Jitter in the digital audio output is related to the audio circuitry and is independent of the DVD format. It's true that jitter at different stages can reduce audio quality, but comparing it to a 12-bit sample size is naive and inaccurate. Numerous reviews indicate that most DVD players sound as good or better than most CD transports. Audio level too low. In truth the audio level is too high on everything else.
Movie soundtracks are extremely dynamic, ranging from near silence to intense explosions.
This is why the line volume from DVD players is lower than from almost all other sources. 133 minutes per side. This is a meaninglessly exact figure. A single-layer disc can easily hold 150 minutes at the typical average video data rate if there's only one audio track. Lowering the data rate slightly can accommodate over three hours on a single layer.