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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
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
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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
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
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
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
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. 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
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
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
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
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
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
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
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
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