DVD: which format? – Technical Section
Rebecca Cannon
An overview of physical DVD formats for the home-studio digital film-maker using Windows, Macintosh and/or Linux operating systems.
When I first heard about DVD in the late nineties, I was thrilled at the prospect of an accessible, high-quality video format with universal playback. I initially expected it to undermine the formatting incompatibilities of NTSC and PAL; of course I’ve since discovered that it doesn’t. DVD is not the shining star of compatibility it first seemed, especially not for people who bought DVD players early on. On PC terminals NTSC and PAL can be circumnavigated; but beyond the PC, DVD retains these playback limitations. It’s also brought with it a slew of other, often incompatible formatting options, not to mention regions, and sometimes unplayable copy-protection systems.
When I set out to buy a DVD burner recently, I was horrified by news that the three leading DVD formats, -R/RW, +RW/R and -RAM, are all incompatible with one another. I was further disturbed to discover that many people I knew who were burning their own DVDs were unable to play them back on set-top players and some other computers. After a fair bit of research into formatting options, their attributes and limitations, the history behind the formats, and future trends in DVD, my initial apprehensions have been alleviated.
Many problems of DVD incompatibility can be overcome. Companies behind the various formats, although in competition with one another, are now, fortunately, aiming towards increased compatibility. For the average film-maker who is considering buying a DVD burner, and for those who have done so but are experiencing problems playing their DVDs, the following information should prove valuable.
Physical and Application formats
The first thing that should be cleared up with any discussion of DVD formats is the difference between physical and application formats. A physical DVD format applies to the actual disc media, as well as the encoding process used to record to it. DVD-RAM, DVD-R/RW, and DVD+RW/R are all physical DVD formats, with their own encoding processes that are incompatible with one another. A DVD-RAM disc must be written on a DVD-RAM drive, and cannot be written on a DVD+RW drive, and vice versa.
An application format describes what kind of data is written to the disc, and the method of writing it to the disc. DVD-Video and DVD-Audio are examples of application formats; they can be written on more than one type of physical DVD format. For example, a DVD-Video can be made on a DVD-R or a DVD+R disc; and a DVD+R disc may hold DVD-Video, DVD-Audio, or a number of other DVD application formats.
Another thing that should be cleared up is the difference between DVD formats and DVD features. Television systems (PAL/ NTSC), 4:3 or 16:9, Dolby Digital or DTS surround sound etc, are sometimes referred to as DVD formats, but this is an incorrect description. They are features of the DVD, and refer only to formatting of the data stored on the disc. They are independent of the physical and application formats of the actual DVD.
Readables, Writables and Rewritables
There are three types of DVDs: Read-Onlys (ROM), Recordables (R), and Rewritables (RW). Read-Onlys are purchased with data already encoded on the disc. They include DVD-Video Hollywood movies, DVD-ROMs with computer applications, games or other data, and DVD-Audio discs.
Recordable DVDs allow you to write once to the disc. -R and +R are the leading recordable DVD formats, and can be used for storing data, burning DVD-Videos and for recording DVD-Videos on set top players. Recordable discs are good for data storage, as there is no fear of accidental erasure. Both +-R have a 30->100 year life expectancy, depending on the actual disc media. -R and +R are not an interchangeable format. They must be written on their respective discs, in their respective drives, but once written they can be read in almost all DVD-ROM drives, if they have DVD-Video burned to them, they will both be read in almost all DVD-Video players (about 95 -99 per cent). DVD-R are not compatible with the earliest DVD-Video players.
Rewriteable DVDs, like their CD-RW counterparts, allow you to rewrite to the disc repeatedly. The two prevalent consumer formats are DVD-RW and DVD+RW, but DVD-RAM is a third Rewriteable format still widely used in the medical, military and industrial imaging industries. DVD+-RW and DVD-RAM must all be written in their respective drives, on their respective media.
DVD+RW, in theory, can always be read by all DVD-ROM drives and all DVD-Video players at any stage. DVD-RW, on the other hand, must be finalized before it can be read in a DVD-Video player, which means it cannot have any more data written to it until it is completely erased and reformatted.
Both DVD+-RW are less compatible than their non-rewriteable counterparts. Some drives and players are confused by the low reflectivity of DVD+-RW media, and try to read them as a dual-layer disc. In other cases a drive or player will not recognize the disc format code, and thus not read the disc at all. Most DVD-ROM drives and DVD-Video players have firmware upgrades available to overcome these problems. DVD+-RW are generally considered between 70-80 per cent compatible with DVD hardware. DVD-RW and DVD+RW can be rewritten about 1000 times.
DVD-RAM has a significantly longer lifespan; it can be rewritten 100,000 times. It was primarily designed for long term, accurate archiving, and should be thought of more as a 4.7GB or 9.4GB removable hard disk than a drive for burning DVD-Videos. DVD-RAM discs cannot be read in non-DVD-RAM drives, including general DVD-Video players and DVD-ROMs. Many people consider them a dead format. When they were released they were the only optical storage device with true random write access, but the DVD+RW logic has been designed to incorporate random write access, and will do so on most operating systems within the next couple of years. Also, the cost-effectiveness that was once a draw card is no longer an issue, with 80GB hard disks well under $200, and a DVD-RAM burner around $500; 9.4GB blank discs between $50-$100 each.
Having said that, according to DVD-Forum in March 2003, DVD-RAM became the market leader in set top DVD video recorders. This was due to successful marketing, and a few consumer-friendly features described below. Generally, these discs cannot be played in most DVD-Video players and DVD-ROM drives, something salespeople do not necessarily feel compelled to mention to their customers.
DVD Forum and DVD Alliance.
DVD was first developed in 1995, when the best elements of two prior formats–the Philips/Sony MMCD and the Toshiba/ Warner SD–were combined. By 1996 specifications for DVD-ROM and DVD-Video had been published, and in late 1996 the first DVD-Video players were on sale in Japan.
In 1997 DVD Forum was established. DVD Forum Ls a volunteer association of hardware manufacturers, software firms and other users of DVD. DVD Forum developed the DVD-R and DVD-RAM formats; the 4.7 GB versions of which have been shipping since 1998, in 2001 they released DVD-RW. DVD-R/RW and DVD-RAM were not backwards compatible with existing consumer DVD-Video and PC DVD-ROM drives. Concern about this led a number of companies to form a new association called DVD Alliance.
DVD Alliance originally claimed to be developing a new format only for computer data, not home video. This was a smokescreen intended to placate DVD Forum. In 2001, DVD Alliance released the DVD+RW format, which is not only backwards compatible with existing devices, but also has many other attributes that make it the most versatile DVD format. Whereas DVD Forum designed DVD-R/RW mostly for video, and DVD-RAM for data storage, DVD+RW was designed from the beginning with both data and video in mind. DVD Alliance later released the DVD+R format, the cheaper, non-rewriteable version of DVD+RW.
There are currently over 200 companies in DVD Forum, lead by Pioneer. DVD Forum also includes Yamaha, Ricoh, Hitachi, Toshiba and Panasonic. DVD Alliance on the other hand is lead by Philips, Sony and HP, and includes Dell, Ricoh, Microsoft, Philips, Yamaha and Verbatim. DVD Alliance has about fifty per cent of the membership of DVD Forum, but most of these companies are members of both associations.
Sony, Apple and Compaq computers come pre-configured with -R/RW burners. No computers come pre-configured with DVD-RAM drives. Dell, HP and Compaq come pre-configured with +RW/R burners.
DVD-R/RW
DVD-R is a write once format that comes in two types: DVD-R(A) for Authoring purposes, and DVD-R(G)for general purposes.
They both require their own disc media and respective burners. DVD-R(A) allows writing to areas of the disc that support CSS (1) and CMF, (2) and is the most compatible format because it was released before consumer DVD players proliferated. However, CSS and CMF are not required by most noncorporate DVD producers, and it is now possible to submit DVD Masters (for duplicating) on any DVD format, so DVD-R(A) is little used.
DVD-R(G), usually referred to as DVD-R, comes in two sizes: 3.95GB and 4.7 GB; and three versions–1.0, 1.9, 2.0–which are not all compatible with one another. People burning to DVD-R often face compatibility problems if they are using the 3.95GB discs and the earlier versions, none of which are recommended if they can be avoided. Unfortunately some earlier drives only support these.
DVD-RW, the rewritable counterpart to DVD-R, has two recording modes: VR and VM. VR mode is basically an unfinalized disc and/or non DVD-Video disc. Like a CD-R, it can have additional sessions of data burned to it until it is finalized. VR mode discs cannot be read by most DVD players and DVD-ROM drives. This is because the finalization process records table-of-contents information into the lead-in and lead-out portions of the disc. VM mode, on the other hand, can be read by most DVD-Video players and DVD-ROM drives as it is finalized, but it cannot be further edited or have any other additional information added to it.
Both VR and VM mode DVD-RW discs must be completely erased and reformatted before they can be rewritten. This is an annoying, time-consuming process. DVDR/RW only uses VBR (3) encoding when in VR mode. It employs the less time-efficient CLV (4) encoding in VM mode. The DVD-RW discs also come in three versions:1.0, 1.1 and 1 .lb. The first version had some compatibility problems but was mostly sold in Japan. DVD-R/RW uses the UDF Bridge (5) file system.
DVD-RAM
DVD-RAM solves problems associated with the reliability and longevity of MO (6) media. Compared to DVD+-RW, DVD-RAM discs last ten times longer, perform 100 times more rewrites, and reduce error rates by 1000 times. DVD-RAM has random write access, and can thus be treated like a hard disk. Applications can run from it and files can be written to or deleted from it.
DVD-RAM has recently become a popular format for set-top DVD video recorders. DVD-RAM video recorders offer many features found on VCRs; e.g. the user can partially overwrite a recording. In addition, on-disc editing means that segments of a program (such as the advertisements) can be removed without any re-recording. Other attractive features include ‘Chasing Playback’, which allows the user to begin recording an entire program, and then later start watching the program from the beginning, while the balance of the program is still being recorded.
The major drawback of DVD-RAM is that it is completely incompatible with other DVD formats. DVD-RAM drives will not play back other DVD formats, (unless the DVD-RAM capacity is part of a multi-format player), and DVD-RAM discs cannot be read in other drives, nor can they be played in most DVD players. People who purchase a DVD-RAM video recorder need to make sure that it is equipped to play back other DVD formats. DVD-RAM video recorders should not be relied upon to make DVDs that are to be given to other people.
DVD+RW/R
DVD+RW/R were developed after DVDR/RW and DVD-RAM, and as a result they overcome many of the problems of the previous formats. For a start, they are backwards compatible with earlier DVD-ROM drives and DVD-Video players. Write speeds are generally faster for DVD+RW than DVD-RW because it always employs VBR encoding.
DVD+R is the non-recordable counterpart to DVD+RW. DVD+R is used similarly to DVD-R, but it offers slightly higher compatibility, can burn faster, and comes in one easy format. Both DVD+R and DVD-R require finalization. Because DVD+R was developed after DVD+RW, some early DVD+RW drives will not write to it (prior to April 2002).
DVD+RW uses UDF. (7) It has substantial benefits over all of the other DVD formats as a result of its file formatting logic. A DVD+RW disc is always, at any stage of any burn, compatible with DVD-ROM drives and DVD-Video players. While recording, the process can be stopped at any time and the disc can be removed and played in a DVD-Video player. DVD+RW do not need to be finalized, and they can be re-written without first being erased and reformatted.
DVD+RW supports both CAV (8) and CLV, which means that, ideally, it is able to perform true random write access, and sustain I/O fragmentation and perform reliably. This means it can be used in the same way that DVD-RAM is–as a removable hard-disk, and also allows set-top DVD+RW recorders to have the same features of DVD-RAM recorders, without any of the incompatibility issues.
Linux is the only PC-based operating system that can currently support random write access with DVD+RW. It will become more widely implemented once support for the EasyWrite (9) system increases. EasyWrite requires an EasyWrite compliant drive and an EasyWrite enabled application and/or operating system. It will be fully implemented in the next version of Microsoft Windows.
Tips
Choice in burner really comes down to budget and needs. Many burners now write in more than one format: dual format burners are generally + and -, and a multi drive may incorporate -RAM. Much of the flexibility of +RW is yet to be implemented, but this format holds the most promise for the future. It should also be noted that DVD+RW/R has strong support from the world’s two largest PC manufacturers, HP/Compaq and Dell.
Prices of DVD writers have dropped thirty per cent in the last six months, and should drop substantially over the next year as the market reaches saturation. Six months ago there was only one multi-format burner available in Australia–there are now already numerous choices in various combinations.
Incompatibility problems are mostly limited to the rewritable formats, and earliest drives, both of which are minority usage. Other incompatibilities have to do with the actual media, so high-quality brands like Pioneer and Verbatim should be used when problems are incurred.
Platforms
All physical DVD formats are available for Microsoft Windows and Macintosh. At the moment Windows DVD authoring software lags behind Apple’s DVD Studio Pro, but Adobe is about to release DVD-Encore that will take up most of the slack.
Linux has had full support for DVD-RAM from day one. DVD-R and DVD+RW have recently become options, but DVD-RW does not appear to be supported. ‘CDRecord Pro’ and ‘Gear Pro’ are (commercial) applications for DVD-R burning. ‘Dvdrtools’ is a patch for (GPL) ‘cdrecord’ that writes to Pioneer DVD-R/RW drives. DVD+RW is available for Linux, Free BSD, OpenBSD and Solaris operating systems using the (GPL) ‘dvd+rw-tools’ utility with ‘cdrtools’. Until Microsoft releases the next version of Windows, this is the only way to use the DVD+RW random write access.
Excellent DVD troubleshooting, tutorials and compatibility lists http: //www.dvdrhelp.com
DVD Forum http://www.dvdforum.com
DVD Alliance http://www.dvdrw.com/
Free DVD email list for professionals
http://www.tully.com/DVDList/dvddemystified.com
Book about dvd technology
http://www.dvdfllc.co.jp/
Format logo licensing corporation
http://www.dvdirect.com/TSS/charts/DVD
AuthoringComparison.htm
dvd software authoring comparisons dvdadept.com
http://www.videoguys.com/DVDburn.html
Players
http://dvd.sourceforge.net/#players
http://www.linux.org/docs/ldp/howto/
Hardware-HOWTO/dvd.html
Drives, burners and player links
dvdrtools (-r)
http://www.nongnu.org/dvdrtools/
dvd+rw-tools
http://fy.chalmers.se/~appro/linux/
DVD+RW/
GearPro Linux
http://www.gearsoftware.com/products/
ProLinux/index.cfm
DVD PHYSICAL FORMATS GB
DVD-ROM
DVD-5, DVD-9, DVD-10 and
VD-18. DVD-5 SS/single-layer 4.7
DVD-9 SS/dual-layer 8.5
DVD-10 DS/single-layer 9.4
DVD-18 DS/dual-layer 17
DVD-RAM 1.0 First Genera- SS
“tion 2.6
DVD-RAM 2.0 SS 4.7
Second Generation DS 9.4
DVD-R/RW First Generation SS 3.95
DVD-R/RW Second Genera- SS
tion 4.7
DVD+RW/R SS 4.7
DVD APPLICATION FORMATS
DVD-Video
DVD-Audio.
DVD-VR
DVD+VR
DVD-Audio Recording (AVA-AR)
DVD Stream Recording
eDVD
SACD: Super Audio CD
Formats for Game consoles (such as Sony
PlayStation 2)
DVD FEATURES
Mulitple Audio Tracks
Multiple Video Tracks
Subtitles
Camera Angles
Chapters
Interactive Menus
Deleted Scenes
Documentary
-ROM/PC friendly features (eg. Chats)
Easter Eggs (hidden surprises)
Parental Locks and Parental control
Production Notes
SeamLess branching
Still Gallery
Theatrical Trailer
Sound Systems
(1) CSS: Content Scrambling System. One of several copy protection systems.
(2) CMF: Cutting Master Format.
(3) VBR: Variable Bit Rate.
(4) CLV: Constant Linear Velocity. With CLV the speed of the disc decreases as data is written to it. Data is written in a spiral, from inside to outside, slowing the disc down further as data is written to the outer edges. A constant transfer rate is thus maintained, making it suitable for real-time video recording.
(5) UDF Bridge: a hybrid file system combining UDF with ISO-9660.
(6) MO: Magneto Optical.
(7) UDF: Universal Device Format. UDF is expected to replace ISO-9660 as a cross-platform file formatting system because it can be both a pre-recorded image and a traditional, random access file system.
(8) CAV: Constant Angular Velocity. With CAV recording, the speed of the disc remains constant, regardless of where the data is physically being recorded to disc. The constant rotation speed enables fast random access, suitable for random write access.
(9) EasyWrite: Mt. Rainier/Easywrite is a file system format specified by Microsoft and Sony, Philips and Hewlett Packard. It allows an optical disc to be used exactly like a floppy disc. Users can have random write access, allowing them to reed/write to the disc from any software. EasyWrite will be compatible with CD-RW and DVD+RW only.
Rebecca Cannon is an experimental animator who also produces copyleft DVD compilations of audio-visual art. Rebecca Cannon is an experimental animator who also produces copyleft DVD compilations of audio-visual art.
COPYRIGHT 2003 Australian Teachers of Media
COPYRIGHT 2003 Gale Group
