|
Items in cart [0] |
Questions? Call 888-624-8373 |
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 246
A.~.6 Video Applications in ITS
Video has many applications in ITS. Traditional ITS video applications have involved Closed
Circuit Television (CCTV) surveillance objectives why Me more pertinent ones presenter! in
Table A.~.6-] In Me "conventional" column. More recently, coinciding wad He emergence of
modem signal processing technology capable of useful pattern recoin functions, ITS
applications for video have expanded to include applications such as loop replacement and
others as presented in Be "Advanced win Modern Signal Processing" column of Me table.
Table A.~.6~1
Application of CCTV Cameras in ITS
Conventional Advanced with Modern Signal
_
_~
· Traffic surveillance supporting · Automated collection of occupancy,
congestion analysis volume, speed and vehicle
classification (Autoscope_ -like)
· Incident validation, seriousness information
assessment and clearance verification
· Enforcement, vehicle management,
· Road hazard evaluation (debris on road, and fee collection through
flooding, large pot holes, etc.) ~automated license plate reading
· Variable message signs and signals · Specific vehicle tracking along a
operational assessment corridor (probe vehicle of
opportunity)
· Roadside Equipment Security
· Wrong way" detection and alarm on
· Roadside lighting failure determination one-way streets
and validation
· ' Fleet management by vehicle
· Security of ITS facilities, parking, toll number/ identification recognition
booths, toll vaults, counting rooms, etc. and automated parking, dock space,
gate assignment, etc.
· Airbome surveillance of traffic corridors
(sky watch traveler information)
· Traffic planning support by surveillance
of mall, entertainment center, sports
center, convention center, park-e-rides,
parking areas, etc.
lids surveillance applications require Me placement of CCTV cameras in Me field (typically at
A- to I-m~le intervals in freeway management systems) and communication of Me video to Me
~;\NCHRPPhase~p~\ NCHRP3-51 · Phase2F~nalReport A1-238
OCR for page 247
controlling TOC and over locations for viewing on wall monitors, at individual operator work
stations, or for retransmission to other agencies, junsdicdons, or public television media. Thus,
rRs's video surveillance requirements require CCTV cameras, video switching, video
transmissions, and video displays. The typical elements of an ITS video surveillance network are
depicted in Figure A.~.6-~. Video substantially alters ITS communication infrastructure
requirements due to Me significantly increased bandw~dWbit rate requirements for transmission
and switching. If the integration goals of llS are to be achieved, video and supporting
communication infrastructure should be implemented wad equipment in compliance USA open
standards and capable of multivendor interoperability.
Jurisdictions implementing ITS systems in He mid 1990s, with significant CCTV video
surveillance, goals face difficult technical implementation decisions due to rapidly emerging
digital video technologies, components, equipment, and standards. In He 3- to 10-year time
frame, these win be He full-featured, most cost effective alternatives for ITS deployments and
integration with the rapidly emerging telecommunication, computer, and multimedia technologies
and~serv~ces. Cutrently, the initial capital cost of Implementing digital video surveillance
systems may be more expensive Han traditional analog alternatives. However, life cycle costs
for emerging digital technologies will undoubtedly be less. Furthermore, the digital technologies
are inherently capable of supporting the local, regional, state, and national integration goals of
llS which will be much more difficult and costly win analog technologies.
This section will discuss CCTV camera technologies, digital video compression technology, and
He Implications for ITS commun~cabon systems.
A.~.6.1 Television Fundamentals
A television camera converts a two-dimensional visual unage to an electrical signal for
transmission to viewers. This conversion process is accomplished by scanning as illustrated in
Figure A.~.6.~-~. The television camera converts die two~imensional optical images on a
frame-by-frame basis into an electrical signal suitable for transmission to a display where He
process is reversed to recreate He image for He viewer.
L;wCH~Whase2~p'` NCHRP3-51 · Phase2FmalReport
Al-239
OCR for page 248
o
·
.
o 5:
c: Id
~ l
o
.
.cn
co
c) ~
LLIJ! m-l may!
r l l ~
o
· -
'a)
~ Q
=~
· _
~ in
~ _ ~
au
C)
.= ~
Cal U) CL
: ~m
.
Z ~
. LLI cr
9~/ i
1\
Q)
o
o
. _
in
. _
a,
._
C:)
D
I) I
O
om --
Lo
_~
Lo
Lo_
-
._
~0
o
C)
_ _,
a) c ~ c51
a) ·- ~0 C
_ ~ ~._ ._
%~ o ~ C _ ,
~ Q) ~
·- a' 0 ° ~ c
~ Ct" ~ O C) >~
3: ~ ' ~ C'
, A
C~
c
. _
o
~n
_'
0
t[D U)
O
-d" 0
._
I 0
-5 ._
O
~ Q
_ - O
U)
z
7~
._
~ Q)
DE
a)
·J
_
_- _
~f ~m!
o
· _
,x ~
1 ~ a'
~ Q
~ O
LIJ ~L-.I m0
U) ~
U' ~o
-f
o
°
U)
5
a
..
.
a)
·
L~
OCR for page 249
For color, Free scans are actually accomplished in the camera for each of the primacy colors
Red, Green, and Blue (R-G-B). A frame is scanned in lines from left to right (horizonal) and top
to bottom (vertical). After scanning a line, the scanning signal is rapidly retraced (blanked at the
receivers to He left for scanning the next line and after vertically scanning all lines of an entire
frame the signal is retraced to Be top left.
The U. S. National Television Systems Committee (NTSC) and most over television standards
do not transmit the R-G-B primary color signals that are scanned by the CCD sensors. When
NTSC television evolved to color in the late 19SOs, it was necessary to devise a color TV
transmission standard that was backward-compatible wad Be large instaDed base of black and
white TVS. To accomplish this, the Free Red, Green, and Blue signals are converted to Free
equivalent signals:
.
· Luminance At= .299 Red + .587 Green ~ .114 Blue) which is perceived as bngh~ess of the
scene for each pixel. This is essentially equivalent to a black and white scene.
· Chrom~nance I, a component - .6 Red - .28 Green - .32 Blue) that is maximum for scene
pixels win orange or cyan hues.
Chrominance Q. a component (EQ= .21 Red - .51 Green - .3 Blue) that is maximum for
scene pixels win green or magenta hues.
Based on extensive testing, it was determined Hat the eye is most sensitive to the fine detail of
luminance En, less so to the chrominace component En, and still less so to the chrom~nace
component EQ. ThUS, the luminance signal is transmitted with a bandwidth of 4.2 MHZ (more
detail), En web a banduad~ of I.5 MHZ (less details, and EQ with a banded of .5 FEZ (even
less detail).
A transmission encoder converts these dlree components to a single composite video signal by
modulating He chrominance (color information) signals onto a subcaliber at 3.5 MHZ using
Inphase (EI) aIId Quadrature (EQ) modulation techniques. The spectrum for this signal overlaps
He spectrum for luminance Ad, also shown ~ Figure A.1.6.1-1. While these signals overlap in
spectrum, crosstalk among He components in the standards is minimized by careful specification
of the subcamer frequency and careful design by equipment manufacturers. Nevertheless,
crosstalk interference is a source of degradation of video image quality. Over intetnabonal
~wa~pha~.rpr\ NCHRP 3-51 · Phase 2 Fmal Report
A1-241
OCR for page 250
standards employ different, incompatible, implementations. Emerging digital TV standards will
improve resolution and color transmission quality.
~ the U.S. National Television Systems Committee (NTSC) color television standard, die key
parameters of this process are:
Scans at 30 frames per second (29.97 fps for color)
Employs interlaced scanning in which two fields are scanned per frame. The first field scans
odd lines and the second scans even lines. Interlacing reduces Me required transmission
bandwidth to half.
512 Lines per frame (interlaced scans half these lines in successive fields)
· Aspect ratio (honzonal to vertical image size ratio) is 4 to 3, resulting in a honzonal
resolution of approximately 340 pixels (i.e. points or vertical lines).
For display, the television receiver must synchronize wad the horizonal and vertical retrace
pulses which are indicated by higher voltages (i.e., blacker Wan black) Man any normal image
intensity. The actual number of honzonal lines and pixels is reduced by He time allocated to
these retrace pulses (85% visible horizonal pixels and 92% of the horizona] lines).
Emerging High Definition television (HDTV) requirements provide enhancements to these
traditional specifications:
Progressive scan is employed where every line is scanned every frame rawer Han alternate
fields. This approximately doubles the required bandwidth for transmission.
Number of lines per frame is increased to ~125 lines, which furler increases bandwidth
requirements.
Aspect ratio will be increased to 16: 9 which creates a wider screen and filrdlerincreases the
bandwidth.
Table A.~.6.~-1 presents a summary of He current U.S. NTSC television standard and He
potential HDTV standard parameters. There is much debate within He television industry as to
whether the evolution should be to ~TV or to a digital transmission standard that is closer to
He current analog NTSC standard in picture quality.
t;\NCHRP`Phasez.rp~\ NCHRP3-51 · Phase2FtnalReport
Al-242
OCR for page 251
Computer industry displays have evolved to scan rates of 60 to 75 fps and resolutions of 1028
honzonal by 768 lines, or better. Although early PC color displays used composite video, Me PC
industry rapidly converted to R-G-B (3) signal interfaces from PC to display. Win We
convergence of multimedia computer and HDTV/digital TV applications, display technology will
be converging and will have fixture ITS implications for cameras, commun~cabon transmission,
and displays.
Table A.~.6.1 ~
Summary of Television Standard Parameters
Video Bandwidth (MHZ)
-
Total Scan Lines Per frame
NTSC
4.2 MHZ
525
1 .
°/0 Visible Lines (remaining allocated to retrace)
Aspect Ratio (width to height)
-
°/O Visible Honzonal Scan
{remaining allocated to retrace)
. _ . l
Frames per Second
A.~.6.2 Closed Circuit television (CCTV] Camera Technologies
HDTV
20 MHZ
1125
.96
16 to 9
The early television cameras emerged from '`iconoscope9, technology developed by V.K
ZwoIykin of RCA in 1939. These cameras were called "image or~icon" which supported "live"
pick-up and emerged in 1946 as a commercial product. This early camera technology was
photoem~ssive and was replaced by cheaper, easier-to-operate, lower-noise, photoconduc~ve
"vidicon" cameras In 1952. The vidicon was the first CCTV camera technology to be deployed
in ITS systems. These cameras were monochrome. The "Plumbicon" photoconductive camera
was introduced In 1963, followed by the "Saticon" camera In 1974.
Charged Coupled Device (CCD) technology emerged in 1969 and became the facilitator for
lower-cost, small, color CCTV cameras of He 1980s. CCD technology evolved from
Department of Defense (DOD) research into more nugged sensors for missiles, using solid state
electronics rather than "vacuum tube" technology. This technology instigated a new market for
affordable color cameras for home use. Today, it is perhaps the CAMCORDER market that is
funding continued improvements in CCD technology. These have included He m~crolens which
~:\NC~Phase~p'\ NCHRP3-51 · Phase2F~nalReport
A1-243
OCR for page 252
achieves more sensitivity and smaller CCD arrays (from 0.5 inch in Me 198Os to 0.33 inch in We
early 199Os, to 0.25 inch in the mid-199Os without compromising resolution).
CCD technology revolutionized CCTV cameras, facilitating employment of chromic capability
in a small, compact, electronic unit. CCDs resulted in Me foBow~ng improvements compared
who old tube technology:
· Cost reduction · Elimination of imaging unit "burn"
· Dynamic resolution (minimal lag) · hnage registration improvement
· Dynamic range (1000:~) · Image stability improvement
· Less sensitivity to vibration · Longer reliability
Improved signal-to-noise (55 dB or greater ~
Lower power consumption
achievable) · Smaller size.
Improved speck response (spectral width
and sensitivity)
CCD technology does have a performance disadvantage over tubes in the areas of smearing and
blooming; however, transidon~ng from frame transfer to interline transfer electronic architecture
provides improvements in these performance parameters. Aliasing is a more significant problem
in CCDs, requiring attention to anti-aiiasing filters, which are employed in modem CCTV
cameras.
Today we are expenenc~ng a new revolution in CCTV camera technology. This revolution was
energized by the CAMCORDER market seeking unproved competitive features at lower cost
and smaller size. Digital Signal Processing (DSP) technology has facilitated new CCTV camera
features and performance.
1
Figure A.~.6.2-1 is a simplified block diagram of a typical CCTV DSP camera. The camera
consists of:
Lens and optical
:\NCHRPPhase:.'p~\ NCHRP3-51 · Phase2FmaIReport A1-244
OCR for page 253
o
-
o
27
· -
-
ash
-
- ~
c!
z
to
e ~1t ~
~ ~1
o
Q
· _
En
a)
An
-
cn
-
~:
z
to
l
z
o
o
· _
· _
s:
s O
LO C)
o
Ha_
a'
* *
· _
{'
m
T T I °
1 ~
C ~
Q)
a) ~
Q C)
1
z
CY
C'
r
i
z
( ~
o ~
o ~
- ~
. -
u)
o
Q
o
- o
~ ~ ·~
c o ~
O O
C) (~ ~-
c._
*
tn
o
*
cn
a'
a'
~5
$-
Q
U)
o
. _
-
D
~n
~ O
_ - 3
· _ . _
0 L0
i ~ I
O O
a) 0
Ill LLJ
_ * *
c
·-
~:
-
C]
y
o
m
CIC 1
~D
|-,
~J
OCR for page 254
.
CCD imaging device
Analog interface circuitry for preamplificabon and camera beaning
A/D converter, usually at the CCD sampling rate
DSP microprocessor that performs traditional analog processing.
D/A converter.
The DSP performs alp He traditional analog signal processing functions (see Figure A.1.6.1-1).
Aperture correction and image enhancement
Color correction for optical system errors and deliberate distortions for human aes~edc
reasons.
Gamma corrections for differences in noise perception at various signal levels
Encoding from R-G-B (Red, Green, Blue) format to standard NTSC composite video
format.
· Other functions, such as ins control, automatic focus, etc.
The above functions have traditionally been accomplished in cameras by analog circuits;
however, DSP technology has become cost competitive with comparable analog technologies and
offers enhanced performance for the replaced analog functions plus He ability to implement
feature enhancements such as electronic image stabilization and electronic zoom. Table
A.~.6.2-1 lists features and benefits of DSP CCTVs compared web traditional analog
implementations. DSP implementations digitize He video image, perform He signal processing
functions, and convert the signal back to analog for interfacing with traditional analog
equipment. As DSP processing power increases, DSP CCTVs will also perform video
compression and the standard camera interface will be digital.
,.~NCHRP\Phase2~p~\ NCHRP 3-51 · Phase 2 Final Report A1-246
OCR for page 255
Table A.~.6.2-1
New Features and Benefits of DSP CCTVs
Feature _
Electronic Zoom Facilitates zoom without light loss, improving
overall sensitivity. Reduces cost of zoom lens.
__ - _ .
Image Stabilization Stabilizes image from wind gusts and mounting
pole resulting vibrations. Especially helpful
when camera and lens are providing the
maximum zoom setting for the field of view
displayed.
Frame-to-Frame Integration While not totally new to CCTV, DSPs facilitate
frame-to-frame integration to improve sensitivity
with compromise in motion.
Integrated Image Analysis Provides extraction of traffic-related parameters
such as vehicle count, classification, and speed
at a more economical cost.
_
Image Quality Potentially improves image quality by reducing
analog components which are subject to drift.
_
.
Dynamic Image Quality Adjustments The dynamic analysis and optimization of image
parametncs is simplistically accomplished at this
time. The DSP camera has significant potential
to achieve a superior image quality compared
with conventional CCTV cameras.
_ .
Built-in Image Annotation While conventional CCTV cameras offer this
capability, the DSP has more flexibility to
generate alphanumeric overlays indicating
camera location, preset used, viewing angles,
etc.
Motion Detection While available in separate electronics using
conventional cameras, the DSP has the potential
to integrate motion detection and security alarm
into the CCTV camera reducing security system
cost.
SizeM/eighVPower Reduction DSP technology reduces components thus
facilitating smaller, lighter-weight, lower-power
cameras. Life cycle cost is reduced and smaller,
lower-cost pan/tilt units may be used.
A.~.6.3 Video Compression
The standard analog video band is 4.25 ME with (typically) a 10 FEZ band
allocated per channel in private networks to assure quality video transmission. A standard
NTSC color signal is 59.94 fields per second or 29.97 frames per second win 525 lines per
frame or 15,734 lines per second. To convert an analog signal to digital requires sampling at
twice Me analog frequency or 8.5 MHZ minimum (Nyquist). It is common practice to over-
sarnple to assure quality of the video is maintained. Typically a digital sampling frequency 4
;\NCHRP~Phase:~p~\ NCHRP3-51 · Phase2F~nalReport A1-247
OCR for page 256
times the banded is recommended by the Society of Motion Picture and Television Engineers
(SMOTE); however, a sampling rate of 14.32 MHZ is frequently used. Samples are typically ~
bits, providing a bit rate of ~14.5 Mbps, requiring a digital bandwidth of 58 MHZ. With limited
communications band typically available, as wed as limited storage capacity of digital
memories, (] minute of digital recording requires 0.76 Gigabytes of memory), die need for video
compression emerged.
Video compression is essential for successful deployment of commercial digital/HDTV
television and multimedia applications. This demand win motivate suppliers to provide cost-
effective semiconductor components and video equipment. It seems clear Hat future cost-
effective video options for ITS-related applications will include systems and equipment based on
these emerging requirements and related standards.
Most video compression algorithms results In some sacrifice in picture quality or modon.
Picture quality is a function of the available transmission band and the compression
algorithm employed. Compression aigor~tluns typically involve trade-offs among the following
factors:
· Frames per second: 30 per second is the U.S. TV standard
· Resolution: lines per frame and pixels per line
· Interframe compression: data from multiple frames are used for compression which makes
.
modon fidelity more difficult to preserve but provides better compression
In~aframe compression: pixel to pixel compression techniques within a single frame
Handles motion better, but provides less compression)
· Several compression techniques (e.g., discrete cosine transfonn, etc.)
· Resulting bit-rate of transmission at a specified quality.
DS-3 codecs are available which consume 14 times the bandwidth compared win popular
alternative dual DS-1 signals. Similarly, a codec is available which combines 6 video signal
inputs into a single, multiplexed (non-standard format) DS-3 channel providing improved
conservation of bandwidth. Where video distribution to multiple ITS desdnabons is desired,
single channel DS-3 video requires costly network switching and transmission options. In
contrast, DS-1 channels may be cost-effec~vely selectively dropped, added, or repeated by
SONET nodes.
WC~R~Phasc:.~p~x NCHRP3-51 · Phase2F~nalReport
A1-248
OCR for page 257
Several standards are emerging which provide compression to data rates from DS-O to I,2, or 4
DS-ls (i.e., 64 kbps to 6.~8 Mbps). The more prominent ones are summanzed in Table
A.1.6.3-1.
Table A.~.6.3-1
Video Compression Standards
H.261 Subset of H.320 Teleconferencing Standard
Developed for video teleconferencing applications with limited subject motion at
low transmission rates, typically starting at 64 Kbps (also 56 Kbps) to T1 in 64
Kbps increments. At these transmission rates this compression scheme is
capable of QCIF resolution of 176 by 120 or CIF resolution of 352 by 240.
_
MPEG MPEG (Motion Picture Experts Group Level 1)
Developed to provide CIF resolution of 352 by 240 (VHS quality) at
transmission rates of 0.7 Mbps to 6 Mbps (primary design goal was to deliver
compact disc video at 1.416 Mbps).
MPEG-2 (Motion Picture Experts Group Level 2)
Developed to provide CCIR resolution of 720 by 480 (broadcast quality) at
transmission rates of 4 Mbps to 8 Mbps. This is the prime candidate algorithm
for digital T\/ in the U.S. The algorithm uses interframe (i.e., multiple frames)
coding techniques.
MPEG-4
A very low bit-rate (below 64 kbps) standard for video communication over
I telephone and cellular/PCS networks.
_
JPEG (Joint Photographic Experts Group)
Originally developed to code still images, recent work on a motion SPED
standard is emerging. Video compression provides resolution to 560 by 240 (S-
VHS quality) at transmission rates from 19 Kbps to 10 Mbps and resolution of
560 by 480 at transmission rates from 10 to 20 Mbps. This algorithm has been
popular in ITS applications because it uses intraframe (i.e., single frame)
I compress on techniques and handles motion video acceptably.
CCl'l l/UU H.261 (also caned P.64) is perhaps He first Open Standard for video compression.
It was developed primarily to support video teleconferencing over telephone circuits as the video
codec under H.320. P.64 involves increments of DS-O (64 kbps) used to support transmission.
The algorithm includes both inter and intraframe compression. Success of the aIgonthm was
L:\NCHRP\Phase2.rprX NCHRP3-51 · Phase2F~nalReport A1-249
OCR for page 258
based on limited motion as a high degree of scene commonality from frame to frame. The
aIgonthm does not work wed for high modon, typical of that expenenced in freeway
surveillance.
CClrl-l/rrU H.324 has recently emerged as a new video teleconferencing standard incorporating
G.723 speech codec, H.263 video codecs, T.120 data interface, H.246 supervision and control,
and H.223 mulUplexer/demultiplexer. It stresses communications over V.34 modems at 2.8
kbps. The H.263 aIgonthm also stresses both inter and in~aframe compression with minimum
acceptable resolution (128 x 96 pixels). H.263 win outperform H.261 in video quality per bit
transmitted; however, it is unsuitable for fun motion video surveillance applications. The G.723
speech codec operates at 5.3 and 6.3 kbps.
The Joint Photographic Experts Group (JPEG) developed a video standard oriented toward
optimum inhaframe compression, to transmit a single video image over telephone lines achieving
high image quality with low communications bandwidth. The JPEG standard was not designed
for motion but rather for still frame communications. Compression ratios of 200: 1 are possible,
with 15: 1 providing a good quality image. The resulting image quality and failure of video
conferencing algorithms to accommodate a high degree of motion has led to the development of a
draft Motion-IPEG (M-TPEG) standard.
The Motion Picture Experts Group (MPEG) in 1990 developed MDEG-l aso 11172), which
was pnmarily oriented toward application in the video disk market (non-~nterlaced). MPEG-T
stresses a balance between inter and intraframe compression and does not address the necessity
for real-time compression. Like JPEG, it uses Discrete Cosine Transfer (DCT) with Huffman
coding. Typical MPEG-1 compression ratio is 40:1. Since CD ROM information is stored
during its manufacturing process (without time constraints), only real-time decompression is
stressed.
MPEG-2 aso 13818) was a continuing development from MPEG-] wig the specification for
video compression defined in mid-1993. MPEG-2 also represents a balance between inter and
in~aframe compression with options for resolution, data rates, and compression complexities.
Five resolutions are defined wig four levels of complexity of algorithms. MPEG-2 requires
about 220 MIPS (million instructions per second) of a modern 32 bit processor to decode in
:~NCHRP~Phase:~p~\ NCHRP3-51 · Phase2F~nalReport
A1-250
OCR for page 259
software. The U.S. draft version of High Definition TV (HDTV) is based on progressive
scanning (versus NTSC: interlaced mode) and MPEG-2 operating in a 6 MHZ transmission layer
bandwidth. Special ICs are emerging to support real-~ne decoding. Encoding is even more
processor-intensive, again stressing He function of non-real-time conversion of film to
compressed digital video for transmission over satellite and cable TV channels. MPEGs~
standard is in the works to achieve bow real-time compression and decompression web a focus
on low bit-rates.
There are other video compression aIgor~ms Hat are not as widely deployed or standardized
which stress specific video compression/decompression needs. Vector Horace is a DOD
aIgon~m (in public domain) developed to support airborne video surveillance and real-time atr-
to-ground data transfer. The video compression algorithm, like JPEG, focuses on a high degree
Of intraf~me compression assuring accommodation of a high degree of change from frame to
frame as the aircraft moves. Similarly, Houston Advanced Research Center (MARC) has
developed a compression algorithm called MARC-C which reportedly can compress a frame up
to 300: I, providing an image of better quality than He lower compression redo of JPEG.
Based on field test results of video compression aIgonthms for ITS freeway applications, a
minimum acceptable data rate seems to be 3.08 Mbps, assuming that a usable quality image is
desired to justify expenditure of a deployed CCTV camera win pan/~It/zoom (P=. Tests
ncludecl various video surveillance angles Including Nine wad traffic flow Weapon) and side-
of-~e-road. Table A.~.6.3-2 illustrates He results. To conserve banded use, some
manufacturers of video compression transceivers are using a dual DS-! interface which allows
the dig~tized/compressed video to be transmitted over standard Synchronous Optical Network
(SONET) and Integrated Services Digital Network (ISDN) leased T-] lines. The receiving video
codec recombines the two (2) DS-! received digital signals into a virtual 3.08 Mbps
communications circuit, creating a very good quality NTSC image of moving traffic. While 6.16
Mbps provides art obviously higher quality image, the additions bandwidth used does not
appear to justify He minimal improvement in image detectability and quality.
it.
L:\NCHR}~lase2.rpt\ NCHRP 3-51 · Phase 2 final Report
A1-25 1
OCR for page 260
Table A.~.6.3~2
Test Results of Video Codes Algorithms for Freeway Applications
Data Rate and Results
Standards | F-T1 | DS-1| Du HI DS-1
50 kbps 1.54 Mbps3.08 Mbps
H.261 ~ R,B,CJ ~R,B,J ~B,J
MPEG-1 R. B. CJ R. B. J B. J
MPEG-2 | R. B. CJ | R. B,J | A |
| VECTOR HORACE (DOD) | R. B. J | R. B,J | ~
M-JPEG (Draft) | R,B,J | R. B,J | A |
A = Acceptable full-motion quality
B = Periodic blocking of image
CJ = Continuous jumping of image
J = Periodic jumping of image
R = Poor resolution
6.16
Mbps
A
A
A
A
A
Finally, some codecs have an integrated control channel which dictates connectivity of a single
codec transmitter to a single codec receiver. This limits Me ability to distribute a single codec
transmi~er's signal output to a number of operations center locations having codec receivers and
having interest in the video simulcast reception. Similarly, camera PrZ control should be
designed considering the priority control scheme of the system and with Me flexibility to allow
distributed control, if required. It is very important that the llS designer properly select codec
to:
Meet high motion requirements of traffic,
Be compliant win communications bandwidth availability,
Meet video signal distribution and reception requirements
Support priority CCTV camera control within distributed system architecture, and
Provide a quality video image display justifying investment in CCTV camera deployment
cost.
Some misconceptions indicate Mat use of digital video is non-cost-effective in systems, and thus
Cat overlay analog video distribution networks should be considered. In reality, banded on a
~NC~RP~Ph~rpt\ NCHEP3-51 · Phase2F~nalReport A1-252
OCR for page 261
SONET network is very economical, especially where dual DS-1 video codecs are considered.
With selective switching of DS-1 signals, Here need not be a I:l correlation of video
transmitters to receivers. The life cycle costs of maintaining two technologies (analog and digital
networks) plus incorporating an analog video distribution system devoid of modern network
management starboards supporting maintainability, make the use of video overlay networks
unwise. Fur~et~ore, most analog video communications systems have proprietary design and
are not implemented with and open architecture, except at NTSC video ports. This is Conway to
Be open architecture objective established for ITS National Architecture. A modem network,
such as SONET, has very him availability and, win video codec, can support multimedia
communications at lower life cycle costs.
A.~.6.4 ITS Video Communication Issues
Figure A.~.6.4-1 provides a simplified block diagram of a typical ITS video surveillance
network. Communication of video for ITS applications involves a one way video circuit from
camera to displayers) and a full duplex (two way) control circuit between Me camera and the
camera control console.
~:\.NCHRP\Phasc2.Ipt ~NCHRP3-51 · Phase2F~nalReport A1-253
OCR for page 262
Representative terms from entire chapter:
video surveillance
it:
o
llJ
c)
>
c:
o
- -
~ In
o ~
~ J
LO A)
A Z
°8
r ~
o I
> ~
Lr)
ADZ
~ O
Z C)
U]
<, ~
' - <
~ Z
Z
0 En
<: '
~ O
O [L]
Z ~
L
A)
Ace
_
L:,
i..
Hi,
\
\
\
/
\
I~ O
J LLJ
111
_ _
~ > to
_ O
~ ._ ~
I
1
1 o
1 cot
1 lo
1
0
