JPH1118073A - Supervisory equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a supervisory equipment that is hardly affected by the effect of external disturbance, where a supervisory range is not limited. SOLUTION: A television signal equivalent to one field corresponding to an object is compressed by the JPEG IC 20, and compressed image data are stored in an HDD 24 according to the instruction of a microcomputer 18. Furthermore, the microcomputer 18 reads a data size of the subtracted image data from the JPEG IC 20 and detects the difference between that data size and a data size of the compression image data compressed precedingly and detects the motion of an object when the difference is a prescribed value or over. Since the motion of the object is detected based on the data size of the compression image data, the motion of the entire image data is detected. Thus, the equipment is hardly affected by external disturbances, where the supervisory range is not limited but only luminance is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monitoring apparatus, and more particularly to a monitoring apparatus used for security cameras, for example, for detecting the movement of a person or an object.

[0002]

2. Description of the Related Art In a conventional monitoring apparatus of this type, an object is photographed by a camera, a luminance signal is extracted from a predetermined area of a part of a television signal corresponding to the object, and the extracted luminance signal is compared between fields. Thus, the movement of the subject is detected.

[0003]

However, in this monitoring apparatus, since the motion is detected based on the change in the luminance signal, the motion may be erroneously detected due to the influence of disturbance. In other words, when the camera connected to the monitoring device is shooting an outdoor scenery or the like, the luminance is significantly different between daytime and nighttime, so that the movement is detected even though there is no actual movement. I was In addition, since a partial area of the television signal is detected, it is difficult to detect, for example, the movement of people in a convenience store as a whole.

[0004] Therefore, a main object of the present invention is to provide a monitoring device in which the monitoring range is not limited and is hardly affected by disturbance.

[0005]

A first aspect of the present invention is a monitoring apparatus for monitoring a subject by a television signal input from a camera, and compresses a television signal at a constant compression ratio to compress compressed image data. The monitoring device includes a compression unit that outputs and a motion detection unit that detects a motion of a subject based on a data size of two consecutive compressed image data.

A second aspect of the present invention is a monitoring apparatus for monitoring a subject by a television signal input from a camera. The monitoring device compresses the television signal to a predetermined data size and outputs compressed image data. A monitoring device includes a compression ratio detection unit that detects a compression ratio of data and a motion detection unit that detects a motion of a subject based on a change in two consecutive compression ratios.

[0007]

According to the first aspect of the present invention, a television signal of a subject input from a camera is compressed by, for example, JP
It is compressed at a constant compression rate by the EG method. The motion detecting means detects a difference in data size between two consecutive compressed image data, and detects a motion of the subject when the difference is equal to or larger than a predetermined value.

In the second invention, a television signal of a subject input from a camera is compressed to a predetermined data size by, for example, a JPEG method by a compression means. The motion detecting means detects a motion of the subject based on a change in two consecutive compression rates detected by the compression rate detecting means. That is, the compression unit generates compressed image data including the table value of the quantization table. Then, for example, a change in the compression ratio is detected based on a change in the table value. If the change in the compression ratio is equal to or greater than a predetermined value, the motion detecting means detects the motion of the subject.

[0009]

According to these inventions, the movement of the subject is detected based on the change in the data size or the compression ratio of the compressed image data, so that the movement of the entire subject can be detected. Therefore, the monitoring range is not limited,
It is less susceptible to disturbance such as a change in brightness only.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG.
Includes an input terminal 12, a television signal corresponding to a subject from a camera (not shown) is input to the input terminal 12, and is converted into digital data by an A / D converter 14. The television signal output from the A / D converter 14 is stored in the field memory 16. When a command for compression is given from the microcomputer 18 to the IC 20, the television signal for one field is transmitted to the IC 20 by the JPE.
The compressed image data is compressed by the G method and temporarily stored in the buffer 22. Then, the compressed image data is transferred to the hard disk drive (HDD) 2 according to the instruction of the microcomputer 18.
4 recorded. The photographing of the subject is continuously performed by a camera (not shown), but the compression of the television signal is executed at predetermined intervals according to an instruction from the microcomputer 18. Also, in the compressed image data, SOI (Start Of Image; End of Still Image), EOI (End Of Image; End of Still Image) and table values of the quantization table used for compression are added to the actually compressed television signal. And so on.

When reproducing the compressed image data recorded in the HDD 24, desired compressed image data is read from the HDD 24 in accordance with an instruction from the microcomputer 18, and given to the IC 20 via the buffer 22. In the IC 20, the compressed image data supplied from the buffer 22 is expanded, and the expanded image data is supplied to the D / A converter 26. The D / A converter 26 converts the expanded image data into analog data, and outputs the converted image data from the output terminal 28 to a monitor (not shown).

More specifically, the IC 20 includes an input terminal 30 as shown in FIG.
Is temporarily stored in a video memory area 32a of a dynamic RAM (DRAM) 32. The television signal stored in the video memory area 32a is processed by the JPE under the control of the memory control circuit 34 or under the control of the CPU 36.
It is compressed according to the G format. That is, the television signal stored in the video memory area 32a is
The CPU 36 performs DCT (discrete cosine transform) on a square pixel block of 8 × 8 pixels, quantizes the DCT coefficients, and performs Huffman coding on the quantized data. The compressed image data obtained by such a process from DCT to Huffman coding (baseline process) is written in the working area 32b. ROM
38, a plurality of quantization tables 3 having different table values
8a is stored, and the quantization table 38a corresponding to the size of the television signal to be compressed is selected. The data size of the compressed image data is recorded in a register 32c provided in the DRAM 32, and the table number of the quantization table 38a used for compression is recorded in a register 32d. The CPU 36 is also connected to the microcomputer 18 via a bus via an interface (not shown), and the microcomputer 18 gives instructions such as reading the data size of the compressed image data, changing the quantization table 38a, and compressing or expanding. Therefore, when the reading of the data size of the compressed image data is instructed, the CPU 36 provides the microcomputer 18 with the data size of the compressed image data recorded in the register 32c.

When decompressing the compressed image data, the HD
Desired compressed image data is read from D24 according to the instruction of the microcomputer 18, and the read compressed image data is
It is temporarily stored in the working area 32b of the RAM 32. Then, the CPU 36 subjects the compressed image data to a process reverse to that at the time of compression. That is, the compressed image data is Huffman-decoded, the decoded data is dequantized, and the dequantized data is ID-coded in units of 8 × 8 pixel blocks.
CT (inverse DCT) is performed. The image data decompressed in this manner is then transferred to the DRA by the memory control circuit 34.
It is developed in the video memory area 32a of M32.

In operation, a television signal corresponding to a subject is converted into digital data by an A / D converter 14 and stored in a field memory 16. Microcomputer 1
When a compression instruction is given from 8, the one-field television signal converted into digital data is output from the field memory 16 to the IC 20, where the television signal is compressed according to the JPEG format. The compressed television signal is supplied to a buffer 22.
The microcomputer 18 reads out the data size of the compressed image data from the HDD 24 via the HDD 24. The microcomputer 18 stores the read data size and the memory 18a.
Is detected, the difference from the data size of the previously compressed image data that has been compressed is detected. If the detected difference is equal to or greater than a predetermined value (several Kbytes in this embodiment), motion is detected.
Then, a movement is warned by a display device (not shown). In this embodiment, the predetermined value is set to several kilobytes, but if this value can be set freely, the level of motion detection can be adjusted. Also, the quantization table 38
The table number of “a” is recorded in the register 32d,
The compressed image data to be compared have the same quantization table 38a.
Is quantized using

The microcomputer 18 performs the above operation in FIG.
The processing is performed according to the flowchart shown in FIG. When the photographing is started, the process is started, and in step S1, the IC 20 performs a compression process on the image data. In step S3, the data size of the compressed image data is read out, and in step S5
Then, the difference between the data size of the previous compressed image data and the data size of the current compressed image data is detected. In step S7, it is determined whether the difference between the data sizes detected in step S5 is equal to or greater than a predetermined value. Step S
If “YES” in step 7, ie, if motion is detected,
In a succeeding step S9, a movement is warned and the process proceeds to the step S11. If “NO” in the step S7, the process directly proceeds to the step S11. In step S11, the data size of the compressed image data read this time is stored in the memory 1
8a, and returns to step S1.

The monitoring apparatus 10 of the other embodiment is the same as the embodiment of FIG. 1 except that the method of detecting motion is different and that the average value of a plurality of table values is recorded in the memory 18a. Duplicate description is omitted. In operation, a television signal corresponding to a subject is converted into digital data by the A / D converter 14 and stored in the field memory 16. The one-field television signal converted into digital data is stored in an IC from the field memory 16.
20 and the IC 20 compresses the television signal according to the JPEG format. Microcomputer 18
Reads the data size of the compressed image data and determines whether the data size is a fixed size (32 Kbytes in this embodiment). If the data size is a fixed size, the compressed image data held in the buffer 22 is recorded in the HDD 24 according to the instruction of the microcomputer 18 and a plurality of table values (three table values in this embodiment) are obtained from the compressed image data. Is taken out. If the data size is not constant, the television signal is compressed again using another quantization table 38a.

The microcomputer 18 calculates an average value for the table value taken out this time, detects a difference between the previously calculated average value recorded in the memory 18a and the currently calculated average value, and determines the difference between the average values as a predetermined value. In the above case, motion is detected,
The movement is warned by a display device (not shown). However,
The plurality of table values are table values extracted from a predetermined table of AC components, and do not include DC components. If the predetermined value can be set freely, the level of motion detection can be adjusted.

That is, the microcomputer 18 processes the flowchart shown in FIG. When shooting starts, processing starts,
In step S21, the television signal is compressed by the IC 20. In step S23, the data size of the compressed image data is read, and in subsequent step S25, it is determined whether the data size of the compressed image data read in step S23 is a predetermined value. If "YES" in the step S25, in a succeeding step S27, a plurality of table values are extracted from the compressed image data.
If "NO" in 25, an instruction to change the quantization table 38a is given in step S29, and the process returns to step S21. In step S31, the average value of the extracted table values is calculated, and in step S33, the difference between the previously calculated average value and the currently calculated average value is detected. Step S3
In 5, it is determined whether the detected difference is equal to or greater than a predetermined value,
If “YES”, that is, if a motion is detected, a motion is warned in step S37 and the process proceeds to step S39. If “NO” in step S35, the process directly proceeds to step S39. In step S41, the average value calculated this time is stored in the memory 18a, and the process returns to step S21.

The monitoring apparatus 10 of the other embodiment is also the same as the embodiment of FIG. 1 except that the method of detecting the motion is different and that a plurality of table values are recorded in the memory 18a. Is omitted. In this monitoring device 10,
As in the other embodiments, the television signal is compressed to a predetermined size, and a plurality of table values (three table values from the AC component in this embodiment) are extracted from the predetermined image from the compressed image data. The microcomputer 18 individually compares the plurality of table values taken out this time with the plurality of table values taken out last time recorded in the memory 18a. The microcomputer 18 detects the movement of the subject when the compared table values are not equal to or greater than a predetermined value (in this embodiment, two or more table values are not equal), and warns the movement by a display device (not shown). . If the number of table values that do not match can be freely determined, the level of motion detection can be adjusted.

In the other embodiments, a plurality of table values are extracted, but one table value (representative table value) may be extracted from a predetermined table. In this case, the one table value retrieved this time and the one retrieved last time recorded in the memory 18a
The two table values are compared, and when the table values do not match, the movement is detected, and the display device (not shown) warns of the movement.

According to these embodiments, the movement of the subject is detected based on the change in the data size and the compression ratio of the compressed image data, that is, the change in the table value.
The movement of the entire subject can be detected. Therefore, the monitoring range is not limited, and it is hardly affected by disturbance such as a change in only the luminance. It should be noted that the IC 20 of the above embodiment is an IC 20 manufactured by Fuji Micro Device Co., Ltd.
“MD36050X” is used.

In the above-described embodiment, the table value A
Although the C component is taken out, when detecting a motion by a change in luminance of the entire subject, the DC value of the table value is used.
The components may be extracted and the DC component table values may be compared. Further, in the above-described embodiment, the data size of the compressed image data is read from the IC 20. However, the data size may be read from the compressed image data held in the buffer 22. At this time, the data size can be known by counting the number of bytes from SIO to EIO of the compressed image data.

Further, in the above-described embodiment, all the compressed image data is recorded in the HDD 24. However, the compressed image data is stored in the HDD 24 only when the movement of the subject is detected.
24 may be recorded.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram showing a JPEG IC of the embodiment in FIG. 1;

FIG. 3 is a flowchart showing a part of the process of the embodiment in FIG. 1;

FIG. 4 is a flowchart showing a part of a process according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Monitoring device 16 ... Field memory 18 ... Microcomputer 20 ... IC 22 ... Buffer 24 ... HDD

Claims (6)

[Claims] 1. A monitoring device for monitoring a subject by a television signal input from a camera, comprising: compression means for compressing the television signal at a constant compression ratio and outputting compressed image data; A monitoring device comprising: a motion detection unit configured to detect a motion of the subject based on a data size of the two pieces of compressed image data. 2. A monitoring apparatus for monitoring a subject by a television signal input from a camera, comprising: compression means for compressing the television signal to a predetermined data size and outputting compressed image data; A monitoring device comprising: a compression ratio detecting unit that detects a compression ratio; and a motion detecting unit that detects a movement of the subject based on two consecutive changes in the compression ratio. 3. The compression means generates the compressed image data including a table value by compressing a television signal according to a quantization table, and the motion detection means includes a table value included in two consecutive compressed image data. 3. The monitoring device according to claim 2, further comprising a compression ratio change detecting unit that detects a change in the compression ratio based on a change in the compression ratio. 4. The compression ratio change detecting means for extracting a plurality of table values from the compressed image data, and an average value calculating means for calculating an average value of the plurality of table values extracted by the extracting means. The monitoring device according to claim 3, further comprising: detecting a difference between the average values of two consecutive compressed image data. 5. A compression rate change detecting means for extracting a plurality of table values from the compressed image data, and a table value equal to or more than a certain value among the plurality of table values of two consecutive compressed image data is individually obtained. The monitoring device according to claim 3, wherein the monitoring device detects whether or not the monitoring condition matches. 6. The monitoring system according to claim 3, wherein said compression ratio change detecting means detects a difference between table values of said two consecutive compressed image data, and takes out means for extracting a representative table value from said compressed image data. apparatus.