You would think that, as an industry, we would learn from the past and would not want to raise the spectre of a repeat of the war between VHS and Betamax from more than 20 years ago. But that is what is happening over the specification of the next generation of DVD disks.

At stake is control of the market for disks that record and play the next generation high definition TV. The US and Japan already broadcast programmes on cable and satellite TV networks in HD, and Europe's first HD satellite TV station started broadcasting this year.
But storing HD programmes needs more capacity on the disks. HDTV streams compressed with MPEG2 run at around 19Mbit/s, so a two hour film needs 17Gbytes of storage, and more for longer films, and that doesn't include any special or interactive features.
So new technology has been developed over the past five years to meet that need for both recordable DVD players in the home and for read-only DVDs.
This new generation DVD technology is based around blue lasers with shorter wavelengths that allow more data to be stored on a disk. One format, called Blu Ray, will allow up to 23Gbytes of data on a single side of a DVD disk, rather than the 4.7Gbyte that is possible with today's technology based on red lasers.
Blu Ray's backers, which include Sony, Philips, Panasonic and 10 other major electronics companies, say this kind of leap in capacity is needed to get the best out of HDTV systems, and the first Blu Ray DVD recorders have already been launched in Japan.
Blu Ray also gives higher data transfer rates of 36Mbit/s by using the shorter wavelength of 405nm of the blue violet laser compared to DVD's 605nm red laser and 11Mbit/s data rate. It also uses a lens with a numerical aperture of 0.85 lens to create a laser spot that is one-fifth the size of the spot used in DVD.
The first version is a single sided recordable disk with 23Gbytes of storage, but a 50Gbyte version that uses two recording layers is planned by Sony and Matsushita for later in the year.
Sony also has a read-only specification, BD-ROM, for pre-recorded disk, which it plans to launch later in the year, which will have a single layer 25Gbyte disk and a dual layer, 50Gbyte disk, and its movie division has said it will release content on BD-ROM in time for the 2005 Christmas sales season.
But there is a competing format for consumer equipment, also using blue laser, that has less capacity but is easier to use and make, say its supporters. The Advanced Optical Disk (AOD) format developed by NEC and Toshiba has just been approved by the industry body for DVDS, the DVD Forum, and re-named HD-DVD.
The key advantage of HD-DVD is that it can be brought to mass production with only minimal adjustments to current DVD production facilities, says Toshiba.
The HD-DVD format defines a 15Gbyte single-layer, single-sided read-only disk and a 30Gbyte dual-layer, ingle-sided, read-only disk.
It uses the same disk structure used in current DVDs-back-to-back bonding of two 0.6mm thick disks and an objective lens with a numerical aperture (NA) of 0.65. This is close to the NA of current DVD systems and so systems can be easily made backwards compatible with ordinary DVDs, which is more difficult and expensive with Blu Ray systems. Toshiba and NEC this as a key advantage for ROM-type disks.
The two companies are also looking at the new MPEG4 part 10 compression standard to fit more data on the disk, as well as using 128bit encryption to protect the content, something that has appealed to the movie studios anxious to prevent pirating of the disks.
"There's now the huge war because there are all these competing formats," said Stewart Vane Tempest, Optical Product Director at UK storage system developer Plasmon, which uses a wide range of different drives to build professional data back-up systems.
"A lot of the difference is down to the media format," says Tempest. "The capacity of HD-DVD is less than Blu Ray, but rather than putting the active recording layer on the top with a protective layer, HD-DVD uses the same polycarbonate substrate as a DVD. That means you can't get the resolution of the laser spot as small and therefore you have less capacity, but because the media construction is similar to DVD and backwards compatible I think it stands a reasonable chance of succeeding."
Plasmon has its own blue laser system, called Ultra Density Optical (UDO), which is aimed at professional storage systems rather than consumer systems, with a 30Gbyte disk in the first generation of products and reaching 120GB by the third generation. The disks are packaged in an ISO standard 5.25 inch cartridge, allowing UDO and existing magneto optic (MO) media to be supported in the same libraries.
"UDO is extremely cost-competitive compared to magnetic disk and DVD library solutions with much greater reliability," said Nigel Street, chief executive of Plasmon. HP has just selected the technology for its StorageWorks optical jukeboxes.
"The integration of Plasmon UDO drives and media into HP's line of optical libraries offers customers the best solution for long-term, permanent archival storage," said Street.
The Blu Ray camp is pushing the higher data capacity and the new approach as future proof and more suited for HDTV applications, but it hasn't offered its ROM specification to the DVD Forum for approval, so HD-DVD is the only ROM format at the moment.
"We think Blu Ray is an important step forward in optical storage technology because it allows capacities of 25Gbytes on a 12cm disk which is a factor of five greater than today's DVD technology," said Wally Heijnemans, Director for Standards at Philips Intellectual Property and Standards.
"We think that such a big step is necessary because usually what you see in the industry of storage standards is a lifetime of 20 to 30 years -- just look at CD and VHS -- so the idea is that when you make a step to a new system then it should be a big step so that it's a solid basis for a long lifetime. That's why we decided that the Blu Ray technology gives the best possibility to realise this."
He points out that DVD disks had significant advantages over VHS tape cassettes, but those advantages aren't there in the move from DVD to HD-DVD where it is only the content that is different.
"Then we come to the question -- does the consumer recognise HD video quality -- and how much money are they willing to pay for that? We think that for many consumers the difference might not be convincing and so there's probably a need for really high quality video to make that step as big as possible and we believe there is both the room and the need to further enrich the content in all sorts of ways such as interactive applications and bonus content and that needs storage capacity," he said.
"When we put these together I think its reasonable to expect that the market for HD video publishing will not develop so quickly, certainly not compared to the explosive development of the DVD market."
He discounts the manufacturing argument. "There is no reason why the Blu Ray disk would be more expensive in cost than HD-DVD," he said. "HD-DVD builds on existing disk technology but at the same time it means that the tolerances on the disk are very tight so the replication has to cope with these very small tolerances and that is a yield issue and a cost factor. Blu Ray disks are stamped just like CDs today, so the production process is extremely simple."
There are also moves to further reduce the cost, using a paper-based substrate -- this is a key advantage for Blu Ray, as only the thin top layer has to be transparent, rather than half the disk like HD-DVD.
Sony has been working with Toppan Printing Company on a substrate that uses paper pulp with plastic soaked into it, making the disks lighter, cheaper and more bio-degradable.
Over half of the disk's weight is pulp, says Sony, but it is still strong enough to prevent the disk from warping. With such a tight numerical aperture and high density data storage, any variations in the disk will give problems in recording and playback.
However, the apaper' disk technology is still at laboratory stage, and volume production technology has to be developed for practical applications, said Toppan.
But the cost difference is negligible when the disks go into high volume production, says Heijnemans at Philips.
"It's almost a repetition of the arguments that we had in the early days of DVD standardisation when we also had debates between Sony and Philips over whether to use the 0.6mm thickness or the 1.2mm substrate from CD, but the reduction to 0.6mm was essential to get the 4.7Gbyte capacity," he said. "What we do in Blu Ray disks is continue down that line of thinking and reduce further the thickness of the substrate to 0.1mm on a carrier of 1.1mm"
While the sensitivity of that upper recording layer means that today the Blu Ray disks have to have a cartridge around them for protection, while the HD-DVD disks are more robust and scratch-resistant. However, developments at TDK could get around that problem.
"We are in a neutral position on the technology, but my view is that there are two big challenges to Blu Ray," said Taro Ikushima, Product Manager for data storage products at TDK.
"The first one is the outer layer covering, because the wavelength is very short so the coating is very thin. On a bare disk the surface is very vulnerable to dust and scratches and that prevents small devices and cost reductions. TDK has developed scratch-proof coating, which we are also using for DVD, for when the consumer needs bare disks," he said.
"Then there is the possibility of using multilayer technology, and we have already developed a four layer Blu Ray disk that gives four times the density, 98Gbytes, so that would be technically feasible," said Ikushima.

As the technology develops, so the difference between the formats reduces. While the new materials from TDK allow Blu Ray disks to dispense with the cartridge, new developments at Toshiba are driving up the density of HD-DVD.
It has demonstrated a high capacity 36Gbyte ual-layer, single-sided recordable disk using an alloy f Germanium-Tellurium-rich Germanium-Antimony-Tellurium-Bismuth (GeSbTeBi) on the recording layers to improve the signal processing and erasability of the data.
Blu Ray does have other potential advantages. There are developments at Philips on a 3in version of the technology that would allow a standard definition film to fit into a device the size of a mini-disk player for portable video applications.
But the uncertainties will hold back the take up of the technology, just like the battle between VHS and Betamax, and it is possible that the ultimate success of a format is determined by the studios and which format they chose to support.
"We can't afford format wars," said Andrew Mullen, General Manager of Communications and New Technologies at LG Electronics in the UK, which is a Blu Ray supporter. "If consumers have any doubt about whether a format will succeed they won't buy it."
"We see Blu Ray as a recordable format with high capacity. People are used to three to four hours on a tape and eight hours in long play, and they want to do that with DVD and that's going to be one of the key drivers for Blu Ray," he said.
"But you have to base your support for technology on what manufacturers are prepared to produce and the majority support Blu Ray, even if it is at odds with the movie studios," said Mullen. "But ultimately we need each other -- without the support of both parties, nothing will work."
With two different consumer formats for disks, based on two different technologies, the potential is there for a repeat of Betamax versus VHS.
While the answer could lie in combining the technologies in one drive -- as DVD+RW, DVD-RW and DVD-RAM have done in the PC world, that will prove too expensive for the consumer market.
The battle for dominance will only become more critical as more HDTV systems roll out and people start demanding high capacity recorders over the next few years.