Composite video signal correction unit for video imaging and video
Contents
1. ieni ided 348 692 698 525 521 526 527 689 673 n one em or iment a signal processing system is provide 348 677 572 that includes See application file for complete search history a a video input 400 operable to receive a first analog video signal and remove the DC voltage offset component 56 References Cited from the video signal to form a DC adjusted analog U S PATENT DOCUMENTS video signal and b DC restore circuitry 416 operable to set an average DC 4 215 371 A 7 1980 Baggett et al voltage ofa first portion ofthe DC adjusted analog video 4 296 437 A 10 1981 Geurts signal to a ground reference voltage to yield a DC 4 340 881 A 7 1982 Stack et al adjusted analog video signal The DC restored analog 4 544 918 A 10 1985 De Haan E h s video signal is then provided to an Analog to Digital or 2 1286 A D converter 112 for conversion into a digital video 4 651 213 A 3 1987 Takimoto A l 4 680 633 A 7 1987 Gerdes et al signal 4 719 584 A 1 1988 Rue et al 4 849 906 A 7 1989 Chodos et al 13 Claims 8 Drawing Sheets Signal Input 400 Comparison Video Signal black burst 7 7 amplitude Comparison 524 To Monitoring Timing Verification Microprocessor 528 US 7 652 723 B1 Page 2 5 659 313 5 689 308 5 798 802 5 818 672 5 867 222 5 892 555 5 952 945 5 986 719 5 990 741 5 995 157 5 995 166 5 995 705 6 016 113 6 107 887 6 127 956 6 147 633 6 160 443 62. L V V NI INNI 15009 MO 236 NOWWOO Q3Q0N31X3 JONVY NOWWOO US 7 652 723 1 1 COMPOSITE VIDEO SIGNAL CORRECTION UNIT FOR VIDEO IMAGING AND VIDEO RECORDING SYSTEMS CROSS REFERENCE TO RELATED APPLICATION The present application claims the benefits of U S Provi sional Application Serial Nos 60 563 751 filed Apr 19 2004 and 60 662 914 filed Mar 15 2005 of the same title and to Patton et al each of which is incorporated herein by this reference FIELD OF THE INVENTION The present invention relates generally to video imaging and video recording systems and specifically to video imag ing and video recording systems including one or more ana log composite video cameras or other video sources and digital display enhancement or recording equipment that incorporates analog to digital conversion means BACKGROUND OF THE INVENTION Video imaging systems are used in a broad variety of applications including telecommunications entertainment security monitoring and the like Video imaging systems are generally placed in one of two categories namely computer and television In television applications baseband video sig nals can follow a number of different formats including the National Television Systems Committee or NTSC standard the U S and Japan standard the Phase Alternating Line or PAL standard the European standard and the High
3. 1 3 performed on the digitized video signal If the digitized video signal is not an accurate and true representation of the video picture captured by the video camera then the DVR algo rithm may falsely detect motion when no motion is present or conversely not detect motion when motion is actually present In the first instance the DVR will rapidly fill its available digital storage medium resulting in loss of data due to either insufficient storage capacity or earlier data being overwritten in the second instance the DVR will not record the desired data at all The common causes of video signal degradation within a video security system are well understood by video engineers and other experienced technical people However video security system installers typically have neither the necessary training to know the causes of video signal degradation the needed test equipment or training to identify the specific cause of degradation in a video system installation nor the knowledge to determine the most cost effective solution even if the cause of a problem is identified Additionally in many installations the level of video signal degradation would be acceptable with an analog video recorder but results in severe picture degradation continuous recording or no recording when a DVR is installed There is currently no system able to simultaneously correct many of the common causes of video signal degradation within a video security sy
4. undated 2 pages cited by examiner U S Patent Jan 26 2010 Sheet 1 of 8 US 7 652 723 B1 A D Converter Digital Display Enhancement And Or Recording Device s 108 Fig 1 Prior Art 652 723 US 7 Sheet 2 of 8 26 2010 Jan U S Patent uv z D oesrig oL SSS Buryuelq Jeujeoqns Jo sepo 6 ysunq 9u S Ot Tm 80 SING Aoi 06 uo10d 9 hl Buryueig 0 7 790i y elg 3Hl 92 0 oosrig oosrl p youod Su s 1 11011 000 056 9145 JO 30 jutod 9506 06 900 067 5 euin esu 99Su 0 jsung 5 sung Bey ysung Aq Aemazaaiq 00 2esu 26 2010 Sheet 3 of 8 US 7 652 723 B1 Signal Correction Unit 304 112 A D Converter Digital Display Enhancement 108 And Or Recording Device s Fig 3 U S Patent Jan 26 2010 Sheet 4 of 8 US 7 652 723 B1 Analog Composite Video Signal IN 436 UN COND CUN Bidirectional Signal Coupler for PZT Bidirectional Signal Bypass for PZT f y 444 Corrected video OUT 400 A C Coupling 420 404 Differential Input 424 408 500 Manual Adjustment 428 412 SignalProcessing Adjustable EQ Manual
5. 7 certain transmission lines such as a coax are frequency dependent For example 1 000 feet of coaxial cable will provide relatively low losses for 2 MHz signals but much higher losses for 40 MHz signal components The latter amplifier configuration is intended to provide a frequency dependent gain that matches the signal losses up to about 100 MHz With reference to NTSC signals the adjustable EQ 412 is intended to adjust the high frequency components of the video signal to the appropriate magnitude or IRE level and the amount of amplification is based at least in part on the previously adjusted gain of the adjustable gain circuitry The adjustable gain is set so that the sync tip 204 is at the correct amplitude For signal components having a frequency above about 1 MHz the signal amplification preferably ranges from about 0 5x to about 4x or from about 3 dB to about 6 dB and even more preferably from about 0 75x to about 2x or from about 1 3 dB to about 3 dB The differential input 404 and adjustable gain and EQ 408 and 412 may each be any suitable circuitry such as an inte grated circuit In a preferred implementation the differential input 404 and adjustable gain and EQ 408 and 412 respec tively are embodied in the EL9110 integrated circuit manufactured by Intersil Corporation The integrated circuit is a single channel differential receiver and equalizer It con tains a high speed differential receiver with five p
6. 900 with an impedance of about 75 2 being most preferred The adjustable gain circuitry 408 allows for adjustment of the video signal amplitude or IRE levels The adjustable gain circuitry 408 can be any amplifier that amplifies equally all of the video signal frequency components by a desired gain This is intended to restore the sync tips 204 to the proper magnitude or IRE level Preferably the signal power is adjusted by an amount ranging from about 0 5x to about 4x or from about 3 db to about 6 db and even more preferably from about 0 5x to about 2 5x or from about 3 db to about 4 db The adjustable EQ circuitry 412 allows for frequency dependant adjustment of the video signal amplitude and is used to compensate for the high frequency roll off that is inherent in many types of transmission lines particularly but not limited to coaxial cable and twisted pair The adjustable EQ 412 may be any amplifier that differentially amplifies only the higher frequency video signal components e g the components have a frequency greater than about 1 MHz In one configuration the amount of amplification is frequency independent or provides fixed or constant gain for frequen cies greater than a selected frequency In another configura tion the amount of amplification is frequency dependent or provides variable gain for frequencies greater than the selected frequency As will be appreciated the losses along US 7 652 723 1
7. Adjustment for Automatic Control i 432 eto sai 504 416 200 o cts 440 Indicator s Distribution D Corrected 1 460a 456 448 460b Legend Video Signal Path arrow indicated flow Alternative Video Path arrow indicates flow Control Signal Path arrow indicates flow US 7 652 723 B1 Sheet 5 of 8 Jan 26 2010 U S Patent JosseoouJdoJolN UOnEOUUSA I U 4 opnyjduue E ysunq oap E 029 j UuosueduuoO Pod 5 YOUAG i nieee 3 95 i i yndjno 59202 9J01S93 SEU ME i 91 21 033002 ules 80r big uogounf teg jeubis jou02 jeuBis yndu US 7 652 723 B1 Sheet 6 of 8 Jan 26 2010 U S Patent 9 biz 06 2 U S Patent Jan 26 2010 Sheet 7 of 8 US 7 652 723 B1 Fig 7 US 7 652 723 B1 Sheet 8 of 8 Jan 26 2010 U S Patent 9 AS OL Q3193NNOO VSA 9 SA AS OL Q3193NNOO YSA SA Q3QN3 319NIS OL TVILLN3 324IG lSVHINOO LXIX AYLINOYIO svig 008 3331310 TYLON od Q
8. THE INVENTION These and other needs are addressed by the various embodiments and configurations of the present invention The present invention is generally directed to a signal correc tion unit that removes noise and or corrects various signal errors prior to conversion of the analog video signal into a digital video signal In one embodiment of the present invention a signal pro cessing method is provided that includes the steps of a receiving a first analog video signal that includes a fixed reference b removing the fixed reference e g DC voltage offset component from the video signal to form an adjusted analog video signal and 20 25 30 35 40 45 50 55 60 65 4 c setting an average voltage of a first portion of the adjusted analog video signal the first portion can for example be one more of the front porch breezeway color burst and back porch to a ground reference voltage to pro duce a restored video signal In one configuration the restored video signal is converted into a digital video signal without the problems caused by unwanted DC offsets and loss of the DC reference voltage from the video signal After removal of the DC offsets and before DC reference voltage restoration the DC adjusted analog video signal may further be passed through a differ ential input to remove ground loop interference To compensate for signal losses in the transmission line from the video so
9. and sent to the monitoring device 504 Inany ofthe above configurations the unit 300 can include redundant power supply circuitry for increased reliability This unit may also include a monitoring and control device to switch to or activate the redundant power supply circuitry when the primary power supply means does not meet prede termined performance specifications Alternatively the unit may include an uninterruptible power supply UPS with alarm means to indicate when the UPS is operating from battery backup The above figures are not intended to limit the functions of the signal processing unit to those elements shown or to indicate that all of these functions are required in every embodiment of the present invention A number of variations and modifications of the invention can be used It would be possible to provide for some features ofthe invention without providing others For example in one alternative embodiment the various modules or components in the unit 300 are implemented in hardware such as a logic circuit and or in software In another alternative embodiment the signal flow is not restricted to the sequence shown Other configurations ofthe same functions are possible and such variations will be rec ognized by video equipment design engineers The present invention in various embodiments includes components methods processes systems and or apparatus substantially as depicted and described herein including va
10. including a Sync Separator operable to send a hold signal during a color burst portion of the DC adjusted composite analog video signal and includ ing said Sync Separator coupled to a buffered logic device operable to set an average voltage during the color burst portion ofthe DC adjusted composite analog video signal and c an Analog to Digital or A D converter operable to con vert the DC restored composite analog video signal into a composite digital video signal 2 The system of claim 1 wherein in the removing step b the DC voltage offset component is removed by capacitive coupling 3 The system of claim 1 wherein the at least a first portion ofthe DC adjusted composite analog video signal is the color burst of the video signal 4 The system of claim 3 wherein the DC restore circuitry comprises an amplifierto amplify the DC adjusted composite analog video signal a time gated sample hold switch circuit to sample the DC adjusted composite analog video signal a switch controller to control the switch setting in the sample hold switch circuit and a coupling capacitor to provide level shifting of the DC restored composite analog video signal wherein during a first time interval the sample hold circuit samples the DC adjusted composite analog video signal wherein the average DC voltage of the sample hold circuit s sample of the at least a first portion of the DC adjusted com posite analog video signal is set to the referenc
11. will be appre ciated significant reductions in video file size equate to lower memory requirements thereby avoiding the need for costly hard drives or limiting the time that the data can be stored While the absolute resolution ofthe system is constrained by the camera resolution and the recording parameters of the Digital Video Recorder or DVR which are typically user defined the resolution can also be impacted by the A D conversion process By providing a compliant video signal to the A D converter the resolution will not be adversely impacted by the digitization of the video signal These and other advantages will be apparent from the disclosure of the invention s contained herein As used herein at least one and at least one or one or more of and or more of or and and or are open ended expressions that are both conjunctive and disjunctive in operation For example each ofthe expressions at least one of A B and at least one of A B or C one or more of A B and or more of A B or C and B and or C means A alone B alone C alone A and B together and C together B and C together and A B and C together The above described embodiments and configurations are neither complete nor exhaustive As will be appreciated other US 7 652 723 1 5 embodiments ofthe invention are possible utilizing alone or in combination one or m
12. 204 784 6 268 814 6 288 658 6 307 492 6 317 473 6 320 627 6 320 917 6 326 911 6 356 221 6 377 196 6 417 794 6 433 723 6 459 447 6 459 458 6 492 924 6 509 796 6 515 542 6 515 600 6 525 609 6 529 248 6 556 158 6 559 788 6 580 465 6 584 365 6 611 537 6 618 480 6 628 730 U S PATENT DOCUMENTS gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt gt 8 1997 11 1997 8 1998 10 1998 2 1999 4 1999 9 1999 11 1999 11 1999 11 1999 11 1999 11 1999 1 2000 8 2000 10 2000 11 2000 12 2000 3 2001 7 2001 9 2001 10 2001 11 2001 11 2001 11 2001 12 2001 3 2002 4 2002 7 2002 8 2002 10 2002 10 2002 12 2002 1 2003 2 2003 2 2003 2 2003 3 2003 4 2003 5 2003 6 2003 6 2003 8 2003 9 2003 9 2003 Dischert et al Nayebi Elmis et al Hilbe Norris et al Sohn Latham et al Nakamura Yamamoto et al Retter et al Kawano Lang Binder Zucker et al Agi Ukawa et al Maalej et al Hatfield Kolsrud Mestdagh et al Berranger et al Stott et al Scott et al Stott et al Gomez et al LeChevalier Kolsrud et al Munoz et al Randall Okada et al Balaban Copley et al Nguyen et al Wang et al Graen Behzad Tsyrganovich Steensgaard Madsen Murphy Sato Blanchard Edens et al Polley et al Stott et al 348 691 348 689 6 640 093 B1 10 2003 Wildhagen 6 653 959 11 2003 Song 6 664 907 12 2003 Knepper et al 6 665 308 B1 12 2003 Rakib et al 6 680
13. 416 restores the true zero volt DC reference to the signal Thus the presence ofthe DC restore circuitry 416 is preferred when AC coupling 400 is employed In a preferred configuration shown in FIG 6 the DC restore circuitry 416 comprises a high fidelity amplifier 700 and a sample hold switch circuit 704 using an external cou pling capacitor to provide level shifting of the video output signal such that a time gated sample ofthe waveform is set to be equal to an external reference voltage usually 0 Volts A buffered Transistor Transistor Logic Complementary Metal Oxide Semiconductor or TTL CMOS logic input signal con trols the switch 710 The gain is set externally by two resis tors The sample hold circuit may be gated on during part of the front porch color burst and or back porch interval of the video signal waveform The video waveform is then fixed for the remainder ofthe line scan interval In a preferred configu ration the circuit functions by setting during the horizontal sync the average DC voltage during the color burst to Vref which is at pin 3 Setting this to ground 0 Volts forces the average DC voltage during the color burst and as a result the back porch 216 to 0 Volts or 0 IRE or ground The hold signal sent to pin 4 goes low during the color burst and it is during that time that the average DC voltage is forced to ground Although any DC restore circuitry may be used the preferred DC restore circuitry is the ZX
14. 680 Bl 1 2004 Mellot 6 683 554 B2 1 2004 Nikai et al 6 684 065 B2 1 2004 Bult et al 6 690 311 B2 2 2004 Lundin et al 6 703 958 B2 3 2004 Noro 6 704 673 B2 3 2004 McTigue 6 734 817 B2 5 2004 Naka et al 6 738 002 B2 5 2004 Ercan et al 6 744 320 B2 6 2004 Nguyen et al 6 744 832 B2 6 2004 Miao 6 759 904 B2 7 2004 Behzad 6 788 230 B2 9 2004 Ahn 6 795 496 Bl 9 2004 Soma et al 6 798 286 B2 9 2004 Dauphinee et al 6 798 293 B2 9 2004 Casper et al 6 803 829 B2 10 2004 Duncan et al 6 816 096 B2 11 2004 Comer et al 6 816 204 B2 11 2004 Limberg 6 822 601 11 2004 Liuet al 6 831 576 B2 12 2004 Geiger et al 6 833 875 Bl 12 2004 Yang et al OTHER PUBLICATIONS Solutions for Ground Loop Interferences VAC Sync Times Issue 1 1994 4 pages Kramer Electronics Ltd User Manual Model 104LN undated pp 1 5 Kramer Electronics Ltd User Manual Distribution Amplifiers Models VM 1010 VM1015 VM 1021 VM 1042 VM 1044 VN 1055 VM 54 undated pp 1 22 The Electric Bullet Newest Technology Topping the Security Dealer Chart www secdealer com Mar 2003 p 20 Micronas Preliminary Data Sheet VPC 3205C VPC 3215C Video Processor Family Oct 19 1998 6251 457 2PD pp 1 48 Conexant Production Data Sheet CX25836 7 Video Decoder 102267A Sep 2004 pp 1 1 6 6 VAC ProSeries Products 1X4 Equalizing Distribution Amplifier FlexPwr for Belden 8281 Cable Video Accessory Corporation
15. Defini tion Standard Definition Digital Television format Intelevision there are three basic levels of baseband signal interfaces In order of increasing quality they are composite video or Color Video Blanking and Sync or CVBS which uses one wire pair Y C or S video which uses two wire pairs and component which uses three wire pairs Each wire pair includes a signal and a ground Composite signals are the most commonly used analog video interface and combine the brightness information luma and the color information chroma and the synchronizing signals on just one cable FIG 2 depicts the horizontal blanking portion of a typical NTSC composite video waveform that includes color infor mation and represents one horizontal scan line The signal includes a front porch 200 which is the area of the signal between the end of the active video and the leading edge of a sync pulse the sync pulse or tip 204 which provides syn chronizing timing information a breezeway 208 which is the area of the signal representing the time between the rising edge of the synch pulse 204 and the start of a color burst 212 the color burst 212 or color subcarrier which is 8 10 cycles ofthe colorreference frequency and is positioned between the rising edge ofthe sync pulse and the start ofthe active video and the back porch 216 which is the time between the end of the color burst and the start of active video In video imaging and video reco
16. FV4089 integrated circuit manufactured by ZETEX The sample hold switch circuit 704 is time gated by a sync separator 708 that is capacitively coupled to the line 432 carrying the amplified and equalized video signal The sync separator 708 samples the amplified and equalized video signal and generates and sends the timing pulse or the hold signal when the sync tip 204 is detected Although the sync tip may be detected using any voltage level of the sync pulse at or below the 5096 level 250 20 IRE the sync tip is preferably detected when the sync pulse voltage hits the 5096 level 250 or 20 IRE The sync separator 708 sends the hold signal to pin 4 After a predetermined time or duration ofthe hold signal the hold signal goes low as noted above The predetermined time is measured from the time that the sync tip is detected and 15 selected so that the hold signal goes low before or during the color burst The predetermined time is typically about 5 06 microseconds The capacitor 750 is a DC blocking capacitor that blocks all of the DC voltages in the video signal as the sync separator may be damaged by a negative DC voltage After passing through the capacitor the signal is suitably adjusted so its voltage does not go negative In a preferred implementation the AC coupling 400 dif ferential input circuitry 404 adjustable gain circuitry 408 adjustable EQ circuitry 412 and DC restore circuitry 416 are located relatively close to
17. al to enable the pin where low is disabled and high is enabled VS which is 5 Volts to the core of the chip 800 and CMEXT which is the logic signal to enable CM range extension where active is high The components of chip 800 are shown in FIG 8 The chip 800 comprises a common mode range extended module 904 an input amplifier 908 a low frequency boost amplifier 912 and high frequency equalizing boost module 916 a control Analog Signal Processor or ASP 920 a gain ASP 924 and additional amplifiers 928 932 and 934 and bias circuitry 938 The common mode extension system is preferably dis connected due to the use of A C coupling 400 The DC restore circuitry 416 measures the average DC voltage of the burst interval or the voltage level of the front porch 200 breezeway 208 and or back porch 216 as com pared to a ground reference and generates a correction voltage to ensure that the blanking portion or the voltage level ofthe front porch 200 breezeway 208 and or back porch 216 of jai 5 30 40 45 65 8 the video signal is at DC ground potential Preferably the DC restore circuitry 416 restores the front porch 200 and the breezeway 208 and back porch 216 or the 0 volt reference point s to the proper position When the AC coupling 400 removes any DC offset from the video signal it effectively removes the DC reference voltage represented by the front porch 200 from the video signal DC restore circuitry
18. ating capacitive couplers on each video input channel Stated another way in each incoming coax transmission line a capacitive coupler is connected in line with each of the center conductor and shield Because the capacitors will not pass DC voltage components such as DC offsets capacitive coupling will remove from the composite analog signal any DC offset or fixed reference on the transmission line 104 In a preferred configuration A C coupling removes all ofthe DC offset in the input composite analog video signal Any suit able A C coupling capacitors may be employed The differential input 404 results in a high impedance path between the unit s input and output signal ground references This high impedance path greatly reduces and most prefer ably eliminates undesirable ground loop currents Specifi cally the differential input references the input video signal 420 between the center conductor and shield of the coax cable The input connector is not grounded and the input signal is not referenced to the ground By isolating the input signal shield from the output signal ground the ground seg ment ofthe signal path is broken The signal input and output impedances are independent of the impedance between the input shield and the output signal ground and are selected to match the impedance ofthe transmission lines typically coax cable 104 and 304 respectively Preferably the differential input impedance ranges from about 50 to about
19. az United States Patent US007652723B1 10 Patent No US 7 652 723 B1 Patton et al 45 Date of Patent Jan 26 2010 54 COMPOSITE VIDEO SIGNAL CORRECTION 4 851 842 A 7 1989 Iwamatsu UNIT FOR VIDEO IMAGING AND VIDEO 4 853 702 A 8 1989 et al RECORDING SYSTEMS 4 982 191 A 1 1991 Ohta 5 012 330 A 4 1991 Bugni 75 Inventors David Patton Louisville CO US 5 057 932 A 10 1991 Lang Richard Frey Louisville CO US 5 086 437 A 2 1992 Tomita Edward Brannan Erie CO US 5 164 839 A 11 1992 Lang 5 218 449 A 6 1993 Ko et al 73 Assignee Video Accessory Corporation Boulder 5 276 517 A 1 1994 Matsuzawa et al CO US 5 280 356 A 1 1994 Hiramatsu 5 341 173 A 8 1994 Hyeon Notice Subject to any disclaimer the term of this 5 422 804 A 6 1995 Clark under 35 5 627 898 A 5 1997 Washino SM y ays 5 644 263 A 7 1997 Clark 21 Appl No 11 082 370 22 Filed Mar 16 2005 Continued Related U S Application Data OTHER PUBLICATIONS 60 Provisional application No 60 563 751 filed on Apr Solutions for Genlocking VAC Sync Times Issue 1 1995 6 pages 19 2004 provisional application No 60 662 914 Continued filed on Mar 15 2005 Primary Examiner Trang U Tran 51 Int CI 74 Attorney Agent or Firm Sheridan Ross P C H04N 5 16 2006 01 52 USCh RSS 348 691 348 692 348 695 57 ABSTRACT 348 525 58 Field of Classification Search 348 691 I bodiment
20. cal and preferably identical amplified output signals so that the out put signal is replicated on a multiplicity of output connectors enabling the user to send the identical signal to multiple locations or video system components In one configuration the amplitudes of the multiple amplified output signals 460a b are each within about 9896 of the amplitude of the input signal 452 Preferably the distribution amplifier 456 is configured to provide a gain of from about 1 0x to about 1 05x or of from about 0 dB to about 0 2 dB with unity gain being most preferred In a typical implementation a 1x2 DA is often required so that the signal from the video source can be routed to two different devices such as a video monitor and a DVR simultaneously and without any loss of signal As shown in FIG 4 the gain and or EQ 408 and 412 may be adjusted manually automatically or a combination thereof Automatic adjustment can be effected by monitoring the output of each video channel and verifying that the ver tical interval synch tip amplitude and or color burst ampli tude of the output signal meets the desired composite video specification or standard The automatic control is effected by asignal processing unit 500 coupled with a monitoring device 504 and one or more feedback indicators 508 The unit 500 controls automatically the gain and EQ circuitry using a con trol feedback loop The operation of the unit 500 e g the settings of the ga
21. ded Graphics Array or XGA type signals over any suitable video interface including not only composite signals but also Y C and component video inter faces The subcomponents of the signal correction unit 300 are depicted in FIG 4 The unit 300 includes Alternating Current or A C coupling 400 differential input circuitry 404 adjust able gain circuitry 408 adjustable Equalizer or EQ circuitry 20 25 30 35 40 45 50 55 60 65 6 412 and Direct Current or DC restore circuitry 416 The A C input coupling accepts large DC voltage offsets on the input analog composite video signal to accommodate most instal lations even unusual combinations of hardware that result in an unacceptably high magnitude DC voltage component The differential input circuitry 404 automatically eliminates or minimizes ground loop interference The automatically and or manually adjustable gain and EQ circuitry 408 and 412 allows for signal optimization even with significant transmission line loss and or low signal levels from the video source The DC restore circuitry 416 automatically provides the correct DC voltage levels on the composite video signal By positioning the above subcomponents on each ofthe video channels the unit 300 can simultaneously process one or more analog composite video signals being conducted or having components being conducted on multiple channels As will be appreciated A C coupling 400 is implemented by loc
22. e digital video signal 10 The system of claim 9 wherein the DC adjusted com posite analog video signal comprises ground loop interfer ence and further comprising between the video input and DC restoring means d differential input means for removing at least most of the ground loop interference from the DC adjusted com posite analog video signal 11 The system of claim 10 further comprising between the differential input and DC restore circuitry e adjustable gain means for amplifying at least a first part of the DC adjusted composite analog video signal to a selected level the at least a part of the DC adjusted composite analog video signal comprising the sync tip US 7 652 723 B1 13 12 The system of claim 11 further comprising after the adjustable gain means and before the DC restoring means f adjustable equalizer means for amplifying at least a second part of the DC adjusted composite analog video signal only at frequencies above a selected frequency wherein the at least a second part comprises the color burst but excludes the sync tip 13 The system of claim 9 wherein the DC restoring means stabilizes at least a second portion of the DC adjusted com 14 posite analog video signal the at least a second portion com prising the sync tip whereby the DC restoring means pro vides a DC restored composite analog video signal in which at least a first portion of the DC restored composite analog video signal is a
23. e voltage and wherein during a second non overlapping time interval the sample hold circuit is set to hold 20 25 30 35 40 45 50 55 60 65 12 5 The system of claim 1 wherein the DC adjusted com posite analog video signal comprises ground loop interfer ence and further comprising between the video input and DC restore circuitry d a differential input to remove at least most of the ground loop interference from the DC adjusted composite ana log video signal 6 The system of claim 5 further comprising between the differential input and DC restore circuitry e adjustable gain circuitry operable to amplify at least a first part of the DC adjusted composite analog video signal to a selected level the at least a first part of the DC adjusted composite analog video signal comprising a sync tip 7 The system of claim 6 further comprising after the adjustable gain circuitry and before the DC restore circuitry f an adjustable equalizer to amplify at least a second part of the DC adjusted composite analog video signal only at frequencies above a selected frequency 8 The system of claim 7 wherein the average DC voltage is set during a first time interval and the DC restore circuitry is further operable during a second non overlapping time interval to stabilize at least a second portion of the DC adjusted composite analog video signal whereby the DC restore circuitry provides a DC restored compos
24. in and EQ circuitry the control signals generated by the unit 500 and the DC restore circuitry 416 is monitored by the device 504 and the device 504 verifies that the post processed signal meets the desired video standard The monitoring unit 504 will generate a control signal to the indicator s 508 which provides confirmation to the user that the processed signal at the output 440 of the video signal correction unit 300 meets specified parameters desired stan dard The indicator s 508 may be visual such as LEDs or a LCD screen display or electrical such as dry contact switch closure or both and may be a local display or a device for remote monitoring or both In one configuration the signal processing unit 500 mea sures the sync tip voltage level and adjusts the gain typically with a control voltage so that the sync tip level meets the signal standard for example 40 IRE for an NTSC video signal The unit 500 also measures the color burst amplitude ofthe signal level and adjusts the EQ typically with a control voltage so that the color burst level meets the signal standard for example 20 IRE for an NTSC video signal The signal processing unit 500 determines the gain and EQ cor rection voltages and may incorporate a microprocessor that measures signal timing and generates one or more control voltages that are sent to the adjustable gain and EQ 408 and 412 The signal processing unit and monitoring device may be but a
25. ite analog video signal in which the at least a first portion of the DC restored composite analog video signal is at DC ground potential and at least a second portion of the DC restored composite analog video signal is not at DC ground potential 9 A signal processing system comprising a video input means for receiving at least a first composite analog video signal the first composite analog video signal comprising a Direct Current or DC voltage offset component and removing at least most of the DC volt age offset component from the video signal to form a DC adjusted composite analog video signal b DC restoring means for setting an average DC voltage of at least a first portion of the DC adjusted composite analog video signal to a reference voltage the reference voltage being equal to ground and the at least a first portion comprising at least one of the front porch breezeway color burst and back door to yield a DC restored composite analog video signal the DC restore circuitry including a Sync Separator operable to send a hold signal during a color burst portion of the DC ad justed composite analog video signal and including said Sync Separator coupled to a buffered logic device oper able to set an average voltage during the color burst portion of the DC adjusted composite analog video sig nal and c an Analog to Digital or A D converter operable to con vert the DC restored composite analog video signal into a composit
26. line is virtually lossless Interference due to ground loops Ground loops result when the ground potential is different between two compo nents within a video system This difference in ground poten tial can result in hum bars on the video picture caused by 60 Hz commercial power or herringbone interference on the video picture caused by AM broadcast signals or a combina tion of 60 Hz and AM broadcast interference that can result in hum bars herringbone blanking color distortion or other degradation to the video picture DC Offset A DC voltage may be superimposed on the video signal by the video source or by another device within the signal path If sufficiently large the DC offset can result in physical damage to the A D conversion means and or to other components within the system Even a small DC offset may not cause noticeable deg radation to the video picture in an analog system but may cause errors in the A D conversion process as described above Many video components utilize AC coupling to eliminate DC offset however this approach results in the signal not having a fixed e g DC reference which is critical to producing an analog composite video signal that fully meets the NTSC or PAL specifications One exemplary application for the present invention is video security systems such as that shown in FIG 1 Such systems typically incorporate a multiplicity of video cameras 100 in continuous operation The analog comp
27. n of the invention has included description of one or more embodiments and certain variations and modifications other variations and modifica tions are within the scope of the invention e g as may be within the skill and knowledge of those in the art after under standing the present disclosure It is intended to obtain rights which include alternative embodiments to the extent permit ted including alternate interchangeable and or equivalent structures functions ranges or steps to those claimed whether or not such alternate interchangeable and or equiva lent structures functions ranges or steps are disclosed herein and without intending to publicly dedicate any patentable subject matter What is claimed is 1 A signal processing system comprising a a video input operable to receive at least a first compos ite analog video signal the first composite analog video signal comprising a Direct Current or DC voltage offset component the video input including Analog Circuit or A C coupling operable to remove at least most ofthe DC voltage offset component from the first composite video signal to form a DC adjusted composite analog video signal b DC restore circuitry operable to set an average DC voltage of at least a first portion of the DC adjusted composite analog video signal to a reference voltage the reference voltage being equal to ground to output a DC restored composite analog video signal the DC restore circuitry
28. nd or recording device s Preferably the unit 300 is separate from or integral with the A D converter When con figured as a separate component the unit 300 is preferably positioned in close proximity to or adjacent to the converter 112 with a transmission line 304 connecting the signal cor rection unit 300 to the camera 100 or composite video source The distance between the composite video source and the signal correction unit 300 may vary between a few feet to over 1 000 feet as determined by the user s require ments Typically the signal correction unit 300 and the A D converter 112 are electronically adjacent to one another and even more preferably are mounted in the same equipment rack More preferably the cumulative signal loss in the com posite video signal along transmission line 304 before being input into the A D converter and digital display enhancement and or recording device s 108 is no more than about 0 25 dB and even more preferably no more than about 0 1 dB The signal transmission line may be any conductor with coaxial or twisted pair being preferred Although the preferred embodiment is discussed with ref erence to NTSC type analog composite video signals it is to be understood that the embodiment can operate equally with other types of video signals such as PAL type video signals HDTV component video signals Red Green Blue or RGB component video signals Video Graphics Array or VGA type video signals and Exten
29. one another Preferably these cir cuit elements are electrically adjacent and even more prefer ably are integrated onto a single circuit board to minimize signal losses simplify impedance matching between circuit elements and minimize undesirable radiation and grounding problems As shown in FIG 4 the input video signal may be prelimi narily fed to a bidirectional signal coupler 436 which sends pan tilt and zoom PZT commands upstream from the signal correction unit 300 output 440 to the composite video source 100 typically a video camera The bidirectional cou US 7 652 723 1 9 pler 436 on the signal correction unit 300 output 440 routes the PZT command signals around the various signal process ing components 400 404 408 412 and 416 of the signal correction unit 300 to the output bidirectional signal bypass 444 and to the coupler 436 The PZT signal originates from the terminating equipment typically a DVR or dedicated PZT control device As will be appreciated routing the PZT sig nals through the unit 300 can substantially degrade not only the quality of the processed video signal but also the PZT command signal quality Depending on the video system configuration the output of the DC restore circuitry 416 may either be the signal 448 outputted by the video signal correction unit 300 or may be the signal 452 inputted to a distribution amplifier DA 456 The DA 456 generates a multiplicity of nearly identi
30. ore ofthe features set forth above or described in detail below BRIEF DESCRIPTION OF THE DRAWINGS FIG 1 is a block diagram of a video imaging system according to the prior art FIG 2 depicts a video signal in accordance with the National Television Systems Committee or NTSC format FIG 3 is a block diagram of a video imaging system according to an embodiment of the present invention FIG 4 is a block diagram of a video signal correction unit according to an embodiment the present invention FIG 5 is a block diagram of a video signal correction unit according to an embodiment of the present invention FIG 6 is a circuit diagram of the DC restore circuitry according to an embodiment of the present invention FIG 7 is a partial circuit diagram of the differential input and adjustable gain and equalizer according to an embodi ment of the present invention and FIG 8 is a partial circuit diagram ofthe adjustable gain and equalizer according to an embodiment of the present inven tion DETAILED DESCRIPTION As depicted in FIG 3 the video signal correction unit 300 of the present invention is positioned upstream of the A D converter 112 and digital display enhancement and or record ing device s 108 and inthe signal path between the device s 108 and the A D converter 112 to correct for the common causes of composite video signal degradation before the com posite video signal is input into the digital display enhance ment a
31. osite video signals from these cameras are transmitted via a transmission line 104 e g coaxial cable twisted pair fiber optics or radio being the most common transmission line to a central loca tion where the video signals may be monitored and are recorded The video monitors and recorders 108 at the central location most commonly accept baseband composite video signals following either the NTSC format or the PAL format Until recently most video security systems utilized analog recorders New systems and upgrades to existing video secu rity systems typically incorporate one or more digital video recorders or DVRs that are designed to accept analog base band video signals A D conversion circuitry 112 which is typically integrated within the DVR is designed to work with either or both of the two signal standards NTSC and PAL When the input video signal is even slightly degraded and does not meet the desired standard the A D conversion pro cess may distort the digitized video signal causing the result ant video picture to be significantly worse in terms of picture quality than would be the case with an analog video recorder Whereas an analog video recorder might record a useable though degraded picture the picture recorded by the DVR may be distorted to such an extent that much or all of the information is lost Additionally many DVRs are designed to detect motion within the video picture based on an algorithm US 7 652 723
32. rding systems analog composite video signals are often converted to a digital video signal for subsequent enhancement display and or record ing While it is desirable that the analog composite video signal input to an analog to digital A D converter fully meets the appropriate composite video standard either the NTSC or PAL standards in practice the composite video signal is often degraded and does not meet the desired stan dard due to some combination of low signal output from the video camera signal loss interference orimproper AC or DC 20 25 30 35 40 45 50 55 60 65 2 signal levels When the analog composite video signal fed to the A D converter is degraded the resulting digital video signal may be distorted For example the sync tip 204 may be disfigured This distortion may be very slight or severe depending on the type and level of degradation to the analog video signal The most common causes of composite video signal dis tortion in video imaging and video recording systems are as follows Signal loss in the transmission means This loss may be due to attenuation mismatched transmission lines splitters or other passive devices within the transmission path Low output from the video source If the signal output from the video camera or other source is not of sufficient ampli tude the video signal at the input to the A D converter may not meet the desired standard even if the transmission
33. re not required to be combined and controlled by a single microprocessor 30 40 45 50 60 65 10 FIG 5 depicts a signal processing unit 500 according to a preferred embodiment of the present invention The basic elements of the signal processing unit 500 are shown inside the heavy dotted box 512 A process timing signal 516 is extracted prior to the signal output Note that the location in the video signal flow where this timing signal is extracted is not limited to the position shown The process timing signal 516 provides needed signal location information to the video signal sync amplitude comparison module 520 the video signal burst amplitude comparison module 524 and the tim ing verification microprocessor 528 The video signal sync amplitude comparison module 520 measures the amplitude of the sync pulse 204 and sends a correction signal if needed to the gain control circuitry 408 and the monitoring device 504 The video signal burst ampli tude comparison module 524 measures the amplitude or peaks ofthe black burst portion ofthe video signal and sends a correction signal if needed to the EQ control circuitry 412 and the monitoring device 504 The timing verification micro processor 528 measures the vertical timing intervals and sync tip timing and compares these measured times to a pre determined time standard An error signal that is proportional to the deviation from the desired time standard is generated
34. ri ous embodiments subcombinations and subsets thereof Those of skill in the art will understand how to make and use the present invention after understanding the present disclo sure The present invention in various embodiments includes providing devices and processes in the absence of items not depicted and or described herein or in various embodiments hereof including in the absence of such items as may have been used in previous devices or processes e g for improving performance achieving ease and or reducing cost of implementation The foregoing discussion of the invention has been pre sented for purposes of illustration and description The fore going is not intended to limit the invention to the form or forms disclosed herein In the foregoing Detailed Description for example various features of the invention are grouped together in one or more embodiments for the purpose of streamlining the disclosure This method of disclosure is not US 7 652 723 1 11 to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim Rather as the following claims reflect inventive aspects lie in less than all features of a single foregoing disclosed embodiment Thus the following claims are hereby incorporated into this Detailed Description with each claim standing on its own as a separate preferred embodiment ofthe invention Moreover though the descriptio
35. rogram mable poles The outputs ofthe pole blocks are summed into an output buffer The equalization length can be set with the voltage on a single pin The gain can be adjusted up or down by 6 dB using a V gazy control signal Additionally a further 6 dB of gain can be switched in to provide a matched drive into a cable The circuit has a bandwidth of about 150 MHz A single input voltage can be used to set the compensation levels for the required length of transmission line The equivalent circuitry of this integrated circuit is shown in FIGS 7 8 Referring to FIG 7 the chip 800 is connected to various leads including CTRL REF the reference voltage for the Vain and Vya pins Verrz which is the control voltage 0 to 1 Volt to set equalization VINP which is the positive differential input VINM which is the negative dif ferential input VS which is 5 Volts to core of the chip 800 CMOUT which is the output of the common mode voltage present at the inputs VGAIN which is the control voltage to set the overall gain the control voltage is from 0 to 1 Volt LOGIC REF which is the reference voltage for all logic signals X2 which is the logic signal low gain 1 and high gain 2 0 V which is 0 Volt reference for the output voltage VSA which is 5 Volts to the output buffer VOUT which is the single ended output voltage referenced to pin 10 which is 5 Volts to the output buffer ENBL which is a logic sign
36. stem With the increasing use of digital video recorders in video security systems the need for such a solution is immediate and grow ing Another application for the present invention is video imaging systems Analog composite video cameras are com monly used to capture video pictures that are converted to a digital video signal then digitally manipulated or enhanced displayed and or recorded Such applications which include medical satellite and airborne imaging systems utilize an A D conversion process as described above and these sys tems may suffer from the same distortion effects described above if the analog video signal input is degraded Since imaging systems typically require the highest possible picture resolution any loss of intelligence due to degradation of the analog composite video system is highly undesirable Another application for the present invention is radar sys tem displays In many radar systems the output from the radar receiver is a composite video signal Many radar sys tems digitally enhance the displayed signal Such systems utilize an A D conversion process as described above and these systems may suffer from the same distortion effects described above if the analog video signal input is degraded Such display systems are utilized to produce the highest pos sible picture resolution and the loss of intelligence due to degradation of the analog composite video system is highly undesirable SUMMARY OF
37. t DC ground potential and at least a second portion of the DC restored composite analog video signal is not at DC ground potential UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO 7 652 723 B1 Page 1 of 1 APPLICATION NO 11 082370 DATED January 26 2010 INVENTOR S Patton et al It is certified that error appears in the above identified patent and that said Letters Patent is hereby corrected as shown below On the Title Page The first or sole Notice should read Subject to any disclaimer the term of this patent is extended or adjusted under 35 U S C 154 b by 1290 days Signed and Sealed this Twenty third Day of November 2010 David J Kappos Director of the United States Patent and Trademark Office
38. urce and low power output from the video source the analog video signal after being passed through the differential input may be further processed by adjustable gain and equalizer circuitry The adjustable gain circuitry amplifies all components ofthe video signal equally while the equalizer circuitry amplifies only higher frequency compo nents Applications for this embodiment of the present invention include but are not limited to security systems video imag ing and radar display systems Until the present invention there has been no single device that specifically corrects for the common causes of composite video signal degradation to ensure that the corrected analog video signal nearly meets or most preferably fully meets the desired composite video standard prior to an Analog to Digi tal or A D conversion process where the resulting digital video signal is enhanced or otherwise digitally manipulated displayed and or recorded The digital replica of the analog video signal can be relatively free of distortion causing the resultant video picture to be of high quality and providing a high degree of accuracy in motion detection as more accurate detection of pixel changes between frames The analog to digital or A D converter dueto the high standard ofthe analog video signal can create fewer artifacts noise and the com pression scheme can work more efficiently As a result the video file size can be reduced significantly As
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