You need to be careful here. The intent of load_backend API is that whoever calls it knows if they will be providing a presentation OR a filename but not both. I have no tested the case where both is not null.

Relevant section from multimedia.py
<pre>
            # Create a filename to record to.
            if presentation is None and filename is not None:
                record_name = get_record_name(extension, filename=filename, path=self.config.videodir)
                presentation = Presentation(filename)
            elif presentation is not None:
                record_name = get_record_name(extension, presentation=presentation, path=self.config.videodir)
            else:
                # Invalid combination you must pass in a presentation or a filename
                logging.error("Failed to configure recording name. No presentation or filename provided.")
                return False
</pre>