There isn't a way to do this. The Client SDK is essentially just a way of using the Lync client via code, even in UI Suppression Mode (which is why you need to have the client installed, and why it starts it as a process in UI Suppression when you start to use the SDK).
Therefore, you're using the client capabilities for the things you're doing in the SDK. As I'm sure you are know, the video display is given to you just as a window containing the video: there is no way to interact with it at all, and no way of changing the encoding/decoding.
(You can't do this in UCMA either: UCMA doesn't support handling video media)