Both audio and video renderers were working off the same invalidation signal
(i.e. changing audio would also trigger a re-render of the video). This is
obviously suboptimal and now they are separate.
Major refactoring work to try sharing as much code as possible between the
video renderers and audio renderers, as well as make them as
platform-independent as possible.
The previous iteration was fairly OpenGL-heavy. It's now been separated into
a base class that is OpenGL independent and a derived class that is
OpenGL-based. Over time this should allow for portability away from OpenGL
if necessary.