3. What are the drawbacks of DVD ?

The DVD specification is fairly complex and the functions required by its virtual command set are somewhat vague, at least in the sense of default behavior. This deficiency creates inadequate and improper testing of players and discs, as well as different default behaviors in case of errors. These problems result in incompatibilities among different DVD players. Some movie discs do not work properly or do not play at all on some DVD players.

Besides the analog macrovision anticopy protection, DVD has built-in digital copy protection to scramble each sector data (this mechanism is known as Contents Scrambling System or CSS). The DVD player has to perform required authentication sequences to retrieve a 5-byte key from the scrambled sector to restore the sector data to its original state. The disc media can also contain regional protection information. DVD created for region 1 does not play in other regions. The regional protection mechanism has become academic since there are many "region-free" DVD players available.

DVD uses the MPEG2 digital compression to store video data. Video created with poor compression engine or encoded with improper data bit rate and encoding parameters, may look fuzzy or blocky (pixelated).

DVD does not support the full HDTV screen resolution (maximum 720 x 480 NTSC and 720 x 540 PAL). Pixel scaling may become obvious on high-quality HDTV screens.

Some DVD players and drives do not support recordable media (either CD-R or DVD-R), or rewritable media (DVD+RW, DVD-RW).

Most standalone DVD players and drives do not support DVD-RAM discs.

Very few players can perform reverse playback at normal or higher speed.