[ excerpt from developer's WWW site ]

A multi-channel MPEG encoder, using the ISO13818 standard and the
dist10 source code. Multi-channel files may have up to 6 defined
channels: Left(L), Right(R), Center(C), Left Surround (LS), Right
Surround (RS) and a Low Frequency Enhancement channel (LFE).

ISO13818 defines 5 multichannel modes (on top of the normal stereo
mode), each of these modes may have an optional LFE channel:

3/2: L, R, C, LS, RS 
3/1: L, R, C, mono surround 
2/2: L, R, LS, RS 
2/1: L, R, mono surround 
3/0: L, R, C 

The "standard" surround sound encoding of "5.1 channels" is achieved
by using mode 3/2 plus an LFE channel.

A multi-channel MPEG file should decode OK on any MPEG decoder. If
the decoder doesn't recognize the multi-channel extensions, then
you'll just get a stereo file containing a down mix of the 5 channels.

WWW: http://www.planckenergy.com/