The IDL interface is available from within the SVN under the idl/ directory. These files provide an independent interface to reading an SPD file from ITTVIS IDL scripts. These files are released under the same licence as SPDLib.
The SPD format uses HDF5 compound datatypes. Since IDL can't pass user-defined structures to the IDL HDF5 readers, there is an overhead when reading the pulse and point data. We're currently looking into ways of improving read performance. For more information contact John Armston.