[plt-scheme] Converting from DrScheme multimedia format to text

Is there a standalone mzscheme script to
(1) detect if a file is in DrScheme multimedia format
  and if so
(2) convert it to text format

Such a script would be useful to automate some simple grading tasks in
courses using DrScheme as a development environment.

If no such script exists, could someone point me to the correct part
of the DrScheme source code to steal code to develop such a script.

Thanks.

-- Allyn
dimock at cs.uml.edu