QuickTime 3 Reference
Once you have selected a data handler component, you must provide a data reference to the data handler. Use the DataHSetDataRef function to supply a data reference to a data handler. Once you have assigned a data reference to the data handler, your application may start reading and/or writing movie data from that data reference. The DataHGetDataRef function allows your application to obtain a data handler's current data reference.
Data handlers also provide a function that allows your application to determine whether two data references are equivalent (that is, refer to the same movie container). Your application provides a data reference to the DataHCompareDataRef function. The data handler returns a Boolean value indicating whether that data reference matches the data handler's current data reference.
For more information on these functions, see "Working With Data References" .