Hi Marcel
I know, the thing is the capabilities negotiation wasn't properly implemented, some functions should have been overrided, sbcdec and sbcenc should be enough to decode/encode, but since sbcparse was missing the same thing sbcenc was, I did the work too.
If a use:
filesrc ! audioconvert ! sbcenc ! fakesink
it works, but that doesn't mean the problem isn't there, it just hasn't ocurred, (the reason is that fakesink accept any kind of buffers, thus negotiation is "everything is ok"), when I put sbcparse (even if its not useful, it's just for testing) the negotiation should succeed, both of them work with sbc, and it isn't succeeding.
Both sbcenc and sbcparse had a problem, the example I gave was only a demonstration of the problem.
Regards
Thiago