Plain Talk About Recordable DVD
Hollywood wanted a storage solution that would deliver:
• High picture quality, better than laser disc
• 5.1 channel high-quality sound
• 135 minutes (2+ hours) of recording
• 3-5 language capabilities plus subtitles
• Multi-aspect ratio
• Copy protection
• Parental lock features
• Low drive, media cost
The computer industry wanted a solution that would deliver:
• Unified format for AV & PC
• Backward CD read compatibility
• Write-once (WORM) and rewritable compatibility
• Single file system for all content, disc types
• Random-access, high reliability
• No mandatory cartridge
• High on-line capacity
• High performance for both sequential, nonsequential data
• Future capacity expandability
• Low cost
Like the different flavors of CDs, there are six official DVD Forum variations or books:
• DVD-ROM -- a high-capacity data storage medium
• DVD-Video -- a digital storage medium for feature-length motion pictures
• DVD-Audio -- an audio-only storage format similar to CD-Audio
• DVD-R -- two write-once, read-many storage formats similar to CD-R. One for professional authoring applications and one for general consumer applications
• DVD-RW -- sequentially rewritable DVD for content development
• DVD-RAM -- random-access rewritable DVD
A third rewritable format, DVD+RW, has been proposed by Philips, HP and others.
All DVD media formats share common parameters for use in a wide range of personal, professional, home and business systems and applications.
While the DVD formats have important technical differences, the charts below have been developed to help content developers and users determine which media is best for them.
General Format Discussion
DVD-R – Today, there are two DVD-R categories – authoring and general use. The first category of DVD-R – authoring -- was designed to meet the needs of professional content developers and software producers. The general category DVD-R was developed for business and consumer applications – data archiving and one-time video recording. While both authoring and general media can be read by all DVD drives – DVD-ROM, DVD-Video, DVD-RW, DVD-RAM and DVD-Video; technical differences make it impossible to write to DVD-R authoring media using a general DVD-R system. Specification differences are:
DVD-RW – DVD-RW is officially referred to as a “re-recordable” format but is commonly called a “rewritable” format. The general-purpose media contains protection technology that prevents copying of CSS-protected discs. DVD-RW media is a sequential read/write media. Scheduled for release by mid-2001, it can also be used for home video recording and streaming computer back-up applications. DVD-RW discs can be overwritten 1,000 times and have a data storage life of 30-50 years. As of December 2000, 39 firms – hardware, media and software producers – supported the technology. Leading manufacturers include Pioneer, Sony, Mitsubishi Chemical, Sharp, Yamaha, LG Electronics and Samsung. A number of next-generation DVD-ROM drives and DVD players will support DVD-RW media.
DVD-RAM -- DVD-RAM (DVD Random Access Memory) is the official DVD Forum-approved rewritable format. DVD-RAM provides 4.7 GB per side storage capacity and uses phase-change technology for recording. Data on the media can be accessed in the same fashion as a hard drive and discs can be overwritten 100,000 times. Today, the technology has more than 100 supporters including Toshiba, Hitachi, Panasonic, LG Electronics, Samsung, Acer, IBM, Compaq, LaCie and others. The 4.7GB single-sided disc is available as a bare disc or with a removable cartridge for reading by a growing number of shipping DVD-ROM readers, DVD players, and DVD-R recorders. Using DVD Forum standard lossless video editing technology, individual 2kB data blocks can be replaced with a high degree of accuracy.
DVD+RW -- Scheduled to be introduced this year, DVD+RW is an alternative rewritable product backed by HP, Philips, Ricoh, Sony and Mitsubishi Chemical. It will have a capacity of 4.7GB per side and should be suitable for real-time video recording and random data recording. When available, the DVD + RW media will look like DVD Forum standard media. The media will not require a cartridge, but a caddy is recommended for “extreme environments” – such as dust, dirt, or handling -- that can damage data. All physical parameters comply with DVD specifications. Using Philips’ unique DVD+RW video format, video will be encoded with a variable bit-rate (VBR) and lossless linking so that individual 32kB data blocks can be replaced.