Abstract:
An image recorder is provided which assures recording even if its primary recorder is inoperable. The recorder includes an image compression processor to compress input images, a buffer to buffer the compressed image data, a first recorder to record the image data, and a second recorder for recording the image data if the first recorder is inoperable. The second recorder typically operates with a recording rate different from that of the first data recorder.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to information recorders provided with multiple recording means, and more specifically, to an image recorder for image recording.  
         [0003]     2. Description of the Prior Art  
         [0004]     The background technology related to this application is described in JP-A-2001-14801. The system described there proposes to “exemplify a monitoring system superior to conventional in terms of image data generation, compression, decompression, and recording, and system management.” An exemplary recording method described therein is defined “to decrease the number of frames in image data per unit time for image recording onto an MO disk  81  for extending the recording time of the MO disk  81 .” 
       BRIEF SUMMARY OF THE INVENTION  
       [0005]     Although a method for decreasing the amount of data to extend recording time is described in the above JP &#39;14801 document, there is no technique described for controlling a recording rate when a main recording means is not available for image recording. Image recorders are often provided as a part of security systems under the control of security firms. Whenever image recorders fail to operate properly, maintenance staff from the security firm must make repair visits to the sites at which the image recorders are located. Security firms and the owners of the security systems bear increased maintenance-related costs if breakdown rates of image recorders arise.  
         [0006]     To decrease the breakdown rate of the recorders, one type of image recorder may include a plurality of recording means provided by a hard disk drive (HDD) and a memory card incorporating semiconductor memory. In this type of system, a large-capacity HDD is generally the first choice for image recording. If the HDD fails to operate correctly, the memory card serves as an alternative for image recording. This configuration enables the system to perform image recording without interruption even with HDD failure, and therefore decreases the breakdown rate of the recorders. With an image recorder that includes the HDD and memory card configurations, image recording can be continuously performed even when the HDD fails, thus eliminating the need for security firm maintenance staffs to immediately make on-site repairs to malfunctioning recorders.  
         [0007]     Of course, image recorders that include HDD and memory card configurations may exhibit problems. One problem with such image recorders is that the memory cards are smaller in capacity in comparison to the HDDs and therefore, if continuous recording employs the recording rate used by the HDDs, the memory cards usually the capacity of the HDDs. Another problem is that the recording rate varies depending on the placement conditions of the image recorders and this tendency results in a variation of recordable time even if the memory cards have the same capacity as the HDDs. Therefore, this problem may undermine any guarantee of accurate recording duration estimates.  
         [0008]     Therefore, even if the system can continue image recording after HDD failure, the recording time made available by the system is unstable. This instability may necessitate on-site supervision and/or adjustments by security firm maintenance staffs or system managers to prevent any gap in recording time periods. The present invention provides an image recorder that is capable of ensuring uninterrupted recording time, irrespective of the image recorder&#39;s placement conditions, and even if its main recording means fails to operate correctly or is unavailable for recording. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a schematic diagram showing an image recorder of a first embodiment of the present invention;  
         [0010]      FIG. 2  is a diagram showing image data recording in the image recorder of the first embodiment;  
         [0011]      FIG. 3  is a sequence diagram of a recording rate calculation process in the image recorder of the first embodiment;  
         [0012]      FIG. 4  is a schematic diagram showing an image recorder of a second embodiment of the present invention; and  
         [0013]      FIG. 5  is a sequence diagram of a recording rate calculation process in an image recorder of a third embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]     Below, embodiments of the present invention are described by referring to the accompanying drawings.  FIG. 1  is a schematic diagram showing an image recorder of a first embodiment of the present invention.  FIG. 1  shows an image recorder  1 , an image compression processing section  101 , a buffer section  102 , a first data recording section  103 , a second data recording section  104 , and a system control section  105 .  
         [0015]     In image recorder  1 , image compression processing section  101  receives an incoming image and applies an image compression process exemplified by MPEG2, MPRG4, JPEG, or others. The result is output as compressed image data. Buffer section  102  buffers the compressed image data provided by image compression processing section  101 . First data recording section  103  records the image data that has been buffered by buffer section  102 . Second data recording section  104  also records the image data that has been buffered by buffer section  102 . System control section  105  exercises control over various processes, including the image compression process in image compression processing section  101 , the buffer process in buffer section  102 , and the image data recording process both in first data recording section  103  and second data recording section  104 . First data recording section  103  serves as main recording means, and is a large-capacity recording medium such as HDD, DVD, or others. Second data recording section  104  serves as alternative recording means to first data recording section  103 , and is a relatively-small-capacity recording medium such as a memory card configured by semiconductor memory. Under normal operation, system control section  105  applies control to make a recording to first data recording section  103 , i.e., the large-capacity recoding medium.  
         [0016]      FIG. 2  is a diagram showing an exemplary method for image data recording control in the image recorder of the first embodiment of the present invention.  FIG. 2  shows input image data  2 A, image data  2 B to be recorded by the first data recording section, image data  1   2 C to be recorded by the second data recording section, image data  2   2 D to be recorded by the second data recording section, and image data  3   2 E to be recorded by the second data recording section. In the image recorder, under normal recording operation, input image data  2 A is recorded into large-capacity first data recording section  103  after being compressed as image data  2 B under compression schemes of low compression rate such as MPEG2. If first data recording section  103  becomes unavailable for the purpose of continuing the recording process, for example due to failures, second data recording section  104  is put in charge for recording as an alternative to first data recording section  103 , and the recording rate is changed image data  2 C for recording into second data recording section  104 . Image data  2 C shown in  FIG. 2  has a reduced frame rate. Alternatively, the compression rate may be increased from low to high, or the recording data may be reduced. Such recording data decimation may be performed at the time of image compression in image compression processing section  101 , at the time of buffering by the buffer section  102 , or at the time of image data recording to second data recording section  104 .  
         [0017]     When the image compression processing section  101  is capable of image compression with a plurality of image compression schemes, before recording into the first data recording section  103 , image data  2 B is normally compressed at a low compression rate with MPEG2, as shown in  FIG. 2 . When first data recording section  103  becomes unavailable for recording, as shown in  FIG. 2 , image data  2 D is compressed at a different, higher compression rate with MPEG4 for recording into second data recording section  104 . Alternatively, as shown in  FIG. 2 , image data  2 E may be compressed, with any different compression scheme with a reduced frame rate, for recording into second data recording section  104 .  
         [0018]     As such, when first data recording section  103  becomes unavailable for recording due to failures or other problems, the recording medium is changed to second data recording section  104  for recording, and the data recording rate is reduced through frame rate decimation and/or compression rate/scheme change. In this manner, second data recording section  104 , with relatively smaller capacity, can be available for long-time recording.  
         [0019]      FIG. 3  is a sequence diagram of a recording rate calculation process in the image recorder of the first embodiment of the present invention. When the first data recording section  103  becomes unavailable for recording due to failures or other problems, system control section  105  executes the above-described process of second data recording section  104  activation and recording rate reduction. Referring to the drawings, the sequence for changing the recording rate will now be described.  
         [0020]     In step  301 , when first data recording section  103  becomes unavailable for recording, system control section  105  calculates the recording rate for making a recording into second data recording section  104 . In step  302 , system control section  105  then checks the capacity of second data recording section  104  that is available for recording. The capacity of second data recording section  104  may be acquired therefrom in step  302 , or previously at system start-up or at the time of the memory card insertion/connection of system-addition for second data recording section  104 . In step  303 , a control parameter is determined to define the length of time that second data recording section  104  is available for image recording. When the control parameter is determined to be a time frame of, for example, 12 hours or a day, the procedure goes to step  305 . When the control parameter indicates a time and date such as 12 o&#39;clock on Monday or 12 o&#39;clock on January 4, the procedure goes to step  304  to calculate time for recording using the current time and the due date. In step  305 , the recording rate per unit time is computed using the capacity of the second data recording section  104 , and the control parameter or the time derived in step  304 . In step  306 , this computed recording rate per unit time is used to determine the factors of image compression scheme, image quality/compression rate, and recording interval. In order to determine the factors of step  306 , a table may be provided in advance for conversion between the recording rate and those factors. In step  307 , the calculation of recording rate is terminated for recording to the second data recording section  104 , and then using the factors determined in step  306 , i.e., the image compression scheme, the image quality/compression rate, and the recording interval, the recording is started into the second data recording section  104 . In an alternative manner embodiment, not only the data rate of the image data, but also the data rate of management information of the image data may be used for computation of the factors determined from the recording rate in step  306 .  
         [0021]     To determine the recording rate per unit time through recording rate calculation in step  305 , the recording rate may be varied according to the time frame, e.g., the recording rate may be set higher during business hours than after business hours. Thus the recording rate according to the circumstances of monitoring objects may be determined, and the time frame during business hours may be monitored more intensively.  
         [0022]     In the above description, the system control section  105  checks the capacity of the second data recording section  104  and the control parameter to automatically determine the image compression scheme, image quality/compression rate, and recording interval. Alternatively, the recording rate may be regarded as the control parameter for determination of image compression scheme, image quality/compression rate, and recording interval factors, or image compression scheme, image quality/compression rate, and recording interval are all directly regarded as the control parameter.  
         [0023]     As such, even if first data recording section  103  does not work correctly, smaller-capacity second data recording section  104  can continuously perform recording with a guaranteed recording time by automatically determining the recording rate for second data recording section  104  using the control parameter, and by performing recording using a recording rate different from the recording rate of first data recording section  103 . Accordingly, even if first data recording section  103  becomes unavailable for recording, after failure detection non-recording time periods are prevented and continuous recording is ensured for a predetermined length of time, such as for 12 or 24 hours or until Monday noon, for example. This continuous recording provides time for security firm staffs to travel to places where the image recorders are located after being alerted by failure detection. Security firms will be able to reduce operation costs by the decreased need for emergency staff allocation for failure support at night and weekends.  
         [0024]     According to the first embodiment of the present invention, an image recorder is provided that is capable of ensuring continuous recording time, irrespective of the image recorder&#39;s placement conditions or of the failure or compromising of the main recording means among its multiple recording means, by using substitute recording means with a recalculated recording rate different from the recording rate of the main recording means. This image recorder decreases operation costs caused by urgent security firm staff dispatch at night and weekends for image recorder failure support and reduces maintenance staff allocation for image recorder maintenance.  
       Second Embodiment  
       [0025]     Turning to  FIG. 4 , a schematic diagram of a second embodiment of the present invention illustrates an image recorder. In  FIG. 4 , frame switch processing section  106  and network transmission/reception processing section  107  are added to the embodiment shown in  FIG. 1 . Frame switch processing section  106  applies a switching process to analog image signals coming from a plurality of input sources, and the resulting images, having been switched on a frame basis, are forwarded to image compression processing section  101 . Network transmission/reception processing section  107  forwards, to buffer section  102 , image data coming from network cameras connected over a network. Network transmission/reception processing section  107  also goes through a control data transmission/reception process to exercise control over the network cameras. System control section  105  exercises control over various processes, including the switching process by frame switch processing section  106 , the image data reception process of network transmission/reception processing section  107 , the transmission/reception process of the control data including the image quality or transmission rate of the image data provided by the network cameras, and the buffering process in buffer section  102  for the image data coming from the input sources. In synchronization with the switching process, image compression processing section  101  is also controlled. Due to control applied to various processes, the image data coming from the input sources can be recorded to the first or second data recording section  103  or  104 .  
         [0026]     According to the second embodiment of the present invention, in the image recorder for recording image data coming from a plurality of input sources, even if first data recording section  103 , serving as main recording means, becomes unavailable for recording due to failures or other problems, second data recording section  104  works as substitute recording means with a recording rate different from that of first data recording section  103 . The substitution of second data recording section  104  for first data recording section  103  as recording means is indicated when second data recording section  104  is put in charge of recording, the recording rate per unit time that resulted from step  305  of  FIG. 3  is allocated among the input sources, and image compression scheme, image quality/compression rate, and recording interval are determined in step  306  for every input source. In the algorithm of allocating the recording rate per unit time among a plurality of input sources, an allocation factor may be simply the number of input sources, or the recording rate ratio among the input sources at the time of recording into first data recording section  103 . Alternatively, allocation may be carried out in such a manner that the recording rate is set higher for any one input source specified by the control parameter. Further, to change the recording rate of the image data coming from the cameras connected over the network, system control section  10 S may forward the control data via network transmission/reception processing section  107 . For data decimation only in the direction of time axis, the data may be decimated when it is recorded from buffer section  102  to second data recording section  104 .  
         [0027]     As such, according to the second embodiment, in the image recorder that receives image data from a plurality of input sources, even if the image recorder&#39;s main recording means among other recorder means does not work correctly, the recording rate is calculated again to derive a different value for use for recording into a substitute recording medium so that the recording time is ensured irrespective of the number of input sources or the placement conditions of the image recorder. This image recorder decreases operation costs caused by urgent security firm staff dispatch at night and weekends for image recorder failure support and reduces maintenance staff allocation for image recorder maintenance. Note here that, in the above description referring to  FIG. 4 , the image inputs for the frame switch processing section are analog. This is not restrictive, and the image inputs can be, but are limited to, digital.  
       Third Embodiment  
       [0028]      FIG. 5  is a sequence diagram of a recording rate calculation process in an image recorder of a third embodiment of the present invention. In  FIG. 5 , steps  501 ,  502 , and  503  are shown in addition to the steps shown in  FIG. 3 .  
         [0029]     Image recorders used for monitoring are required to have an alarm recording capability for recording any important data with high image quality. When crime or alarm detection occurs, this capability serves to monitor sensors, for example. For alarm recording, a recording is required to be made with high image quality, i.e., at a higher recording rate. Therefore, if an alarm recording is to be made into second data recording section  104  during operation as substitute recording means, the recording rate is required to be higher for alarm recording than the rate determined in step  305  of  FIG. 3  so that the larger recording capacity will be used. This results in a recording time that is shorter than the time originally guaranteed by the image recorders. As shown in step  501  of  FIG. 5 , prior to the recording rate calculation process, system control section  105  computes the usable recordable capacity to be reserved for the alarm recording prior to an alarm alert. In the process of step  303 , the recordable capacity of the second data recording section is subtracted by the capacity needed for alarm recording, and the resulting capacity is used for computation.  
         [0030]     By reserving the capacity for alarm recording in step  501 , it becomes possible to guarantee the recordable time even if an alarm recording is required. The amount of the capacity for alarm recording to be reserved in step  501  is not restricted, and may be for one-time recording or plural-time recording. In preparation for the next alarm recording after an alarm recording is made, the recording rate may be calculated again by going through the sequence of  FIG. 5  for the recording rate calculation. In step  502 , a determination is thus made as to whether or not the recording rate is recalculated after an alarm recording, and if the recording rate is determined to have been recalculated, the remaining recording time is calculated incorporating the time taken for the recording by second data recording section  104  in step  503 . For example, assuming that an alarm recording is required after 1.5 days out of the guaranteed time of 2 days, this is the algorithm for an exemplary case of ensuring recording for the remaining 0.5 day.  
         [0031]     As such, according to the third embodiment of the present invention, in an image recorder capable of alarm recording, even if its main recording means among other recording means does not work correctly, recordable capacity is reserved for alarm recording and the recording rate is calculated again to derive a different value for use for recording into a substitute recording medium so that the recording time is ensured. This image recorder decreases operation costs caused by urgent security firm staff dispatch at night and weekends for image recorder failure support and reduces maintenance staff allocation for image recorder maintenance.  
         [0032]     According to the first to third embodiments, an image recorder is provided that is capable of ensuring recording time irrespective of the image recorder&#39;s placement conditions and even if its main recording means fail to work correctly, i.e., even if the main recording means is not available for recording.