Wegener Communications UNITY 4600 - Manual (Page 18)

General Information
12 800032-01 Rev. G www.wegener.com
1.5 Glossary of Terms and Abbreviations
Term Definition
Ad avail, digital The opportunity for a local program splicer to insert local content in the MPEG PES streams
in substitution for “regular” network-distributed programming. The avail is bounded by
“splice out” and “splice in” points. "Splice points" are seamless insertion points (located for
the splicer by DPI messages) where the compressed stream may be broken and
substituted without frame-by-frame interruption of video.
Ad avail, analog The opportunity for local users to switch from the network-supplied programming to locally-
generated content (commercials). This is signaled by use of DTMF tones or closures of cue
relays.
Alarm A condition or notification of a condition that prevents proper Unity 4600 functioning.
Application Software The main host software which sets up the unit hardware, runs the process of acquiring
transport stream sources, sets up and monitors the demux and decompression processes,
monitors unit operations, and interfaces with the network and local users.
ASI (or DVB-ASI) An “asynchronous” bit-serial physical interface for transport streams. Transmitting and
receiving functions are designed such that the time relationships between all packets and
their timing references are unchanged.
Audio Language
Descriptor Legacy 3-character MPEG descriptor applied to a program’s audio streams. It was
originally allocated to designate languages, but is now used for generic identification.
Automated Recovery
(or Recovery)
The mechanism used when the Unity 4600 is unable to acquire a valid transport stream,
loses network control or detects an invalid control stream, or is unable to deliver the
required services using its current settings. The unit automatically begins attempting
operations under "backup" unit settings stored in the presets table until it can return to
normal operation or is stopped by local user command.
Boot loader Software residing in non-writable zone of flash which executes at unit reset. It will verify and
load the preselected application.
CA See "Conditional Access".
COMPEL
®
Wegener's network control software that may be used to manage your Unity 4600 as well
as other hardware.
Conditional Access Wegener’s system for securing the transmitted transport stream from unauthorized access.
It features distribution of ciphered authorizing messages within a special PID. Upon
deciphering in secure processors within the IRD, these messages continuously update the
IRD with the current descrambling key.
DPI Digital Program Insert. A special message, borne in an MPEG PID associated with a
particular program, that signals the boundaries of ad avails.
DTMF Dual-Tone Multi-Frequency. Tone signaling system used by the legacy telephone system.
Tone pairs represented each of the keyboard items 0-9, *, and #. This system may be used
to control external cueing equipment.
DVB Digital Video Broadcast working group. This is a shorthand designation for a group of
industry standards that provide enhancements in the use of MPEG transport streams. (For
example, one DVB standard defined the standard way QPSK-modulated carriers would
convey these streams over satellite world-wide.)
E
b
/N
0
Energy-per-bit per Noise density-per-Hertz. This is a unitless ratio that expresses signal-to-
noise ratio in carrier transmission systems that convey digital data. A quality measurement
for any such system is the E
b
/N
0
needed to just convey the digital data within acceptable
error rates. This is called the “E
b
/N
0
threshold”.