MP4 and subtitle streams?

[mtrooper]

I've tryed iso mpeg4 produced by dvix 5 (foud it soulved quite a lot of problems, esp. relating to decoding speed if you encoded movie with goodies - now it flyes :)) and came to a problem: how do you put subtitle streams in it?

Thanks

P.S.: Didn't know where to posit it (either in subs forum or there...but since it is probably more MPEG4/divx related...)