Glossary of Video Terms and Acronyms - Isotest

Video Terms and Acronyms
Glossary
B-ISDN (Broadband Integrated Services Digital Network) – A mechanism
by means of which telephone companies will be able to carry television
signals (and, probably ATV signals) digitally, probably via optical fibers.
ISDN systems are considered broadband if they carry at least 45 Mbps, the
DS3 rate, currently used for delivery of broadcast television signals. If and
when B-ISDN reaches homes it will be a powerful competitor to other delivery
mechanisms, potentially able to perform a computer-television function.
Bit (Binary Digit) – a) Contraction of binary digit. A single digit in a binary
number. b) A binary representation of 1 or 0. One of the quantized levels
of a pixel. c) An instruction in a data transmission, usually part of a word
(byte) with high status = 1, and low status = 0.
Bit Bucket – Any device capable of storing digital data, whether it be
video, audio, or other types of data.
Bit Budget – The total amount of bits available on the media being used.
In DVD, the bit budget of a single sided/single layer DVD5 disk is actually
4.7 GB.
Bit Density – See Packing Density.
Bit Depth – The number of levels that a pixel might have, such as 256
with an 8-bit depth or 1024 with a 10-bit depth.
Bit Error – The incorrect interpretation of a binary bit by a message processing
unit.
Bit Error Rate (BER) – a) This term is used in High Density Digital
Recording (HDDR), or High Density Recording (HDR), or other such names
and refers to the number of errors a specific magnetic tape may contain,
and is expressed in errors per data bits, such as one in 106 or one error in
one million data bits. b) The average probability of a digital recording system
reproducing a bit in error. Note: IEEE 100 defines error rate as “the
ratio of the number of characters of a message incorrectly received to the
number of characters of the message received.” Bit error rates typical of
current digital tape recording are: digital video tape, about 106 ; digital
instrumentation tape, about 109 ; digital computer tape, about 1012 .
Bit Packing Density – The number of bits recorded per track length unit,
usually expressed in terms of kilobits per inch (KBPI) or bits per millimeter
(BPMM).
Bit Parallel – Byte-wise transmission of digital video down a multi-conductor
cable where each pair of wires carries a single bit. This standard is
covered under SMPTE125M, EBU 3267-E, and ITU-R BT.656 (CCIR 656).
Bit Plane – Video RAM containing formatted graphics data for VGA and
SVGA systems where four or more bit planes can be addressed in parallel.
A bit plane is sometimes called a map.
Bit Rate – a) The rate at which the compressed bit stream is delivered
from the storage medium to the input of a decoder. The digital equivalent
of bandwidth. b) The speed at which bits are transmitted, usually
expressed in bit per second (IEEE 100). Video information, in a digitized
image for example, is transferred, recorded, and reproduced through the
production process at some rate (bits/s) appropriate to the nature and
capabilities of the origination, the channel, and the receptor. c) The amount
of data transported in a given amount of time, usually defined in Mega
(million) bits per second (Mbps). Bit rate is one means used to define the
18 www.tektronix.com/video_audio
amount of compression used on a video signal. Uncompressed D1 has a bit
rate of 270 Mbps. MPEG-1 has a bit rate of 1.2 Mbps.
Bit Rate Reduction – a) Schemes for compressing high bit rate signals
into channels with much lower bit rates. b) A reduction in the real-time
transmission rate in digital format, usually to facilitate recording, transmission,
broadcast, display, etc., or even to comply with fixed limitations.
Various algorithms appropriate for video signals may be employed from
arbitrary resampling to more complex processing with the objective of
reducing the transmission of redundant information in the image and possibly
eliminating image content that will not be obvious in the final specified
display. Bit rate reduction is also appropriate and employed in audio
records, either associated with video or standing alone.
Bit Rate, Real-Time – When the information is obtained from a continuously
varying source, and the information is being transmitted continuously
without buffering, it is exchanged at the real-time bit rate. Within the production
sequence, it is actually only the image capture (i.e., camera and its
recording system) that is required to be in real-time. The balance of production,
including post-production operations, can be at a fraction of realtime
if a more desirable result is achieved. (Subsequent to production, the
final display must, of course, also be in real-time.)
Bit Rate, Recording – The bit rate required of a recorder mated to a
video camera or functioning in the origination, post-production, or distribution
is generally greater than the concurrent bit rate, real-time because of
the error correction designed into the recording format. This “overhead”
may increase the bit rate, sometimes by as much as one-third, and frequently
sets a practical limit in systems design. Examples in the following
table are intended only to clarify the definition. They indicate the range of
some systems currently considered and a first estimate of their challenges.
Probable Recording Rate, Mbits/s (1, 2)
Bits Maximum CCIR CCIR
Per Levels Rec 601-2 (3) Rec 709 (3)
Pixel Defined 4:2:2 4:4:4 4:2:2 4:4:4
8 (3) 256 227 (4) 340 1290 1940
10 1024 284 426 1610 2420
12 4096 340 510 1940 2910
(1) All systems postulated employ field rates of 60 or 59.94 Mbits/s, component
encoding and 2:1 interlace. Progressive scan systems at the same
frame rates would have double these bit rates.
(2) Estimates for gross data recording rates assume the same ratio of overhead
to data bits in component format recording as that in the D-1
standard.
(3) CCIR Recommendations 601-2 and 709 document 8-bit and 10-bit sampling,
based upon sampling frequencies that are integral multiples of
2.25 MHz (i.e., 13.5 MHz for Rec 601-2).
(4) The D-1 standard recording format is defined by SMPTE 224M and its
related SMPTE Recommended Practices and Engineering Guidelines.
Bit Serial – Bit-wise transmission of digital video down a single conductor
such as coaxial cable. May also be sent through fiber optics. This standard
is covered under ITU-R BT.656 (CCIR 656).