The standard home video LaserDisc was 30 cm (12 in) in diameter and made up of two single-sided aluminum discs layered in plastic. Although appearing similar to compact discs or DVDs, LaserDiscs used analog video stored in the composite domain (having a video bandwidth approximately equivalent to the 1-inch (25 mm) C-Type VTR format) with analog FM stereo sound and PCM digital audio. The LaserDisc at its most fundamental level was still recorded as a series of pits and lands much like CDs, DVDs, and even Blu-ray Discs are today. However, while the encoding is of a binary nature, the information is encoded as analog pulse width modulation with a 50% duty cycle, where the information is contained in the lengths and spacing of the pits. In true digital media the pits, or their edges, directly represent 1s and 0s of a binary digital information stream. Early LaserDiscs featured in 1978 were entirely analog but the format evolved to incorporate digital stereo sound in CD format (sometimes with a TOSlink or coax output to feed an external DAC), and later multi-channel formats such as Dolby Digital and DTS.
How large was a standard LaserDisc?
30 cm (12 in) in diameter