PHYSICAL, LOGICAL AND FILE SYSTEM STANDARDS

What writable DVD formats are available?
There are five kinds of writable DVD technology (DVD-R, DVD+R, DVD-RW, DVD+RW and DVD-RAM). Similar to CD-Recordable (CD-R), DVD-R and DVD+R discs are write-once incorporating a dye recording layer to which information is irreversibly written by means of a laser heating and altering it to create a pattern of marks mimicking the pits of a prerecorded (pressed/molded) DVD. DVD-RW and DVD+RW, on the other hand, closely resemble CD-ReWritable (CD-RW) by employing a phase-change recording layer that can be repeatedly changed and restored by the writing laser (approximately 1000 times). DVD-RAM also uses phase-change technology but can be rewritten roughly 100,000 times. With its hard sectors, random access capabilities and optional cartridge, DVD-RAM more closely resembles traditional disc-based storage media than do DVD-RW and DVD+RW. This separates DVD-RAM somewhat from the prerecorded DVD format that provides the basis for most DVD discs.

Due to technological limitations when it was introduced in 1997, DVD-R employed 635 nm wavelength laser technology to store 3.95 GB per 12 cm disc (DVD-R version 1.0). Capacity was increased to 4.7 GB per disc in 1999 (DVD-R version 1.9). In 2000, DVD-R was split (DVD-R for Authoring version 2.0 and DVD-R for General version 2.0). DVD-R (Authoring) continues to use a 635 nm laser and remains available in limited form as do 3.95 GB discs for some highly specialized applications while the less expensive DVD-R (General) is more widely used and employs the same 650 nm laser wavelength as other DVD formats.

In 1999 DVD-RW was introduced only in Japan (version 1.0) with 4.7 GB 12 cm discs incorporating an embossed information area (for content protection) unreadable by nearly all DVD devices. This was changed in 2000 (version 1.1) to make discs broadly compatible.

DVD-RAM first appeared in 1998 offering 2.6 GB of storage per 12 cm disc (version 1.0) growing to 4.7 GB in 1999 (version 2.0). A 1.46 GB 8 cm disc was introduced in 2000 (version 2.1).

Originally, a 3.0 GB version of DVD+RW was proposed but no products were ever released. DVD+RW came to market in 2001 with a capacity of 4.7 GB per 12 cm disc while DVD+R arrived in 2002.

What specifications govern writable DVD discs?
As is the case with CD-R and CD-RW, all DVD disc formats are governed by a variety of industry specifications or “books” defining their mechanical properties, optical signal characteristics, physical arrangement, writing methods and testing conditions. In addition, various documents also deal with file systems as well as applications.

Specifications for DVD physical formats (DVD-ROM, DVD-R, DVD-RW, DVD-RAM) and applications (DVD-Video, DVD-Audio, DVD-ENAV, DVD-VR, DVD-AR, DVD-SR) were established and are continually updated (increases in writing speed, etc.) by the DVD Forum (originally DVD Consortium), an association of manufacturers founded in 1995 by Hitachi, Matsushita Electric, Mitsubishi Electric, Pioneer, Philips Electronics, Sony, Thomson, Time Warner, Toshiba and JVC.

DVD+R, DVD+RW and DVD+MRW (Mount Rainier) format specifications were created and are maintained by the DVD+RW Alliance, a separate group of manufacturers established in 1997 by Philips Electronics, Hewlett-Packard, Mitsubishi Chemical, Ricoh, Sony and Yamaha. The DVD+VR and DVD+R Video application formats are the creation and responsibility of Philips Electronics.

Over the years many DVD physical formats have also developed into ECMA International and ISO/IEC standards. The composition of these manufacturer groups and standards bodies continues to change and expand.

DVD Physical Format Standards
(ECMA International and ISO/IEC)

What is the DVD-Video format?
DVD-Video (DVD-V) is an application format released by the DVD Forum in 1996. Originally designed to meet the requirements of the film industry for distributing commercial movies on prerecorded (pressed) discs, the DVD-Video format applies equally to writable DVD. Updates were undertaken in 2000 to officially accommodate DVD-R (General) and DVD-RW and again in 2001 for DVD-RAM. DVD-Video format can also be used with DVD+R and DVD+RW.

Typically, discs written in DVD-Video format can be played back using any DVD video player or computer DVD-ROM drive employing appropriate software (subject to that device’s physical compatibility with the specific type of disc). Among its features, the DVD-Video format supports one main stream of video (MPEG-1, MPEG-2) with up to nine separate camera angles, as many as eight audio streams (Dolby Digital, MPEG-1, MPEG-2, LPCM, DTS), a maximum of 32 subpicture streams (graphic overlay) together with navigation menus, still images, simple interactivity, random accessibility plus many other extras.

Depending upon the capabilities of the computer installed DVD recorder, hardware and software used, DVD-Video format discs can be written using material transferred from either digital or analog sources. Digital material (such as video from a DV or writable DVD camcorder) is typically read directly from that device using an IEEE 1394 (FireWire/i.LINK) or USB interface and computer files (such as WMA, QuickTime, AVI, MPEG) from a hard drive. To record analog sources (such as VHS tapes, laserdiscs and cable broadcasts) signals are first digitized through a video capture card or similar IEEE 1394/USB unit. By using authoring software supporting the DVD-Video format, transferred material can sometimes be simply written to disc or processed into a more involved title employing creative tools and by adding further material.

Writable DVD camcorders as well as professional and consumer electronics (CE) recorders are all-in-one systems incorporating video and audio capture combined with authoring and disc writing. Typically, DVD-R and DVD-RW capable devices offer a “Video mode” selection to write those discs in DVD-Video format. Keep in mind that not all products exploit the full range of DVD-Video features and that there may be additional restrictions to consider. For example, it is generally not possible to partially write discs on one recorder and “finalize” them or add new material using a different recorder. Check with the manufacturer for specific details.

What are the DVD Video Recording, DVD+RW Video and DVD+R Video formats?
The DVD-Video format was initially designed to place static material on disc and not to seamlessly manage successive real time recording and editing from cable, satellite and other live video sources (like a VCR). To address this, several additional application formats were developed for use by consumer devices including writable DVD camcorders and consumer electronics (CE) recorders. The first of these is the DVD Video Recording (DVD-VR) format released by the DVD Forum in 1999 for DVD-RW and DVD-RAM and later updated in 2000 to accommodate DVD-R (General). Philips Electronics then followed in 2001 and 2002 with its own DVD+RW Video (DVD+VR) and DVD+R Video formats for DVD+RW and DVD+R discs. Since many DVD-Video format features are not required for home recording applications, these formats offer an abridged selection of capabilities while adding some of their own.

Typically, DVD-RW and DVD-RAM capable recorders offer a “VR mode” selection to write those discs in DVD-VR format while DVD+RW and DVD+R recorders automatically write DVD+RW and DVD+R discs in the appropriate DVD+VR and DVD+R Video format. However, DVD-VR differs significantly from the original DVD-Video format. As a result, only devices specifically designed to be DVD-VR compatible (for example, units marked “RW compatible” and “DVD Multi”) can play DVD-VR recorded discs. DVD+VR and DVD+R Video closely resemble the DVD-Video format and, as such, maintain playback compatibility with most DVD devices. Keep in mind that not all products exploit the full range of features offered by these formats and that there may be additional restrictions to consider. Check with the manufacturer for specific details.

What is The Universal Disc Format (UDF)?

The Universal Disc Format (UDF) specification was first released by the Optical Storage Technology Association (OSTA) in 1995 and is designed to be a common logical file system for all removable optical storage media. Over the years various updates to UDF have been introduced to add new capabilities. So with DVD, UDF 1.02 is the standard file system used for DVD-Video, DVD-Audio and DVD-ROM prerecorded and writable discs. UDF 1.5 is frequently employed for incremental writing while UDF 2.0 applies to DVD-RW and DVD-RAM discs written in the DVD Video Recording (DVD-VR) format.

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