Thanks for the reply.

So in fact I have tried some of your suggestions...

The sites are record from provide no information about the streaming properties, I don't use a streaming media player that gives me those properties either but i'd be happy to try one if you point it out to me, I was not sure how to use the soft you mention (Proxomitron) so could not get bit-rate negotiation...
I have tried however to record a stream and check the bit-rate but i am not sure how to do that... When I record a file I get this uncompressed large wave file that weighs several tens of Mb that I then encode to mp3.

Any further help would be welcome.

Thanks again!