Unlike a CD, a DVD consists of two sides made of plastic which are stuck together. These sides are also called layers. Data can be pressed at a far higher density on both layers than on a CD, giving the DVD a considerably greater storage capacity. DVD Duplication and DVD Replication are 2 different processes.
Depending on the amount of data, there are the following options:
- A single layer is pressed (DVD-5 up to 4.7 GB). As with a CD, the data is read from the bottom layer of the DVD by the laser of the DVD player and converted into image and sound signals.
- Two layers are pressed (DVD-9 up to 8.7 GB). With this kind of DVD, the top layer is also copied. The top layer can be read by the DVD player's laser from underneath because the bottom layer has a semi-transparent mirror. The laser can read the data from the top layer through this mirror.
- Even more is possible (DVD-10 up to 9.4 GB). The capacity can be increased even further by copying the DVD on both sides. The procedure for playing a DVD-10 is similar to that of LPs andndash; the DVD is turned over in order to play the second side.
Authoring
How does the film get from the reel to the disc?
To begin with, there is always a professional source master which is converted through a hardware encoder into MPEG-2 format. This is the required format for further processing.
Menus are created depending on the customer's requirements, allowing the viewer to choose the content of the DVD directly (e.g. chapters), or make a selection from different types of content (such as special features).
During the authoring process, the audio and video content is linked to the menus which have previously been created. The actual programming takes place during the pre-mastering stage, as authoring is also referred as. This is done with specialist authoring software such as Sonic Creator.
At every single stage of this process, all operations are carefully checked and on completion go through another full inspection.
If the authoring has been undertaken by OK Media and copy protection is to be included, the customer receives a copy in the form of a DVD-R once the inspection has taken place, so that he too can check if everything is as he expects. Once the customer has signed it off, the input medium (DLT - Digital Linear Tape) then continues through the mastering process.
Another option is for the customer to provide a DLT directly. In this event it proceeds directly to the mastering stage without any further signing off and checking.
Mastering
Up to 2 glass masters is produced during the mastering process. A powerful laser beam transmits the data from pre-mastering on to a photo-resistant layer, creating what are known as andquot;pitsandquot;. After the laser process, the photo-resist layer is chemically cleaned to allow it to then be metallized with nickel. This process is repeated for each layer until all of the data are complete.
A DVD has two fathers
The glass master is used as the template to produce the 'father', a nickel disc approximately 300andmicro;m thick. The father can now be used as a stamper, but only for small runs. Depending on which type of DVD it is, up to two fathers are required for the production of each DVD.
For large runs, you need a mother
The 'mother' is then produced from the father. Practically any number of stumpers can be made from the mother. We call this process the 'family development'.
Now the pressing and sticking can begin
For the pressing process, both stumpers are placed in the mould of the injection molding machine. The pit structure (containing the information) of the mothers are filled with liquid polycarbonate. Once they have cooled off, one half is coated with aluminum or silicon (the semi-transparent mirror for DVD-9). Both discs are stuck together with a UV curing adhesive. The DVD is now complete and ready to play.
DVD finishing
The DVDs have still to be printed of course. Using silkscreen or offset processes we print text, images or graphics onto the DVD - creativity knows virtually no bounds. We will be glad to show you samples of particular printing techniques. All the lacquers and colours guarantee a high level of durability.

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