Audio "identification"

[takearushfan]

Hi,
I noticed that when I use DVD-lab Pro, it will identify a stream as "Dolby 1.0", "Dolby 5.1" or "Dolby 2/0", etc. However, it only does this if I extract the AC3 stream from a DVD and leave the file unaltered...
If I *do* alter the file, for whatever reason, and use BeSweet to create a new AC3, DVD-lab Pro doesn't identify it the same way. Sure, it'll say that it's 6 or however many channels (to be honest, I forget *exactly* what it displays), but it doesn't include the "Dolby" part...
How does DVD-lab Pro know that it isn't Dolby encoded, or, "official", if you will? Is there a header/tag included in AC3s that help identify them?
Also, does anyone know of some "official" Dolby encoding software? I shudder to think of the price, but I'm curious about what's out there.
Thanks again,
Justin

[guns1inger]

Certified Dolby encoding can be quite cheap, although it goes up with more channels. There is a certified Dolby encoder plugin for TDA for underUS$30, but it is 2.0 only. For 5.1 you need to look at either some of the prosumer editors (Vegas, Premiere) or the standalone encoders like Surcode. There are quite a few 5.1 encoding apps around if you google.