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QuickTime 4 API Documentation

QuickTime 4 Reference

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The Decompression Data Source Structure

The CDSequenceDataSource structure contains a linked list of all data sources for a decompression sequence. Because each data source contains a link to the next data source, a codec can access all data sources from this field. The CDSequenceDataSource structure is defined as follows:

struct CDSequenceDataSource {
    long                        recordSize;
    void *                      next;
    ImageSequence               seqID;
    ImageSequenceDataSource     sourceID;
    OSType                      sourceType;
    long                        sourceInputNumber;
    void *                      dataPtr;
    Handle                      dataDescription;
    long                        changeSeed;
    ICMConvertDataFormatUPP     transferProc;
    void *                      transferRefcon;
    long                        dataSize;
};
typedef struct CDSequenceDataSource CDSequenceDataSource;
typedef CDSequenceDataSource *CDSequenceDataSourcePtr;

Field descriptions

recordSize
Specifies the size of the record.

next
Contains a pointer to the next source entry. If it is nil , there are no more entries.

seqID
Specifies the image sequence that this source is associated with.

sourceID
Specifies the source reference identifying this source.

sourceType
A four-character code describing how the input will be used. This value is passed to this parameter by the CDSequenceNewDataSource function when the source is created.

sourceInputNumber
This value is passed to this parameter by the CDSequenceNewDataSource function when the source is created.

dataPtr
Contains a pointer to the actual source data.

dataDescription
Contains a handle to a data structure describing the data format. This is often an image description handle.

changeSeed
Contains an integer that is incremented each time the dataPtr field changes or that data that the dataPtr field points to changes. By remembering the value of this field and comparing to the value the next time the decompressor or compressor component is called, the component can determine if new data is present.

transferProc
Reserved

transferRefcon
Reserved

datasize
Specifies the size of the data pointer to the dataPtr field.

© 1999 Apple Computer, Inc.

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