(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2002/0005895A1
`(43) Pub. Date:
`Jan. 17, 2002
`Freeman et al.
`
`US 2002OOO5895A1
`
`(54) DATA STORAGE WITH OVERWRITE
`(75) Inventors: William T. Freeman, Acton, MA (US);
`William S. YeraZunis, Acton, MA
`(US); Walter A. Hiatt, Waltham, MA
`(US)
`Correspondence Address:
`Dirk Brinkman
`Patent Counsel
`Mitsubishi Electric, ITA
`201 Broadway, 8th Floor
`Cambridge, MA 02139 (US)
`(73) Assignee: Mitsubishi Electric, ITA
`(21) Appl. No.:
`09/947,393
`(22) Filed:
`Sep. 7, 2001
`Related U.S. Application Data
`(63) Continuation of application No. 08/906,493, filed on
`Aug. 5, 1997.
`
`Publication Classification
`
`(51) Int. Cl." ............................... H04N 7/18: H04N 9/47
`(52) U.S. Cl. ............................................ 348/143: 348/149
`
`ABSTRACT
`(57)
`A compact video image recording device for recording video
`images before and after a triggering event and which utilizes
`no moving parts is disclosed. The recording device includes
`at least one camera wherein each camera comprises a lens
`and a Video image Sensor. Each Video image Sensor gener
`ates an electronic Signal representative of a Video image
`impinging the respective Sensor. The output of each image
`Sensor is processed, compressed and generally employed to
`produce frame data which are Successively Stored in a
`Successive frame locations of a Semiconductor memory
`organized as a circular buffer memory. Upon the occurrence
`of a triggering event, a additional frames are Stored in the
`buffer memory and further storage of frames then termi
`nates. A video record is thus created of Video images
`received both before and after the triggering event via a
`device which contains no moving parts and which can
`withstand Substantial shock and vibration.
`
`
`
`

`

`Patent Application Publication
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`Jan. 17, 2002. Sheet 1 of 7
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`US 2002/0005895 A1
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`Patent Application Publication Jan. 17, 2002 Sheet 2 of 7
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`16
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`26
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`-66
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`Patent Application Publication Jan. 17, 2002. Sheet 3 of 7
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`US 2002/0005895 A1
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`102
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`104
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`Patent Application Publication Jan. 17, 2002. Sheet 4 of 7
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`US 2002/0005895 A1
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`120
`
`124
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`136
`Yes -
`Employ Modified
`Frane Rate
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`132
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`No
`138
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`

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`Patent Application Publication Jan. 17, 2002. Sheet 5 of 7
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`US 2002/0005895 A1
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`Patent Application Publication Jan. 17, 2002 Sheet 6 of 7
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`US 2002/0005895 A1
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`Patent Application Publication
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`Jan. 17, 2002. Sheet 7 of 7
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`US 2002/0005895 A1
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`

`US 2002/0005895 A1
`
`Jan. 17, 2002
`
`DATA STORAGE WITH OVERWRITE
`
`GOVERNMENTAL RIGHTS
`0001. Not Applicable
`
`RELATED APPLICATIONS
`0002) Not Applicable
`
`BACKGROUND OF THE INVENTION
`0003. The present invention relates to video recording
`devices and more particularly to a Video camera which
`Stores Successive frames in at least one circular buffer
`memory and which may continue to Store frames for a period
`following the occurrence of a triggering event.
`0004 Numerous applications exist in which it is desirable
`to retain a Video record for evidentiary or historical pur
`poses. For example, in an automobile, or on a bicycle or
`motorcycle, it would be desirable to record a video image of
`the circumstances existing immediately prior to an accident
`after an accident. Additionally, in Security applications, it
`would be highly desirable to be able to record a video image
`of the circumstances existing immediately prior to an event
`triggering an alert condition and following the triggering of
`Such a condition. Additionally, in numerous other applica
`tions it would be desirable to be able to create a video record
`of circumstances existing both before and after a triggering
`eVent.
`0005. A number of image recording devices are well
`known in the art. In time lapse photography a series of still
`pictures are taken over a period of time. Such pictures are
`typically taken with a periodically actuated Still or a motion
`picture camera and employ photographic film. The cameras
`are loaded with a limited Supply of film and the camera must
`be reloaded when the Supply of film is exhausted. Accord
`ingly, Such devices are not well Suited for applications in
`which it is desired to record images over a long period of
`time when only a very Short period of time is of interest and
`the particular period of interest cannot be predicted.
`0006. In security applications, a video camera is often
`employed to record a Video image on magnetic tape on a
`continuous basis. When the tape is exhausted it must be
`replaced.
`0007 Both photographic cameras employing photo
`graphic film and Video cameras utilizing magnetic tape as
`the recording media employ mechanical transport mecha
`nisms which are Susceptible to failure when Subjected to
`Shock and vibration. Accordingly, Such devices are ill Suited
`for use in applications and environments in which shock and
`vibration are the norm.
`0008 For the above reasons, a video recording device
`would be desirable which could record video frames on a
`continuing basis and capture a video record of circumstances
`Surrounding a triggering event occurring at an unpredictable
`time. It would further be desirable for Such a device to be
`compact, lightweight, cost effective and avoid the aforemen
`tioned deficiencies of prior art Video recording devices
`employing mechanical transports.
`
`SUMMARY OF THE INVENTION
`0009. In accordance with the present invention, a video
`recording device is disclosed which is contained within a
`
`compactly sized housing. One or more video image Sensors
`are mounted to the housing. Alternatively, one or more Video
`image Sensors are provided which are electrically coupled to
`the housing via wires So as to permit the image viewing area
`to be Selected freely via Suitable mounting of the Sensors by
`a user. The Video recording device records Video frames
`Successively in at least one circular buffer memory orga
`nized as a continuous loop overwriting the oldest frame
`within the respective buffer memory with a more recently
`received frame. Upon receipt of a triggering event, a pre
`determined number of additional frames are recorded within
`the circular buffer memory at which point recording ceases.
`A plurality of circular memory buffer groups may be pro
`vided to extend the overall recording time for the device by
`Selectively storing video data Samples to the respective
`buffer groups. The foregoing Video recording device can be
`fabricated as a compact transportable unit which employs no
`moving parts and which has relatively low power consump
`tion facilitating battery operation in certain embodiments.
`0010 More specifically, a video camera is provided
`which compares a lens and a video image Sensor. The lens
`is employed to focus a video image on a Video image Sensor
`Such as a charge coupled device Sensor or an artificial retina
`as hereinafter discussed. The output of the Video image
`Sensor comprises an analog signal which is coupled to one
`or more A/D converters. The A/D converter(s) is sampled to
`generate a digital representation of the Video image Sensor
`analog output signal. A predetermined number of digital
`Samples comprise one video frame. The digitized output
`Signal(s) from the A/D converter(s) is coupled to a central
`controller in the form of a microprocessor or any other
`Suitable controller. The microprocessor compresses the digi
`tized frame data and Stores the compressed frame data in the
`next Sequential location of the circular buffer. In one
`embodiment, the digitized frame data is encrypted prior to
`Storing the same in the buffer So as to prevent unauthorized
`access to Such data. The circular frame buffer comprises a
`semiconductor memory such as DRAM or any other suitable
`high Speed Semiconductor memory.
`0011. Upon detection of a trigger event, the video record
`ing device records a predetermined number of additional
`frames and then ceases to record further frame data. In this
`manner, a video event record is obtained which commences
`prior to the triggering event and extends in time after the
`triggering event. Triggering events may include an acceler
`ometer output Signal crossing a predetermined threshold, a
`Signal employed to initiate air bag deployment in an auto
`mobile, a signal representing a recognized change in a video
`image or acoustic Signal, a Signal indicative of a Security or
`fire alarm condition, a button actuated by a user, or any other
`Suitable activation Signal known in the art. Further, an
`activation button is provided which permits a user to take a
`single frame “snapshot” which is retained within the buffer
`memory until purged upon user activation of a purge button.
`0012. A serial output channel is provided to permit
`recorded frame data to be downloaded to a computer for
`Viewing.
`0013 The above described apparatus thus provides a
`Video recording device which has high reliability, is com
`pact, cost effective and Suitable both for consumer and
`commercial applications.
`
`

`

`US 2002/0005895 A1
`
`Jan. 17, 2002
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`0.014. The invention will be more fully understood by
`reference to the following Detailed Description of the Inven
`tion in conjunction with the drawings of which:
`0.015
`FIG. 1 is a pictorial view illustrating an application
`for use of the Video recording device of the present inven
`tion;
`0016 FIG.2a is a pictorial view of a housing for a video
`recording device in accordance with the present invention in
`which a camera comprising a lens and image Sensor is
`mounted within the housing;
`0017 FIG. 2b is a pictorial view of an alternative
`embodiment of a housing for the Video recording device of
`FIG. 1 in which the camera is disposed external to the
`housing and in electrical communication with Video pro
`cessing circuity (not shown) disposed within the housing;
`0.018
`FIG. 3 is an electrical block diagram of a video
`recording device in accordance with the present invention;
`0.019
`FIG. 4a is a simplified schematic representation of
`a circular memory buffer employed within the video record
`ing device of FIG. 3;
`0020 FIG. 4b is a representation of a semiconductor
`memory buffer employed in the Video recording device of
`FIG. 3 to implement a circular memory buffer and associ
`ated head and tail pointers,
`0021
`FIG. 5 is a flowchart illustrating the recording
`method in accordance with the present invention;
`0022 Pig. 6 is a table illustrating one storage technique
`for Storage of Video data in the Semiconductor memory
`buffer;
`0023 FIG. 7 is a table illustrating an alternative storage
`technique for Storage of Video data in the Semiconductor
`memory buffer; and
`0024 FIG. 8 is a table illustrating a further alternative
`Storage technique for Storage of Video data in the Semicon
`ductor memory buffer.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`0.025. An application of a video recording device 2 in
`accordance with the present invention is illustrated in FIG.
`1. The recording device 2 is mounted within a first vehicle
`4 which has come to a stop behind a Second vehicle 6 at an
`interSection. Vehicle 6 has also come to a stop at the
`interSection, however, has backed up So as to impact vehicle
`2 causing damage to vehicle 4. It would be highly desirable
`for the driver of vehicle 4 to have an evidentiary record
`which establishes that the accident was caused by vehicle 6
`Since it would normally be presumed in Such a circumstance
`that the driver of vehicle 4 was the cause of the accident. The
`Video recording device 2 in accordance with the present
`invention generates Such a record by continually recording
`Video frames in a circular buffer at a predetermined frame
`rate. In response to a trigger event, Such as an air bag
`activation signal or a button activated by the driver, the
`Video recording device records a predetermined number of
`additional frames before ceasing to record further frames. In
`the foregoing manner, the driver of vehicle 4 can establish
`
`the true cause of the accident. The foregoing example is
`provided Solely as an illustration of the operation of the
`Video recording device 2 of the present invention.
`0026. A housing 10 for a video recording device 2 in
`accordance with the present invention is depicted in FIG.
`2a. The housing 10 includes a camera comprising a lens 12
`and a video image Sensor (not shown) which may comprise
`a charge coupled device (CCD), an artificial retina, or any
`other Suitable optical Sensor operative to provide output
`Signals when a Video image impinges the Sensor. By way of
`illustration, the sensor may comprise a model TC241 CCD
`array manufactured by Texas Instruments or an artificial
`retina Such as identified and described volume 372, number
`197 NATURE, 1994 which is incorporated herein by refer
`ence. The lens 12 is Specified to have appropriate optical
`characteristics and is oriented So as to focus a Video image
`of the desired field of view on the video image sensor. While
`the housing of FIG.2a illustrates the use of a Single camera,
`multiple cameras may be employed and Selectively oriented
`to capture images at desired viewing angles. For example,
`one camera may be positioned at the forward edge 14 of the
`housing 10 and a Second camera at the trailing edge 16 of the
`housing 10 to capture images at 180° viewing angles.
`Additionally, by way of example, cameras may be disposed
`on the leading edge 14 and a side edge 17 of the housing 10
`So as to capture Video imageS along orthogonal viewing
`angles. It is further understood that any desired number of
`cameras may be employed.
`0027. Another embodiment of a video recording device
`assembly in accordance with the present invention is
`depicted in FIG.2b. The I video recording device illustrated
`in FIG.2b includes a housing 18 and a camera 20 which is
`disposed external to the housing 18. The lens 22 focuses a
`Video image on the Sensor 24 which, in the preferred
`embodiment, produces an electrical output Signal for com
`munication to a Video signal processor. The Sensor 24
`communicates the electrical output signal via wires 26 to the
`Video signal processor disposed within the housing 18. The
`wires 26 may be coupled to the circuitry (not shown) via a
`connector or alternatively may be hardwired to Such cir
`cuitry. While a Single video image Sensor 20 is depicted in
`FIG. 2b, as with respect to FIG. 2a, the video recording
`device in accordance with the present invention may employ
`multiple cameras 20 which may be selectively mounted and
`positioned at desired Viewing angles So as to permit a
`corresponding number of Video images to be captured.
`0028. The housings illustrated in FIGS. 2a and 2b may
`be fabricated in a PCMCIA configuration with a PCMCIA
`connector disposed at one end So as to permit the housing to
`be inserted into a laptop computer or any other Suitable
`computer having a PCMCIA interface to permit viewing of
`images captured within the Video recording device.
`0029. A block diagram of the video recording device in
`accordance with the present invention is depicted in FIG. 3.
`As illustrated in FIG. 3, the recording device includes a
`camera 40 and video electronics 42. The camera 40 is
`comprised of a lens 44 which is disposed a predetermined
`distance d from the Surface of an image Sensor 46. The
`image Sensor 46, as described above, may comprise a charge
`couple device array, an artificial retina, or any other Suitable
`image Sensor operative to provide an output signal repre
`Sentative of a Video image which impinges upon the Sensor.
`
`

`

`US 2002/0005895 A1
`
`Jan. 17, 2002
`
`In a preferred embodiment employing a CCD array as the
`Sensor 46, the CCD array produces an analog output Signal
`which in electrically coupled to an analog to digital con
`verter 48 via a signal path 50. The analog to digital converter
`may comprise a model AD 775 A to D converter manufac
`tured by Analog Devices, Inc. or any other Suitable analog
`to digital converter. Support electronicS 52 are provided
`which include a clock generator which is coupled to the
`analog to digital converter 48 to permit the sensor output 50
`to be sampled at predetermined intervals and other conven
`tional timing circuitry. The analog to digital convertor 48
`generates a digital representation of the Sensor output signal
`50. A predetermined number of samples of the sensor output
`Signal 50 comprise a single Video frame. For example, in one
`exemplary embodiment, each frame contains 256 horizontal
`Samples by 128 vertical Samples yielding an uncompressed
`size of 32,768 bytes. Sixty four such frames can be stored in
`a two (2) megabyte memory.
`0030 Generally, color images require approximately
`thirty (30) percent more storage space. One could thus tore
`approximately fifty (50) frames of uncompressed color
`image information in the two (2) megabyte memory.
`0.031) For images of the above identified sizes a com
`pression ratio of four to one (4:1) is readily achievable. Such
`would permit 256 black and white images or 200 color
`images to be stored in the two (2) megabyte memory. At a
`recording rate of ten (10) frames per Second, the two (2)
`megabyte memory will accommodate thus accommodate 25
`Seconds of black and white images or 20 Seconds of color
`images. A greater recording interval may be achieved by
`employing a lower Sampling rate or by utilizing a larger
`memory.
`0.032 The output of the analog to digital converter is
`electrically coupled to inputs of a central control processor
`54 via Signal path 56 which comprises a parallel Signal bus.
`The central control processor 54 in a preferred embodiment,
`may comprise an M32RD microprocessor which is com
`mercially available from Mitsubishi Electric, any other
`Suitable microprocessor, an Application Specific Integrated
`Circuit (ASIC) or any other suitable implementation of a
`central control processor operative to perform the presently
`described functions.
`0033. The central control processor 54 is coupled to a
`semiconductor memory 58 which comprises a DRAM a in
`preferred embodiment. Within the M32RD device refer
`enced above, two (2) megabytes of DRAM is incorporated
`in the commercially available device. Thus the micropro
`cessor 54 and the DRAM 58 may be obtained as a single
`integrated circuit. Additional Semiconductor memory 60
`may be coupled to the microprocessor 54 via a bus 62 in the
`event that it is desired to increase the Semiconductor
`memory capacity of the Video recording device. It may be
`desired to increase the memory capacity of the recording
`device to permit a greater number of frames to be captured
`or to accommodate the Storage of Video images received
`from plural cameras.
`0034. The central control processor 54 executes a control
`program which is stored within a Read Only Memory
`(ROM). The ROM 64 is coupled to the central control
`processor via bus 66. The central control processor 54 is
`provided with a number of inputs 68 which permit activation
`of the video recording device and control of the device by a
`
`user. Exemplary inputs comprise, an event Sensor 70, a
`“capture” button 72, a “still button 74 and a “purge” button
`76.
`0035). Additionally, the central control processor 54
`includes a serial output channel 78 which permits stored
`Video images to be downloaded to an external video device
`for viewing. In one embodiment, the Serial output channel is
`compatible with the well known Xmodem serial protocol. It
`is appreciated that any Suitable Serial channel protocol may
`be employed.
`0036) The central control processor 54 receives succes
`Sive Samples of frame data from the analog to digital
`converter 48 and compresses the received frame data in
`order to reduce the Storage capacity for the captured video
`data. One image compression technique which may be
`employed is disclosed in U.S. Pat. No. 4,917,812 to Adelson
`and Simoncelli. While any Suitable compression technique
`may be employed, in a preferred embodiment of the inven
`tion, an asymmetric compression technique (known in the
`art) is used which minimizes the computational load on the
`central control processor to compress the image data during
`compression of the image data at the expense of greater
`complexity in the decompression algorithm. The use of an
`asymmetric compression technique thus places greater pro
`cessing demands on the processor which will ultimately
`perform the decompression which, is likely to comprise a
`personal computer (PC), a workstation, or Some other com
`puter which generally possesses the necessary processing
`Speed to perform Such decompression or which is not
`burdened by the constraint of real time processing. In this
`manner, the video electronics 42 are not burdened with
`additional cost associated with added processing power.
`0037 Following the compression of the frame data, the
`central control processor Stores the compressed data within
`the semiconductor memory 58. The semiconductor memory
`58 is structured as a circular memory buffer as illustrated in
`FIG. 4a. Thus, following compression, each compressed
`video frame is stored in the next Successive frame buffer
`location and any frame data continued in Such location is
`overwritten. For example, referring to FIG. 4a, if the last
`frame were stored at location 3 of the circular buffer 90, the
`Subsequent video frame would be stored at location 4 of the
`circular frame buffer. The video recording device, absent
`receipt of Some trigger event from the Sensor 54 or activation
`of other input by the user, continues to Store captured frame
`data in Successive locations of the circular buffer, overwrit
`ing previously received frame data Stored in respective
`buffer locations with the most recently received frame data.
`0038. The operation of the circular buffer is described
`with more particularity below and with respect to FIG. 4b.
`The Semiconductor memory buffer is sized to as to permit
`the desired number of frames to be concurrently stored in the
`buffer. The buffer 100 utilizes a plurality of bytes to store
`each frame as illustrated in frame buffer locations 0 and n.
`The Specific number of bytes required for a particular frame
`is dependent upon the resolution of the Video image Sensor
`46, the Sampling rate of the analog to digital converter 48,
`and the efficiency of the compression algorithm.
`0039 Associated with the semiconductor memory buffer
`58 (and additional buffer memory 60 if such is employed)
`are a tail pointer 102 and a head pointer 104. The head
`pointer points to the address of the frame buffer location for
`
`

`

`US 2002/0005895 A1
`
`Jan. 17, 2002
`
`Storage of the next frame data. Such address is offset in the
`respective frame to address the respective byte for the frame
`data being Stored. For Simplicity, the operation of the buffer
`is explained with respect to the frame addresses recognizing
`that plural locations are utilized within the buffer to store the
`data associated with any given frame.
`0040. The head pointer 104 points to the location for
`Storage of the incoming frame data. Thus, if the next frame
`data is to be Stored in location 4, the head pointer is set to
`location 4. Once all of the data corresponding to frame 4 has
`been Stored in the buffer, in normal operation and in the
`absence of a trigger event, the head pointer is incremented
`to point to frame number 5. AS an example, assume a
`semiconductor memory buffer 58 is employed in which
`n=127; i.e. the frame buffer is capable of storing 128 frames
`of data. It is further assumed for purposes of the present
`example that it is desired to have half of the captured frames
`precede the trigger event and half of the frames follow the
`trigger event. The head pointer 104 is incremented following
`the Storing of each respective frame. In normal operation,
`the tail pointer is incremented each time the head pointer is
`incremented, however, the tail pointer comprises an address
`which lags the head pointer by Sixty four. In the circular
`buffer frame address 0 follows frame address n (i.e. 127 in
`the present example).
`0041. Upon detection of a trigger event, the tail pointer
`ceases to increment while frames continue to be Stored in
`Subsequent frame locations. A test is performed prior to
`Storing frame data to determine whether the frame location
`for the data to be stored is one location preceding the tail
`pointer in which case the frame data pertaining to that frame
`is Stored. No Subsequent frames are Stored in the frame
`buffer. Thus, following the trigger event, the buffer contains
`frame data commencing at a location Z and ending at a
`location Z-1, i.e. if the tail pointer Stopped incrementing
`upon detection of a trigger event when pointing to address
`6, the last captured Video image would be Stored in location
`5 and further image capture and Storage would cease.
`0042. The sensor 54 may comprise any sensor which
`provides a trigger output Signal in response to a condition
`which is desired to initiate the capture of the Video image or
`images occurring prior to and following the occurrence of
`the trigger output Signal, For example, the Sensor may
`comprise an accelerometer, an airbag deployment Sensor of
`the type normally used in automobiles to initiate the deploy
`ment of an air-bag, a Security or fire alarm alert condition
`Sensor used to detect movement, glass breakage, unautho
`rized entry Such as found in a burglar alarm for example fire
`or Smoke, an acoustic Signal characteristic of a Specific event
`Such as gunshots, or any other signal indicative of a Specified
`event. Moreover, while a single sensor 70 is illustrated for
`Simplicity, it should be appreciated that plural Sensors may
`be employed to activate the capture of Video images by the
`present Video recording device and that Video image capture
`may be initiated by any one of Such Sensors or a combination
`of Such Sensors.
`0043. Upon detection of a trigger event from the sensor
`70, the central control processor 54 receives only a prede
`termined number of additional frames and Stores Such
`frames in the semiconductor memory 58 in the successive
`frame locations within the circular buffer 90. Following the
`recording of the predetermined number of additional frames,
`
`the Video recording devices ceases to record further frame
`data. Thus, if the central controller is programmed to record
`half the number of frames which are capable of being stored
`within the semiconductor memory 58 or 58 and 60, as
`applicable, the Video frame data Stored within the circular
`buffer corresponds to an equal number of Video frames
`captured prior to the trigger event and after the trigger event.
`It is appreciated that any desired percentage of frames may
`be captured prior to or after the trigger event by Specifying
`how many frames are to be captured and Stored after the
`trigger event.
`0044) In one preferred embodiment, it is envisioned that
`the Semiconductor memory will Support the Storage of 5
`frames of Video data per Second for approximately 30
`Seconds. Thus, the memory will Support the Storage of
`approximately 150 video frames. If it is desired to record the
`same number of frames before and after detection of a
`trigger event from sensor 70, seventy five additional frames
`would be recorded and stored in the circular buffer 90
`Subsequent to the detection of the trigger event. It should be
`appreciated that the number of frames that are recorded
`before and after are a matter of design choice, the only
`limitation being that the total number of frames to be
`recorded not exceed the frame capacity of the Semiconductor
`memory. Thus, in the above example in which the video
`electronics include DRAM Supporting storage of 150 video
`frames, if it was desired to obtain a record which provided
`ten percent of the frame data prior to the trigger event and
`ninety percent of the frame data following the trigger event,
`an additional 135 frames would be recorded and stored
`Subsequent to the trigger event.
`0045 Referring again to FIG. 3, the video electronics 42
`and sensor 46 are powered by a DC regulator which may
`derive input power from an AC Source, when Such is
`available, from a vehicle battery, or from batteries Such as
`AA cells or any other suitable batteries. When powered by
`a vehicle battery, it is recognized that in the event of an
`accident or in Some cases, when the vehicle is turned off, the
`vehicle battery power may cease to provide power. In Such
`event, the battery cells provide an alternative Source of
`power to permit the buffers 58 and 60 to be periodically
`refreshed (should DRAMs be employed), Since the refresh
`current is extremely low for DRAMs, the data captured
`within the buffer may be maintained for many weeks before
`the captured Video data is lost. It is estimated that two or four
`AA cells will Support full operation of the Video recording
`device for between two and five hours of recording opera
`tion thus permitting fully portable operation of the unit on,
`for example, a bicycle or in any other application in a steady
`Source of power is not readily available, at a minimal cost in
`added weight. It is also estimated that two (2) to (4) AA
`battery cells will maintain the contents within memory for
`between one (1) and (4) months.
`0046) The video recording device is provided with a
`capture button 72 which Serves as a user activatable trigger
`event. Thus, a user of the device may initiate video capture
`by pushing the capture button 72. Upon activation of the
`capture button, a trigger Signal is provided to an detected by
`the central control processor 54. The operation of the video
`electronicS 42 upon user activation of the capture button 72
`is otherwise as described with respect to the occurrence of
`a trigger event in response to a trigger signal provided by the
`Sensor 70.
`
`

`

`US 2002/0005895 A1
`
`Jan. 17, 2002
`
`0047. The still button 74 is optionally provided and
`coupled to the central control processor 54. Upon activation
`of the Still button, the Video electronics captures a video
`frame and stores the frame within the buffer memory 58 or
`the extended buffer memory 60. In one embodiment, a frame
`which is stored as a result of the activation of the still button
`74 is stored in a protected memory buffer area which is not
`employed as a part of the circular buffer 90. In another
`embodiment of the Video recording device, the captured
`frame is Stored within a frame location within the circular
`buffer, however, the frame is protected from overwriting
`while video capture within the circular buffer continues.
`Such may be accomplished via tagging protected frame
`locations containing captured Still frames and checking to
`determine whether a frame location is protected prior to
`writing to the frame location. Alternatively, a “still frame
`may be Stored at the upper, lower or Some other designated
`portion end of the circular buffer and the head and tail
`pointers controlled So as not to result in the overwriting of
`the “still frame.
`0.048. The