For transferring a movie to DVD, there are several steps in the mastering process. First, the movie is transferred from film to videotape. Then the videotape must be viewed to identify certain sequences. For example, if the DVD is to have a parental lockout feature, the offensive material must be noted so that it can be excluded from playback to children. If the DVD will use "pan-and-scan" instead of a widescreen format, then codes must be entered to identify which parts of the image are to be scanned scene-by-scene.

The data must be encoded using the MPEG2 digital video encoding standard. In this process, the billions and billions of bits of information in the original image are compressed into a bit stream that will fit the capacity of the DVD disk by eliminating redundancies. MPEG2 uses a variable bit rate encoder; that is, fewer bits are used to encode a less complicated image and more bits are used to encode a more complex image. If the bit rate were constant, the quality of the image would vary, because some sections are more complex than others. Because of the variable bit rate, however, the quality of the final image is consistent.

Similarly, the audio tracks must also be compressed into the Dolby digital format. The DVD format supports Dolby Digital AC-3, in two-channel or 5.1 channel surround sound (the "5" and the ".1" are five standard channels and a subwoofer). Each audio stream is encoded independently of the video and then combined.

The compressed video, audio, and subpicture streams are combined into a single data stream and transferred to the source of the input data for mastering, Digital Linear Tape (DLT). This tape was developed for its high data capacity and high rate of data transfer. It also has excellent error-detection and correction specifications.

Back |  Home |  Top