I tried reproducing any playback issues with LAV (both hardware or not), but all tests i did with channel changing on my DVB worked just fine. No black screen, no other funny issues. I recently gave a hint to Yaobing for something he should look into in MCs TV code for channel changes, but since no-one of us suffers from such problems, we cannot reliably say what helps and what doesn't.
The first thing you need to fix such problems is a way to reproduce them, and if you don't have that, there is nothing you can do but stab in the dark (and i'm far too busy for that)