The ROM in DVD-ROM stands for read-only memory. It means that, while the manufacturers of the discs encode them with data, a consumer can only access, not change, the data stored within. The ability to ship computer programs and other data on discs that left the earlier floppy disks far behind has truly revolutionized the computer industry. Now, bulk replication of DVD-ROMs is possible, which helps in the quick and inexpensive transfer of large amounts of information. A DVD-ROM can hold a minimum of 4.7GB, sufficient for a full-length movie. Its specification supports disks with capacities of from 4.7GB to 17GB and access rates of 600 KBps to 1.3 MBps. A special characteristic of the DVD-ROM drives is that they are backward-compatible with CD-ROMs. This implies that DVD-ROM players can play old CD-ROMs, CD-I disks, and video CDs, as well as new DVD-ROMs. New versions of DVD players can also read CD-R disks. DVD-ROMs use MPEG-2 to compress video data. Replication, mastering included, involves pressing discs in production lines that spit out a new disc every few seconds. Replication equipment, costing millions of dollars, comprises a variety of machines that are used to create a glass master and metal stamping masters, stamp substrates in hydraulic molds, apply reflective layers, bond substrates together, print labels, and insert discs in packages. Most replication plants test some discs before mass duplication. Unlike DVD-ROM mastering, DVD-Video mastering may include one more step for CSS encryption, Macrovision, and regionalization. One can develop DVD-ROMs with multimedia software tools like Macromedia Director, Quark mTropolis, and C++. DVD-ROMs that utilize DVD-Video's MPEG-2 video and multi-channel Dolby Digital or MPEG-2 audio need audio/video encoding. Replicated DVD products might be supplied to the customer in bulk packets of 100, or finished and inserted into jewel cases with the paper parts. If you yourself do the insertion and source your own printing, the cost for DVD replication can be lower. |
