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 theSGGetChannelInfofunction, 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
SGGetSrcVideoBoundsfunction 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 theSGSetVideoRectfunction to specify a part of the source video boundary rectangle to be captured by the channel. TheSGGetVideoRectfunction 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 theSGSetVideoCompressorTypefunction to specify the type of image compressor to use. You can determine the type of image compressor currently in use by calling theSGGetVideoCompressorTypefunction. You can specify a particular image compressor and set many image-compression parameters by calling theSGSetVideoCompressorfunction. You can determine which image compressor is being used and its parameter settings by calling theSGGetVideoCompressorfunction.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 theSGGetVideoDigitizerComponentfunction to determine which video digitizer component is supplying data to a specified channel component. You can set a channel's video digitizer by calling theSGSetVideoDigitizerComponentfunction. If you change any video digitizer settings by calling the video digitizer component directly, you should inform the sequence grabber 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. Sequence grabber components provide functions that allow you to filter the input video data.
TheSGSetCompressBufferfunction sets a filter buffer for a video channel. TheSGGetCompressBufferfunction returns information about your filter buffer.You can work with a video channel's frame rate by calling the
SGSetFrameRateandSGGetFrameRatefunctions. You can control whether a channel uses an offscreen buffer by calling theSGSetUseScreenBufferandSGGetUseScreenBufferfunctions.
Subtopics
- SGGetSrcVideoBounds
- SGSetVideoRect
- SGGetVideoRect
- SGSetVideoCompressorType
- SGGetVideoCompressorType
- SGSetVideoCompressor
- SGGetVideoCompressor
- SGSetVideoDigitizerComponent
- SGGetVideoDigitizerComponent
- SGVideoDigitizerChanged
- SGSetCompressBuffer
- SGGetCompressBuffer
- SGSetFrameRate
- SGGetFrameRate
- SGSetUseScreenBuffer
- SGGetUseScreenBuffer
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