How do I make a multichannel mp2/mp3(eg more than 2) out of an AC3 stream??(original AC3 has 5 channels)

And with wich program can I see how may channels an mp2 or mp3 has?

I have read the guide that is posted here on putting a multichannel mp2 in a SVCD...buth somehow it's not working....can't get the right conversion...

Please....help me....share your wishdom with me...and make me happy...