Quote Originally Posted by Woochifer
As T noted, DTS is one of the standard formats for Blu-ray -- it was merely optional for DVDs (notice that any DVD with a DTS track also has a DD track). Since the format is scalable from DTS-HD, it just makes sense that more Blu-ray titles are now authored using a DTS audio track.

The great thing about DTS on Blu-ray is that for people like me who use an older receiver, the DTS track that gets output through the optical digital audio output is the 1.5k version, not the half-bitrate version that DVDs use.

DD on Blu-ray also uses a higher bitrate that's audibly superior to the 448/384k DD tracks used on DVDs.
I have a Toshiba HD DVD player -- using the Toslink input to my older AVR. I can toggle through the audio tracks and definitely hear the difference. Although, i don't recall seeing a DTS option..maybe HD DVDs didn't arrive with DTS optional. Anyway, the additional bitrate turns up the heat. Can't wait for my blu-ray player in July.