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Introduction
DVD+RW supports lossless linking/sector replacement across the entire disc
DVD+RW offers DVD+VR support
DVD+RW supports defect management
DVD+RW supports addressing during recording
DVD+RW has a 2.4 times higher basic writing speed
DVD+RW and DVD+R media only come in one type
DVD+RW offers quick background formatting
Optional: DVD+RW system offers Mount Rainier (EasyWrite) support
Optional: DVD+RW system supports both CAV and CLV writing
Some conclusions
Comparison table



This article compares DVD PC drives. If you want to compare the different recordable DVD systems for video recorders, refer to DVD+RW vs. DVD-RW Video Recorders compared.


Introduction

When the DVD+RW Alliance set up the standards for the DVD+RW format, they included compatibility with existing DVD-Video players and DVD-ROM drives as a key requirement into the specification. DVD+RW is the only format that was build from scratch to be compatible with DVD and to act as a logical -compatible- addition to the popular DVD system. While other formats might also offer some level of compatibility, they won't offer any of the convenience, high-performance or robustness of the DVD+RW format, as this would sacrifice the compatibility with current readers. Since the DVD-R/-RW format lacks most of DVD+RWs functionality, is less suitable for data and video applications, as we will outline in this comparison article.

DVD-RAM discs are incompatible with DVD due to their complete mechanical difference (the discs are housed in a cartridge like a floppy diskette) and different way of logically writing to a disc. Since a DVD-RAM disc could never be read in a normal DVD-ROM drive or DVD-Video player, a DVD-RAM disc can hardly be called DVD, and will not be discussed further in this article.

In this article we will compare DVD-R and DVD-RW with DVD+R and DVD+RW, and point out why DVD+R/+RW has many advantages over DVD-R/-RW when used for computer data storage or video recording.


DVD+RW supports lossless linking/sector replacement across the entire disc

Only DVD+RW offers very accurate lossless linking within the basic specification of the system. This means that it can replace individual sectors on the disc at any given location. This results in the writing of sectors on the disc that remain fully compatible with existing DVD-ROM drives (and even the more critical DVD-Video players in case you are creating a DVD-Video disc). This is DVD+RW's most powerfull feature, which allows for all kinds of behaviour that's not possible with other recordable DVD systems. For example, you can replace the menu of a disc within seconds, without the need of rewriting the entire disc. On top of this, lossless linking allows for high performance drag-'n-drop applications like packet writing or Mount Rainier support (see below). DVD-RW does not offer this degree of lossless linking capability. It might optionally support some form of buffer underrun protection, but this is something different from "lossless linking", as it does not allow the user to replace sectors on a written disc.


DVD+RW offers DVD+VR support

DVD+RW drives offer DVD+VR (DVD+RW Video Recording) support. Contrary to the VR format that can be found on DVD-RW video recorders, the DVD+VR is fully compatible with existing DVD-Video players, without sacrificing all the neat editing functionality. Using a DVD+VR capable authoring tool, you could for example change the background of the menu, edit out commercials or replace a part of a video recording, all within a matter of seconds and without the need of rewriting the entire disc. Since DVD-RW cannot change the contents of a disc already written, you need to rewrite the entire disc when you made a change to it.


DVD+RW supports defect management

DVD-RW does not support any form of defect management within the basic system, which could lead to reading errors in a DVD-ROM drive or even hangups of a DVD-Video player when your disc contains a minor error. DVD+RW incorporates a defect management system by default which was designed to be 100% invisible to existing drives and players, so that the discs can be read as if they were normal DVD-ROM or DVD-Video discs.


DVD+RW supports addressing during recording

DVD-RW does not allow address information (which is stored in land pre-pits on a DVD-RW disc) to be read during the recording process, hence it's impossible to locate at what position of the disc the writing process is taking place. When the writing process is being interrupted due to a shock of the drive, it's nearly impossible to return to the previous writing location. DVD+RW allows the address information (stored in the disc's wobble signal) to be read during recording, so that in case of a writing problem, the writing can be continued at the previous location. This feature also allows for the lossless linking principle as explained above: since a DVD+RW drive knows when to stop recording, it can accurately replace parts of a disc at sector level.


DVD+RW has a 2.4 times higher basic writing speed

The basic writing speed of DVD+R and DVD+RW is 2.4x speed. This means that any DVD+R/+RW drive will write all DVD+R and DVD+RW media at least at 2.4x speed. Most newer models will write both disc formats at 4x speed on 4x speed media, otherwise they will write at 2.4x speed.
For DVD-RW, the basic writing speed is 1x. Newer generations will write 2x certified media at 2x speed, otherwise they will write at 1x speed. Also for DVD-R, the basic writing speed is 1x. Although all DVD-R/-RW drives are capable of writing DVD-R media at 2x speed, you need certified media to do so, otherwise a DVD-R disc will be written at 1x speed. Newer drives offer 4x writing speed for 4x certified media, but these drives will write 2x certified media at 1x speed.


DVD+RW and DVD+R media only come in one type

DVD+RW and DVD+R discs only come in one type (with the sole exception that for 4x speed writing, you need 4x speed media). There's no difference in discs for PC or video recording usage, discs for professional authoring or consumer usage, discs with and without several forms of copy protection, or discs with a smaller capacity than the standard 4.7 GB.
With DVD-R, you have "authoring" and "general" drives, each with their own writing media (which can not be used in drives of the other type) and the discs come in different capacities (3.95 or 4.7 GB). DVD-RW discs come with and without CPRM copy protection (for usage on DVD-RW video recorders), and in different versions (1.0 and 1.1), with the 1.0 discs not allowing you to make DVD-compatible recordings on a DVD-RW video recorder.


DVD+RW offers quick background formatting

When you want to use your rewrtitable DVD discs, the discs needs to be formatted first. With DVD+RW, this format procedure is performed in the background, invisible to the user, and nearly without consuming any time. The drive starts formatting a small portion of disc first (lead-in area and part of the data area, required to start writing). It then resumes for the remaining portion automatically in the background when there is no writing or reading operation (Background Formatting). This feature enables to start initial writing immediately. Background formatting shall be suspended should additional reading/writing be required. Discs that are only partially formatted can be ejected from the drive, maintaining the compatibility with existing DVD-ROM drives, and formatting automatically continues when you re-insert the disc. Older DVD-RW drives required you to format a full disc at 1x speed, so you had to wait for over one hour before you can start recording to the disc. With some newer -RW drives you can use some form of a software application to perform a quick format which has to be initiated by the user. It cannot be interrupted, so you have to wait for it to complete before you can start writing to the disc.


Optional: DVD+RW system offers Mount Rainier (EasyWrite) support

DVD+RW is the only recordable DVD system that may optionally offer drives with Mount Rainier-based drag-'n-drop support, also known as EasyWrite. The Mount Rainier specification was set up by Microsoft, Compaq/HP, Philips and Sony, and was originally designed for new CD-RW drives. For DVD+RW, the group created the DVD+MRW specification. The specification allows for various advantages over normal packet-writing software, such as full random access, Defect Management handled by the drive (or by a dedicated Read-Only device driver), Physical formatting performed in background by the drive (without interaction with the host computer), the disc will be available for use immediately after insertion and ejecting the disc before the Background Formatting process is completed is possible. As Mt. Rainier support will be a standard feature of upcoming Microsoft Windows releases, you won't need any software application to use your DVD+RW discs as big removable floppy disks. Drives with DVD+MRW support are currently appearing on the market and when they become available, you may use the same DVD+RW discs you already use with your current DVD+RW drive. DVD-RW will never offer Mt. Rainier (EasyWrite) support, as it is not part of its specification.


Optional: DVD+RW system supports both CAV and CLV writing

Besides CLV operation, DVD+RW drives may optionally also support recording in CAV mode. CLV (Constant Linear Velocity) is usually used in audio or video recorders (such as CD-Audio recorders or DVD-Video recorders). Using CLV, the drive's spinning speed is decreased from the beginning to the end of the disc. CAV (Constant Angular Velocity) allows the disc to spin at a constant rate, enabling faster access times. To maintain compatibility and recording space on the disc, the laser in a DVD+RW drive just burns "faster" (or actually at a larger power) at the beginning of a disc, so that all pits are equally as big and the discs are equally as compatible with current DVD players and drives as a disc recorded in CLV mode. CAV recording might be important in applications where writing speed and access times are critial. No current DVD+RW drives support CAV, but when they become available, they will use the same DVD+RW media that you already use with your current DVD+RW drive. DVD-RW will never offer CAV recording, as it is not part of its specification.


Some conclusions

If you choose your DVD writer to be a DVD+RW product...

  • ...you have the unique advantage of lossless linking, allowing you to replace parts of a disc without the need of rewriting the entire contents
  • ...you can use the DVD-Video compatible DVD+VR format, allowing you to make changes directly on the recorded disc
  • ...you have the advantage of defect-management during writing, for a more robust performance and less writing errors
  • ...you are better protected against shocks during writing, since the exact location can be found even during recording
  • ...you can write at 2.4 times faster basic writing speeds, resulting in better performance and faster completion of your DVD discs
  • ...you only have to worry about one kind of recordable and one kind of rewritable discs
  • ...you can immediately start recording to a disc, as formatting takes place in the background
  • ...you can optionally use all the benefits of Mount Rainier (EasyWrite) drag-'n-drop support
  • ...you can optionally write discs in CAV mode, enabling for much higher performance in data applications


    Comparison table

    Feature   DVD+RW    DVD-R/RW
         
    Lossless linking / replace sectors Yes -
    DVD+VR support (Edit DVD-Video directly on-disc) Yes -
    Build-in defect management Yes -
    Addressing during recording Yes -
    Minimal writing speed 2.4x DVD 1x DVD
    Background formatting Yes -
    Optional Mt. Rainier (EasyWrite) support Yes -
    Optional CAV support Yes -