pascal OSErr SetMediaDataRef(Media theMedia, short index, Handle dataRef, OSType dataRefType);which is also what the prototype in the include file says.
But the actual description for the "index" field says:
"Contains a pointer to a short integer. The Movie Toolbox returns the index value that is assigned to the new data reference...This is wrong. SetMediaDataRef returns a short, not a pointer (as defined in the APIs).