Continuous recording system, method, and recording medium recording continuous recording program and capable of being read by computer

An analog video signal inputted from a video camera is converted into digital video data in a real-time manner by a real-time encoder and is transmitted. A video server has a plurality of storing devices, stores the inputted digital video data into any one of the storing devices in a real-time manner, and transmits the digital video data read out from any one of the storing devices to a video reproducing terminal apparatus. A long time recording processing unit stores the digital video data sent from the real-time encoder into the plurality of storing devices of the video server while sequentially switching the storing devices, thereby continuously recording the digital video data.

BACKGROUND OF THE INVENTION 
The present invention relates to continuous recording system and method for 
storing an analog video signal inputted from a video camera to a video 
server while encoding the analog video signal to digital video data of 
MPEG2 or the like in a real-time manner and also relates to a recording 
medium in which a continuous recording program has been recorded and which 
can be read by a computer. More particularly, the invention relates to 
continuous recording system and method for continuously storing digital 
video data into a video server for a long time and also relates to a 
recording medium in which a continuous recording program has been recorded 
and which can be read by a computer. 
Hitherto, in a system for unmanned-monitoring abnormality of a structure 
such as a debris barrier or the like which prevents a natural disaster, an 
object to be monitored is photographed by installing a video camera, and a 
video signal from the video camera is recorded on, for example, a video 
tape of a VTR apparatus. When abnormality such as a dam collapse occurs, 
the recorded video tape is reproduced and a state and causes of the 
abnormality are analyzed from the recorded monitor video image. A 
continuous recording system for recording a video image photographed by 
the video camera to a video tape is required to continuously record video 
images for a long time such as one month, one year, or the like and has to 
continuously record video images for a long time without dropping out any 
video image. 
In the conventional continuous recording system for recording video images 
photographed by a video camera to a video tape, however, since the 
recording operation cannot be performed temporarily when the video tape is 
replaced, it is difficult to continuously record video images without 
dropping out any video image. In a case such that abnormality occurs 
during a tape replacement, consequently, there is a problem that a 
precious video image is lost. Since a recording time per video tape is 
limited, the number of recorded video tapes naturally increases. When 
abnormality occurs, since the relevant video image is searched while 
reproducing the video tape, enormous trouble and time are needed. 
SUMMARY OF THE INVENTION 
According to the invention, there is provided a continuous recording system 
for storing data encoded by a real-time encoder into a video server for a 
long time without dropping out any data. 
A continuous recording system of the invention comprises: a real-time 
encoder for converting an analog video signal inputted from a video camera 
into digital video data in a real-time manner and transmitting; a video 
server which has a plurality of storing devices (disk groups) and stores 
the inputted digital video data into any one of the plurality of storing 
devices in a real-time manner and transmits the digital video data read 
from any one of the plurality of storing devices to a video reproducing 
terminal apparatus; and a long time recording terminal apparatus having a 
long time recording processing unit for sequentially storing the digital 
video data sent from the real-time encoder while switching the plurality 
of storing devices of the video server, thereby continuously recording the 
video data. The long time recording processing unit requests the video 
server to prepare a recording operation to a specific recording device on 
the basis of a recording start instruction, allows the real-time encoder 
to start an encoding on the basis of a notification of completion of the 
recording preparation from the video server, stores the transmitted 
digital video data into the storing device in the video server while 
receiving it, and monitors a predetermined switching interval time. The 
long time recording processing unit requests the video server to prepare 
the recording to the next storing device at a stage when the switching 
interval time approaches, establishes a recording preparation completion 
state in which the switching can be performed, and switches a storage 
destination of the digital video data from the storing device in which the 
data is at present being stored to another storing device in the recording 
preparation completion state at a time point when a switching timing 
corresponding to the switching interval time comes. According to such a 
continuous recording system of the invention, the video data having a 
length which exceeds a capacity of the storing device can be continuously 
recorded without interruption and the video image is not dropped out. In 
cooperation with a function for reproducing the video data during the 
storage, a video image during the recording can be also monitored. In 
cooperation with a database, a video image at an arbitrary time can be 
easily monitored among a number of video files. Further, by collectively 
showing video files of the plurality of storing devices as one file, a 
troublesomeness to switch the video images upon reproduction can be 
reduced. 
The long time recording processing unit determines a storing device having 
a vacant capacity equal to a storing capacity corresponding to a preset 
switching interval time as a storage destination. If a storing device 
having a vacant capacity cannot be assured, the storing device having the 
oldest storage contents is erased and is determined as a next storage 
destination, thereby enabling a semipermanent recording operation to be 
performed. The long time recording processing unit has: a long time 
recording control block in which a predetermined switching interval time, 
a video file name to be stored, and the number and names of storing 
devices as storage destinations have been defined; a storing thread which 
is activated upon completion of the storage preparation of the video 
server, acquires a using right of a buffer for transfer provided for the 
real-time encoder and activates the encoder on the basis of definition 
information of the long time recording control block, thereby transmitting 
digital video data and storing into the storing device in the video 
server; and an encoder operation processing unit for transferring an 
operating instruction from the storing thread to the real-time encoder and 
allowing transmission of the digital video data to be controlled. The long 
time recording processing unit activates a new storing thread 
corresponding to a storing device on the switching destination side and 
establishes a recording preparation completion state at a stage near the 
switching interval time of the storing device in the video server, allows 
the old storing thread before the switching to release the buffer using 
right at the time point of switching, allows the new storing thread to 
acquire the buffer using right, and switches the storage of the digital 
video data to the next storing device. Further, there is provided a 
management server for managing the operations of the video server and the 
long time recording processing unit and resources of the video data stored 
in the video server. The management server comprises: a video data table 
for managing a file name, a recording start time, a recording end time, a 
file size, and the like of a video file stored in the storing device in 
the video server; a storing device information table (disk group 
information table) for managing a device name, a whole capacity, a vacant 
capacity, and the like of the storing device in the video server; and a 
contents manager for determining the storing device on the storage 
destination side in the video server by referring to the video data table 
and the storing device information table in response to a storage 
preparation request from the long time recording processing unit and 
responds a storage preparation completion. 
In another embodiment of the long time recording processing unit, the 
switching operation to the next storage destination is prepared just after 
the start of the recording. That is, the preparation of recording to a 
specific storing device is requested to the video server on the basis of a 
recording start instruction, the encoding of the real-time encoder to 
which the completion of the recording preparation was notified from the 
video server is started, and the transmitted digital video data is stored 
into the storing device in the video server while being received. Just 
after the start of the storage to the storing device in the video server, 
the preparation of the recording to the next storing device is requested 
to the video server, and the recording preparation completion state in 
which the switching can be performed is established. By preliminarily 
obtaining the completion of the recording preparation to the next storage 
destination just after the start of the recording, a drop-out of the video 
data when an error occurs during the recording is minimized. The switching 
interval time is monitored and, at a time point when the switching 
interval time comes, the storage destination of the digital video data is 
switched from the storing device in which the data is at present being 
stored to another storing device in the recording preparation completion 
state. 
In another embodiment of the long time recording processing unit, by 
storing the digital video data from the real-time encoder into two storing 
devices in the video server in parallel, reliability is increased. In this 
case, when the storage destination is switched to the next storing device, 
if the storage to both of the storing devices is normally finished, only 
the stored contents of one of the storing devices are left and the stored 
contents of the other storing device are erased. If the storage to one of 
the storing devices is normally finished and the storage to the other 
storing device is abnormally finished, the stored contents of the storing 
device in which the storage was normally finished are left. 
In another embodiment of the long time recording processing unit, when a 
predetermined event occurs, the stored contents of the storing device from 
the occurrence of the event to a predetermined time in the past are read 
out and copied to another storing device for refuge. When all of video 
images which are recorded for a long time are not necessary and some event 
occurs, by storing the video images before the event, the necessary video 
images can be certainly stored with the necessary minimum capacity. 
In another embodiment of the long time recording processing unit, high 
picture quality data and low picture quality data are transmitted from the 
real-time encoder and stored in two storing devices in the video server in 
parallel. When a predetermined event occurs, the high picture quality 
video data from the occurrence of the event to a predetermined time in the 
past is copied into the storing device for refuge and is left. When no 
event occurs, the low picture quality data is copied into the storing 
device for refuge at the time of switching of the storing device and is 
left. Since the capacity of the video data is proportional to the picture 
quality, the low picture quality data is stored when no event occurs, 
thereby reducing the storing capacity, and the high picture quality data 
of a predetermined time is left when an event occurs, thereby enabling an 
analysis of abnormality or the like to be performed by clear images. 
The high picture quality data from the real-time encoder is a data stream 
of MPEG2 and the low picture quality data is a data stream of MPEG1. 
Occurrence of an event that is discriminated by the long time recording 
processing unit is determined by a detection signal of a sensor. The long 
time recording processing unit discriminates the event occurrence from the 
digital video data sent from the real-time encoder. For example, a large 
image change is detected from parameters of the data stream of MPEG2 sent 
from the real-time encoder and the event occurrence is discriminated. The 
storing device provided in the video server is a large capacity storing 
device using a disk array. 
According to the invention, a continuous recording method for storing data 
encoded by a real-time encoder into a video server without dropping out 
any data for a long time is provided. The continuous recording method 
comprises: 
a video data converting step of converting an analog video signal inputted 
from a video camera to digital video data in a real-time manner by a 
real-time encoder and transmitting; 
a long time recording step of continuously recording the digital video data 
sent from the real-time encoder by storing the data while sequentially 
switching a plurality of storing devices in a video server; and 
a recording and reproducing step of reading out the digital video data 
stored in the storing device in the video server in a real-time manner and 
transmitting to a video reproducing terminal apparatus. 
The details of the continuous recording method are basically the same as 
those of the system. 
Further, according to the invention, there is provided a recording medium 
in which a continuous recording program for storing data encoded by a 
real-time encoder into a video server for a long time without dropping out 
any data has been recorded and which can be read by a computer. The 
recording medium has a long time recording processing module for 
continuously recording the digital video data from the real-time encoder 
which converts and transmits an analog video signal inputted from a video 
camera in a real-time manner by storing the data while sequentially 
switching the plurality of storing devices in the video server. The 
details of the recording medium are also basically the same as those in 
case of the system. 
The above and other objects, features, and advantages of the present 
invention will become more apparent from the following detailed 
description with reference to the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
System Construction 
FIG. 1 is a block diagram of a system construction of a continuous 
recording system of the invention. The continuous recording system of the 
invention comprises: a video camera 10; a real-time encoder 12; a long 
time recording terminal apparatus 14; a video server 16; a video 
reproducing terminal apparatus 20; and a management server 22. The video 
camera 10 is installed at a photographing location as a monitoring target 
such as a debris barrier or the like and inputs a photographed color 
analog video signal to the real-time encoder 12 in a system activating 
state. As a video signal from the video camera 10, a color video signal 
of, for example, NTSC is used. The video camera 10 can be fixedly set or 
can be also constructed so as to horizontally or vertically operate a 
predetermined monitoring range by a servo motor or the like. The real-time 
encoder 12 converts the analog color video signal inputted from the video 
camera 10 into predetermined digital video data in a real-time manner and 
generates the converted data. For instance, the real-time encoder 12 
converts the inputted color video signal of NTSC into a data stream of 
MPEG2 and/or MPEG1 and outputs the data stream. In this instance, ISO/IEC 
standard names in MPEG1 and MPEG2 are as follows. 
______________________________________ 
MPEG1: ISO/IEC11172-2 video 
Established in 1992 
ISO/IEC11172-3 audio 
Established in 1992 
MPEG2: ISO/IEC13818-2 video 
Established in 1994 
ISO/IEC13818-3 audio 
Established in 1994 
______________________________________ 
The long time recording terminal apparatus 14 allows the real-time encoder 
12 to start the encoding on the basis of a recording start instruction of 
the system, thereby storing the digital video data transmitted from the 
real-time encoder 12 into a storage destination of any one of disk groups 
18-1 to 18-n as a plurality of storing devices provided in the video 
server 16 in a real-time manner. In this instance, the long time recording 
terminal apparatus 14 monitors a predetermined switching interval time 
based on a capacity which can be stored to each of the disk groups 18-1 to 
18-n provided in the video server 16. For example, when the present time 
first approaches the switching interval time during the storage of the 
digital video data in which the disk group 18-1 is designated as a storage 
destination, the long time recording terminal apparatus 14 executes a 
storage preparing request to the disk group 18-2 as a next storage 
destination and forms a switching preparation completion state to the next 
storage destination before the present time reaches the switching interval 
time, thereby making it possible to switch to the next storage destination 
at a switching timing without dropping out the digital video data. The 
management server 22 manages the operations of the long time recording 
terminal apparatus 14 and video server 16 and also manages the storing 
states of the disk groups 18-1 to 18-n as storing devices provided in the 
video server 16 and recorded resources which have already been stored. As 
for video data stored in the video server 16, the video data is read out 
and transferred via an ATM network 28 on the basis of a reading request 
from the video reproducing terminal apparatus 20, so that the recorded 
image can be monitored by a monitor on the video reproducing terminal 
apparatus 20 side. The video data is transferred to the video reproducing 
terminal apparatus 20 in a real-time manner and can be also monitored by 
the monitor while storing into the video server 16. 
FIG. 2 is a functional block diagram of the continuous recording system of 
FIG. 1. The real-time encoder 12 comprises an NTSC/MPEG converting unit 32 
and a real-time encoding data buffer 34. The NTSC/MPEG converting unit 32 
receives the NTSC color video signal serving as an analog video signal 
from the video camera 10, converts the video signal into the stream of the 
digital video data of MPEG1 or MPEG2, and transfers the stream to the long 
time recording terminal apparatus 14 through the real-time encoding data 
buffer 34. As such a real-time encoder 12, for example, FMM EP-202 
manufactured by Fujitsu Ltd. can be used. In the normal using state, the 
real-time encoder 12 transmits the data stream of MPEG2 to the long time 
recording terminal apparatus 14. The long time recording terminal 
apparatus 14 is realized by a computer such as personal computer, 
workstation, or the like and realizes a function of a long time recording 
processing unit 36 by a continuous recording program provided by the 
invention. The long time recording processing unit 36 comprises: a storing 
thread 38; a real-time encoder operation processing unit 40; and a long 
time recording control block 42. The storing thread 38 is activated by a 
recording start instruction for the long time recording system and 
executes the transmission of the MPEG2 stream due to the encoding 
activation of the real-time encoder 12 and the storage of the MPEG2 stream 
to the video server side by capturing a using right of the real-time 
encoding data buffer 34 provided in the real-time encoder 12. When the 
disk groups on the video server side are switched, a new storing thread 
corresponding to the switching destination is activated in association 
with a switching preparation, a buffer using right of the storing thread 
before the switching is released at the switching timing, and the buffer 
using right is transferred to the new thread after the switching, thereby 
switching the storage destination of the MPEG2 stream. The real-time 
encoder operation processing unit 40 instructs the operating processes of 
the activation and stop of the encoding of the real-time encoder 12 by the 
storing thread 38 and the capture and release of the buffer using right. 
Various kinds of control parameters necessary for the processing operation 
of the long time recording processing unit 36 have been stored in the long 
time recording control block 42. 
In FIG. 2, the video server 16 in FIG. 1 is divided into two video servers 
16-1 and 16-2. The video server 16-1 has a video control process 44-1 and 
two disk groups 18-1 and 18-2. The video server 16-2 has a video control 
process 44-2 and two disk groups 18-3 and 18-4. Each of the disk groups 
18-1 to 18-4 uses a disk array in which a plurality of data disks and one 
parity disk are constructed in a plurality of ranks. Each of the video 
control processes 44-1 and 44-2 performs the real-time writing to any one 
of the disk groups 18-1 to 18-4 serving as a storage destination of the 
MPEG stream from the real-time encoder 12 by an instruction from the 
long-time recording processing unit 36 via the management server 22. The 
video control processes 44-1 and 44-2 also transfer the MPEG data streams 
in a real-time manner or due to the reading from the disk group in 
response to a reproducing request from the video reproducing terminal 
apparatus 20 in FIG. 1. As video servers 16-1 and 16-2 as mentioned above, 
for example, a video server system (VSS) known as F6407A manufactured by 
Fujitsu Ltd. can be used. In the video server system, it is possible to 
properly select the disk groups within a range from the minimum 
construction of two groups to the maximum construction of 16 groups. In 
case of the two disk groups as a minimum construction in FIG. 2, 25.8 GB 
corresponding to a capacity in which the data stream of MPEG2 transmitted 
from the real-time encoder 12 at 6 Mbps can be recorded for about seven 
hours is guaranteed. As a transmitting speed of the ATM network from the 
long time recording terminal apparatus 14 to the video control precesses 
44-1 and 44-2, 6 Mbps is guaranteed by using, for example, ATM-LAN. With 
respect to, for instance, ATM-LAN for the video reproducing terminal 
apparatus 20 side in FIG. 1, the transmitting speed depends on the number 
of video reproducing terminal apparatuses 20, namely, the number of 
clients. For instance, the transmitting speed is set to 6 Mbps for up to 
44 clients, 3 Mbps for up to 64 clients, and 1.5 Mbps for up to 104 
clients. It will be obviously understood that the ATM network 28 may be an 
ATM public network. The management server 22 comprises: a contents manager 
46; a video data table 48; and a disk group information table 50. The 
video data table 48 stores and manages information regarding video files 
stored in the disk groups 16-1 to 16-4 provided in the video servers 16-1 
and 16-2. Information regarding the disk groups 18-1 to 18-4 themselves 
provided in the video servers 16-1 and 16-2 has been stored and is managed 
in the disk group information table 50. The contents manager 46 decides 
the disk group serving as a storage destination having a vacant capacity 
requested by referring to the disk group information table 50 on the basis 
of a request from the long time recording processing unit 36 and provides 
the decided disk group to the long time recording terminal apparatus 14 
and video servers 16-1 and 16-2 side. The contents manager 46 also records 
and updates information of the video files into the video data table 48 in 
accordance with the recording to the video servers 16-1 and 16-2 by the 
long time recording processing unit 36. 
FIG. 3 shows the details of the long time recording control block 42 
provided in the long time recording processing unit 36 in FIG. 2. In the 
long time recording control block 42, a switching interval time 52, a 
prefix of a video file name 54, a video file serial number 56, a stored 
video file name 58, the number 60 of disk groups on the storage 
destination side, and disk groups 62 on the storage destination side have 
been stored. According to the embodiment, the switching interval time 52 
defines a time during which the data stream of MPEG2 transmitted from the 
real-time encoder 12 at 6 Mbps can be stored by a capacity of one disk 
group. For example, one hour is set as a switching interval time 52. As a 
prefix 54 of the video file name, since the video file name has been 
defined as "CAMERA1-5. MP2" in the embodiment, "CAMERA1-" as a prefix of 
the video file name is registered. As a next video file serial number 56, 
for example, "5" is registered. The stored video file name 58 is defined 
by "video server name, disk group name, and video file name". For 
instance, "/VSS1/DG1/CAMERA1-5. MP2" is registered. As the next number 60 
of disk groups on the storage destination side, the four disk groups 18-1 
to 18-4 in the video servers 16-1 and 16-2 in FIG. 3 are designated. The 
last disk groups 62 on the storage destination side are defined by 
combinations of the server names "VSS1 and VSS2" of the video servers 16-1 
and 16-2 and the group names "DG1 and DG2" in accordance with the order of 
the disk groups 18-1, 18-2, 18-3, and 18-4. 
FIG. 4 shows the video data table 48 provided in the management server 22 
in FIG. 2. Information regarding the recording of video data to the disk 
groups 18-1 to 18-4 provided in the video servers 16-1 and 16-2 has been 
stored in the video data table 48. That is, recording data location 
information 64, recording start time 66, recording end time 68, and a file 
size 70 of an image file in which kilobyte is used as a unit have been 
registered in the video data table 48. Explaining in more detail, the 
stored video file names 58 in the long time recording control block 42 in 
FIG. 3 have been sequentially registered in the recording data location 
information 64 in accordance with the storing order. The recording start 
time 66 is shown by year/month/day and hour/minute/second. The recording 
end time 68 is also similarly shown by year/month/day and 
hour/minute/second. The file size 70 indicates a size of a recording file 
per disk group. Since the video data has been continuously stored in the 
whole region, the same size of 2,764,800,000 kB is set. 
FIG. 5 is the disk group information table 50 provided in the management 
server 22 in FIG. 2. Information regarding the storage of the disk groups 
18-1 to 18-4 provided in the video servers 16-1 and 16-2 has been 
registered in the disk group information table 50. That is, a disk group 
name 72, a whole capacity 74, and a vacant capacity 74 have been 
registered in the disk group information table 50. 
FIG. 6 shows the encoding data buffer 34 provided in the real-time encoder 
12 in FIG. 2. In the embodiment, the real-time encoder 12 and long time 
recording terminal apparatus 14 mutually transmit and receive the video 
data via the encoding data buffer 34 provided on the memory. Since the 
encoding data buffer 34 is used as a ring buffer, a control area is 
provided at the head, a read pointer 78 and a write pointer 80 are 
recorded, and the remaining portion is used as a buffer area 82. 
FIG. 7 is a time chart of the continuous recording process of the invention 
which is performed in the system construction in FIG. 2. First, when the 
recording start is instructed to the long time recording terminal 
apparatus 14, the disk group 18-1 of the video server 16-1 is determined 
as a storage destination in the management server 22. On the basis of the 
decided disk group, a storage preparing request 100 is issued from the 
long time recording terminal apparatus 14 to the disk group 18-1, 
specifically speaking, to the video control process 44-1 of the video 
server 16-1 through the management server 22. When the storage preparation 
of the disk group 18-1 to the storage preparing request 100 is completed, 
a completion 102 of the storage preparation is responded to the long time 
recording terminal apparatus 14. The long time recording terminal 
apparatus 14 which received the response of the completion 102 of the 
storage preparation allows the real-time encoder 12 to start the encoding. 
Thus, a video signal from the video camera 10 is converted into video data 
104 of MPEG2 in a real-time manner and is stored into the disk group 18-1 
serving as a storage destination via the long time recording terminal 
apparatus 14 in a real-time manner. On the other hand, the long time 
recording terminal apparatus 14 monitors an arrival to, for example, one 
hour as a switching interval time to decide a switching timing 110 from 
the recording start to the next storage destination. When the present time 
approaches the switching timing 110, for example, the disk group 18-2 is 
decided as a next storage destination, a storage preparing request 106 is 
issued to the disk group 18-2, specifically speaking, to the video control 
process 44-1 of the video server 16-1 via the management server 22. It is 
sufficient to set a timing of the storage preparing request 106 into a 
time point which is preceding to the switching interval time by only a 
time necessary for the switching preparation. For example, it is 
sufficient to set the timing into a time point before one to a few 
minutes. When the storage preparing request 106 is received and the 
storage preparation of the disk group 18-2 is completed, the response of 
the completion 108 of the storage preparation is returned to the long time 
recording terminal apparatus 14. In this state, the long time recording 
terminal apparatus 14 establishes the storage preparation completion state 
for the next disk group 18-2 into a time point before the switching timing 
110. After the completion 108 of the storage preparation was established, 
when arrival of the switching timing 110 due to the elapse of one hour 
serving as a switching interval time is determined, the long time 
recording terminal apparatus 14 switches the storage destination from the 
disk group 18-1 so far to the disk group 18-2 serving as a next storage 
destination in the storage preparation completion state and stores the 
video data from the real-time encoder 12 into the disk group 18-2 in a 
real-time manner. In this instance, when the storage destination of the 
video data is switched from the disk group 18-1 to the disk group 18-2, a 
response of a storage completion 112 is replied to the long time recording 
terminal apparatus 14 side by the disk group 18-1. On the management 
server 22 side, when the response is received, the recording end time 68 
and file size 70 are registered into the video data table 48 in FIG. 4. 
The vacant capacity regarding the disk group 18-1 is updated in the vacant 
capacity 76 in the disk group information table 50 in FIG. 5. 
Subsequently, the long time recording terminal apparatus 14 restarts the 
time monitor of one hour serving as a preset switching interval time at 
the timing when the storage destination is switched to the disk group 
18-2. When the present time approaches the next switching timing, for 
example, the disk group 18-1 is decided as a storage destination and a 
storage preparing request 114 is issued. When the storage preparation is 
completed in the disk group 18-1, a completion 116 of the storage 
preparation is replied. In this instance, since the past video data has 
already been stored in the disk group 18-1 and there is no vacant area, 
old recorded data in the disk group 18-1 is erased in response to the 
storage preparing request 114, a vacant capacity necessary for the next 
recording is assured, and after that, the completion 116 of the storage 
preparation is replied. Consequently, in the continuous recording process 
of the time chart of FIG. 7, the video data from the real-time encoder 12 
is continuously recorded while alternately switching the disk groups 18-1 
and 18-2 every preset switching interval time. 
FIG. 8 shows flows of the video data and the control signals in the 
continuous recording process by the time chart of FIG. 7 with respect to 
the functional block diagram in FIG. 2. When receiving the recording start 
instruction, the long time recording processing unit 36 of the long time 
recording terminal apparatus 14 requests the determination of the storage 
destination to the management server 22. In response to the request, the 
contents manager 46 of the management server 22 decides, for example, the 
disk group 18-1 of the video server 16-1 as a first storage destination 
with reference to the video data table 48 and disk group information table 
56. The long time recording processing unit 36 accepts the connection of 
the disk group 18-1, so that the preparation is completed. When the 
preparation of the storage destination is completed, the long time 
recording processing unit 36 activates the storing thread 38 and activates 
the encoding of the NTSC/MPEG converting unit 32 of the real-time encoder 
12 via the real-time encoder operation processing unit 40. Simultaneously, 
the stream of MPEG2 video data is transmitted by capturing the using right 
of the real-time encoding data buffer 34 and the video data is written 
into the disk group 18-1 of the video server 16-1 serving as a first 
storage destination in a real-time manner under the control by the video 
control process 44-1. During the real-time storage of the video data to 
the disk group 18-1, the long time recording processing unit 36 monitors 
the switching interval time set by the long time recording control block 
42. When the present time approaches the switching timing by the switching 
interval time, the long time recording processing unit 36 activates a new 
storing thread which is used for the recording of the next storage 
destination and further issues a preparing request of the next storage 
destination to the management server 22. When receiving the storage 
preparation request, the contents manager 46 of the management server 22 
decides, for example, the disk group 18-2 of the video server 16-1 as a 
next storage destination with reference to the video data table 48 and 
disk group information table 50. When a vacant capacity can be assured, 
the contents manager 46 connects the disk group 18-2 to the long time 
recording processing unit 36. When the present time reaches the switching 
timing in the storage preparation completion state of the disk group 18-2 
serving as a next storage destination, the using right of the real-time 
encoding data buffer 34 of the real-time encoder 12 owned by the storing 
thread 38 in which the video data had been stored in the disk group 18-1 
is released, the buffer using right is transferred to the new storing 
thread activated in correspondence to the disk group 18-2 serving as a 
next storage destination. Therefore, the storage of the data stream of 
MPEG2 from the real-time encoder 12 to the disk group 18-1 is finished and 
the mode is switched to the start of storage to the disk group 18-2. In 
association with the end of storage to the disk group 18-1 at the 
switching timing, the contents manager 46 of the management server 22 
updates necessary information in the video data table 48 and disk group 
information table 50. In a manner similar to the above, the continuous 
recording of the video data by the switching of the storage destination 
according to the order of the disk groups 18-1, 18-2, 18-3 and 18-4 is 
repeated at, for example, every switching timing for determining the set 
switching interval time. 
Continuous Recording Process 
FIG. 9 is a flowchart for the whole continuous recording process according 
to the invention. When a recording start instruction is received in step 
S1, a recording starting process is executed in step S2. In step S3, a 
check is made to see if the present time is a switching preparation start 
time. When the present time reaches the switching preparation start time, 
a recording switching process is executed in step S4. When the recording 
switching process is finished, the presence or absence of a recording end 
instruction is discriminated in step S5. Until the recording end 
instruction is issued, the discrimination about the switching preparation 
start time in step S3 and the recording switching process in step S4 are 
repeated. When there is the recording end instruction in step S4, a 
recording end process is executed in step S6. 
FIG. 10 shows the details of the recording starting process in step S2 in 
FIG. 9. When a recording start instruction is issued to the long time 
recording processing unit 36, the long time recording terminal apparatus 
14 executes a long time recording initializing process in step S1. As 
shown in a flowchart of a subroutine of FIG. 11, in the long time 
recording initializing process, the initialization of the real-time 
encoder operation processing unit 40 and the connection of the contents 
manager 46 provided in the management server 22 are executed in step S1. A 
storage destination deciding process is executed in step S2 in FIG. 10. In 
the storage destination deciding process, as shown in a flowchart of a 
subroutine of FIG. 12, as a head element, for example, the disk group 18-1 
serving as "/VSS1/DG1" is captured as a storage destination disk group 
from the storage destination disk groups 62 of the long time recording 
control block 42 in FIG. 3 in step S1. In step S2, as a video file name of 
the captured storage destination disk group 18-1, a video file name 
"/VSS1/DG1/CAMERA1-5. MP2" is formed by a combination of the prefix 54 of 
the video file name and video file serial number 56 of the long time 
recording control block 42 in FIG. 3 and the storage destination disk 
group 62 captured in step S1. 
Referring again to FIG. 10, when the storage destination deciding process 
is finished in step S2, a vacant capacity assuring process to assure a 
vacant capacity into the decided storage destination is executed in step 
S3. When the vacant capacity can be assured in step S4, step S5 follows. 
When the vacant capacity cannot be assured, the processing routine is 
returned to step S2 and the storage destination deciding process is again 
executed and the vacant capacity is assured. The details of the vacant 
capacity assuring process in step S3 are as shown in a subroutine in FIG. 
13. In the vacant capacity assuring process, first in step SI, a file size 
of the video file is calculated from the switching interval time. It is 
sufficient to calculate a rough estimate as a file size. In step S2, a 
vacant capacity of the decided storage destination disk group is obtained 
from the disk group information table 50 in FIG. 6 provided for the 
management server 22. When it is decided in step S3 that the obtained 
vacant capacity is sufficient, the processing routine is returned to the 
processing routine in FIG. 10. The processing routine advances from step 
S4 to a process in step S5. When the vacant capacity is insufficient in 
FIG. 13, step S4 follows. The video files included in the storage 
destination disk group are retrieved from the video data table 48 in FIG. 
4 and the oldest video file is taken out and deleted, thereby assuring the 
vacant capacity. The vacant capacity is again checked in step S3. In the 
embodiment, the video files are stored by using the whole disk group. 
Therefore, when the vacant capacity is not enough, by deleting all of the 
video data included in the storage destination disk group, the vacant 
capacity is assured. For example, in FIG. 8, the disk groups 18-1 to 18-4 
of the video servers 16-1 and 16-2 are sequentially switched as a storage 
destination and the video data is stored. During the storage to the last 
disk group 18-4, the next switching destination becomes the first disk 
group 18-1. Since there is obviously no vacant capacity in the disk group 
18-1, in this case, all of the video data in the disk group 18-1 serving 
as a next storage destination is deleted, thereby assuring the vacant 
capacity for the next storage. 
Referring again to FIG. 10, when the vacant capacity can be assured in step 
S4 by the vacant capacity assuring process in step S3, step S5 follows. 
The storing thread 38 is activated like a long time recording processing 
unit 36 in FIG. 8 and a storage preparing request is issued via the 
management server 22 to the video control process 44-1 of the video server 
16-1 having the disk group 18-1 as a first storage destination which was 
decided. In response to the storage preparing request, the video control 
process 44-1 of the video server 16-1 executes a write preparing operation 
of the video data to the disk group 18-1. By receiving the connection of 
the storage preparation completion from the video server 16-1, it is 
notified to the storing thread 38 in step S6. Thus, a writing path of the 
video data to the disk group 18-1 serving as a storage destination is 
established from the storing thread 38. In step S7, when the storing 
thread 38 instructs the start of the encoding to the real-time encoder 
operation processing unit 40, the start of the encoding is instructed from 
the real-time encoder operation processing unit 40 to the NTSC/MPEG 
converting unit 32 of the real-time encoder 12. At the same time, the 
using right of the encoding data buffer 34 is captured. Thus, the encoding 
such that the stream of the video data of MPEG2 of the video image 
photographed by the video camera 10 is transmitted from the real-time 
encoder 12 and is stored from the storing thread 38 to the disk group 18-1 
of the video server 16-1 serving as a storage destination in a real-time 
manner is started. 
FIG. 14 is a flowchart for the processing operation of the storing thread 
38 provided in the long time recording processing unit 36 in FIG. 8. In 
the long time recording processing unit 36, when the present time 
approaches the switching timing which is determined by the switching 
interval time, the storing thread 38 is activated. In step S1, a process 
for waiting for the storage preparation completion from the video server 
is performed. That is, simultaneously with the activation of the storing 
thread, the storage preparation is requested to the video server having 
the disk group serving as a storage destination and the system waits for 
the connection. In response to the preparing request, when the storage 
preparation by the connection of the storing device of the video server 16 
is completed, step S2 follows. A capturing process of the buffer using 
right for requesting the using right of the real-time encoding data buffer 
34 provided in the real-time encoder 12 via the real-time encoder 
operation processing unit 40 and waiting for the capture of the using 
right is executed. When the buffer using right can be captured, the 
storage of the video data sent by the encoding of the real-time encoder 12 
into the disk group of the storage destination is started. Thus, in step 
S3, a recording start time is recorded into the video data table 48 of the 
management server, namely, into the location information of the relevant 
video data of the recording start time 66 in the video data table 48 
having the contents of FIG. 4. When the recording of the video data is 
started, a check is made in step S4 to see if there is a recording end 
instruction or there is a request for capturing the buffer using right to 
switch to the next storage destination. If there is none of the recording 
end instruction and the capture of the buffer using right, the system 
waits for the accumulation of the data into the real-time encoding data 
buffer 34 in step S5. When a predetermined amount of data is accumulated, 
the buffer data is transmitted and stored into the disk group as a storage 
destination by the storing thread 38 in step S6. When the present time 
approaches the switching timing based on the switching interval time, as 
shown in the time chart of FIG. 7, a new storing thread corresponding to 
the next storage destination is activated and the storage preparing 
request 106 is issued. A storage preparation completion state by the 
connection of the disk group 18-2 serving as a next storage destination is 
obtained for the storing buffer which was newly activated in response to 
the storage preparation completion 108. When the present time reaches the 
switching timing in the storage preparation completion state for the next 
storage destination, the new storing thread corresponding to the next 
storage destination requires the buffer using right. When the request for 
the buffer using right by the new storing thread for switching is 
discriminated in step S4, step S7 follows. The buffer using right held by 
the storing thread so far is released and transferred to the new storing 
buffer as a new storage destination. In step S8, the path to the video 
server having the disk group of the storage destination is disconnected. 
In final step S9, the recording end time 68 and file size 70 are recorded 
into the video data table 48 in FIG. 4 and the series of processes are 
finished. With respect to the storing thread which was newly activated in 
association with the switching of the storage destination, processes 
similar to those of the storing thread in FIG. 14 are also executed. 
FIG. 15 is a flowchart for the recording switching process in step S4 in 
FIG. 10. When the present time approaches the switching timing designated 
by the switching time interval, first in step S1, the next storage 
destination of the video file is determined. A vacant capacity is assured 
in step S2. When the assuring of the vacant capacity fails in step S3, the 
processing routine is returned to step S1 and the processes are again 
executed. The details of the process for assuring the vacant capacity are 
the same as those in the flowchart of FIG. 13. When the vacant capacity 
can be assured, the new storing thread is activated and the storage 
preparation is requested to the video server 16 in step S4. In step S5, 
the connection in association with the storage preparation completion from 
the video server 16 is accepted and is notified to the new storing thread. 
When the switching timing is discriminated in step S6, the old storing 
thread transfers the buffer using right to the new storing thread and the 
encoding is taken over and finished, thereby switching the storage 
destination. 
FIG. 16 is a flowchart showing the details of the recording end process in 
step S6 in FIG. 9 as a subroutine. In the recording end process, in step 
S1, an end instruction is issued to the storing thread which is at present 
operating and the storing thread which receives the end instruction 
disconnects the video server. In step S2, the storing thread disconnects 
the contents manager 46 of the management server 22. In final step S3, the 
process of the real-time encoder operation processing unit 40 is finished 
and the encoding operation of the real-time encoder 12 is stopped. 
FIG. 17 is a time chart for another embodiment of the continuous recording 
process according to the invention. The embodiment is characterized in 
that the recording preparation for the next storage destination is 
executed just after the switching of the storage destination. Thus, a 
drop-out of the video data when an error occurs during the recording can 
be minimized. When the recording start is instructed to the long time 
recording terminal apparatus 14, the storage preparing request 100 is 
issued to the disk group 18-1 decided as a first storage destination. 
After waiting for a reply of the storage preparation completion 102, the 
recording of the video data 104 from the real-time encoder 12 is started. 
When the recording of the video data 104 is started, in the embodiment, 
the disk group 18-2 serving as a next storage destination is immediately 
determined and the storage preparing request 106 is issued. By receiving a 
reply of the storage preparation completion 108, a switching possible 
state for the disk group 18-2 serving as a next storage destination is 
established just after the start of the recording. The switching possible 
state denotes that the storing thread corresponding to the disk group 18-2 
serving as a next storage destination is activated and the system is in a 
switching waiting state due to the capture of the buffer using right by 
the arrival at the switching timing 110 based on the switching interval 
time. As mentioned above, by completing the recording preparation for the 
next storage destination just after the switching of the storage 
destination, if an error should occur before reaching the switching 
timing, the storage destination is immediately switched to the next disk 
group 18-2 in the preparation completion state without needing to wait for 
a time that is required for deciding the storage destination and preparing 
after an error occurred. The drop-out of the video data when the error 
occurs can be minimized. Even in the case where the present time reaches 
the switching timing 110 and the storage destination is switched from the 
disk group 18-1 to the disk group 18-2 and a reply of the storage 
completion 112 is derived from the disk group 18-1, the storage preparing 
request 114 is issued to the disk group 18-1 serving as a next storage 
destination just after the reception of such a reply, a response of the 
storage preparation completion 116 is derived, and a storage switching 
possible state for the disk group 18-1 is always produced even during the 
recording to the disk group 18-2. 
FIG. 18 is a flowchart for the continuous recording process according to 
the embodiment of executing the time chart of FIG. 17. The recording 
starting processes based on the recording start instruction in steps S1 
and S2 are the same as those in the flowchart of FIG. 9. However, in step 
S3 subsequent to the recording start, a recording switching preparing 
process for the next storage destination is immediately performed. After 
that, a check is made in step S4 to see if the present time reaches the 
switching preparation start time. The recording switching process in step 
S5 after reaching the switching preparation start time, the discrimination 
about the end instruction in step S6, and the recording end process in 
step S7 when there is the end instruction are the same as those in steps 
S4, S5, and S6 in FIG. 9. 
Parallel Recording 
FIG. 19 shows another embodiment of the invention. The embodiment is 
characterized by raising the reliability by always recording the same 
video image into two storage destinations. When receiving the recording 
start instruction, the long time recording processing unit 36 provided for 
the long time recording terminal apparatus 14 requests the management 
server 22 to capture the two disk groups serving as storage destinations. 
For example, two disk groups 18-1 and 18-2 provided in the video server 
16-1 are determined as storage destinations and a necessary vacant 
capacity is assured. When the disk groups 18-1 and 18-2 as two storage 
destinations can be decided, the long time recording processing unit 36 
activates the storing thread 38 and issues the storage preparing request 
to the video control process 40-1 of the video server 16-1. In response to 
the storage preparing request, when the storage preparation for the disk 
groups 18-1 and 18-2 is completed, a storage preparation completion 
response is made to the long time recording processing unit 36 and the 
video server 16-1 is connected. Subsequently, the storing thread 38 
activates the NTSC/MPEG converting unit 32 of the real-time encoder 12 
through the real-time encoder operation processing unit 40 and captures 
the using right of the encoding data buffer 34, thereby sending the stream 
of the video data of MPEG2 and starting the parallel storage of the video 
data into the two disk groups 18-1 and 18-2 of the video server 16-1 
serving as storage destinations. When the parallel storage of the video 
data is started, the long time recording processing unit 36 monitors a 
switching preparation start time when the present time approaches the 
preset recording switching interval time. When the present time reaches 
the switching preparation start time, two disk groups in which the video 
data is subsequently stored, for example, the disk groups 18-3 and 18-4 of 
the video server 16-2 are determined as storage destinations and a vacant 
capacity is assured. The storage preparing request is sent to the video 
server 16-2 side by the activation of the new storing thread to store the 
video data after the switching. The connection of the video server 16-2 
side based on the response of the storage preparation completion is 
received. When the present time reaches the switching timing based on the 
switching interval time in this state, the storing thread before switching 
releases the buffer using right and transfers the buffer using right to 
the new storing thread in the storage preparation completion state after 
the switching. Therefore, the storage destinations of the video data are 
switched from the parallel storage into the disk groups 18-1 and 18-2 of 
the video server 16-1 to the parallel storage into the two disk groups 
18-3 and 18-4 of the video server 16-2. By this switching, as for the same 
two disk groups 18-1 and 18-2 of the video server 16-1 in which the 
recording was finished, if the recording operations for both disk groups 
are successful, one recording data, for example, only the recording data 
of the disk group 18-1 is left and the recording data of the other disk 
group 18-2 is erased. When it is recognized by the end of the recording 
that the recording of either one of the disk groups 18-1 and 18-2 fails, 
the recording data of a normal one of the disk groups in which the 
recording doesn't fail is left. By the parallel recording to the two 
storage destinations as mentioned above, even if the recording on one 
storage destination side fails during the recording, so long as the 
recording on the other storage destination side continues, the video image 
is not lost. When the recordings to both of the storage destinations are 
successful, the recording data of one storage destination is deleted. 
Therefore, a vain operation due to the double preservation of the 
recording data can be omitted. 
FIG. 20 is a flowchart for the processing operation of the parallel 
recording in FIG. 19. When there is a recording start instruction in step 
S1, the recording starting process is executed in parallel to the two 
recording destinations on the video server side in step S2. During the 
recording, a check is made in step S3 to see if the present time has 
reached the switching preparation start time. When the present time 
reaches the switching preparation start time, step S4 follows. Next two 
storage destinations are prepared and a recording switching process for 
switching the storage destinations at a switching timing is executed. When 
the recording switching is finished, a check is made in step S5 to see if 
the recordings to both of the two storage destinations in which the 
recording was finished are successful. When both of the recordings are 
successful, the recording data of one storage destination is left in step 
S6. If either one of the recordings fails, the recording data of the 
successful storage destination is left in step S7. By repeating the 
processes in steps S3 to S7 as mentioned above until the recording end 
instruction is issued in step S8, the video data is continuously recorded. 
When there is the end instruction, a recording end process is executed in 
step S9 and the series of processes are finished. 
Preservation of Necessary Video Data 
FIG. 21 shows another embodiment of a continuous recording system according 
to the invention. The embodiment is characterized in that when all of the 
video images recorded for a long time are not necessary, only the 
necessary video data is refuged and preserved by using a sensor and 
recording resources can be effectively utilized. A detection signal from a 
sensor 84 to monitor a state of a monitoring target of the video camera 10 
is inputted to the long time recording terminal apparatus 14. As a sensor 
84, for example, in the case where the monitoring target by the video 
camera 10 is a monitoring video image of a structure such as a debris 
barrier, a sensor to detect a destruction of the structure as a monitoring 
target is used. In the case where the monitoring video image by the video 
camera 10 is a target for the purpose of security to monitor persons who 
pass an entrance/exit of facilities, a sensor to detect the passage of the 
persons is used. When a notification of the occurrence of an event is 
received by the detection signal from the sensor 84, the long time 
recording processing unit 36 of the long time recording terminal apparatus 
14 copies the video data from the position that is preceding to the 
present time point of the event occurrence by the time designated by the 
user from the video data of the disk group of the storage destination 
which is at present recording into the disk group for refuge. For example, 
since four disk groups 18-1 to 18-4 are provided in the video servers 16-1 
and 16-2, three disk groups 18-1 to 18-3 among them are designated as 
storage destinations which are used for switching of the continuous 
recording and the remaining disk group 18-4 is decided as a storage 
destination to refuge the recording data as much as a predetermined time 
when the notification of the event occurrence is received from the 
detection signal of the sensor 84. Therefore, for example, when the disk 
group 18-1 is determined as a storage destination by the long time 
recording processing unit 36 and the notification of the event occurrence 
is received by the detection signal from the sensor 84 during the 
recording of the video data, the long time recording processing unit 36 
allows the video control process 44-1 of the video server 16-1 to execute 
a copying process for copying the video data from the position that is 
preceding to the present time point of the disk group 18-1 during the 
recording by the time designated by the user into the disk group 18-4 for 
refuge. Thus, the video data as much as a predetermined time corresponding 
to the event occurrence based on the detection signal of the sensor 84 is 
preserved in the disk group 18-4 for refuge. In case of constructing a 
monitoring system for monitoring a destruction of a structure and a 
security system for monitoring the entering/leaving of the persons, only 
the necessary video data can be automatically refuged and preserved. 
FIG. 22 is a flowchart for the processing operation of an embodiment in 
which the necessary video data is automatically refuged and preserved in 
FIG. 21. When there is a recording start instruction in step S1, a 
recording starting process is executed in step S2. In step S3, the arrival 
at the switching preparation start time is monitored. When the present 
time reaches the switching preparation start time, a recording switching 
process for deciding the next storage destination, establishing the 
storage preparation completion before switching, and switching the storage 
destination at a switching timing is executed in step S4. Thus, the 
continuous recording is performed while successively switching the storage 
destination. When there is a notification of the event occurrence from the 
sensor during the recording in step S5, step S6 follows. The recording 
data which is preceding to the present time point by a predetermined time 
is copied into the disk group for refuge. The continuous recording in 
association with the notification of the event occurrence from the sensor 
is repeated until there is an end instruction in step S7. If there is the 
end instruction, a recording end process is executed in step S8 and the 
series of processes are finished. 
FIG. 23 shows another embodiment of the invention characterized in that the 
necessary video data is left as high picture quality data due to the event 
occurrence by the sensor detection signal. In the continuous recording 
system of the invention, in case of converting the video image into 
digital data and storing, there is a proportional relation between the 
picture quality and the data size. Therefore, it is necessary to leave the 
video images when an event to be monitored doesn't occur. However, in a 
case such that it is sufficient that the picture quality is low, as for 
the video data except for the case of the occurrence of an event, the 
picture quality is reduced and the resultant video data is stored, so that 
a storing capacity which is required on the storage destination side can 
be saved. In the embodiment of FIG. 23, an NTSC/MPEG2 converting unit 32-1 
for encoding the high picture quality data and an NTSC/MPEG1 converting 
unit 32-2 for encoding the low picture quality data are provided and can 
transmit the MPEG2 high picture quality data and MPEG1 low picture quality 
data to the long time recording terminal apparatus 14 side via encoding 
buffers 34-1 and 34-2 in a real-time manner, respectively. In order to 
enable the high picture quality data and the low picture quality data to 
be transferred and stored in parallel, a long time recording processing 
unit 36-1 for the high picture quality and a long time recording 
processing unit 36-2 for the low picture quality are provided for the long 
time recording terminal apparatus 14. Each of the long time recording 
processing units 36-1 and 36-2 has the storing thread 38, real-time 
encoder operation processing unit 40, and long time recording control 
block 42. On the basis of a recording start instruction, the long time 
recording processing units 36-1 and 36-2 decide, for example, the disk 
group 18-1 of the video server 16-1 as a storage destination of the MPEG2 
high picture quality data and the disk group 18-2 as a storage destination 
of the MPEG1 low picture quality data and record the encoded high picture 
quality data and low picture quality data in parallel, respectively. 
During the recording of the high picture quality data and low picture 
quality data to the disk groups 18-1 and 18-2 of the video server 16-1 as 
mentioned above, if the notification of the event occurrence as a 
monitoring target such as destruction of a structure, passage of persons, 
or the like is received by the detection signal of the sensor 84, the long 
time recording processing unit 36-1 for the high picture quality requests 
the video control process 44-1 of the video server 16-1 to execute the 
process such that the video data that is preceding to the time point of 
the event occurrence by a predetermined time designated by the user is 
copied and preserved into a predetermined disk group for refuge. As a disk 
group for refuge of the high picture quality data, for example, the disk 
group 18-6 among the four disk groups 18-3 to 18-6 provided in the video 
server 16-2 has previously been designated. Therefore, when there is the 
event occurrence notification by the detection signal of the sensor 84, 
the video data that is preceding to the time point of the event occurrence 
by the predetermined time in the disk group 18-1 is copied and preserved 
into the disk group 18-6 for refuge. When the present time reaches a 
predetermined switching interval time during the parallel recording of the 
high picture quality data and the low picture quality data to the disk 
groups 18-1 and 18-2, the storage destinations are switched to the disk 
groups 18-3 and 18-4 of the video server 16-2 decided as next storage 
destinations. With respect to the disk groups 18-1 and 18-2 in which the 
recording is finished by completion of the switching, in the video data of 
the low picture quality recorded in the disk group 18-2, the low picture 
quality data of the recording portion other than the high picture quality 
data refuged to the disk group 18-4 for refuge due to the event occurrence 
is extracted and copied into the disk group 18-4 for refuge. Thus, if 
there is no event, the low picture quality data of a small capacity is 
stored as a low picture quality video file into the disk group 18-4 for 
refuge every switching interval time. If there is the event occurrence 
during the recording, the high picture quality data as much as a 
predetermined time until the event occurrence is preserved as video files 
corresponding to the event occurrence. Thus, the video images of the 
necessary portion corresponding to the event occurrence can be left as 
high picture quality video data without increasing a storing capacity for 
preservation. 
FIG. 24 is a flowchart for the processing operation of an embodiment in 
which the necessary portion is left as video data of a high picture 
quality in FIG. 23. When there is a recording start instruction in step 
S1, two storage destinations on the video server side are designated and a 
parallel recording starting process of the video data of the low picture 
quality and high picture quality is executed in step S2. When the present 
time reaches a switching preparation start time during the parallel 
recording in step S3, step S4 follows. A recording switching process for 
preparing the next two storage destinations and switching them at a 
switching timing is executed. After completion of the recording switching 
process, the recording data of the low picture quality is copied to the 
disk group for refuge in step S5. When there is a notification of the 
event occurrence by the detection signal from the sensor during the 
recording in step S6, the recording data of the high picture quality that 
is preceding to the present time point by a predetermined time is copied 
into the disk group for refuge in step S7. The above processes are 
repeated until a recording end instruction is issued in step S8. 
FIG. 25 shows another embodiment of the invention in which the same event 
occurrence as that in FIG. 23 is discriminated, the video data of a high 
picture quality is stored with respect to only the necessary portion, and 
the other portions are stored as low picture quality data. The embodiment 
is characterized in that the event occurrence is discriminated by 
analyzing a parameter of a head-out of the MPEG2 data stream as high 
picture quality video data which is sent from the real-time encoder 12 
irrespective of the detection signal from the sensor. To discriminate the 
event occurrence from the parameter of the MPEG2 data stream, an event 
discriminating unit 86 is provided for the long time recording processing 
unit 36-1 for the high picture quality data provided in the long time 
recording terminal apparatus 14. The event discriminating unit 86 detects 
a change in image from a parameter included as header information in the 
data stream of MPEG2. When there is a rapid image change, the event 
occurrence is decided. As a parameter of MPEG2 which can be used to detect 
the image change, for example, differential information of the image can 
be used. That is, a DCT coefficient is described at the lowest level of 
the data structure of MPEG2. As the DCT coefficient is smaller, a 
difference between the image and a reference picture plane is smaller. 
Therefore, a threshold value of the DCT coefficient to discriminate a 
magnitude of the image change is set and when the DCT coefficient 
exceeding the threshold value is obtained, the event occurrence due to the 
large image change is discriminated. 
As a parameter corresponding to the DCT coefficient, there are the 
following parameters. 
______________________________________ 
DDSL (DCT DC Size Luminance) 
DDSC (DCT DC Size Chrominance) 
DDD (DCT DC Differential) 
FDC (First DCT Coefficients) 
SDC (Subsequent DCT Coefficients) 
______________________________________ 
Therefore, it is sufficient to use any one of them. As another method of 
discriminating the event occurrence from the parameter of the data stream 
of MPEG2, there is a method of using information of a motion vector. 
Information regarding the movement of a macro block from the reference 
picture plane exists in the data of MPEG2. The macro block is a block 
obtained by collecting a plurality of DCT conversion blocks and dividing 
the picture plane into a few blocks. As motion information of the macro 
block, there are 
______________________________________ 
MHC (Motion Horizontal Code) 
MVC (Motion Vertical Code) 
______________________________________ 
As the motion information of the macro block is larger, the image change is 
larger, so that the event occurrence can be discriminated by it. Further, 
as a method of discriminating the event occurrence by detecting the image 
change from the data stream of MPEG2, there is a method of using the 
number of intramacro blocks. In MPEG2, although the difference from the 
reference picture plane is used, when the difference is too large, a block 
which directly describes the image information is used instead of the 
difference irrespective of the P picture or the I picture. Such a block is 
called an intramacro block. Therefore, if the presence of the intramacro 
block is detected, it is detected that there is a large change in image, 
so that the event occurrence can be discriminated by it. As a method other 
than the above methods, the event occurrence can be discriminated by 
detecting the image change by using a proper parameter of MPEG. When the 
event discriminating unit 86 determines the event occurrence by detecting 
that the image change is large from the data stream of MPEG2, in a manner 
similar to the embodiment of FIG. 23, for instance, while the high picture 
quality data is at present being recorded in the disk group 18-1 and the 
low picture quality data is at present being recorded in the disk group 
18-2, with respect to the video data of the high picture quality of the 
disk group 18-1, the video data which is preceding to the time point of 
the event occurrence by a predetermined time designated by the user is 
copied and preserved into, for example, the disk group 18-2 of the video 
server 16-2 which has been preset as a storage destination for refuge. 
When the present time reaches a predetermined switching interval time and 
the recording mode is switched from the recording to the disk groups 18-1 
and 18-2 to the recording to the disk groups 18-3 and 18-4 serving as next 
storage destinations, the low picture quality recording data in the 
portion in which the high picture quality recording data refuged due to 
the event occurrence is removed from the low picture quality recording 
data in the disk group 18-2 in which the recording has been completed is 
copied into the disk group 18-6 for refuge. 
FIG. 26 is a flowchart for the processing operation in case of 
discriminating the event occurrence from the data stream of the high 
picture quality of MPEG2 in FIG. 25. The recording process is 
fundamentally the same as that in case of discriminating the event 
occurrence from the detection signal of the sensor in FIG. 24 except that 
the presence or absence of the event occurrence is discriminated from the 
high picture quality data, namely, from the data stream of MPEG2 in step 
S6. 
FIG. 27 shows an embodiment of a recording medium in which the continuous 
recording program to execute the continuous recording process of the 
invention has been recorded and which can be read by a computer. As a 
recording medium, there are a removable recording medium 200 such as 
CD-ROM, floppy disk, or the like, a storing device 204 of a program 
provider 202 who provides a program by a line 206, and further, a memory 
device 210 such as RAM, hard disk, or the like of a processing apparatus 
208 in which the program has been installed. The program provided by the 
recording medium is loaded into the processing apparatus 208 and is 
executed in the main storage. 
According to the invention as mentioned above, by recording the digital 
video data while switching the storing devices serving as storage 
destinations, the video data of a length exceeding a capacity of one 
storing device serving as a storage destination can be continuously 
recorded without causing a drop-out of the video data. By continuing the 
recording while cyclically switching the storing devices serving as a 
plurality of storage destinations, a semipermanent continuous recording 
can be realized. Further, the event occurrence as a monitoring target is 
discriminated during the recording, the video data of the necessary 
portion is automatically refuged and preserved, and the video data of the 
necessary portion corresponding to the event occurrence is preserved 
without increasing the storing capacity for preservation and can be 
efficiently utilized for an image analysis after the event occurrence or a 
search of causes of the event occurrence. Owing to the association of the 
long time recording function and the recording function of the video 
server, by reproducing the video data during the recording in a real-time 
manner and transmitting to a reproducing terminal, the video image during 
the recording can be also monitored in a real-time manner. By associating 
the resources of the continuous recording of the video server with a 
database, a video image at an arbitrary time can be searched from a number 
of recorded video files and can be easily monitored. Further, with respect 
to the recording data divisionally preserved as a plurality of video files 
in the video server, by using the associating function for allowing the 
recording data to be seen as one continuous file, the recording video 
images can be continuously monitored without needing to switch the images 
on a video file unit basis. 
Although the above embodiments have a form such that the long time 
recording terminal apparatus 14, video server 16, video reproducing 
terminal apparatus 20, and management server 22 are distributed and 
arranged through ATM networks 26, 28, and 30 as shown in FIG. 1, either 
the distributive arrangement or the collective system can be properly 
determined as necessary. 
In the above embodiments, although the management of the operations of the 
long time recording terminal apparatus 14 and video server 16 and the 
management of the recording resources of the video server 16 have been 
performed by the management server 22, the function of the management 
server 22 can be also provided for the long time recording terminal 
apparatus 14 side or video server 16 side instead of the exclusive-use 
apparatus. 
Further, in the system configuration of FIG. 1, the analog video signal 
from the video camera 10 has been encoded into the digital video signal in 
a real-time manner and has been continuously recorded. However, it will be 
obviously understood that the video signal from the video camera 10 is 
once recorded to the VTR and, after that, it is reproduced and supplied to 
the real-time encoder 12 as necessary, thereby continuously recording to 
the video server 16. 
The invention, further, is not limited by the numerical values shown in the 
above embodiments. Moreover, the invention incorporates proper variations 
and modifications within the purview of the spirit of the invention 
without departing from the objects of the invention.