One of my daughters gave me the Pink Floyd ‘Pulse’ DVD set for Fathers’ Day yesterday. Absolutely brilliant concert from 1994, with superb sound. I was startled to find under audio options that you can select Dolby Digital 5.1 sound at either 448kbps or 640kbps. The latter is common on Blu-ray, but is not part of the DVD specification, and a warning in the booklet that comes with the discs suggests that it may not work with some systems.
Still, it worked with mine and it sounded excellent. Better than the 448kbps version? Who knows. I switched quickly between the two, and my impression was that the 640kbps version was a decibel or two louder than the 448kbps version, so that would immediately invalidate any A-B comparison without a great deal of setting up.