From Wikipedia, the free encyclopedia
Videocassette format
D-3
is an
uncompressed
composite
digital video
format invented at
NHK
and introduced commercially by
Panasonic
. It was launched in 1991 to compete with
Ampex
's
D-2
.
D-3 uses half-inch
metal particle tape
at 83.88 mm/s (compare to D-2's 19 mm and 131.7 mm/s). Like D-2, the
composite video
signal is sampled at four times the color subcarrier frequency, with eight bits per sample. Four channels of 48 kHz 16?20 bit PCM audio, and other ancillary data, are inserted during the
vertical blanking interval
. The aggregate net (error corrected) bitrate of the format is 143 Mbit/s, and because the codec is lossless, it has been used in data applications.
Camcorders
were available which used this format, and are to date the only digital tape camcorders to use a lossless encoding scheme. The
D-5
digital component video format, introduced in 1993 by Panasonic, uses the D-3 transport and tape running at roughly double D-3 speed. The D-3 transport in turn is derived from the
MII
transport. D-3/D-5 tapes come in small (161 mm × 96 mm × 25 mm), medium (212 mm × 124 mm × 25 mm), and large (296 mm × 167 mm × 25 mm) cassettes, with format-specific recognition holes. Maximum D-3 runtimes (in the Fujifilm lineup) are 50, 126, and 248 minutes.
The D-3 format is now regarded as obsolete. In the early 1990s the
BBC
embarked on a massive project to copy its older video tapes onto D-3 for archival, but the D-3 cassettes themselves have become obsolete and are being transferred to modern digital video standards. There is doubt
[1]
over whether the surviving D-3 machines will last long enough to play the 340,000 tapes which the corporation holds.
[2]
References
[
edit
]
External links
[
edit
]