Patent Publication Number: US-11651594-B2

Title: Systems and methods of legibly capturing vehicle markings

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/720,272, filed Dec. 18, 2019, issued on Dec. 8, 2020 as U.S. Pat. No. 10,860,866 (“the &#39;866 Patent”). The &#39;866 Patent in turn is a continuation of U.S. patent application Ser. No. 15/269,144, filed Sep. 19, 2016, issued Dec. 31, 2019 as U.S. Pat. No. 10,521,675. The disclosures of the above-disclosed applications are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND 
     1. Field 
     Embodiments of the invention are broadly directed to legible video capture of license plate data. More specifically, embodiments of the invention record video of a scene using systems and methods that increase the likelihood of capturing at least one frame in which a license plate or other identifiable vehicle marking is legible. 
     2. Related Art 
     Mobile recording systems, such as car-mounted cameras, serve many purposes for law enforcement officers and other first responders, such as documentation of events, collection of evidence, and improvement of training. One important function of recording systems used by law enforcement is the capture of license plate data. Capturing license plate data or other markings of a vehicle, suspect, victim, bystander, fellow officer, or a scene&#39;s surroundings may be key in proving guilt or innocence or locating parties of interest. Of course, to be of use in such matters, written characters (e.g., numbers, letters, punctuation, logos, hazardous waste symbols, symbols) captured in recorded images, such as a license plate, must be legible. In many situations, legible video capture of license plate data and other vehicle markings or scene surroundings is made difficult by factors such as high motion, darkness, and/or interference from sources such as light, smoke, or fog. 
     Typical systems and methods for license plate recognition attempt to improve legibility of license plates through improved illumination of the scene. Improving illumination requires bright lights that may be costly, distracting, power consumptive, ineffective, and/or logistically difficult to implement quickly. Other systems perform advanced processing to improve captured images but may be expensive, slow, and require very high processor dedication. What is needed is an improved system and method for video capture of legible license plate data and other vehicle markings or scene surroundings that does not require additional or enhanced illumination of a scene. 
     SUMMARY 
     Embodiments of the invention provide systems and methods for legibly capturing license plate data using a video camera. A first embodiment of the invention is directed to a method of scanning for a legible marking on a vehicle using a video camera with two or more recording attributes. Upon acquiring an indication to begin a scan with a video camera, a first recording attribute is adjusted within a first scan range, between a first lower limit and a first upper limit. Thereafter, a second recording attribute is adjusted within a second scan range, between a second lower limit and a second upper limit. A portion of the scan that includes a legible marking on a vehicle is stored in a memory associated with the video camera or otherwise accessible by the video camera. 
     A second embodiment of the invention is directed to an image capture system including a video camera with at least a first recording attribute and a second recording attribute, a storage device, and a processor. The processor is configured to adjust a first recording attribute within a first scan range between a first lower limit and a first upper limit, adjust a second recording attribute within a second scan range, between a second lower limit and a second upper limit, and store in memory a portion of the scan that includes a legible marking on a vehicle. 
     A third embodiment of the invention is directed to a method of scanning for a legible marking on a vehicle using a video camera with two or more recording attributes. Upon acquiring an indication to begin a scan with a video camera, a first recording attribute is adjusted within a first scan range, between a first lower limit and a first upper limit. Next, a second recording attribute is adjusted within a second scan range, between a second lower limit and a second upper limit. Thereafter, a determination is made as to whether or not a marking on a vehicle has been legibly captured. Based on this determination, further steps may occur, including initiation of additional scanning or storage of a portion of video data. 
     This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Each of the above embodiments may include further recording devices, hardware, or steps not explicitly described. Other aspects and advantages of the invention will be apparent from the following detailed description of the embodiments and the accompanying drawing figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       Embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein: 
         FIG.  1 A  is a diagram of elements comprising embodiments of the invention; 
         FIG.  1 B  is a further diagram of elements comprising embodiments of the invention; 
         FIG.  2 A  is an illustration of an ideal clear image of a vehicle with legible markings thereon; 
         FIG.  2 B  is an illustration of a clear image of a vehicle with a license plate having illegible markings; 
         FIG.  2 C  is an illustration of an unclear image of a vehicle with a license plate having legible markings; 
         FIG.  3    is an illustration of a display of embodiments of the invention for presenting representative images of a license plate and soliciting user response; 
         FIG.  4    is a first flow diagram of steps that may be performed in embodiments of the invention; 
         FIGS.  5 A,  5 B, and  5 C  illustrate a second flow diagram of steps that may be performed in embodiments of the invention; and 
     
    
    
     The drawing figures do not limit the invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention. 
     DETAILED DESCRIPTION 
     The following detailed description references the accompanying drawings that illustrate specific embodiments in which the invention can be practiced. The embodiments are intended to describe aspects of the invention in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments can be utilized and changes can be made without departing from the scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense. The scope of the invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled. 
     In this description, references to “one embodiment,” “an embodiment,” or “embodiments” mean that the feature or features being referred to are included in at least one embodiment of the technology. Separate references to “one embodiment,” “an embodiment,” or “embodiments” in this description do not necessarily refer to the same embodiment and are also not mutually exclusive unless so stated and/or except as will be readily apparent to those skilled in the art from the description. For example, a feature, structure, act, etc. described in one embodiment may also be included in other embodiments, but is not necessarily included. Thus, the current technology can include a variety of combinations and/or integrations of the embodiments described herein. 
     Embodiments of the invention provide systems and methods of capturing video data that adjust recording attributes of one or more video cameras to scan for a legible image of a license plate or other identifying characters or markings on a vehicle. Further, embodiments of the invention determine whether or not a legible image has been captured, and may take additional steps based on the determination. The additional steps may include rescanning the scene or storing the image data. 
     Turning to the figures, and particularly  FIG.  1 A , a first embodiment of a recording system  10  is described.  FIG.  1 A  includes an intermediate recording device manager  12  (or “manager  12 ”), a vehicle recording device  14  mounted in a police vehicle  16  (or other first responder&#39;s vehicle) and communicatively coupled (e.g., synced) to the recording device manager  12 , and a personal recording device  18 . Personal recording device  18  may be carried by a police officer  20  or other first responder and wirelessly synced to the recording device manager  12 . The recording device manager  12  is operable to detect when the vehicle recording device  14 , personal recording device  18 , or any other synced device in range has started recording and to broadcast or transmit a signal to other synced recording devices in range, instructing recording by the respective device. The recording device manager  12  may also generate time stamps and unique serial numbers for a data recording, and create or collect metadata and transmit such time stamps, unique serial number, and metadata to the recording devices  14 ,  18  for corroborating the recorded data. For illustrative purposes, the recording system  10  includes the vehicle recording device  14  and the personal recording device  18 , but it will be understood that duplicate or additional devices, such as audio recorders, thermal imagers, security cameras, radios, radar and LIDAR scanners, and electronic weapons, can be synced to the recording device manager  12 . Specifically, multiple recording devices  14 ,  18  can be synced with the manager  12  simultaneously. 
     In embodiments of the invention, the vehicle recording device  14  and personal recording device  18  are each video cameras operable to record data, including without limitation, audio data and video data. Moreover, the recording devices  14 ,  18  are also operable to record or generate metadata associated with the recording, such that the data recorded by the devices  14 ,  18  includes the audio data, the video data, and/or the metadata associated with either or both of the audio and video data. Examples of metadata for an audio or video recording include a location (as determined by a GPS) where the data was recorded, a user who recorded the data or was otherwise associated with the recording device  14 ,  18  (e.g., an officer driving a police vehicle or an officer wearing the personal recording device  18 ), the time stamp and/or unique serial number, a trigger for the data recording event (e.g., what prompted a data capture scan by the recording devices), and other data related to the recorded event. Additionally, as further discussed below, the metadata may include or link to data derived from identifying marks on a subject vehicle. 
     The recording device manager  12  is illustrated in  FIG.  1 A  as a standalone device but can be incorporated into other devices, such as a laptop (including external computing device  22 ), a radio, a recording device (including the vehicle recording device  14 ), a mobile communications device, a battery pack, or an electronic weapon. The recording device manager  12  may be permanently or removably mounted anywhere in the police vehicle  16 , such as on the dashboard, center console, or windshield. Alternatively, the recording device manager  12  can be carried or worn by the police officer  20 , such as on his utility belt or in his pocket. 
     Exemplary hardware included in embodiments of the invention is illustrated in  FIG.  1 B . Computer  102  can be a laptop computer, as illustrated as external computing device  22  of  FIG.  1 A . Depicted with computer  102  are several components, for illustrative purposes. In some embodiments, certain components may be arranged differently or absent. Additional components may also be present. Included in computer  102  is system bus  104 , whereby other components of computer  102  can communicate with each other. In certain embodiments, there may be multiple busses or components may communicate with each other directly. Connected to system bus  104  is central processing unit (or “processor”)  106 . Also attached to system bus  104  are one or more random-access memory (RAM) modules  108 . Also attached to system bus  104  is graphics card  110 . In some embodiments, graphics card  110  may not be a physically separate card, but rather may be integrated into the motherboard or the processor  106 . In some embodiments, graphics card  110  has a separate graphics-processing unit (GPU)  112 , which can be used for graphics processing. Also on graphics card  110  is GPU memory  114 . A display  116  may be connected (directly or indirectly) to graphics card  110  for user interaction. In some embodiments no display is present, while in others it is integrated into computer  102 , or detached physically and remotely connected to computer  102 . Similarly, peripherals such as keyboard  118  and mouse  120  may be connected to system bus  104 . Like display  116 , these or other peripherals may be integrated into computer  102 , remotely connected, or absent. Also connected to system bus  104  is local storage  122 , which may be any form of computer-readable media, and may be internally installed in computer  102  or externally and removably attached. 
     Computer-readable media include both volatile and nonvolatile media, removable and nonremovable media, and contemplate media readable by a database. For example, computer-readable media include (but are not limited to) RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile discs (DVD), holographic media or other optical disc storage, magnetic cassettes, magnetic tape, magnetic disk storage, and other magnetic storage devices. These technologies can store data temporarily or permanently. However, unless explicitly specified otherwise, the term “computer-readable media” should not be construed to include physical, but transitory, forms of signal transmission such as radio broadcasts, electrical signals through a wire, or light pulses through a fiber-optic cable. Examples of stored information include computer-useable instructions, data structures, program modules, and other data representations. 
     Finally, network interface card (NIC)  124  is also attached to system bus  104  and allows computer  102  to communicate over a network. NIC  124  can be any form of network interface known in the art, such as Ethernet, ATM, fiber, Bluetooth, or Wi-Fi (i.e., the IEEE 802.11 family of standards). NIC  124  may connect computer  102  to a local network, optionally via a CAN bus  26 , as further described below. The local network may in turn connected to Internet, or in some embodiments computer  102  may itself be directly connected to Internet. 
     Returning to  FIG.  1 A , external computing device  22  may be coupled to recording device manager  12  via wired or wireless connection. The external computing device  22  can be a laptop, tablet, mobile device, smartphone, or other computing device. The external computing device  22  displays a graphical user interface (GUI) by which the police officer  20  or other user may view recorded data and make selections regarding the recording system  10 . As further described below, external computing device  22  may function as an input/output device to allow an officer to judge the legibility of characters captured in video data. External computing device  12  may include a central processing unit (CPU) and one or more random-access memory (RAM) modules, as well as a graphics card and display for user interaction. In some embodiments no display is present, while in others it may be spaced apart from and coupled to an external computing device  22 . Similarly, peripherals such as keyboard and mouse may be coupled to external computing device  22 . Like the display, these peripherals may be integrated into external computing device  22  or absent. External computing device  22  may be touch-sensitive, allowing an officer to input data or make selections via tap, swipe, or other gesture. 
     A power source  24  may be electronically connected to the vehicle recording device  14  through dedicated wiring. The power source  24  supplies power to each of the electronic components of the vehicle recording device and, in embodiments of the invention, to the recording device manager  12  and/or the personal recording device  18 . In embodiments of the invention, the power source  24  is the police vehicle&#39;s battery but can be another power source, such as a battery cartridge of the external computing device  22 . 
     The electronic connection between the recording device manager  12 , the vehicle recording device  14 , and the personal recording device  18  optionally includes a control area network (CAN) bus  26 , which “directs traffic” for incoming and outgoing signals based on indicated importance or other factors and follows an algorithm for determining the order in which (or whether) signals are transmitted. 
     The vehicle recording device  14  is operable to record audio, video, and/or other data. In some embodiments, the vehicle recording device  14  is a video recording device such as one produced by Digital Ally, Inc., including the DVM100, DVM250, DVM250Plus, DVM250Law, DVM400, DV440Ultra, DVM470, DVM500, DVM500Plus, and DVM750. As described below, in some embodiments the vehicle recording device  14  is operable to receive a signal of a triggering event, while in other embodiments the vehicle recording device  14  utilizes the CAN bus  26  and is operable to receive time stamps and metadata in addition to the signal of a triggering event. The vehicle recording device  14  can be incorporated into the police vehicle&#39;s rear view mirror, dashboard, spotlight, or other locations associated with the police vehicle  16  or may be a stand-alone unit mounted within or on the police vehicle  16 . The vehicle recording device  14  may receive power from the power source  24  through dedicated wiring. In addition to the exemplary vehicle recording devices listed above, a vehicle recording device is further described in commonly-owned U.S. Pat. No. 8,520,069, issued Aug. 27, 2013, entitled “Vehicle-Mounted Video System with Distributed Processing,” the entirety of which is incorporated by reference herein. 
     The personal recording device  18  is small, portable, wearable, easily concealed, and is operable to record audio, video, thermal, chemical, or other data. The personal recording device  18  can be worn by the officer  20 , such as on the officer&#39;s shirt, hat, eyeglasses or sunglasses, electronic weapon, breath analyzer, or other device accessed or used by the officer. The personal recording device  18  is operable to receive a signal instructing the device  18  to begin or stop scanning (as discussed in further detail below), a signal indicative of a triggering event, and time stamps and metadata corresponding to the recordings. Additionally, the personal recording device  18  may further include a clock for determining a time corresponding to when a particular item of data was recorded. An exemplary personal recording device is the “FIRSTVU HD” produced by Digital Ally, Inc. and further described in U.S. Pat. No. 9,019,431, issued Apr. 28, 2015, and commonly assigned with the present application, the entirety of which is hereby incorporated by reference into the present application. 
     Recordings generated by the recording devices  14 ,  18  and associated metadata may be temporarily or permanently stored in a local memory element (hereinafter “memory”), such as a memory of the particular recording devices  14 ,  18 , and/or a memory of external computing device  22  located in the police vehicle  16 . The recording devices  14 ,  18  may alternatively or additionally be allowed to upload recordings to an external server or storage device. The external server or storage device could be a large-capacity storage device  28 , such as a DVR housed in the vehicle, or may be a centralized computing device, such as housed at a police precinct. These examples are not meant to be limiting; any form of data storage and duplication is intended within embodiments of the invention. 
     An exemplary scenario of the recording system  10  in use is now described for illustrative purposes. The recording system  10  may be used by the police officer  20  to record video data during an event such as a traffic stop. The recording device manager  12  may be mounted near the vehicle recording device  14 , such as on the windshield of the police vehicle  16 , or may be integrated within a housing of the vehicle recording device  14 . Alternatively, the recording device manager  12  may be mounted anywhere within the police vehicle  16  that allows for the recording device manager  12  to communicate (either via a wired or wireless connection) with the vehicle recording device  14 . In embodiments of the invention, the vehicle recording device  14  is oriented in a forward direction relative to a front of the vehicle to record the traffic stop, and in yet further embodiments, multiple vehicle recording devices  14  may be mounted in or on the vehicle and oriented in different directions relative to the vehicle, such as backwards towards a rear of the vehicle, and to the left and right sides of the vehicle. The personal recording device  18  is mounted to the police officer&#39;s person or is otherwise carried by the police officer  20 , such as on a lanyard, belt, or shoulder. In embodiments of the invention, the personal recording device  18  may include a GPS, an RFID, or another type of location or identification feature or sensor (not shown) that informs the recording device manager  12  of the relational location of the personal recording device  18  to the recording device manager  12 . Alternatively, the officer may carry on their person a GPS (such as housed within or associated with a mobile communications device), RFID, or other type of location or identification sensor. Recording system  10  may include additional sensors not illustrated in  FIG.  1 A , such as a rangefinder. Data collected from such sensors may be stored along with video, audio, and metadata, and may be used in detection of trigger parameters or determination of scan range limits, as further discussed below. 
     Embodiments of the invention are not intended to be limited to the traffic stop situation described above. Embodiments may be stationary or mobile camera systems employed by businesses to record the identity of vehicles arriving and departing from a parking lot. Alternatively, embodiments may be employed in maritime settings, such as for tracking of shipping containers. In other embodiments of the invention, a military installation may use a camera system to pre-screen vehicles approaching a secure location. Any system including one or more video recording devices that scan for a legible image of a marking on a vehicle may fall within embodiments of the invention. 
     Returning to the law enforcement example, in embodiments of the invention, the recording device manager  12  may activate a data capture scan (or simply “scan”) from vehicle recording device  14  and/or personal recording device  18  responsive to a triggering event (also more simply known as a “trigger”). Examples of a triggering event may include, for example, turning on the vehicle&#39;s siren and/or signal lights, an indication that the vehicle is parked, an electronic detection of a subject car or a license plate, an accelerometer measurement outside a pre-established norm, a position of the vehicle and/or officer as measured by a GPS, a vehicle crash event, the police vehicle  16  attaining a threshold speed (e.g., 80 m.p.h.), activation of an electronic weapon, opening of the vehicle door, and/or activation of a radar or the radar detecting a subject car&#39;s speed at or over a pre-determined speed. In embodiments, the recording device manager  12  may receive a signal from, for example, the vehicle recording device  14 , external computing device  22 , or police vehicle  16  indicative of a triggering event. In response to receipt of the signal, or based on a type of triggering event as evidenced by the signal, the recording device manager  12  may instruct recording by the vehicle recording device  14  or the personal recording device  18  to begin a scan. As an exemplary scenario, the recording device manager  12  may receive a signal identifying a triggering event of a police vehicle  16  being placed in park while the vehicle signal lights are activated. Upon receipt of the signal, the recording device manager  12  sends a signal to either or both of the vehicle recording device  14  or the personal recording device  18  to instruct the devices  14 ,  18  to begin a scan. It should be appreciated that other types of triggering events and exemplary scenarios can be employed. 
     Alternatively, a data capture scan may be activated manually based on a user&#39;s manual selection, for instance via a police officer&#39;s button press of recording device manager  12 , vehicle recording device  14 , or external computing device  22 . A manual selection may be made remotely from a fob carried by police officer  20  or a control integrated into the structure of personal recording device  18 . In embodiments of the invention, a manual selection may be made by a remote user, such as by a dispatcher at a police station. As further discussed below, whether initiated via a trigger or via manual indication, a scan serves to adjust one or more recording attributes between a lower limit and upper limit to search for a legible image of a license plate or other vehicle marking. 
       FIGS.  2 A-C  illustrate examples of images captured by a recording device such as vehicle recoding device  14  of a subject vehicle  200 , 204 , 208  with a license plate  202 , 210  during a typical traffic stop situation introduced above.  FIG.  2 A  illustrates a captured image of a subject vehicle  200  during a traffic stop occurring on a clear day with ideal recording conditions. Factors such as the make, model, color, damage, decals, bumper stickers, etc. of vehicle  200  can be distinguished in the captured video data, as well as the actions of figures in the scene. In particular, the license plate  202  of vehicle  200  is legible. Under such conditions, the license plate  202  will likely be clearly readable from portions of the video data captured (which may be motion video and/or still frames) by a human observer and/or a computer character recognition program. 
       FIG.  2 B  illustrates a similar situation to that illustrated in  FIG.  2 A , only in this instance the traffic stop is occurring at night, when recording conditions are less ideal. A subject vehicle  204  identical to vehicle  200  in  FIG.  2 A  has been pulled over, and an image is captured from vehicle recording device  14  mounted forward-facing in police vehicle  16 . The subject vehicle  204  can again be distinguished by factors such as make, model, color, etc., though perhaps to a lesser extent than in  FIG.  2 A . However, interference from sources such as the headlights of police vehicle  16  reflecting from the rear  206  of subject vehicle  204  has washed out the image of the license plate, making it completely illegible. This effect is known as “bloom,” and inhibits the ability of a user or computer program to definitively determine the identity of subject vehicle  204  from the recorded video data. As seen in  FIG.  2 B , the effect of bloom can be impactful enough to saturate the recording camera in region  206  of the image, such that the license plate cannot be seen at all. 
       FIG.  2 C  illustrates the traffic stop situation a third time, again occurring at night as in  FIG.  2 B . A subject vehicle  208  identical to vehicles  200 , 204  in  FIGS.  2 A-B  has been pulled over, and an image is captured from vehicle recording device  14  mounted forward-facing in police vehicle  16 . In illustrated image capture of  FIG.  2 C , one or more recording attributes of vehicle recording device  14  have been adjusted such that the bloom effect of the reflected headlights has been minimized. The subject vehicle  208  as a whole is actually much less distinguishable in terms of make, model, color, etc. compared to subject vehicle  204  of  FIG.  2 B , but the critical information of license plate  210  is legibly captured. The video data recording illustrated in  FIG.  2 C  may be less likely to capture any events happening in the recorded scene but is valuable for establishing proof of the identity of subject vehicle  208 . 
     Embodiments of the invention adjust one or more recording attributes of one or more video recording devices, such as vehicle recording device  14  or personal recording device  18 , to scan for at least one frame of a legible image of markings on a vehicle, such as those on a license plate. As in the example illustrated in  FIG.  2 C , the frame containing legible markings for which the recording devices are scanning may be dark, obscured, unfocused, or otherwise unclear with respect to any elements of the scene other than the license plate (or other vehicle markings of interest). This is not intended to be limiting, as the legible frame may present a clear view of all elements of the scene, as in  FIG.  2 A . Examples of recording attributes that may be adjusted include gain, shutter speed, focus, white balance, sharpness, backlight compensation, iris aperture, or any other applicable adjustable attribute of the recording devices. 
     Because adjusting the recording attribute(s) of the recording devices  14 , 18  to legibly capture the license plate  200 , 210  may reduce visibility of other elements in the recorded scene, embodiments of the invention may not permanently set the recording attributes to such values. Doing so is unnecessary, as only a single legible frame is needed for identification purposes. Additionally, permanent adjustment of the recording attributes might require significant computation to determine the appropriate values and may render the recording less valuable as a documentation of events in the scene. Rather, in embodiments of the invention, selected recording attributes are only temporarily adjusted to scan for a legible image of a marking on a vehicle, such as a license plate. For example, a recording attribute such as gain may be adjusted across a range of values, searching for a single value within that range at which the license plate is legible. In embodiments of the invention, one or more recording devices  14 , 18  perform a scan for legible markings on a vehicle while other recording devices  14 , 18  continue recording video data using normal recording attributes. In this way the portion of recorded video occurring during the scan is recorded as usual. It should also be appreciated that embodiments of the invention may employ a dedicated vehicle recording device  14  for capturing the image or scanning the vehicle for markings. 
     The scan range for a particular attribute includes a lower limit and an upper limit, each of which may be a predetermined limit programmed into memory, may be selected manually by a user, or may be dynamically selected by the recording system  10  based on factors such as the time of day, a sensed ambient light level, or a distance measurement. Such a distance measurement may be, for instance, from the recording device  14 , 18  to the subject vehicle  200 . Alternatively, a distance measurement may be estimated by an officer  20  and entered via external computing device  22 . Manual selections may be presented to the user as multiple choice selections based on the user&#39;s evaluation of the visibility of the scene, such as a “low-light” scan range, “high interference” scan range, or “long distance” scan range. These scan ranges are meant only as examples, and are not intended to be limiting in any way. 
     A recording attribute may be adjusted within a scan range by a continuous “sweep” of the scan range or may be adjusted incrementally by set values. The incremental values by which a recording attribute is adjusted may be uniform increments, which may be predetermined increments programmed into memory or may be selected manually by a user. Alternatively, uniform increments may be dynamically selected by the recording system based on sensed parameters such as the time of day, a sensed ambient light level, or a distance measurement. Like the scan range limits, the increments of adjustment of a recording attribute within a scan range may be presented to the user as multiple choice selections based on their evaluation of the visibility of the scene, such as “low-light” adjustments, “high interference” adjustments, or “long distance” adjustments. Again, these are meant only as examples, and are not intended to be limiting in any way. 
     In the course of performing a scan for a legible marking on a vehicle, embodiments of the invention may adjust more than one recording attribute within respective scan ranges, each scan range including a respective upper and lower limit. For example, a scan may adjust gain between a minimum level of 30% and a maximum level of 70% and also adjust shutter speed between 0.02 and 0.05 seconds. The adjustments may be done simultaneously, or may be performed independently of one another, with the value of one recording attribute adjusted while the other is held at a static value. Specifically, a first recording attribute may remain at a first value within its first scan range while a second recording attribute is adjusted within its second scan range, and the second recording attribute may remain at a second value within its second scan range while the first recording attribute is adjusted within its first scan range. 
     In some embodiments, the value of a given recording attribute may be adjusted throughout a scan range multiple times, with the values of other recording attributes held at different static values each time. For instance, gain may be adjusted between a 30% lower limit and a 70% upper limit while the shutter speed is held at 0.025 seconds, and then adjusted again between the same limits while the shutter speed is held at 0.05 seconds. The shutter speed may then be adjusted one or more times while the gain is held at one or more static values. Static values may be predetermined, selected by a user, or determined dynamically by the system upon initiation of a scan. The above examples are not intended to be limiting. In embodiments of the invention, more than two recording attributes may be adjusted simultaneously or independently while other recording attributes are held static. Specifically, a scan may include a third scan range including a third upper limit and a third lower limit. For example, a single scan may adjust shutter speed, gain, and white balance between upper and lower limits. Any combination of increments, selected type and number of recording attributes, upper and lower limits, and independence or simultaneity of adjustments are intended within embodiments of the invention. 
     In embodiments of the invention, representative image captures from a scan may be presented to a user on a display, as illustrated in  FIG.  3   . As discussed below, a user may respond to one or more images presented on the display via touch or through a separate input device to indicate success or failure of the scan and/or select further steps to be performed.  FIG.  3    is intended only as an illustration of a display presented in embodiments of the invention, and is not intended to be limiting. 
       FIG.  4    broadly illustrates steps performed in operation of an embodiment  400  of the invention. These steps may be performed during an event such as a traffic stop, where a video recording of a subject vehicle  200 , 204 , 208  needs to capture a legible image of a license plate  202 , 210 . Prior to step  402 , one or more recording devices  14 , 18  may or may not already be active, recording, and/or storing video data. At step  402 , an indication to begin a scan is provided to the system. As discussed above, this indication to begin may be provided by a user&#39;s manual input or based on one or more sensed trigger parameters. In some embodiments, the indication to begin a scan may activate one or more recording devices  14 , 18  and/or cause them to temporarily or permanently store video data. In response to the received indication, a scan is initiated by the system based on a program stored in memory, user input, and/or sensed parameters. At step  404 , a first recording attribute, such as gain, is adjusted within a first scan range. The first scan range is bound by an upper limit and a lower limit, which may be predetermined, based on sensed parameters, or manually selected by a user. While the first recording attribute is being adjusted, all other recording attributes may be held at selected values. The selected static values for each recording attribute not being adjusted may be predetermined, based on sensed parameters, or manually selected by a user. At step  406 , the first recording attribute is held at a static value while a second recording attribute, such as shutter speed, is adjusted within a second scan range. Again, while the second recording attribute is being adjusted, all other recording attributes may be held at selected values, which again may be predetermined, based on sensed parameters, or manually selected by a user. In embodiments of the invention, these steps may be performed for three or more recording attributes within their respective scan ranges. Further, the adjustment of each recording attribute within their respective scan ranges may alternatively be performed simultaneously, to achieve a faster (though possibly less robust) scan. 
     At step  408 , a determination is made as to whether or not markings on a vehicle, such as those appearing on a license plate, have been legibly captured. In embodiments of the invention, representative frames from a scan may be presented via a display (such as on external computing device  22 ) for confirmation and/or selection by a user. As seen in  FIG.  3   , in embodiments of the invention a display screen  300  is presented to a user with frames  304 ,  306 , and  308  selected from a scan. Frame  304  has the clearest image of the vehicle, but has no legible license plate data as explained in relation to  FIG.  2 B . Frames  306  and  308  have dark, blurry, or otherwise obscured images of the vehicle, but have successfully captured the license plate data needed for identification. A user may respond to these displayed frames  304 , 306 , 308  via touching the screen or use of a separate input device to select one or more that include legible data. For instance, an officer  20  may select frames  306  and  308 , indicating that the license plate  123 XYZ is legible in each of these frames. Next, the officer may tap button  310  in response window  302  to store the selected frames in memory, associated with the video data captured of the traffic stop event. A text recognition program may then extract the data from one or more of the selected frames. At this point, the system proceeds to step  410  in which data from the license plate may be saved, possibly as metadata relating to the captured video data. For instance, the title of the stored video may be appended with the recognized license plate data. Additionally or alternatively, metadata related to the captured video data may include a link to a still image of the license plate data stored in memory. 
       FIG.  3    further includes buttons  312  and  314  in response window  302 , as well as timer  316 . Button  312  may be pressed by an officer  20  to indicate that a scan should be cancelled. This may be of use, for example, in case a traffic stop is uneventful or another officer has already documented the scene. Selection of button  312  may allow a user to rescan the scene if none of the frames  304 , 306 , 308  have legibly captured the license plate data. Selection of Rescan button  312  may initiate a modified scan, as further described below. Finally,  FIG.  3    displays a timer  316 , indicating a remaining amount of time before a timeout occurs. The total amount of time allowed before timeout may be programmed into memory or set by the user. Upon expiration of timer  316 , the system may automatically cancel the scan, rescan, or initiate a modified scan. Alternatively, upon timeout the system may proceed to step  410 , storing all of the displayed frames  304 , 306 , 308  in memory. 
     In other embodiments, step  408  may be performed initially by a computer text recognition algorithm. The algorithm may select representative frames from the scan and extract text from each frame, searching for a string of text that fits the appropriate format of a license plate. Alternatively, the algorithm may run continuously during the scan, and may halt the scan upon recognition of a string of characters in a valid format, such as in a license plate format. Valid formats may be stored in memory. In embodiments of the invention, the computer-recognized screen may be presented to a user along with an image frame from which it was extracted for user confirmation of successful license plate capture. At this point, the system proceeds to step  410  in which data from the license plate may be saved, possibly as metadata relating to the captured video data. 
     As has been described above, computer and/or user determination of successful capture of a legible image of a marking on a vehicle may initiate storage of at least a portion of the scan that includes the legible marking. However, in the event that capture of a legible image is determined to be unsuccessful, the system may perform an additional scan. The additional scan may activate automatically or in response to selection by a user. The additional scan may use recording attributes, scan ranges, and adjustment increments that are identical to those of the prior scan(s). Alternatively, the additional scan may be a modified scan, differing from the prior scan(s) in any or all of these elements. 
     A modified scan may be beneficial in situations with particularly difficult viewing conditions to provide an increased likelihood of capturing a legible image of a marking on a vehicle. The modified scan may simply select one or more different recording attributes for adjustment, such as gain and frame rate rather than white balance and focal distance. The modified scan may adjust the same recording attributes, but choose different upper and/or lower limits, modifying the scan range of one or more of the recording attributes. Modified upper and lower limits may define a larger scan range in a modified scan for a particular recording attribute, and/or may shift the original scan range. A modified scan may alternatively or additionally change the simultaneity of adjustment of recording attributes. For example, if in a previous failed scan, gain and white balance were adjusted within their respective scan ranges simultaneously, in a subsequent modified scan gain may be held at a static value while white balance is adjusted and vice versa. Any or all of the modifications discussed may be employed in a given modified scan, as well as any other modifications not expressly described. 
     While reference has been made above to the various components and techniques of embodiments of the invention, the description that follows will provide further examples systems and processes that may be added in embodiments of the invention. The description below is intended to merely exemplify steps that may be taken in practice of operation of embodiments of the invention and is not intended to be limiting. Further steps that may be performed in practice of some embodiments of the invention are illustrated in  FIGS.  5 A-C  and herein described. 
       FIG.  5 A  begins at step  502 , corresponding to step  402  of  FIG.  4   , in which an indication to begin a scan is provided to the system by a human or computer. The indication may be in response to one or more trigger parameters such as an indication that a police vehicle  16  is parked, a computer detection of a subject car, a detection of a license plate  200 , an activation of a vehicle siren, and an activation of signal lights. At step  504 , the lower and upper limits of the first scan range are determined for a first recording attribute. These limits may be predetermined, selected by a user, or determined dynamically based on sensed parameters such as a sensed light level. At step  506  the system determines whether or not the first recording attribute will be adjusted by uniform increments. If the increments are uniform, the process proceeds to step  508 , at which the system determines whether the size of the uniform increments has been predetermined and stored in memory, or if the size needs to be determined based at least partially on sensed factors. If they are predetermined, the system proceeds to step  510 , adjusting the first recording attribute between the first upper and lower limits using the uniform increments. If sensed factors must be taken into account, the system does so at step  512  before proceeding to the adjustment at step  510 . 
     Returning to step  506 , if the increments of adjustment are not uniform, the process proceeds to step  514 , at which the system determines whether or not the system should perform a continuous sweep through across the scan range. If this determination is yes, the system adjusts the first recording attribute in this way at step  516 . If the determination at step  514  is no, the system adjusts the first recording attribute using a set of predetermined or random non-uniform increments at step  518 . 
     Each of these regimes of adjustment of the first recording attribute converge at step  520 , at which the preceding process (beginning at step  504 ) is performed once again, this time with respect to the second recording attribute. In step  520 , as in step  504 , the system determines the upper and lower limits for the second scan range, corresponding to the second recording attribute. Again in steps  522 ,  524 ,  528  and  530  ( FIG.  5 B ), determinations are made about how the second recording attribute is to be scanned within the second scan range. Each of these determinations are made in the same manner as the decision points at steps  506 ,  508 , and  514 , resulting in adjustment of the second recording attribute at steps  526 ,  528 , or  534 . The determinations made for adjustment of the second recording attribute may or may not be the same as those made for the first recording attribute. For example, the first recording attribute may be gain, adjusted by 1% increments from 50% to 100%, while the second recording attribute, may be white balance, adjusted continuously from the minimum to maximum white balance available to the system. This is meant only as an example, and is not intended to be limiting. Any combination of recording attributes, scan ranges, and scan regimes is intended to be within embodiments of the invention. 
     Specifically, at step  520 , the lower and upper limits of the second scan range are determined for a second recording attribute. These limits may be predetermined, selected by a user, or determined dynamically based on sensed parameters such as a sensed light level. At step  522  the system determines whether or not the second recording attribute will be adjusted by uniform increments. If the increments are uniform, the process proceeds to step  524 , at which the system determines whether the size of the uniform increments has been predetermined and stored in memory, or if the size needs to be determined based at least partially on sensed factors. If they are predetermined, the system proceeds to step  526 , adjusting the second recording attribute between second upper and lower limits using the uniform increments. If sensed factors must be taken into account, the system does so at step  528  before proceeding to the adjustment at step  526 . 
     Returning to step  522 , if the increments of adjustment are not uniform, the process proceeds to step  530 , at which the system determines whether or not the system should perform a continuous sweep across the second scan range. If this determination is yes, the system adjusts the second recording attribute in this way at step  532 . If the determination at step  530  is no, the system adjusts the second recording attribute using a set of predetermined or random non-uniform increments at step  534 . 
     Regardless of the determinations made, all of these regimes of adjustment of the second recording attribute converge at step  536 . At this step the system determines whether or not a third attribute is to be adjusted within a third scan range. If so, the process proceeds through steps  538 ,  540 ,  542 ,  544 ,  546 ,  548 ,  550 , and  552  for determining the method of adjusting the third recording attribute. These steps are performed in the same manner as previously performed for the first and second recording attributes. These steps may be repeated for an arbitrary number of recording attributes, as determined by the system and/or a user. 
     Specifically, at step  538 , the lower and upper limits of the third scan range are determined for a third recording attribute. These limits may be predetermined, selected by a user, or determined dynamically based on sensed parameters such as a sensed light level. At step  540  the system determines whether or not the third recording attribute will be adjusted by uniform increments. If the increments are uniform, the process proceeds to step  542 , at which the system determines whether the size of the uniform increments has been predetermined and stored in memory, or if the size needs to be determined based at least partially on sensed factors. If they are predetermined, the system proceeds to step  544 , adjusting the third recording attribute between the third upper and lower limits using the uniform increments. If sensed factors must be taken into account, the system does so at step  546  before proceeding to the adjustment at step  544 . 
     Returning to step  540 , if the increments of adjustment are not uniform, the process proceeds to step  548 , at which the system determines whether or not the system should perform a continuous sweep across the third scan range. If this determination is yes, the system adjusts the third recording attribute in this way at step  550 . If the determination at step  548  is no, the system adjusts the third recording attribute using a set of predetermined or random non-uniform increments at step  552 . 
     When the final recording attribute has been adjusted (which in the case of  FIG.  5 C  is the third recording attribute) the system proceeds to step  554 , where a determination is made of the legibility of the markings captured by the scan. This may be determined by a user in step  556 . For example, the system may display one or more captured images of markings to a user for confirmation of success. Alternatively, computer text-recognition software may independently determine the success or failure of the scan. Via either approach, if in step  558  the system determines a successful capture of a legible image of markings on a vehicle, a portion of the scan including the markings is stored in memory at step  560 . If, however, in step  558  the system determines an unsuccessful capture of a legible image of markings on a vehicle, the system proceeds to step  562  to determine whether an additional scan should be performed. This step may be performed automatically by the system or in response to user input. Determination of initiation of an additional scan by a user may be subject to a timeout, as described above. If an additional scan is rejected at step  562 , the system quits at step  564 , returning to its initial condition of waiting for an indication to begin a scan. If an additional scan is initiated at step  562 , the system returns to step  502  to repeat the entire process. The additional scan may be identical to the first or may be a modified scan, differing in number or type of recording attributes adjusted, methods of adjustment, and/or scan ranges as described above. 
     It should be appreciated that, while the above disclosure is directed mainly to the field of law enforcement, some embodiments of the invention may be employed for any pursuit requiring legible video capture of information. Embodiments of the invention may be used in any setting or field, such as military or road maintenance vehicles, to maximize the likelihood of capturing a legible image of readable characters using a video camera. In embodiments of the invention, readable characters may be identified from sources other than license plates, such as billboards, street signs, bumper stickers, or apparel. Further, though the description above uses a car as subject vehicle  200 , 204 , 208 , embodiments of the invention could equivalently be employed to identify a subject boat, trailer, motorcycle, etc. Embodiments of the invention may be used by private individuals or businesses to help prevent fraud, identify visitors, or track shipments. The law enforcement field discussed is merely exemplary and should not be construed as limiting.