DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

CENELEC EN 50049-1:1989
IEC 60933-1, Interconnections and
matching values – Part 1: 21-pin
connector for video systems – Application
No. 1.
IEC/TR 60933-2, Interconnections
and matching values – Part 2:
21-pin connector for video
systems – Application No. 2.
When a consumer VCR is placed into a “trick” mode
(such as pause, slow play, or fast forward), a
nonstandard progressive-scanned signal is produced.
In these modes, the VCR inserts synthetic sync into the
vertical interval. In pause, video information comes
from just one field, making it difficult or impossible to
determine the parity of the field being played back.
SCART interface
In about 1980, a French company, Péritel, devised an
interface between a television set and a VCR. The interface
was proposed to the Syndicat des Constructeurs
d'Appareils Radioélectriques et de Télévision, where it
became known as SCART. It was standardized by
CENELEC, and then later by IEC (in two “applications”
or versions). The interface is ubiquitous television
receivers, VCRs, and other consumer video equipment
in Europe.
Equipment has one or more 21-pin sockets. A cable
with a (male) plug at each end connects equipment.
Stereo audio, composite video, and control signals are
conveyed in both directions. R’G’B’ video signals are
input-only.
Heterodyne (color-under) recording
Heterodyne (or color-under) video recording is ubiquitous
in low-cost videocassette recorders, including
3 ⁄4-inch (U-matic), 1 ⁄2-inch Betamax, VHS, S-VHS,
Video-8 (8 mm), and Hi8. The luma and modulated
chroma components of the NTSC or PAL input signal
are separated prior to recording. In most color-under
VCRs, luma bandwidth is less than 2.5 MHz, and
chroma bandwidth is about 300 kHz. Luma is recorded
by FM in a manner similar to direct recording. Chroma
is mixed down to a low-frequency subcarrier between
600 kHz and 700 kHz, and recorded directly on tape,
with the luma FM carrier acting as a bias signal.
Upon playback, the recorded color-under chroma is
mixed onto a crystal-stable 3.58 MHz subcarrier. This
locally generated subcarrier free-runs with respect to
CHAPTER 49 CONSUMER ANALOG NTSC AND PAL 583