I dun think MP3 was ever meant to compress 5.1. I''m not too entirely sure if it''s possible to encode anyway or how. Just think about it, the point of compression is to make a little file. Even compressed, a 5.1 file is 3 times as large as regular stereo files.

As well, compression works of this lovely idea called psychoacoustics. In other words it gets rid of everything that we can''t hear, or don''t think we can hear. As well, it converts sections of music from stereo to mono. This is all well and good, involving math and such that most fourth year bachelor of science students would be loathe to touch, for a stereo file. Now add in three more channels and a subwoofer I don''t think the human brain can handle those kind of equations.

I realize that I have been no help, and do really hope that someone else comes along and makes an even bigger ass of me :D

RM

You can use something like Vegas to mix a 5.1 track (used to be made by Sonic Foundry, bought out by Sony). It can export to AC3.

MP3 certainly can''t do surround sound, however ogg vorbis is capable of it... I''m not sure if it''s actually been developed/enabled in the codec yet, but it is definitely in the spec.

But back to the original posters question.. You probably need to buy a software package that will allow you to mix and save 5.1 tracks. Sonar might do it, but don''t quote me on that.

I''m not aware of anything you can download for free (but that doesn''t mean there isn''t something...).

To bake your own AC3 files get hold of BeSweet and AC3Machine from Doom9.net. I''m not sure about the legality of distributing AC3 files created by an un-licensed Dolby encoder, so bear that in mind.