DVD Demystified

What’s Wrong with DVD
Synchronization Problems
When certain discs are played in certain players, there is a “lip sync” breakdown
where audio lags slightly behind the video or in some cases slightly
precedes the video. Perception of the sync problem is highly subjective—
some people are bothered by it, whereas others cannot discern it at all. The
cause is a complex interaction of as many as four factors:
1. Improper matching of audio and video tracks in the DVD
encoding/authoring process
2. Poor sync techniques during film production or editing (especially
postdubbing or looping)
3. Loose sync tolerances in the DVD player
4. Delay in the external decoder/receiver
Factor 1 or 2 usually must be present in order for factor 3 or 4 to become
apparent. Some discs with severe sync problems have been reissued after
being reencoded to fix the problem. In some cases the sync problem in the
player (factor 3) can be fixed by pausing or stopping playback and then
restarting or by turning the player off, waiting a few seconds, and then
turning it back on. Unfortunately, there is no simple answer and no single,
simple fix. Player manufacturers and disc producers need to cooperate to
nail down and fix the various causes.
Feeble Support of Parental
Choice Features
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Hollywood was quick to request a parental management feature for DVD
but very slow to actually use it. DVDs can be designed to play a different
version of a movie depending on the parental level that has been set in the
player. By taking advantage of the seamless branching feature of DVD,
objectionable scenes can be skipped over automatically or replaced during
playback. This requires that the disc be carefully authored with alternate
scenes and branch points that do not cause interruptions or discontinuities
in the soundtrack. Unfortunately, very few multirating discs have been produced.
Hollywood studios are not convinced that there is a big enough
demand to justify the extra work involved (shooting extra footage, recording
extra audio, editing new sequences, creating branch points, synchronizing