There aren't any writing classes yet except for rtp dump.
I kinda explained it in the thread about aac, it would need to be done manually as this time.
I have played with just about every media api available, they all have various shortcomings and none of them work nicely together :-(
If your doing things on different platforms e.g. desktop vs silverlight this gets worse and then if you even have to think about changing to mono everything has to change yet again.
It's totally possible to use media foundation or transcode api with the rtp and rtsp clients, and I even am fairy sure it does under the hood.
If you need anything at all let me know!