Mastering has been the most important step of the replication process of CD and DVD media. But the increased requirements of mastering HD DVD or Blu-ray media is even more complicated, and changes the involved workflow.

In order to create a DVD from a popular movie there are several steps that must be followed. The content should be transferred from photographic film to a high quality video tape. The video and audio tracks must be converted, encoded and multiplexed. Next, the resulting "image" is transferred to a data tape master (DLT). This master tape is then used to create a glass master which is used in replication to create the individual DVDs, using a Laser Beam Recorder (LBR). The last process is called mastering.

Compared to DVD, the high-density formats pose a number of challenges such as smaller pits, tight mechanical tolerances, decreased track pitch etc. As a result, mastering has become a harder process.

For the high-density formats (HD DVD-ROM and BD-ROM), Philips has been working on the concept of using a Deep-UV Laser Beam Recorder for photoresist mastering for BD-ROM.

The company is also considering another method for mastering, called Liquid Immersion Mastering, which is claimed to offer more flexibility but it is not yet ready to be applied as a mass-production technology.

Another Blu-ray backer, Sony, showcased its Phase Transition Mastering (PMT) technology two years ago. The company has launched its PTR-3000 system for BD which is considered to be the mass production mastering method for BD-ROM. Sony claims that the PMT method is more economically efficient compared to traditional mastering processes with photoresist, since it requires only five steps (cleaning, resist coating, cutting, developing and stamper plating) out of the twelve demanded by the first method.

PTM technology uses a special inorganic resist which is comprised of metal oxide. It utilizes a chemical heat reaction generated from the changing phase of amorphous to crystal, instead of photo resist, in the fine pitch recording of electron beam or deep UV laser. This laser uses 405nm wavelength consumer blue laser to make the smaller pit. The crystallized region becomes soluble in developing fluid. The result is a recorded mark smaller than the laser spot.

But the real challenge comes in the encoding stage. This is due to the copy protection system that has been proposed and developed for both HD DVD and BD: Advanced Access Content System (AACS).

The AACS system requires some significant changes in the workflow of creating a master disc. The images must be processed in servers in order to be prepared for mastering. A set of keys as well as an encryption algorithm must be applied to the image. But the keys must be obtained from the AACS LA, the AACS licensing authority. Since the acquisition of these certificates cannot be done in advance, this interaction between the plant and the licensing authority must be done real time. As a result, any delay in this essential transaction is critical and will impact in the production of the plant.

Although AACS is expected to find a more adequate way to interact with the mastering plants, all these challenges in the mastering process are expected to keep most replicators away from making serious investments in their own mastering equipment for BD and HD DVD. It is more likely that real demand for new equipment will take off next year.