differences between dts and ac3? white paper or other links?

[ecc]

I was able to listen to DTS with one of the ac3 filters in media player classic and was wowed by how different some films sounded in dts (even when listening through a two speaker set-up or headphones). Some films that I pretty much knew well in terms of sound (through 2.0 and relatively sedate 5.1 mixes [or upmixes] sounded much more enveloping than ever before. The Italian disc of LA CHIESA has a DTS Italian mix that sounds like a big budget film viewed in a theatre - once again, this is just listening to it through stereo headphones - and L'APPARTEMENT already sounded lively and directional in 5.1 AC3 but even better in dts. Other discs I did not notice much of a difference between 5.1 and dts (even in terms of volume) but perhaps they are more distinct with a correct speaker setup.

My question is can anyone direct me to some webpages or downloadable technical papers that discuss dts itself or the differences between it and ac3 encoding?

I'm used to doing heavy amounts of research so don't worry about whether something might be too technical for a newbie. I've looked at SurCode's guides for their dts encoder and ac3 encoder and they look pretty much the same in terms of the user interface so I'm interested in what goes on beyond that as well as anything on the differences in mixing before the individual mono files are created.

Also, does anyone know why some DTS tracks read as 2 channels instead of 6 on the media player (or even on DVD player displays when toggling between tracks with the 'audio' button)? I'm sure they must be 6 channel but are they mislabeled or differently encoded? I was under the impression that DTS was always 6.1 or more channels.

[edDV]

http://en.wikipedia.org/wiki/Digital_Theater_System
http://en.wikipedia.org/wiki/AC3

[BJ_M]

http://www.dtsonline.com/media/uploads/pdfs/dtsposition.pdf
http://www.dtsonline.com/media/uploads/pdfs/dolbyrvu.pdf
http://www.dtsonline.com/media/uploads/pdfs/history,whitepapers,downloads.pdf