This article is presented here as it appeared, in slightly updated form, in the June 1999 edition of Replication News, which had apparently vanished when this site was migrated in 2002.
by Bob Niland|
Editor's note: Nearly everyone is in agreement that DVD is quickly replacing the laserdisc as the videophile format of choice. Despite both technologies utilizing a laser that reads pits, they are decidedly different beyond the obvious distinction (i.e., the size of the disc, 12-inch laserdisc vs. 5-inch DVD). The author explains why the video data on a laserdisc is not digital.
Despite what some legacy advertising might have led you to believe, laserdisc is not digital video. It's not always digital audio, either. This is not surprising considering that the original "LaserVision" was basically a 1972 technology. LD video is pulse FM.
There is a single track consisting of a continuous spiral of pits and "lands" (non-pits). Encoded on that track are the composite video (luminance, chrominance, sync, info), one or two analog audio channels and a RedBook-style stereo digital PCM audio or DTS digital audio data stream. Dolby AC-3 audio may also be present, and replaces one of the analog audio carriers. Side, track, time, frame and other control signals are encoded, during pre-mastering, in both the Red Book subcodes (if present) and in non-displayed scan lines in the vertical blanking interval of the composite video signal.
In over-simple terms, the video signal is represented by the pit-to-pit spacing and the audio is represented in the difference between pit/land length.
Bob Niland, a laserdisc enthusiast, maintains a website at