Pioneer president Kaneo Ito noted that the company did not want to repeat the frustrations it had encountered in the laser disk (LD) market, where it was a leading player. "LD users strongly requested a recordable LD system, but we could not answer their demand at that time, because of technology limitations," Ito said. "That's why we're the first in the world to introduce a DVD-RW recorder. It is a very important strategic product for us."

Pioneer developed the DVD-RW format and proposed it to the DVD Forum. Approved last month, the physical DVD-RW format calls for a 4.7-Gbyte capacity per each disk side and guarantees more than 1,000 rewrites. DVD-RW is designed for sequential, linear video recording and lacks a random block recording function. Since the format uses only the groove tracks to store data, as do DVD-Video and DVD-R, Pioneer claims it will be an easy matter to equip read-only DVD systems with the capability to read DVD-RW disks.

Pioneer will offer the recorder at 250,000 yen (about $2,450) in Japan and plans to introduce the product overseas next year. The company plans monthly production of 10,000 units and intends to promote the product aggressively. It demonstrated that zeal by launching its recorder immediately following the DVD Forum's approval of the physical RW format, opting not to wait for formal publication of the format documents.

Early backers of the format, Pioneer said, include Hitachi Maxell, Kenwood, Mitsubishi Chemical, Mitsubishi Electric, Pioneer Video, Ricoh, Sharp, TDK and Victor Co. of Japan (JVC). Some of DVD-RW's proponents are expected to introduce recorders based on the format next spring.

Incompatible DVDs

Full compatibility among all DVD family members is implicit in the basic DVD concept. But the gradual addition of new spins on the basic format has bred incompatibility problems.

DVD-RW is the latest format to be added to the DVD family. For video recording applications, the DVD Video Recording format, version 1.0, was defined in October. (Since DVD-Video was defined without taking recording into consideration, it does not allow editing and lacks the functions needed for recording.)

"The Video Recording format was defined to realize real-time processing. There is already a DVD-RAM recordable format, but for PC applications, real-time processing is not mandatory," said Kazuhiro Tsuga, director of the visual information group at Matsushita's Multimedia Development Center. Tsuga chaired the discussion group that drafted the Video Recording format.

Under that format, video data is compressed at real-time into MPEG-2 at a variable bit rate to make efficient use of disk capacity. Video streams are not necessarily continuous on a disk after multiple rewrites. The format provides disk space management functions and guarantees continuous recording and playback during seek time when the head jumps to chase the discontinuous streams. A table maintains address data for all groups of pictures to enable such playback functions as fast forward, rewind and slow motion, as well as editing functions. To guarantee real-time processing, the format requires use of a buffer in the recorder.

The format works with the DVD-RAM and DVD-RW formats. It comes into play on the physical layer of those recordable formats to define how to handle real-time processing for video recording.

The DVD Forum is also working on an Audio Recording format in preparation for the use of DVD-RAM and DVD-RW for pure audio recording.

Some observers fear the proliferation of formats will lead consumers into a maze. At present, there are seven kinds of 120-cm-diameter optical recordable disks whose capacity exceeds 1 Gbyte. The DVD family includes 2.6-Gbyte and 4.7-Gbyte DVD-RAM, 3.9-Gbyte and 4.7-Gbyte DVD-R (specs for the latter have not been finalized yet) and 4.7-Gbyte DVD-RW.

Outside of the DVD family are the 3.0-Gbyte DVD+RW, proposed by Sony/Philips (despite the inclusion of DVD in its name, it is not a DVD disk format), and 5.2-Gbyte MVDisc (multimedia videodisk), proposed by NEC. NEC introduced the GigaStation videodisk recorder, based on the MVDisc format, in Japan in September.

Three of the seven DVD formats — 4.7-Gbyte DVD-RAM, 4.7-Gbyte DVD-RW and 5.2-Gbyte MVDisc — have been or will be used for consumer recorders.

Hitachi, Matsushita and Toshiba developed recorder prototypes based on 4.7-Gbyte DVD-RAM in September to make clear their commitment to the recording format. The companies intend to introduce DVD-RAM based recorders within the next year.

Even without a challenge outside of the DVD family, there are already enough incompatibility problems inside of DVD. Current DVD-Video players do not read DVD-RAM, DVD-RW or disks based on the Video Recording format. Pioneer's DVD-RW recorder does not read DVD-RAM, and there is no guarantee that DVD-RAM recorders will read DVD-RW.

DVD-RW has a low reflection rate, rendering the disks unreadable by current DVD-Video players. Pioneer claims that a simple hardware change will enable DVD-Video players to read DVD-RW disks. But it will take roughly half a year for Pioneer to come up with compatible DVD-Video players.

"As the DVD-RW disk is much simpler than the DVD-RAM disk, the DVD-RW recorder will have an advantage over DVD-RAM recorders in cost," said Masami Morishita, manager of videodisk recorders for the new-product-planning department of Pioneer Home Entertainment Co.

What's digital?

Pioneer's DVD-RW recorder, NEC's GigaStation and the DVD-RAM recorder prototypes all lack digital video input and output and will come with conventional analog video in/out terminals and S-terminals.

"Conversion between analog and digital takes place every time the disk is recorded. Some deterioration could occur, but the noise level is not high, as in analog-to-analog dubbing," a Pioneer executive said.

Though digital video content and digital TV programming are emerging, all content should be converted once into analog and then digitized into the DVD video recording format because of the lack of accord on copy protection mechanisms.

Pioneer's DVD-RW recorder uses the Copy Generation Management System (CGMS) and Macrovision copy protection schemes. The recorder won't play illegally copied disks. Blank DVD-RW disks will not record data from disks that use the Contents Scrambling System (CSS).

Even if the copyright issue is resolved, another practical, technical problem exists. Most Japanese consumer electronics manufacturers plan to use the IEEE 1394 interface for digital data transmissions between future consumer products. But "no command set has been defined for digital videodisk recorders, and no one can say when it will be ready," pointed out Morishita of Pioneer.

There is yet another obstacle to direct digital recording: DVD recorders use MPEG-2 compression, but that doesn't mean that digital TV broadcast streams compressed in MPEG-2 can be recorded directly. No company has come up with a solution for efficiently handling the different formats for video data.

Unless those issues are resolved, observers said, digital disk recorders will remain analog content recorders that merely offer better operability than tape-based video recorders.