[MEncoder-users] which audio codec?

[bayrouni]

Hello all,

I am using mencoder to convert all my DVDs, mpeg files  to 
matroska(x264,ac3).

But I am wondering, what is the best choice for the audio supported by 
mencoder?

Keeping ac3, is really  a good choice? (I have in mind the number of 
channels)
I read something about aac, but aac is not free, isn't it? and it will 
lose the number of channels, isn't it?

and what about using musepack or flac  format, aren'nt they good choice ?

I am not sure at all what to use as audio codec :(
The ideal (for me) is to keep the number of channels if possible, but it 
not mandatory.  I care about quality...

Thanks in advance
Bayrouni