The input media to
master DVD's is called DLT tape. This stands for Digital Linear
Tape. Why was DLT tape chosen for DVD input media? Storage
capacity. The capacity of a single sided DVD is 4.7gbytes. In order for
this type of media to be manufactured, a high capacity storage solution
was needed. 8mm Exabyte did not have the capacity at the time, but other
factors were involved including reliability and data integrity.
Quantum 4000 Drive
was developed for high data capacity and high data rate transfer. DLT
technology provides both the capacity and performance demanded by
data-intensive applications, and features a much longer drive life than
previous technologies. It also offers one the best error-detection and
correction specifications in the industry. This is very important for
any application, but in terms of DVD mastering---even more so---because
errors encountered during the mastering of the DVD image requires
remastering and this wastes time and money.
Compared to helical scan
technology, DLT transfer rate is better by a factor of 3, its capacity
is about 3 times and head life is about 5 times that of helical scan
heads. DLT uses a stationary head which allows quicker access times.
- Disc Description Protocol
production houses use sophisticated encoding equipment when preparing a
DVD image for production. When all the video, audio and authoring is
assembled it is then transferred to a DLT tape as an image file. This
tape also contains some files called "DDP". This stands for
Disc Description Protocol. This is an industry standard for describing
the contents of various types of CD's and DVD's. This information
"tells" the LBR how to arrange the data and what type of data
it is. This is very important for DVD mastering.
Technologies on the Horizon
With DLT technology's
inherent ability to deliver high capacity, data integrity and
reliability, it was the input of choice for DVD. But computer technology
never stops and new technologies are emerging which in time may also be
suitable (MO7), but we'll just have to wait and see.
Plumer, DVD Technical Manager