Glossary
Numerics A B C D E F G H I J L M N O P
Q R S T U V W Y
© 2011 Harmonic Inc. 228 ProView 7000 v.2.4, Rev. A
VIA
Video Input Adapter. Accepts either composite or digital video and generates digital video
components for Harmonic SD DiviCom encoders.
VOD
Video On Demand.
VP
Virtual Path. A group of VC s that provides the sequential unidirectional transport of ATM cells.
VPC
Virtual Path Connection. A concatenation of VPs. Analogous to a VCC, but at the VP layer. VPCs
are unidirectional.
VPI
Virtual Path Identifier. A unique numerical tag of a VP . An eight-bit field (on the UNI ) in
the
ATM cell header that indicates the virtual path over which the cell should be routed. The VPI
logically divides the cable into one or more virtual paths. Each virtual path can have its own
bandwidth limitation.
VPN
Virtual Private Network.
VPS
Video Program System (protocol). A VBI service (used in some countries in Europe) that
controls the start and stop record times for VPS-capable VCRs. For example, a viewer sets a VPS-
capable VCR to record a program scheduled for 7:00 pm, but the network delays the start of the
program to 7:10 pm because of a news interruption. Rather than recording at 7:00, the VPS-
capable VCR does not begin recording until 7:10 when it receives the VPS signal.
VRN
Video Rich Navigation.
W
WSS
Wide Screen Signaling. WSS is an analog waveform carried in Line 23 of a 625-line (PAL) video
signal. As a type of
VBI signaling, it conveys the aspect ratio of the image, and can be used by
WSS-capable televisions to determine the correct display mode. For example, standard (4:3),
widescreen (16:9), or <letterbox> (16:9 on 4:3). Strictly speaking. It is being obsoleted by AFD
over time.
Y
Y (luminance)
Brightness component of a video signal.
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