Will high-definition DVD or 720p DVD make current players and discs obsolete

Not for a long time. HD-DVD is just becoming available. HD stands for both high density (more data on a disc) and high definition (better quality picture). The first commercial Blu-ray HD-DVD recorders appeared in Japan in April of 2003, over 7 years after DVD was introduced there. The recorders are designed for home recording only (not for playing pre-recorded HD movies), and only work with Japan's digital HD broadcast system.

New DVD formats will slowly supersede the original DVD format, but new players will play old DVD discs and will often make them look even better (with progressive-scan video and picture processing). However, new HD-DVD discs won't be playable in older DVD players (unless they are special hybrid discs in both HD and SD format). Your collection of standard DVDs will be playable for many years to come, and titles will only become "obsolete" in the sense that you might want to replace them with new high-definition versions. Consider that U.S. HDTV was anticipated to be available in 1989, yet it was not finalized until 1996 and did not appear until 1998. Has it made your current TV obsolete yet?

See 3.13 for more details of HD-DVD, and 6.5 for more on the future of DVD.

Ironically, computers supported HDTV before settop players, because 2x DVD-ROM drives coupled with appropriate playback and display hardware met the 19 Mbps data rate needed for HDTV. This led to various "720p DVD" projects, which use the existing DVD format to store video in 1280x720 or 1920x1080 resolution at 24 progressive frames per second. It's possible that 720p DVDs can be made compatible with existing players (which would only recognize and play the 480-line line data).

Note: The term HDVD has already been taken for "high-density volumetric display."

Some have speculated that a "double-headed" player reading both sides of the disc at the same time could double the data rate or provide an enhancement stream for applications such as HDTV. This is currently impossible since the track spirals go in opposite directions (unless all four layers are used). The DVD spec would have to be changed to allow reverse spirals on layer 0. Even then, keeping both sides in sync, especially with MPEG-2's variable bit rate, would require independently tracking heads, precise track and pit spacing, and a larger, more sophisticated track buffer. Another option would be to use two heads to read both layers of one side simultaneously. This is technically feasible but has no advantage over reading one layer twice as fast, which is simpler and cheaper.

See 2.9 for more information about HDTV and DVD.