DTS: How do I create a disc that is DTS compatible?

I don't get the whole DTS things. I bought the Apple Pro Training Series book for DVDSP 4, completed the tutorial (the one about the Tiger) and burned the disc. I played it on a DTS system and it worked perfectly!! Then I created another disc of my own which contained movie clips (scenes from various movies) First I imported all of the clips into iMovie, exported the file to Quicktime, then imported the Quicktime file into DVDSP. This time the disc would NOT work on a DTS system (although it works perfectly on my computer and on my home DVD player which is NOT DTS) Im going out of my mind on this - spent over 40 hours preparing this project. Is there anyone who can CLEARLY EXPLAIN what is going on here? Im not good with all the DVDSP jargon yet, so please break it down for me. Thank you very much.