Utility Functions for Sequence Grabber Channel Components(IM: QC)

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Chapter 6 - Sequence Grabber Channel Components / Sequence Grabber Channel Components Reference

Utility Functions for Sequence Grabber Channel Components
Sequence grabber components provide several utility functions that your channel component can use. This section discusses those functions.
The SGAddMovieData function lets you add data and sample references to a movie.
Alternatively, you can use the SGWriteMovieData function to add data to a movie, and the SGAddFrameReference and SGGetNextFrameReference functions to keep track of sample references prior to creating a QuickTime movie from recorded data.
The SGSortDeviceList function allows you to sort the entries in the device list that you create for the sequence grabber when it calls your SGGetChannelDeviceList function (which is discussed on page 6-57).
The SGChangedSource function allows you to tell the sequence grabber that you have changed your source device.
The SGAddFrameReference and SGGetNextFrameReference functions take a pointer to a frame information structure as a parameter. The SeqGrabFrameInfo data type defines the format of a frame information structure.
struct SeqGrabFrameInfo {
   long        frameOffset;   /* offset to the sample */
   long        frameTime;     /* time that frame was captured */
   long        frameSize;     /* number of bytes in sample */
   SGChannel   frameChannel;  /* current connection to channel */
   long        frameRefCon;   /* reference constant for channel */
};
Field Description

frameOffset
Specifies the offset to the sample. Your channel component obtains this value from the SGWriteMovieData function, described on page 6-84.
frameTime
Specifies the time at which your channel component captured the frame. This time value is relative to the data sequence. That is, this time is not represented in the context of any fixed time scale. Rather, your channel component must choose and use a time scale consistently for all sample references.
frameSize
Specifies the number of bytes in the sample described by the sample reference.
frameChannel
Identifies the current connection to your channel.
frameRefCon
Contains a reference constant for use by your channel component. You can use this value in any way that is appropriate for your channel component. For example, video channel components may use this value to store a reference to frame differencing information for a temporally compressed image sequence.

Subtopics

SGAddMovieData

SGWriteMovieData

SGAddFrameReference

SGGetNextFrameReference

SGSortDeviceList

SGChangedSource