBuffer and SGGetUseScreenBuffer functions.

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Subtopics

SGGetSrcVideoBounds

SGSetVideoRect

SGGetVideoRect

SGSetVideoCompressorType

SGGetVideoCompressorType

SGSetVideoCompressor

SGGetVideoCompressor

SGSetVideoDigitizerComponent

SGGetVideoDigitizerComponent

SGVideoDigitizerChanged

SGSetCompressBuffer

SGGetCompressBuffer

SGSetFrameRate

SGGetFrameRate

SGSetUseScreenBuffer

SGGetUseScreenBuffer