RTP Codecs implementations are spaghettifying(?)

[ha-ves]

I haven't had time to think of proper solution, but the problem is as more PR of adding codecs (and/or its transport mechanism) I feel like the codebase is turning into bigger and bigger spaghetti.

e.g., RTP framing are a growing if/else statements for all supported codecs.

Maybe should also pull the de/packetizer to framing instead of branching-off on receive/send.

[sipsorcery]

Definitely worth considering any improvements. That being said it's only video codecs that need packetisation and at the current rate a new one only appears every 5 years or so.