QuickTime 3 Reference

Parameter Alternate Data Type

This atom defines a preferred data type for the parameter. If the system your application is running on does not support this preferred data type, the data type specified in the parameter data type atom will be used instead.

Use the alternate data type atom if you would prefer to use a data type that is not supported on all platforms, and use the parameter data type atom to specify a fall-back data type for systems that do not support your preferred data type.

For example, if the parameter alternate data type is kParameterTypeDataColorValue , the parameter holds a value of type CMColor on systems that have the ColorSync extension. On systems that do not have ColorSync, whatever is specified in the parameter data type (such as an RGBValue ) is used instead.

This atom's data is stored in a ParameterAlternateDataType data structure, which in turn relies on the ParameterAlternateDataEntry data structure.



 
typedef struct

{

    OSType      dataType;       // The type of the data

    QTAtomType  alternateAtom;  // The atom to use for alternate data

} ParameterAlternateDataEntry;



typedef struct

{

    long                            alternateCount;

    ParameterAlternateDataEntry     alternates[];

} ParameterAlternateDataType;

dataType: This field in the ParameterAlternateDataEntry structure can take one of the following values:

The parameter alternate data type atom is optional.