half bitrate dts is 754K, full bitrate is 1509k. With full bitrate there is definitely a noticeable improvement in fidelity vs standard DD, but it also takes a lot of space on the disc, so full movies in 1509k movies were rare. Now with Blu Ray and HD DVD, they can easily fit 1509k tracks on there with no problem. I noticed this with Sleepy Hollow on BluRay, the original was 754, but the BD is 1509k.