(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2002/0191952 A1
`(43) Pub. Date:
`Dec. 19, 2002
`Fiore et al.
`
`US 2002O191952A1
`
`(54) DATA RECORDING AND PLAYBACK
`SYSTEMAND METHOD
`(75) Inventors: John T. Fiore, Derwood, MD (US); K.
`Stephen Book, Fairfax, VA (US);
`Wayne L. Kilmer, Sartell, MN (US)
`Correspondence Address:
`NIXON PEABODY, LLP
`8180 GREENSBORO DRIVE
`SUTE 800
`MCLEAN, VA 22102 (US)
`(73) Assignee: Monitoring Technology Corporation,
`Fairfax, VA
`(21) Appl. No.:
`10/118,311
`(22) Filed:
`Apr. 9, 2002
`Related U.S. Application Data
`(60) Provisional application No. 60/282,162, filed on Apr.
`9, 2001.
`
`Publication Classification
`
`(51) Int. Cl." ..................................................... H04N 5/781
`(52) U.S. Cl. .............................................. 386/46; 386/125
`
`(57)
`
`ABSTRACT
`
`A data recording and playback System and method with a
`memory device adapted to receive and temporarily Store
`input signal data as data frames with time Stamps, the
`memory device having addresses associated thereto, and a
`circular Storage buffer having a memory mapped file with
`Same address Space as the memory device for Storing the
`input signal data. In one embodiment, an event controller
`provides an event Signal associated to time of an event, and
`an event processor is provided that copies plurality of data
`frames Stored in the circular Storage buffer that have time
`Stamps proximate to the time of the event. Another embodi
`ment is adapted to allow playback of Stored input signal data
`from the circular Storage buffer without interrupting Simul
`taneous recording of new input signal data into the circular
`Storage buffer.
`
`
`
`

`

`Patent Application Publication Dec. 19, 2002 Sheet 1 of 8
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`US 2002/0191952 A1
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`Signal Control
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`ralyzer
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`Storage A.
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`7
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`Circular
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`Patent Application Publication Dec. 19, 2002 Sheet 2 of 8
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`US 2002/0191952 A1
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`2
`t
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`2O
`24 M
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`Access
`Control
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`34-
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`33.
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`B2
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`Client
`Circular
`Storage
`Control
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`User
`Playback
`Control
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`37
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`3 6
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`Network
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`Patent Application Publication Dec. 19, 2002 Sheet 3 of 8
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`US 2002/0191952 A1
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`50
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`Compression
`On 2
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`Compress
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`Analyze
`incompressed 2
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`o
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`Compressed
`Signal Data
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`Analyze
`Uncompressed
`Signal Data
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`Add Timestamp, and
`Analysis Data to
`Signal Data
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`Add Signal Data to
`Circular Buffer
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`

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`Patent Application Publication Dec. 19, 2002 Sheet 4 of 8
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`US 2002/0191952 A1
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`Playback
`Window
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`Event position
`indicator
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`73
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`Patent Application Publication Dec. 19, 2002 Sheet 5 of 8
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`US 2002/0191952 A1
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`Connect to
`Circular Buffer
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`Get requested
`buffer position
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`Real-time
`position?
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`/ O
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`1H
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`14)
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`Get newest
`data
`in
`buffer
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`Gettime of requested
`position and get data
`nearest to this
`time
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`Get oldest data
`in buffer
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`ls data
`gompressed?
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`yes
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`DeCOmDress
`p
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`Also
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`Display signal
`and analysis
`data
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`Requested
`position in
`eattime mode
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`Has user
`requested a new
`position?
`/56
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`Patent Application Publication Dec. 19, 2002 Sheet 6 of 8
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`US 2002/0191952 A1
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`/08
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`Y
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`/o
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`Maximum Frame Index
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`Last frame in buffer
`Space allocated for largest frame size
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`...
`Format 128
`Frame 1 Header: Time Stamp
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`...
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`Frame 1 Header: Offset
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`Frame 1 Header: Size
`Frame 1: Frane Data
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`Offset from frame virtual memory page
`boundary to data header
`Size of the data block
`Data block
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`Framen Header Time Stamp
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`Framen Header: Size
`Framen: Frame Data
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`Patent Application Publication Dec. 19, 2002 Sheet 7 of 8
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`US 2002/0191952 A1
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`Client MMBuffer Winw
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`A82
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`Biskrive
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`isk drive N.
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`Data
`Page
`Request
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`Mapped
`View
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`Wiew
`(Frame)
`Mapped
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`/2O
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`Composed of i-P
`pages of data
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`Cient
`Wiewer
`Task
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`A3 O
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`Patent Application Publication Dec. 19, 2002 Sheet 8 of 8
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`US 2002/0191952 A1
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`Signal Control
`Digitizer
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`Compressor
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`Storage t
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`Control
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`Fig. I).
`
`

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`US 2002/0191952 A1
`
`Dec. 19, 2002
`
`DATA RECORDING AND PLAYBACK SYSTEM
`AND METHOD
`0001. This application claims priority to U.S. Provisional
`Application No. 60/282,162 filed Apr. 9, 2001, the contents
`of which are incorporated herein by reference.
`
`BACKGROUND OF THE INVENTION
`0002) 1. Field of the Invention
`0003. The invention generally relates to a data recording
`and playback Systems for monitoring processes or occur
`rences of events which allows the replay and/or analysis of
`a time Sampled signal.
`0004 2. Description of Related Art
`0005. Event recording and playback devices used to
`monitor and record events typically fall into one of two
`types. VCR and tape recording type devices permit the
`recording of a Video and/or other Signal and allows later
`playback of these signals. Other recording and playback
`devices utilize a circular Storage buffer during recording in
`which recent data over-writes the older data. For instance,
`U.S. Pat. No. 6,035,367 to Laws discloses a computer file
`System having looped file Structure for data collection of
`asynchronous events. Thus, Laws reference describes a
`System that records to a circular Storage buffer. However, the
`System described in Laws terminates recording when a
`predetermined event occurs.
`0006 Other known devices for event recording and play
`back maintain a circular storage buffer of recorded signal in
`the manner described above and respond to an event or a
`trigger by transferring the contents of the circular Storage
`buffer to an intermediate Storage location based on prede
`termined pre-trigger and post-trigger times. U.S. Pat. No.
`6,136,338 to Johnson, et al., U.S. Pat. No. 5,845,240 to
`Fielder, and U.S. Pat. No. 5,821,990 to Rudt, et al. each
`describe Such event recording and playback Systems that
`utilize a circular Storage buffer which either Stops recording
`upon the occurrence of an event, or extracts the data related
`to the event and Stores the data at an intermediate Storage
`location as a plurality of Sequential files, each file containing
`a very Small time duration. After the data related to the event
`is extracted and Stored, playback of the recorded data is
`made possible by retrieving the Stored data from the inter
`mediate Storage location. However, these technologies do
`not allow Simultaneous recording and playback of these
`Signals.
`0007. The recording of data signals using circular storage
`buffers are also known in consumer electronics products as
`well. Such known consumer products include devices manu
`factured by TiVo(R) and ReplayTV(R) which are designed to
`record broadcast video. Such devices have a live TV mode
`in which they simultaneously record and playback television
`broadcasts from a circular storage buffer. U.S. Pat. No.
`5,701,383 to Russo, et al., and U.S. Pat. No. 5,371,551 to
`Logan et al. describe Such consumer television type Systems.
`In particular, Logan et al. discloses a time delayed digital
`Video system that utilize concurrent recording and playback
`that is implemented by a Subsystem digital memory where
`Semiconductor RAM memory and a disk memory are oper
`ated by a microprocessor Such that incoming Signals are
`constantly recorded as received while, at the same time,
`delayed Signals are being read from the memory Subsystem
`
`at a different memory location Selected by the microproces
`Sor to provide a user-Selected time delay.
`0008 However, the technology used in the above
`described consumer devices do not interface to external
`events. In other words, these consumer devices are not
`asSociated to a triggering event but are merely operated to
`begin collection of data at a particular time. In addition, Such
`time delaying consumer Systems are implemented utilizing
`proprietary hardware architectures and internal program
`ming. Consequently, the known consumer devices cannot be
`readily used to monitor external events and to record and
`playback Such monitored events.
`0009 Furthermore, such proprietary hardware architec
`tures and internal programming are not readily transferable
`to event recording and playback devices described above
`which are typically implemented using a programmable
`computer Such as personal computers, Servers, or the like. In
`particular, it is desirable to provide an event recording and
`playback System that is flexible enough to be readily adapted
`for application in different environments and to receive
`information from a variety of monitoring Sensors. For
`instance, depending on the particular application, variety of
`Sensors Such as vision cameras, audio Sensors, vibration
`Sensors, thermal Sensors, and the like may be used, indi
`vidually, or in combination. Therefore, a computer based
`implementation of the event recording and playback devices
`is desirable Since Such computers provide the flexibility to
`be adapted for various applications.
`0010 Current computer based video recording and play
`back Systems. Such as those Suggested in the reference Rudt
`et al. and Fielder have significant limitations and disadvan
`tages in that the event data captured and Stored in the
`intermediate Storage location cannot be easily viewed. Each
`of the plurality of files Stored in the intermediate Storage
`must be retrieved and viewed. Alternatively, two or more of
`the files may be retrieved and combined to provide a more
`continuous playback of a longer time interval. However, it
`is often desirable for the user of the event recording and
`playback device to quickly view or otherwise access the
`Stored data for a Segment of time monitored, and to quickly
`move on to another Segment of time monitored. Having to
`retrieve one or more of the plurality of files that are stored
`in the intermediate Storage location, and/or to compile a
`plurality of files is cumberSome and time consuming.
`0011. Therefore, there exists an unfulfilled need for a data
`recording and playback System for monitoring processes or
`occurrences of events which avoids the disadvantages of the
`prior art. In particular, there exists an unfulfilled need for
`Such a data recording and playback System that allows easy
`and rapid viewing of the recorded data.
`
`SUMMARY OF THE INVENTION
`0012. In addition to the above discussed disadvantages,
`in evaluating computer based data recording and playback
`Systems, the present inventors have realized that Such prior
`art Systems yielded temporal and Video resolutions which
`are inadequate to observe real-time processes and/or events
`which often occur instantaneously and intermittently. In
`particular, many monitored events may occur in less than a
`200 millisecond time interval over a prolonged interval of
`many hours. However, the present inventors uncovered that
`if there are other instructions being executed by the proces
`
`

`

`US 2002/0191952 A1
`
`Dec. 19, 2002
`
`Sor of the computer at that particular instant in time when the
`event occurs, or if the computer's bus causes even an
`instantaneous delay in transferring the required instructions,
`the event may not be captured by the data recording and
`playback System. This limitation is manifested as “dropped
`frames' which are frames of real-time data which have not
`been captured and Stored into the circular Storage buffer.
`Because dropped frames are not recorded, Such frames are
`lost forever and thus, processes or events which occurred
`during the dropped frames cannot be retrieved at a later time
`resulting in the loSS of potentially very critical data.
`0013 The present inventors have found that typical rea
`Sons for dropped frames in computer implemented data
`recording and playback Systems are inadequate disk band
`width, and multi-tasking operating System time Slice Star
`Vation. In Such situations, the task which enters the frames
`into the buffer cannot accept the next frame from the
`digitized video input before the next frame arrives. It has
`been found that limitations on disk file size, multi tasking,
`and file access times all limit both the resolution and
`duration of the circular Storage buffer that can be maintained
`while minimizing dropped frames.
`0.014.
`In addition, the present inventors found that the
`previously discussed limitations and disadvantages of prior
`art data recording and playback Systems in which plurality
`of files Stored in the intermediate Storage location must be
`retrieved and/or compiled exacerbates the likelihood that
`there will be additional dropped frames when the data
`recording and playback System is implemented via a com
`puter. More specifically, as the operator retrieves and/or
`compiles the files Stored in the intermediate Storage location,
`the resources of the processor and the bus of the computer
`become occupied and likelihood of delayS in executing
`instructions to record and Store the data into the intermediate
`Storage location increases thereby resulting in the increased
`likelihood of dropped frames.
`0.015 Thus, in the prior art data recording and playback
`Systems, processor, buS Speeds, and design do not provide
`enough reliability in execution of Such instructions and
`delays, and correspondingly, dropped frames, become inevi
`table if the resources of the computer implemented data
`recording and playback System is at all diverted during data
`recording. This effectively precludes the operator of the data
`recording and playback System from Viewing the Stored data
`at the same time as when data is being recorded.
`0016. Therefore, there exists a further need for a data
`recording and playback System that also allows the analysis
`and/or replay of a time Sampled Signal while minimizing the
`likelihood of dropped frames.
`0.017. In view of the above, one advantage of the present
`invention is in providing a data recording and playback
`System that allows easy and rapid viewing of the recorded
`data.
`0.018. In addition, the present invention also has the
`advantage of providing a data recording and playback Sys
`tem that allows the analysis and/or replay of a time Sampled
`Signal.
`Furthermore, the present invention further has the
`0.019
`advantage of providing Such a data recording and playback
`System that minimizes the likelihood of dropped frames.
`
`0020. These and other advantages are attained by a data
`recording and playback System in accordance with one
`embodiment of the present invention having a monitoring
`device that provides an input Signal data, a memory device
`adapted to receive and temporarily Store the input Signal data
`from the monitoring device as data frames with time Stamps,
`the memory device having addresses associated thereto, and
`a circular Storage buffer having a memory mapped file with
`Same address Space as the memory device, the circular
`Storage buffer being adapted to receive the temporarily
`Stored input signal data from the memory device, and to
`Store the input Signal data in the memory mapped file.
`0021. In accordance with the preferred embodiments, the
`circular Storage buffer Stores recent data frames over aged
`data frames in the memory mapped file. The memory device
`may be a random acceSS memory of a computer. In this
`regard, the circular Storage buffer may be provided on at
`least one hard disk drive of the computer and the input Signal
`data Stored in the memory device Storage buffer is trans
`ferred to/from a file system.
`0022. One embodiment of the data recording and play
`back System also includes an event controller that provides
`an event Signal associated to time of an event. An event
`database is provided for Storing event Signal data, and an
`event processor is provided that copies a plurality of data
`frames Stored in the circular Storage buffer that have time
`Stamps proximate to the time of the event into additional
`Secondary memory mapped files, each containing a single
`event, indexed from the event database. An access controller
`may be provided which is adapted to retrieve the plurality of
`data frames that have time Stamps proximate to the time of
`the event from the event database, the event database being
`provided in at least one hard disk drive of a computer in one
`embodiment. The access controller may be connected to a
`network to allow remote access thereof. In Such an embodi
`ment, the System may be provided with at least one client
`device connected to the network, the client device Such as a
`computer being adapted to remotely control the access
`controller. In this regard, the client device may include a
`display device for displaying the plurality of data frames
`copied from the circular Storage buffer.
`0023 The data recording and playback system may also
`be provided with a digitizer that digitizes the input signal
`data when the input Signal data is an analog signal. The
`present invention may be especially advantageously used to
`record and playback Video and audio signals. If the input
`Signal data contains redundant information, a compressor
`may be provided to compress the input Signal data prior to
`Storage in the circular Storage buffer. The memory mapped
`file in accordance with one embodiment of the present
`invention is adapted to allow playback of Stored input Signal
`data from the circular Storage buffer without interrupting
`Simultaneous recording of new input signal data into the
`circular Storage buffer.
`0024.
`In accordance with other aspects of the present
`invention, a method of recording and playback of data is
`provided. Moreover, a computer executable Software for
`implementing the System and method of the present inven
`tion is also disclosed.
`0025 These and other advantages and features of the
`present invention will become more apparent from the
`
`

`

`US 2002/0191952 A1
`
`Dec. 19, 2002
`
`following detailed description of the preferred embodiments
`of the present invention when Viewed in conjunction with
`the accompanying drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`0.026
`FIG. 1 is a schematic illustration of a data record
`ing and playback System in accordance with one embodi
`ment of the present invention which is implemented through
`a network.
`0.027
`FIG. 2 is a schematic illustration of one embodi
`ment of a signal processor that may be used in implementing
`the data recording and playback System of the present
`invention.
`0028 FIG. 3 is a schematic illustration of one embodi
`ment of a Server that may be used in implementing the data
`recording and playback System of the present invention.
`0029 FIG. 4 is a schematic illustration of one embodi
`ment of a client device that may be used in implementing the
`data recording and playback System of the present invention.
`0030 FIG. 5 is a logical flow diagram of how the signal
`processor of FIG. 2 may be operated.
`0.031
`FIG. 6 is a schematic illustration of a graphical
`user interface which may be used to interface with the data
`recording and playback System.
`0.032
`FIG. 7 is a screen shot of a computer implemented
`graphical user interface of FIG. 6.
`0.033
`FIG. 8 is a logical flow diagram of how the data
`recording and playback System of the present invention may
`be operated in accordance with one embodiment.
`0034 FIG. 9 is a file format table showing the file
`Structure in accordance with one embodiment.
`0035 FIG. 10 is a functional schematic illustration of the
`circular Storage buffer interfacing with the client devices.
`0036 FIG. 11 is a frame by frame illustration of how the
`circular Storage buffer is accessed the client devices.
`0037 FIG. 12 is a schematic illustration of a data record
`ing and playback System in accordance with another
`embodiment of the present invention which is implemented
`in a Single Stand alone computer.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`0.038. As will be evident from the discussion below, the
`present invention provides a data recording and playback
`System that avoids the disadvantages of known data record
`ing and playback Systems by allowing easy and rapid
`Viewing of the recorded data, and allowing analysis and/or
`replay of a time Sampled signal. In addition, it should also
`be evident from the discussion below that the present
`invention further avoids a significant limitation of prior art
`devices by providing a data recording and playback System
`that minimizes the likelihood of dropped frames.
`0.039
`FIG. 1 is a schematic illustration of a data record
`ing and playback System 2 in accordance with one embodi
`ment of the present invention which is implemented through
`a network 4. The network 4 may be any type of a network
`Such as a local area network, wireleSS network, wide area
`
`network, or the Internet. It should, however, be noted that
`whereas the illustrated embodiment of the data recording
`and playback System 2 described in detail below is imple
`mented via network 4, in other embodiments, the data
`recording and playback System of the present invention may
`also be implemented in a Single computer with components
`for performing the functions of various devices described
`with respect to the network implemented embodiment. In
`Such a single computer implementation, the computer Sys
`tem bus may be considered to be the network of the data
`recording and playback System and thus, falls within the
`Scope of the present invention.
`0040. The illustrated embodiment of the data recording
`and playback System 2 includes a signal processor 10
`connected to a monitoring device 6. The monitoring device
`6 may be any type of a device for monitoring Such as a Video
`camera, microphone, a Sensor, etc, that functions as a signal
`Source for providing an input Signal data to the Signal
`processor 10. For instance, the monitoring device 6 would
`provide a Video, audio, or other type of time Sampled Signal
`respectively for the various examples noted. The data
`recording and playback System 2 also includes a Server 20
`that controls and maintains the databases of the data record
`ing and playback System 2 in the manner further described
`below.
`0041. In addition, the server 20 is also connected to an
`external event Source 8 that provides an event signal to the
`Server 20, the event Signal being associated to an external
`event. The event Source 8 may be a logic pulse generated by
`an independent system which indicates that an important
`event has occurred. The external event Source 8 may also be
`a Sensor used in conjunction with the monitoring device 6
`that provides an event Signal when Sensor is actuated, the
`actuation of the Sensor only occurring when the triggering
`external event occurs. In this regard, the external event
`Source 8 may also be a processor in another embodiment
`which analyzes the input Signal data to determine whether an
`event has occurred, and provides an event Signal when an
`event is determined to have occurred.
`0042. Furthermore, the data recording and playback sys
`tem 2 in accordance with the illustrated embodiment of FIG.
`1 is provided with client devices 30 and 30' that are remotely
`located to allow users of the data recording and playback
`System 2 to access the recorded data in the manner further
`described below. In the above regard, each of the noted
`components of the data recording and playback System 2 and
`their operation are described herein below.
`0043 FIG. 2 shows a schematic illustration of the signal
`processor 10 in accordance with one embodiment of the
`present invention. AS can be seen, the Signal processor 10 is
`in communication with monitoring device 6 that provides an
`input Signal data to the Signal processor 10 Such as a video,
`audio or other type of Signal. The Signal processor 10
`includes a digitizer 11 which receives the input Signal data
`from the monitoring device 6, and digitizes the Signal data
`if the input signal data is an analog signal. Of course, if the
`Signal is already in digital form, the digitizer 11 is bypassed.
`AS previously noted, the Signal may be a Video signal, an
`audio signal, or other Signals that may be in analog or digital
`form. In other embodiments, the input Signal data may be a
`Vibrational Signal, optical light signal, etc., and correspond
`ingly, may be provided by an appropriate monitoring Sensors
`or devices.
`
`

`

`US 2002/0191952 A1
`
`Dec. 19, 2002
`
`0044) Depending on the nature of the input signal data
`provided by the monitoring device 6, if the digitized input
`Signal data is highly repetitive or redundant, a compressor 12
`compresses the input signal data by applying an appropriate
`compression algorithm known in the art to reduce the
`Storage requirements for the input signal data. For instance,
`if the monitoring device 6 is a video camera which provides
`a Video Signal, the Video signal may be compressed using the
`known video compression algorithms MJPG or MPEG, for
`example. Of course, in cases when the compression of the
`Signal data is not appropriate, the compressor 12 is bypassed
`So that the input Signal data is not compressed.
`004.5 The signal control 13 sets the sample rate and gain
`of the digitizer 11, and also sets the compression parameters
`for the compressor 12. In addition, the Signal control 13
`accesses the data access control of the Server 20 discussed in
`further detail below to retrieve these configuration param
`eters. The Signal processor 10 in accordance with one
`preferred embodiment of the present invention, may be
`implemented on a computer with a video frame capture and
`a compressor card, the details of which are known in the art
`and therefore, omitted here.
`0046) The analyzer 18 applies various pattern recognition
`algorithms automatically to the data from the digitizer 11 or
`the compressor 12 to identify any deviations form normal
`behavior of the signal from monitoring device 6 that may be
`of interest. For instance, in the case of an audio Signal the
`analyzer may trigger an event on the Sudden change of
`amplitude, or in the case of a Video Signal, on the Statistically
`Significant change in brightness or contrast. More Sophisti
`cated analyses can be performed that trigger an event when
`the nature of the Signal matches a reference Signal. The
`analyzer 18 passes analysis data about each frame to the
`Storage control 14 for Storage in the circular Storage buffer
`15, the details of which is described below. Once the
`analyzer 18 triggers an event, it sends a message to the event
`control 22 with the time Stamp and other analysis data to
`initiate the event capture processing.
`0047 The storage control 14 provided in the signal
`processor 10 receives the digitized and/or compressed input
`Signal data from the monitoring device 6, and Stores the
`input Signal data and the analysis data in the circular Storage
`buffer 15 together with a time stamp for each record. In this
`regard, the circular Storage buffer 15 has two unique posi
`tions, the head and tail. The head represents the position in
`the circular Storage buffer 15 having the most recent Signal
`data, and the tail position represents the position in the buffer
`having the oldest Signal data that is leaving the circular
`storage buffer 15, i.e. being overwritten by the most recent
`signal data. The circular storage buffer 15 is preferably
`implemented as a memory mapped file. AS Such, the input
`signal data is swapped between the RAM 19 and file system
`17 as needed.
`0.048. In this regard, the input signal data from the
`monitoring device 6 is Stored as data frames into the circular
`storage buffer 15 by the storage control 14. The signal
`processor 10 also includes an event processor 16 that is
`adapted to extract data frames Starting from a data frame that
`is a predetermined number of data frames before the external
`event time provided by the server 20 as described in further
`detail below, and ending a predetermined number of data
`frames after the external event time. The extracted data
`
`frames are then stored in file system 17 thereby providing a
`permanent record of the data frames before, during, and after
`the event prior to the data frames being overwritten in the
`circular storage buffer 15 by more recent data frames. In
`addition, the event processor 16 of the present embodiment
`is also adapted to mark the input signal data being Stored in
`the circular storage buffer 15 when an event occurs to
`thereby flag the location of an occurrence of an external
`event in the circular Storage buffer 15, Signal to mark the
`input Signal data being provided by the event processor 16.
`0049 FIG.3 shows a schematic illustration of a server 20
`that may be used in the data recording and playback System
`10 in accordance with one embodiment. As shown in FIG.
`1, the server 20 is connected to an external event Source 8
`which provides an event signal that notifies the server 20 that
`an external event of interest has occurred. AS previously
`described, the external event Source 8 may be a Sensor or a
`processor used in conjunction with the monitoring device 6.
`The external event source 8 provides the event signal to
`event interface 21, the details of the event interface 21
`depending on the type of event signal provided. In one
`embodiment, the event interface 21 may be an external relay
`closure or applied Voltage level that is used to cause a Serial
`port interrupt. In more Sophisticated embodiments of the
`event interface 21, serial, TCP/IP or FTP protocols can be
`implemented that transfer additional data as well. Therefore,
`in accordance with the illustrated embodiment, the event
`Signals are additional inputs to the data recording and
`playback System that are not Stored continuously, but are
`used to indicate the occurrence of an important event.
`Further in this regard, the event Signals may be initiated
`manually by the user of the data recording and playback
`System 10 as well using an input device Such as a keyboard,
`mouse, etc. So that a particular data frame in the circular
`Storage device may be manually marked.
`0050. The event control 22 of the server 20 determines
`the time in which the event signal is received from the
`external event Source 8 and Stores this time Stamp associated
`to the external event in event database 23. In addition, in
`alternative embodiments where more Sophisticated inter
`faces are used, the additional data provided by Such inter
`faces is also stored in the event database 23 by the event
`control 22.
`0051) The server 20 of the illustrated embodiment of
`FIG. 3 also includes a database access control 24 that
`regulates access to the event database 23, and allows acceSS
`ing of the time Stamp Stored in the event database 23 when
`queried in the manner described in further detail below.
`Moreover, the event control 22 of server 20 sends an event
`signal via the network 4 to the event processor 16 of the
`Signal processor 10 to mark the input Signal data being
`stored in the circular storage buffer 15 as the external event
`is detected. In addition, the event Signal Sent by the event
`control 22 of the server 20 to the event processor 16 of the
`Signal processor 10 may also be used to trigger the event
`processor 16 to extract the Signal data from the circular
`Storage buffer, and to Store the data frames into the file
`system 17 in the manner previously described, the data
`frames extracted preferably including those immediately
`before, during, and immediately after the time of the event.
`As previously noted, the event database 23 may further be
`utilized to Store System configuration information Such as
`the names of input Signal data, various parameters for the
`
`

`

`US 2002/0191952 A1
`
`Dec. 19, 2002
`
`digitizer 11, compressor 12, and the circular Storage buffer
`15, as well as computer names and event data.
`0.052
`FIG. 4 is a schematic illustration of the client
`device 30 that may be used to implement the data recording
`and playback system 2 of FIG. 1. It should be appreciated
`that whereas only the client device 30 shown in FIG. 1 is
`described in detail hereinbelow, client device 30' may also
`be implemented in a similar manner. The primary function
`of the client device 30 is to playback the data frames from
`the signal processor 10 with event annotation from the
`Server 20 So that the Signal data may be viewed and analyzed
`by the user of the data recording and playback System 2. In
`this regard, the client 30 is provided with user playback
`control 31 which may be used to specify numerous playback
`parameterS Such as the position of the circular Storage buffer
`15 to be played back, to specify the event to be played back
`from event datab