Theora DirectShow filters assembly

Hello everybody,

I intend to use Theora as a live video codec in a research project. This project is based on live video broadcast over a poor/slow link, which means lots of frames lost and low bandwith.

Until now, it used XViD codec for video compression, which is a working solution but a lot blocky. I made some test with Theora and it looks better in a similar situation.

Now, I would like to make a real test using all my home made DirectShow filters (10+) in a GraphEdit pipe. To do that, I need to encode/decode/display a stream using Theora ( to be able to monitor video quality after passing throught the encoder ).

My question is : why is it not possible for me to connect Theora decoding filter just after a Theora encoding filter ? I was able to do that with XViD and many other codecs. Aren't encoded frames directly sinkable by the decoder ?

To resume a simple situation which is not working in GraphEdit, let's image this :

 VideoCaptureSource ( webcam ) => TheoraEncoder => TheoraDecoder => VideoRenderer

Thanks in advance for your help.

Olivier.