What's are some ways of testing complex data types such as video, images, music, etc. I'm using TDD and wonder are there alternatives to "gold file" testing for rendering algorithms. I understand that there's ways to test other parts of the program that don't render and using those results you can infer. However, I'm particularly interested in rendering algorithms specifically image/video testing. 
The question came up while I was using OpenCV/Python to do some basic facial recognition and want to verify its correctness. 
Even if there's nothing definitive any suggestion will help.
What's wrong with the "gold file" technique?  It's part of your test fixture.  Every test has a data fixture that's the equivalent to the "gold file" in a media-intensive application.
When doing ordinary TDD of ordinary business applications, one often has a golden database fixture that must be used.
Even when testing simple functions and core classes of an application, the setUp method creates a kind of "gold file" fixture for that class or function.
What's wrong with that technique?  Please update your question with the specific problems you're having.
Testing complex datatypes?