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     This story was printed from CdrInfo.com,

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1. Formats

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Do you feel that your CDR/W storage capabilities are small ? Do you want more space ?..Then Writable DVD is the solution for you..Yes ?..Not so True..All companies that involved into DVD consorium have not decided at a common standard. Lets see which techonologies are running right now..

Today is avaiable :

- DVD-Recordable (DVD-R): DVD is the de-facto standard from DVD Forum. It can record only 1 time so it will unlikely used for home recording.

- DVD-Rewritable (DVD-RW): Its a special format of DVD-Video and uses a special disc stucture and substrata which can be written up to 1000 times.

- DVD Random Access Memory (DVD-RAM): This standard is backed up from Matsushita. It uses a caddy and has a different disc structure that makes it more suitable to high-speed computer access than for video recording.

- DVD-ReWritable (DVD+RW): It uses a simular 4.7GB phase change land-and groove disc as DVD-RW but it's incompartible with DVD-RW.

Other upcoming formats (outsiders..):

- AS-MO (formerly MO7) holds 5 to 6 GB.
-NEC's MMVF (Multimedia Video Format) is completely incompartible with any other DVD format and it holds 5.2 GB.

Both are expected to read DVD-ROM but not DVD-RAM or first-generation DVD+RW. MMVF is similar to DVD-RW and DVD+RW, using two bonded 0.6mm phase-change substrates, land and groove recording, and a 640nm laser.

- Terastor is and 20GB optical format. It is incompartible with DVD thanks to different disc structure format.

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2. DVD-R

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DVD-R (Book D of the DVD Forum) is the record-once writable DVD format

Tech

Read Pioneer's DVD White Paper

Media

Uses organic dye polymer technology, like CD-R, and is compatible with almost all DVD drives and players. A future version of the drive will support DVD-RW media.Media costs about $45, and is available from Pioneer and TDK. DVD-R and DVD-RW discs are expected to last anywhere from 50 to 300 years, about as long as CD-R discs. First-generation capacity was 3.95 GB but was extended to 4.7 GB later.

Where we could possible read it?

DVD-R produces the DVD discs that played at all DVD's around.

Price

DVD-R are available from Pioneer currently priced about $5.400.

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3. DVD-RW

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DVD-RW (Book F of the DVD Forum) is the rewritable version of DVD-R

Tech

It uses a phase-change recording layer, much like CD-RW,  groove recording with address info on land areas for synchronization at write time (land data is unnecessary during reading).

Media

Initial capacity will be 4.7 GB. DVD-RW media don't require a caddy or cartridge, but maybe some though some drives may take the additional precaution of requiring that the disc be in a caddy.

Where we could possibly read it?

Developed by Pioneer based on DVD-R, using the similar track pitch, mark length, and rotation control, DVD-RW will be playable in most DVD drives and players. But seems that some DVD-Video players, when fed a DVD-RW disc, "see" the lower reflectivity and "assume" that they should be trying to read a dual-layer disc. It is expected that will be fixed by firmware upgrade.

Price

Pioneer's coming drive estimated about $1600. The media (4.7GB) around $20.

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4. DVD-RAM

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DVD-RAM (Book E of the DVD Forum) is a mixture of storage technologies from magneto optical (MO), phase change (PD and CD-RW), and even magnetic hard drives.

Tech

It use phase change as a recording material, "wobbled land and groove" recording method, embossed pits for header (addressing) information, Zoned Constant Linear Velocity (ZCLV) rotational control, and is a random-access, non-sequential medium.

Media

Media ,using a phase-change recording layer, can be either single-sided in a removable cartridge (2.6GB) or double-sided in a permanent cartridge (5.2GB).Future DVD-RAM discs may use a contrast enhancement layer and a thermal buffer layer to achieve higher density. Hitachi has announced reaching 4.7 billion bytes by reducing mark size from 0.41/0.43 microns to 0.28/0.30 microns and track pitch from 0.74 microns to 0.59 microns.The new DVD-RAM has a double-sided capacity of 9.4 gigabytes and is suitable for editing and accessing various multimedia information such as movies and music, it said. The new drive is compatible with current 2.6 gigabyte DVD-RAM discs, and is capable of reading other DVD and CD formats. Today prices are about $40 for 5.2 GB & $25 for 2.6 GB capacity disk.Media is available from Hitachi Maxell, Mitsubishi, Mitsui, and TDK.  Cartridge dimensions are 124.6mm x 135.5mm x 8.0mm.

Where we could possible read it?

One issue for DVD-RAM is that removing the media from the cartridge may compromise rewritability. And depending on the choices left to drive manufacturers, a DVD-RAM drive may or may not read CD-R, CD-RW, or PD.

DVD-RAM-compatible readers will require servos to handle switching between the lands and grooves. Also will need a decoder to handle scattered 32K ECC Blocks, something not needed for DVD-ROM and DVD+RW, since their blocks are continious.

Price

DVD-RAM is available from Toshiba, Hitachi, and Panasonic, are available in internal and external, SCSI and IDE models, and are priced between $500 and $700.

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5. DVD+RW

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DVD+RW is a format backed by Sony, Philips, Hewlett-Packard, Ricoh, and Yamaha.

Tech

It uses phase change, groove-only recording like CD-RW. Other characteristics include the use of CAV wobble for addressing, CAV or CLV rotational control for providing choice between raw data transfer and faster data access, and that DVD+RW is a sequential medium (also like CD-RW, not to mention CD-Audio and CD-ROM).

Capacity - Media

Capacity is 3GB per side. The media looks just like CD or DVD-ROM and does not require a cartridge. Second-generation DVD+RW drives, which will appear around mid 2000, will support 4.7 billion bytes and are expected to write CD-Rs and CD-RWs. The 4.7G DVD+RW format will use a high-frequency wobbled groove that allows it to eliminate linking sectors.This change, plus the option of no defect management, allows DVD+RW discs to be written in a way that should be compatible with most existing DVD-Video players and DVD-ROM drives, as well as DVD-R, DVD-RW, and DVD-RAM drives.

So where we could possible read it?

A DVD+RW drive will be able to read CD-ROM, CD-R, and CD-RW media, as well as DVD Video and DVD-ROM but will not be compatible with DVD-RAM discs. Because of reflectivity differences, linking sectors, and defect management, DVD+RW discs can't be read by existing DVD-Video players or DVD-ROM drives, except for the very newest drives from Sony and Philips.

Price

Expect them around $500-800 when shipped.

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6. FAQ

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FAQ - Page 6

Tell me some specification about DVD laser and media!

DVD-R uses a 635nm recording laser, while the read-only and rewritable DVD formats use a 650nm laser. DVD-RAM, DVD-RW, and DVD+ RW media use a non-wavelength-sensitive phase-change recording layer; DVD-R uses wavelength-sensitive dye.

Can all DVD-Video players play DVD-R?

Most can, but certain older models seem to be less "forgiving" of the record-once media.

Can DVD Players read DVD-RAM discs?

DVD-RAM discs are only readable on DVD-RAM drives at this time, with one exception-the Panasonic (Matsushita) & Hitachi DVD-ROM drives.

Can DVD-RAM or DVD-R drives write on blank CD-R or CD-RW discs?

No, not in the current generation of products. However Pionner & Panasonic plan to add it into future models.

If I had a DVD-R or DVD-RAM or DVD+RW drive, could I use it to copy DVD read-only discs?

Yes. But the disc must not be protected, the capacity is less than one side of the media you are recording to.

How can I make a "backup" from a Original DVD into a DVD-R drive?

It seems that all DVD discs are currently copy protected and the media is only 3.9GB per side (pressed DVD single layer is 4.7GB per side). So right now you will have problem.

But with new DVD-RAM discs of 5.2GB cannot copy the 4.7GB DVD-ROMs?

DVD mastering machines aren't set up to accept DVD-RAM as input. One reason is the capacity-you'd have to make two images, one for each side, and then have the mastering facility splice them together into a single image on DLT. For logical reasons, this is not advantageous-an application requiring over 2.6GB of capacity could not be tested as a whole, and it could not be tested in an actual DVD-Video player. DVD-RAM is not targeted at what DVD-R supposed to do.

OK..now give me a complete matrix so i can see the differnces between various formats

Format	DVD-R	DVD-RW	DVD-RAM	DVD+RW
Avaible	Now	Q2 1999	Now	Q2 1999
Recording Layer	Dye	Phase change	Phase change	Phase change
Capacity/side (Current)	3.9GB	4.7GB	2.6GB	3GB
# of Rewrites	0	1,000	100,000	100,000
Read/write	Sequential	Sequential	Random	Either
DVD formats not read	RAM and +RW	RAM and +RW	DVD+RW	DVD-RAM
Non-DVD formats read	CD-ROM/R	CD-ROM/R	CD-ROM/R, PD	CD-ROM/R
Formats re/written	DVD-R	DVD-R, DVD-RW	DVD-RAM, PD	DVD+RW
Write method	Wobbled groove	Wobbled groove	Wobbled land/groove	Wobbled groove
Price	$5.400	$1600	$500-$800	$500-$800
Media Price	$45	$16	$25	$25

Where i can read more?

Pioneer's DVD White Paper
Writable DVD: A Guide for the Perplexed
DVD Techonology
Robert's DVD Info
The DVD Resource Page
DVD FAQ