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Claims  |
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What is claimed is:
1. A video monitoring system comprising:
a sending station for outputting a video signal indicative of an image of
an object;
a receiving station including monitor means for reproducing an image from
the video signal; and
a communication path established between the sending station and the
receiving station only when monitoring is required through the monitor
means,
wherein said sending station comprises:
pickup means for at all times picking up the image of the object and
outputting the video signal indicative of the image;
memory means for storing a video signal on the object corresponding to a
particular event to be monitored, said memory means including a frame
memory having a capacity to store an image signal of at least one field;
sensor means for detecting the occurrence of the particular event to be
monitored; and
control means for storing in said memory means the video signal outputted
from the pickup means in accordance with the detection of the occurrence
of the particular event by said sensor means and for reading the video
signal stored in said memory means to transmit the video signal to said
receiving station after a communication path is established between said
sending station and said receiving station,
wherein said control means puts said memory means in a write-enabled state
in which the video signal outputted from said pickup means can be written
at all times and, when said sensor means detects the occurrence of the
particular event, said control means puts said memory means in a
write-disabled state to maintain the video signal already stored in said
memory means.
2. A video monitoring system according to claim 1, wherein said
communication path includes a control signal path for transmitting a
control signal to establish a logical connection between said sending and
receiving stations and a video signal from said sending station to said
receiving station when said sending and receiving stations are logically
connected,
the video signal outputted from said pickup means and the video signal
stored in said memory means being transmitted to said receiving station
through said video signal path on a time division manner after the
establishment of the communication path.
3. A video monitoring system according to claim 2, wherein the video signal
stored in said memory means is transmitted to said receiving station
through said video signal path only when said receiving station makes a
request for transfer of the video signal through said control signal path.
4. A video monitoring system according to claim 2, wherein the video signal
stored in said memory means is transmitted to said receiving station
through said video signal path unconditionally before the video signal is
outputted from said pickup means and after the communication path is
established between said sending and receiving stations.
5. A video monitoring system according to claim 2, wherein said receiving
station includes a copying memory for copying and storing the video signal
read out from said memory means and received through said video signal
path, and supplies the video signal copied and stored in said copying
memory to said monitoring means at any required point of time.
6. A video monitoring system according to claim 1, wherein said
communication path includes a control signal path for transmitting a
control signal to establish a logical connection between said sending and
receiving stations and a video signal from said sending station to said
receiving station when said sending and receiving stations are logically
connected,
the video signal outputted from said pickup means and the video signal
stored in said memory means being transmitted to said receiving station
through said video signal path on a frequency division manner after the
establishment of the communication path.
7. A video monitoring system according to claim 6, wherein the video signal
stored in said memory means is transmitted to said receiving station
through said video signal path only when said receiving station makes a
request for transfer of the video signal through said control signal path.
8. A video monitoring system according to claim 6, wherein the video signal
stored in said memory means is transmitted to said receiving station
through said video signal path unconditionally before the video signal is
outputted from said pickup means and after the communication path is
established between said sending and receiving stations.
9. A video monitoring system according to claim 6, wherein said receiving
station includes a copying memory for copying and storing the video signal
read out from said memory means and received through said video signal
path, and supplies the video signal copied and stored in said copying
memory to said monitoring means at any required point of time.
10. A video monitoring system according to claim 1, wherein said
communication path comprises a control signal path for transmitting a
control signal to establish a logical connection between said sending and
receiving stations, and a first and second video signal paths for
transmitting the video signal from said sending station to said receiving
station when said sending and receiving stations are logically connected
to each other;
the video signal outputted from said pickup means after the establishment
of said communication path being transmitted to said receiving station
through said first video signal path, and the video signal stored in said
memory means being transmitted to said receiving station through said
second video signal path.
11. A video monitoring system according to claim 10, wherein said receiving
station includes a copying memory for copying and storing the video signal
read out from said memory means and received through said second video
signal path, and supplies the video signal copied and stored in said
copying memory to said monitoring means at any required point of time.
12. A video monitoring system comprising:
a plurality of sending stations each for outputting a video signal
indicative of an image of an object;
a receiving station including monitor means for reproducing an image from
the video signal; and
a communication path selectively established between the plurality of
sending stations and the receiving station to thereby monitor the video
signal from a particular sending station through the monitor means when
monitoring is required,
wherein each of said sending stations comprises:
pickup means for at all times picking up the image of the object and
outputting the video signal indicative of the image;
memory means for storing a video signal on the object corresponding to a
particular event to be monitored, said memory means including a frame
memory having a capacity to store an image signal of at least one field;
sensor means for detecting the occurrence of the particular event to be
monitored;
first control means for storing in said memory means the video signal
outputted from the pickup means in accordance with the detection of the
occurrence of the particular event by said sensor means; and
second control means for transmitting to the receiving station data on the
identification of the sending stations selectively connected to the
receiving station together with data on detection of the occurrence of the
particular event by said sensor means,
whereby after a communication path is established between a sending station
and said receiving station, the stored video signal is read from said
memory means and transmitted to said receiving station, and wherein said
first control means puts said memory means in a write-enabled state in
which the video signal outputted from said pickup means can be written at
all times and, when said sensor means detects the occurrence of the
particular event, said first control means puts said memory means in a
write-disabled state to maintain the video signal already stored in said
memory means.
13. A video monitoring system according to claim 12, wherein said
communication path comprises a plurality of control signal paths
simultaneously established between the corresponding sending stations and
the single receiving station for transmitting control signals therethrough
and a video signal path selectively established when required for
transmitting a video signal from said respective sending stations to said
receiving station where said respective sending stations and said
receiving station are logically connected to each other; and
said second control means in each of said sending stations transmits data
on the detection of the particular event and data on identification of
that sending station through said the corresponding control signal path to
said receiving station; and
said receiving station further comprises:
display means for visually displaying data on the identification of a
sending station corresponding to the transmitted data on the detection of
the particular event on the basis of the transmitted data;
sending station selecting means for instructing the establishment of the
video signal path between said receiving station and any particular
sending station; and
third control means for establishing the video signal path through said
control signal path between said receiving station and said particular
sending station, and fetching through the established video signal path
the video signal outputted from said pickup means of said particular
sending station and the video signal stored in said memory means by making
a request for transmission of the video signals.
14. A video monitoring system according to claim 13, wherein said receiving
station includes a copying memory for copying and storing the video signal
read out from said memory means and fetched through said video signal path
and said third control means inputs the video signal copied and stored in
said copying memory to said monitoring means at any required point of
time.
15. A video monitoring system according to claim 12, wherein said
communication path comprises a plurality of control signal paths
simultaneously established between the corresponding sending stations and
the single receiving station for transmitting control signals therethrough
and a first and a second video signal path selectively established when
required for transmitting a video signal from said respective sending
stations to said receiving station where said respective sending stations
and said receiving station are logically connected to each other; and
said second control means in each of said sending stations transmits data
on the detection of the particular event and data on identification of
that sending station through said the corresponding control signal path to
said receiving station; and
said receiving station further comprises:
display means for visually displaying data on the identification of a
sending station corresponding to the transmitted data on the detection of
the particular event on the basis of the transmitted data;
sending station selecting means for instructing the establishment of the
video signal path between said receiving station and any particular
sending station; and
third control means for establishing the video signal path through said
control signal path between said receiving station and said particular
sending station, fetching through the first video signal path the video
signal outputted from said pickup means of said particular sending
station, and fetching through the second video signal path said the video
signal stored in said memory means by making a request for transmission of
the video signals.
16. A video monitoring system according to claim 15, wherein said receiving
station includes a copying memory for copying and storing the video signal
read out from said memory means and fetched through said video signal path
and said third control means inputs the video signal copied and stored in
said copying memory to said monitoring means at any required point of
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to video monitoring systems applied to systems such
as security systems, industrial television (ITV) systems, etc., and more
particularly to a video monitoring system applied to an environment where
a communication path between a sending station which acquires the video
signal and a receiving station which receives and monitors the video
signal by means of a display or the like is established only when
monitoring the video signal is required.
2. Description of the Related Art
A conventional video monitoring system has a dedicated transmission path
fixedly provided between the sending station and the receiving station.
However, according to the conventional video monitoring system, the
transmission path is always established even in an ordinary state where
monitoring is not required.
At present, a video monitoring system has been considered in which there is
provided a switching networks for selectively connecting the sending
station and the receiving station only when monitoring the video is
required.
However, in such system the establishment of a communication path
(telephonic communication path) through the switching network takes
considerably long time. Therefore, although the establishment of the
communication path is started immediately after the occurrence of a
particular event to be monitored such as an abnormality is detected, it is
impossible to monitor the most important video images during the initial
period of occurrence of the event. In other words, monitoring of the video
images becomes possible after the communication path has been established,
and therefore monitoring is not from the occurrence of the event, but from
the establishment of the communication path.
In case that the video monitoring system is used in a security system, only
video images generated some time after invasion of a robber can be
monitored by the receiving station. In case that the video monitoring
system is used in an ITV system, only video images generated some time
after the occurrence of abnormality can be monitored. Accordingly, such
monitoring systems cannot provide important video images to be monitored.
SUMMARY OF THE INVENTION
The present invention is made in view of the above-described situations,
and therefore, it is an object of the present invention to provide a video
monitoring system capable of establishing a communication path between the
sending station which acquires the video signal and the receiving station
which monitors the acquired video signal through a display only when
monitoring is desired and capable of reliably monitoring video images
immediately after the occurrence of a particular event to be monitored.
In order to achieve the above object, the sending station comprises a
memory for storing a video signal on an object corresponding to a
particular event to be monitored, a sensor for detecting the occurrence of
a particular event to be monitored, and a control unit for storing in the
memory the video signal outputted from an image pickup device in
accordance with the detection of the occurrence of the particular event by
the sensor, whereby after a communication path is established between the
sending station and the receiving station, the stored video signal is read
from the memory and transmitted to the receiving station.
The video signal stored in the memory is transmitted to the receiving
station at any time. The video signal may directly be transmitted to the
receiving station after the establishment of the communication path or in
accordance with a request for transmission of such video signal from the
receiving station.
Thus, the video signals generated immediately after the sensor detects the
occurrence of a particular event, which are usually most important in the
security system or ITV system, can be stored in the memory. Accordingly,
even though a considerable time is dissipated for the establishment of the
communication path, the video signals stored in the memory can be
monitored after the establishment of the communication path. Video signals
picked up after the establishment of the communication path can, of
course, be monitored on a real time basis.
The memory may be a frame memory whose capacity is large enough to store at
least one field of video signals outputted from the pickup device. The
video signals stored in the frame memory can be monitored with a minimum
resolution.
The use of memory means having a large capacity permits acquisition of
video images of a plurality of screens lasting several seconds to several
minutes. When the control unit places the memory in a write-enabled state
and stores in the memory image signals corresponding in quality to the
storage capacity of the memory when the sensor detects the occurrence of a
particular event, the time dissipated for the establishment of the
communication path is compensated for by a time corresponding to the
storage capacity of the memory means (in more accurately, the time
additionally including the pickup speed of the pickup device and the speed
at which the video signal is written into the memory) to thereby maintain
important videos generated during that time.
Of course, any process may be adopted for controlling the memory to store
the video signals in the memory. For example, the memory may always be in
a state where video signals outputted from the pickup device can be
written. When the sensor detects the occurrence of the particular event,
the memory may be disabled any more to store so as to reserve the video
signals already stored.
In case that an ISDN network is used as the switching network which
connects the sending station and the receiving station, the communication
path is constituted by a control signal path which delivers and receives a
control signal for logical connection between the sending and receiving
stations and a video signal path to transmit the video signal from the
sending station to the receiving station when the sending and receiving
stations are logically connected. If the video signal path is a single
path, the video signal stored in the memory and the video signal outputted
from the pickup device on a real time basis are transmitted from the
sending station to the receiving station using the video signal path on a
time or frequency division manner. If the video signal path includes the
two separate paths, the video signal stored in the memory and the video
signal outputted from the pickup device on a real time basis are
transmitted through the corresponding video signal paths to the receiving
station.
In any of the above cases, if a copy memory which copies and stores the
video signal read from the memory and transmitted through the video signal
path is provided in the receiving station and the video signal copied and
stored in the copying memory is delivered to the monitor at any required
time, the video signal stored in the memory and the video signal outputted
from the pickup device on a real time can rapidly be switched and
reproduced in the receiving station.
If there is a plurality of such sending stations and video signals acquired
by the respective sending stations are monitored together by a single
receiving station, the video monitoring system according to the present
invention is also advantageous.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of the system structure of a first embodiment of
a video monitoring system according to the present invention.
FIG. 2 schematically illustrates the structure of a transmission path shown
in FIG. 1.
FIG. 3 is a flowchart indicative of the illustrative operation of the
system of the FIG. 1 embodiment.
FIG. 4 is a flowchart indicative of a further illustrative operation of the
system.
FIG. 5 is a block diagram of the system structure of a second embodiment of
a video monitoring system according to the present invention.
FIG. 6 is a block diagram of a modification of the system structure of the
second embodiment shown in FIG. 5.
FIG. 7 is a block diagram of the system structure of a third embodiment of
the video monitoring system according to the present invention.
FIG. 8 schematically illustrates an indicator disposed on a control console
of the third embodiment of FIG. 6.
FIGS. 9A-9E are block diagrams which schematically illustrate variations of
use of a frame memory which can be arranged in the respective systems of
the above embodiments.
FIG. 10 schematically illustrates the structure of a bus in each of the
above systems and presupposed especially when the frame memory is used in
the form of FIG. 9(E).
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a first embodiment of a video monitoring system according to
the present invention.
As shown in FIG. 1, the system basically includes a video transmitter 1 as
a sending station, a video receiver 2 as a receiving station, and a
transmission path 3 which logically connects the transmitter and receiver
such that they can transmit and receive various signals using, for
example, an ISDN network.
The video transmitter 1 is connected to a television camera 11 which acts
as a pickup device which at all times picks up an object to be monitored,
and a sensor 15 which senses the occurrence of a particular event such as
abnormality to be monitored.
When the video monitoring system is used, for example, as the ITV system,
the sensor 15 is a level sensor, a temperature sensor or a video sensor
called a motion detector which detects the specified move and state of the
object. If the video monitoring system is used as the security system, a
door sensor or an infrared sensor is used which is known as sensing the
presence of an invader by sensing the temperature of his body or as
sensing the presence of an invader due to interruption of infrared rays.
The video transmitter 1 includes an A/D (analog-to-digital) converter 12
having various functions necessary for converting an analog video signal
outputted from the television camera 1 to a digital video signal as well
as for converting the digital video signal to image data (Although such
functions cannot simply be called "analog-to-digital conversion", we call
them so for simplicity of the description), frame memories 13A and 13B for
temporarily storing the A/D converted video signal, a network interface 14
which performs a predetermined switching operation such as processing call
origination between the transmitter 1 and the receiver 2 through the
transmission path 3 using the ISDN network, and a controller 16 which
systematically controls those elements as a transmitter which transmits a
required video.
Frame memories 13A and 13B each has a capacity large enough to store the
A/D converted video signal, for example, of one frame, temporarily and are
prescribed with reference to application in the present embodiment as
follows:
(1) Frame memory 13A:
This memory is used to store the video signals outputted from television
camera 11 and corresponding to a particular event on a monitored object;
and
(2) Frame memory 13B:
This memory is used as buffer means for adjusting the timing at which the
video signals outputted from television camera 11 and obtained by picking
up the state of the object after the communication path is established
between the transmitter and the receiver 2 are transmitted on a real time
basis.
Writing/reading a video signal corresponding to the application of these
memories 13A and 13B is controlled collectively by the controller 16.
The controller 16 includes, for example, a microcomputer which starts up
the A/D converter 12 on the basis of a signal indicative of the detection
of the particular event by the sensor 15 to convert the video signal
outputted from television camera 11 to a digital signal, writes one frame
of the converted video signal into the frame memory 13A for storing
purposes, writes the subsequent digitally converted video signal into the
frame memory 13B while making call origination to the network interface 14
to perform a process for logical connection between the transmitter 1 and
the receiver 2 though the transmission path 3. Such video signal
processing and subsequent video signal transmission performed mainly by
the controller 16 will be described in detail later with reference to FIG.
3 or 4.
The video receiver 2 includes a network interface 21 to perform a
predetermined switching operation in conjunction with the network
interface 14 to establish a communication path between the receiver 2 and
the transmitter 1 on the basis of a call received through the transmission
path 3, a frame memory 22 which temporarily stores the (digital) video
signal received from the transmitter 1 after the establishment of the
communication path, a D/A converter 23 having various functions necessary
for converting the digital video signal read from the frame memory 22 to
an analog video signal as well as for reproducing the analog signal as
images (such functions are simply called A/D in the specification) and a
controller 25 which systematically controls the respective operations of
those elements.
A CRT display 24 connected to the video receiver 2 reproduces as a
monitored image the analog video signal outputted by the D/A converter 23.
A control console 26 connected to the video receiver 2 is used by the
operator to input a request for switching between the video signal (stored
in the frame memory 13A), for example, existing at the occurrence of the
particular event and the subsequent real-time video signal (transmitted
through the frame memory 13B), etc. If such a switching request is input
through the control console 26, the resulting command is transmitted to
the controller 25 and hence to the controller 16 of the video transmitter
1 through the network interface 22, transmission path 3 and the network
interface 14. When the controller 16 receives such request, it switches
the frame memory the reading of which is controlled by the controller 16
at that time from the frame memory 13B to the memory 13A or vice versa.
Also, as will be described in greater detail, call origination can be made
from the receiver 2 to the transmitter 1 through the console 26.
The frame memory 22 provided in the receiver 2 has a capacity to store, for
example, one frame of the image signal, like the frame memory 13A or 13B
and temporarily stores the video signal received from the transmitter 1
and mainly used as buffer means for adjusting the timing at which the
monitored image is reproduced on the display 24.
FIG. 2 shows on example of the communication path established as
transmission path 3 of FIG. 1. As mentioned above, the communication path
is established as the transmission path 3 on the basis of call origination
from either one of the sending and receiving ends. In the present
embodiment, as shown in FIG. 2, part of the band is allocated to a channel
used for transmission and reception of various control signals and the
remaining band portion is allocated to channels for transmission of the
video signals, which are transmitted in a multiplexed manner on a time or
frequency division basis.
If compression is required for suppressing the redundancy of the video
signal transmitted through the transmission path 3 in this way, an
encoding/compression unit (not shown) in the network interface 14 provided
in the video transmitter 1 compresses such video signal and restores the
video signal through a decoding/expansion unit (not shown) in the network
interface 21 provided in the video receiver 2.
FIG. 3 shows one example of the procedures of acquisition and transmission
of the monitored video performed by the system of the present embodiment,
which will be described in detail below with reference to FIG. 3. Assume
here that the video signals existing at and after the occurrence of a
particular event such as, for example, an abnormal water level, to be
monitored as in an ITV system used to monitor the water level in a dam
have importance.
If now the sensor 15 (in this case, for example, a water level sensor)
detects the occurrence of a particular event such as an abnormal water
level, and a detection signal from sensor 15 indicative of the occurrence
of such abnormal event is input to the controller 16 of the video
transmitter 1 (step 301 in FIG. 3), the video transmitter 1 is started up
in response to this signal. The video transmitter 1 then acquires the
video signal to be monitored and transmits the acquired video signal in
the manner recited below:
(1) When the controller 16 receives the detection signal, it first enables
the A/D converter 12, puts the frame memory 13A in a write-enabled state,
converts to a digital video signal an analog video signal corresponding to
the video of the object (in this case, for example, a region where danger
is expected to occur when an abnormal water level occurs in a dam) when
the monitored particular event is detected, and stores the converted
signal in the frame memory 13A (step 302 in FIG. 3). Writing image signals
into the frame memory 13A is made until the frame memory 13A (in the
present embodiment, for one frame of the video signal) is filled to
capacity and then writing and reading are inhibited to maintain the stored
video signals. After writing into the frame memory 13A is inhibited, the
other frame memory 13B is put in write and read-enabled state and the
subsequent videos of the object are temporarily stored in the frame memory
13B and then sequentially read out.
(2) Simultaneously with such control over the frame memories, the
controller 16 sends an indication of call origination to the network
interface 14 through which it starts to perform a call operation to
establish a communication path between the transmitter and the video
receiver 2 (step 303 in FIG. 3). Whether the communication path is
established or not is determined by the reception, by the network
interface 14, of an acknowledge signal returned by the video receiver 2 in
response to the call origination (step 304 in FIG. 3).
(3) When the controller 16 determines that the communication path between
the transmitter 1 and the receiver 2 is established through such call
operation, it delivers the video signals, sequentially written into and
fetches from the frame memory 13B, as indicating the so-called real time
videos of the object, to the network interface 14 and transmits these
signals to the video receiver 2 through the established communication path
(step 305 in FIG. 3). The video receiver 2 fetches the thus transmitted
video signals through the network interface 21, sequentially writes the
fetched video signals through control provided by the controller 25 into
the frame memory 22, while reading these signals sequentially from the
memory 22 and converting (demodulating) these read digital video signals
through the D/A converter 23 to analog video signals. The video receiver 2
further inputs the demodulated analog video signals to the CRT display 24
to reproduce the transmitted video signals. If the operator makes a
request for transfer of the videos stored at the occurrence of the
particular event, or a request or instruction to terminate the monitoring
operation, etc., through the control console 26 at the video receiver 2,
the video receiver 2 reports such request or instruction through the
controller 25 to the controller 26 of the video transmitter 1;
(4) When the controller 16 (video transmitter 1) receives a request for
transfer of the stored video (step 306 in FIG. 3), it, for example,
switches the addressing to switch the frame memory from which the video
signal is to be read from the memory 13B to the memory 13A, reads the
video (image) signal stored in the frame memory 13A while sending the
video signal to the video receiver 2 through the network interface 14
(step 307 in FIG. 3);
(5) After the controller 16 (video transmitter 1) has transmitted the video
stored in the frame memory 13A in response to the transfer request, it
again switches the frame memory from which the video signal is to be read
from the frame memory 13A to the frame memory 13B and transmits the above
mentioned so-called real-time video of the object to the video receiver 2
(step 309 in FIG. 3), and, if the controller 16 receives an instruction
for terminating the monitoring operation (step 308 in FIG. 3), the
controller 16 causes the network interface 14 to switch off the line and
returns the A/D converter 12 and frame memories 13A and 13B to their
inactive states, namely, temporarily terminates its processing and waits
for the next reception of the detection signal from the sensor 15.
As just described above, according to acquisition and transmission of the
video signal of the object by the system of this embodiment, the video of
the object existing after the occurrence of a particular event such as an
abnormal water level to be monitored can be monitored efficiently. The
video signal existing at the occurrence of the particular event to be
monitored can be reliably captured and stored and the stored video can be
reproduced for monitoring purposes at any point in time which the operator
desires.
As mentioned above, FIG. 3 shows the procedures of acquisition and
procedures of transmission of the videos to be monitored in the video
monitoring system applied to an ITV system where the videos of the object
existing at and after the occurrence of the particular event to be
monitored have significance. Another example in which the video to be
monitored is acquired and transmitted in the video monitoring system of
the embodiment applied to the security system will be described with
reference to FIG. 4. As mentioned above, in the security system, a video
existing at the occurrence of a particular event (in this case, "there is
an invader") such as the video of the coverage to be monitored by the
television camera 11 when somebody unlawfully invades the coverage is most
important.
If the sensor 15 (in this case, for example, a door sensor) senses the
occurrence of a particular event (the presence of an invader, etc.) and
the resulting detection signal is input to the controller 16 of the video
transmitter 1 (step 401 in FIG. 4), the video transmitter 1 is started up
on the basis of the detection signal as in the previous embodiment. The
started video transmitter 1 acquires and transmits the video to be
monitored through the controller 16 in the steps recited below:
(1) Receiving the detection signal, the controller 16 first enables the A/D
converter 12, puts the frame memory 13A in a write-enabled state, converts
to a digital video signal the analog video signal corresponding to the
video of the object (in this case, for example, the inside of a room to be
monitored, for example) at the time when a particular event to be
monitored has been detected, and stores the converted signal in the frame
memory 13A (step 402 in FIG. 4). Writing the video signals into the frame
memory 13A is performed until the frame memory 13A is filled to capacity,
writing and reading are then inhibited for maintaining the stored video
signals, as mentioned above. After writing into the frame memory 13A is
inhibited, the other frame memory 13B may be put in write- and
read-enabled state. Alternatively, especially in this case, the other
frame memory 13B may be put in a write-disabled state at this time;
(2) The controller 16 give to the network interface 14 an indication to
make call origination simultaneously with the control of the frame
memories, and starts call origination to establish a communication path
between the transmitter 1 and the receiver 2 through the network interface
14 (step 403 in FIG. 4). Whether the communication path has been
established or not is determined by the reception, by the network
interface 14, of an acknowledge signal returned by the video receiver 2 in
response to the call origination (step 404 in FIG. 4);
(3) When the controller 16 determines that the communication path has been
established between the transmitter 1 and the receiver 2 through such call
origination, it puts the frame memory 13A in a read-enabled state and
transmits the video signal stored in the memory 13A to the video receiver
2 through the network interface 14 and the established communication path
(step 405 in FIG. 4). The video receiver 2 fetches the thus transmitted
video signal through the network interface 21, sequentially writes the
fetched video signals into the frame memory 22 through the controller 25,
sequentially reads those signals from the memory 22 and converts
(demodulates) the thus read digital video signals through the D/A
converter 23 to analog video signals. The video receiver 2 further inputs
the thus obtained analog video signals to the CRT display 24 to reproduce
the transmitted videos. This causes the video of the object at the time of
occurrence of the particular event to be outputted through the display 24
for monitoring purposes. When the operator makes a request for
transmission of the subsequent real-time video of the object or a request
or instruction for termination of the monitoring operation through the
console 26 at the video receiver 2, the video receiver 2 reports this fact
to the video transmitter 1 through its controller 25;
(4) When the controller 16 (video transmitter 1) receives a request for
transmission of the real time video (step 407 in FIG. 4), it switches the
frame memory, to be controlled, from the memory 13A to the memory 13B to
put the frame memory 13B thereafter in a read-write enabled state,
delivers into the network interface 14 the video signals, sequentially
written into and sequentially read out from the memory 13B, as showing the
so-called real time video of the object and transmits the video signal to
the video receiver 2 through the communication path (step 408 in FIG. 4);
and
(5) When the controller 16 (video transmitter 1) receives an instruction to
terminate the monitoring operation in the meantime (step 406 in FIG. 4),
it causes the network interface 14 to cut off the line, returns the A/D
converter 12 and frame memories 13A and 13B to their inactive states,
namely, temporarily terminates the processing and waits for the next
arrival of the detection signal from the sensor 15.
As mentioned above, according to the process for acquiring and transmitting
the video in the manner shown in FIG. 4, the video of the object existing
at the occurrence of the particular event and regarded as the most
important is surely captured and stored. After the establishment of the
communication path, such video can immediately be monitored, so that a
very high reliability system is constructed as the security system.
While the control procedures shown in FIGS. 3 and 4 are beforehand written
and registered as a control procedure program for the controller 16 of the
video transmitter 1 in a program memory (not shown), it is optional which
of the controlling procedures of FIGS. 3 and 4 is to be selected in the
system of the FIG. 1 embodiment. Namely, a convenient control procedure
may be selected in accordance with the property of an applied system such
as an ITV system or a security system.
The videos are registered in any form into the system of the embodiment.
Only one of the control procedures shown in FIGS. 3 and 4 may be
registered in the program memory to support that control procedure.
Alternatively, both the control procedures may be registered in the
program memory to support them and one of those control procedures may be
selected and carried out by setting a dip switch (not shown) or the like.
While in the above embodiment each frame memory 13A, 13B, 22 has been
illustrated having a storage capacity for a one-frame video signal,
selection of such memory capacity is optional. Especially, | | |
