Working With Channel Characteristics
Sequence grabber components use channel components to obtain digitized data from external media. After you create a channel for a sequence grabber component (by calling theSGNewChannelfunction, which is described on page 5-29), you must configure that channel before you start a preview or record operation. The sequence grabber component provides a number of functions that allow you to configure the characteristics of a channel component. Several of these functions work on any channel component. This section discusses these general channel configuration functions.In addition, sequence grabber components provide functions that are specific to the channel type. Apple currently provides two types of channel components: video channel components and sound channel components. See "Working With Video Channels" beginning on page 5-73 for information about the sequence grabber configuration functions that work only with video channels. See "Working With Sound Channels" beginning on page 5-88 for information about the sequence grabber configuration functions that work only with sound channels.
Use the
SGSetChannelUsagefunction to specify how a channel is to be used. You can restrict a channel to use during record or preview operations. In addition, this function allows you to specify whether a channel plays during a record operation. TheSGGetChannelUsagefunction enables you to determine a channel's usage.The
SGGetChannelInfofunction allows you to determine whether a channel has a visual or an audio representation.The
SGSetChannelPlayFlagsfunction allows you to influence the speed
and quality with which the sequence grabber displays captured data. TheSGGetChannelPlayFlagsfunction lets you determine these flag settings.The
SGSetChannelMaxFramesfunction establishes a limit on the number of frames that the sequence grabber will capture from a channel. TheSGGetChannelMaxFramesfunction allows you to determine that limit.The
SGSetChannelBoundsfunction allows you to set the display boundary rectangle for a channel. Use theSGGetChannelBoundsfunction to determine a channel's boundary rectangle.The
SGSetChannelVolumefunction allows you to control a channel's sound volume. Use theSGGetChannelVolumefunction to determine a channel's volume.The
SGSetChannelRefConfunction allows you to set the value of a reference constant that is passed to your callback functions (see "Video Channel Callback Functions" beginning on page 5-95 for information about the callback functions that are supported by video channels).Use the
SGGetChannelSampleDescriptionfunction to retrieve a channel's sample description. TheSGGetChannelTimeScalefunction allows you to obtain the channel's time scale.You can modify or retrieve the channel's clipping region by calling the
SGSetChannelCliporSGGetChannelClipfunction, respectively. You can work with a channel's transformation matrix by calling theSGSetChannelMatrixandSGGetChannelMatrixfunctions.
Subtopics
- SGSetChannelUsage
- SGGetChannelUsage
- SGGetChannelInfo
- SGSetChannelPlayFlags
- SGGetChannelPlayFlags
- SGSetChannelMaxFrames
- SGGetChannelMaxFrames
- SGSetChannelBounds
- SGGetChannelBounds
- SGSetChannelVolume
- SGGetChannelVolume
- SGSetChannelRefCon
- SGGetChannelSampleDescription
- SGGetChannelTimeScale
- SGSetChannelClip
- SGGetChannelClip
- SGSetChannelMatrix
- SGGetChannelMatrix
Main | Top of Section | What's New | Apple Computer, Inc. | Find It | Feedback | Help