KR0176172B1 - Method for reproducing the record of a supervisory camera and apparatus suitable for them - Google Patents

Abstract

In the monitoring system, a recording method for reducing the amount of data of a screen to be recorded, a reproduction method corresponding thereto, and a recording / reproducing apparatus suitable therefor are disclosed.

The recording method of the surveillance system according to the present invention comprises the steps of: digitally converting a screen shot of the background of the surveillance space and storing it as a background screen in a memory and a recording medium; Converting the captured screen of the surveillance space into a digital signal; Detecting a difference screen having a difference component between the digitally converted screen and a background screen stored in the memory; And sequentially recording the difference screen on the recording medium.

The recording method of the surveillance system according to the present invention can significantly reduce the screen data to be recorded by storing the difference screen between the background screen of the surveillance space and the photographed screen stored in advance so that the recording capacity of the recording medium can be efficiently used. This has the advantage.

Description

Recording and playback method of surveillance camera system and apparatus suitable therefor

1 is a block diagram showing a conventional surveillance camera device.

2 is a flowchart showing one embodiment of a recording method according to the present invention.

3 is a flowchart showing one embodiment of a reproduction method according to the present invention.

4 is a block diagram showing a recording / reproducing apparatus according to the present invention.

The present invention relates to a monitoring system, and more particularly, to a recording method for reducing the amount of data of a screen to be recorded, a reproduction method corresponding thereto, and a recording / reproducing apparatus suitable therefor.

The surveillance system stores the captured image on a video tape or a hard disk of a computer in order to record a surveillance space.

A video tape records an analog signal, and recording is generally performed by an intermittent recording type time lapse video tape recorder (time lapse VTR).

In the case of using a hard disk of a computer, the captured image is digitally converted and recorded after compression is performed using still image coding to reduce the recording capacity. Therefore, the recording capacity can be used more efficiently than in the case of recording analog signals. In the case of a monitoring system for intermittent recording, since moving picture coding is difficult to use, most still picture compression coding is performed.

However, since still picture compression coding compresses only by correlation within a picture, it is difficult to expect a compression rate over a certain limit.

SUMMARY OF THE INVENTION An object of the present invention is to provide a new recording method capable of recording a screen shot at a high compression rate in a surveillance system for recording a screen shot in a surveillance space by solving the above problems.

Another object of the present invention is to provide a reproduction method corresponding to the above recording method.

A further object of the present invention is to provide an apparatus suitable for the above recording / reproducing method.

In the recording method of the monitoring system according to the present invention to achieve the above object in the recording method of the monitoring system for recording the screen shot in the surveillance space on the recording medium, by digitally converting the screen shot the background of the surveillance space Storing in a memory and a recording medium as a background screen; Converting the captured screen of the surveillance space into a digital signal; Detecting a difference screen having a difference component between the digitally converted screen and a background screen stored in the memory; And sequentially recording the difference screen on the recording medium.

The recording method according to the present invention is further characterized by further comprising the step of compressing and encoding the difference picture.

According to another aspect of the present invention, there is provided a reproducing method of a monitoring system for reproducing recorded data on a recording medium, the method comprising: reading and storing a background screen recorded on a recording medium in a memory; Reading out the difference screen recorded on the recording medium; And synthesizing the read difference screen with the background screen stored in the memory.

The reproduction method according to the present invention comprises the steps of: determining whether the difference screen is a compressed screen; And, in the case of a compressed screen, further comprising performing back compression coding.

According to another aspect of the present invention, there is provided a recording apparatus comprising: an analog to digital converter for digitally converting a screen generated from a surveillance camera; A first memory configured to store a background image digitally converted by the analog to digital converter; A comparator for comparing the screen digitally converted by the analog to digital converter and a screen stored in the first memory to detect a difference screen; A second memory for storing a difference screen provided by the comparator; And a recording unit which sequentially records the background screen stored in the first memory on the recording medium and sequentially records the difference screen stored in the second memory.

According to another aspect of the present invention, a reproducing apparatus includes: a reading unit which reads a background screen and a difference screen recorded on a recording medium; A first memory configured to store a background screen provided by the reader; A second memory configured to sequentially store the difference screen provided by the reader; A synthesizer for synthesizing the background screen provided from the second memory and the difference screen provided from the second memory in the first memory; And a digital analog converter for converting the synthesized screen provided from the synthesizer into an analog signal and outputting the analog signal.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing a recording and reproducing processing unit of a conventional monitoring system, and shows an example of digitally converting a screen shot and storing it in a computer hard disk.

In the apparatus shown in FIG. 1, the switching unit 10 selectively inputs one of the video signals CVS1 to CVSn provided from a plurality of surveillance cameras (not shown). An analog-to-digital converter (hereinafter referred to as an ADC) 12 converts an analog signal provided from the switching unit 10 into a digital signal. The frame capturing unit 14 captures digitally converted image data at predetermined intervals. The data compressor 16 compresses and outputs frame-by-frame image data provided by the frame capturing unit 14 using a still image encoding technique. The compression-converted screen output from the data compression unit 16 is recorded on a hard disk (not shown) under the control of the recording / reading control unit 18.

The memory 20 stores identification information of frames recorded or read on the hard disk, for example, the start / end address of each frame, the number of the corresponding camera, time information, and the like, to randomly extract data necessary for playback and search. To be able.

The data recovery unit 21 receives the screen data read from the hard disk and performs reverse compression encoding. The screen data restored by the data recovery unit 21 is converted into an analog video signal CVS through a digital-analog converter (hereinafter referred to as DAC) 22 and provided to a monitor or television receiver (not shown).

In the apparatus shown in FIG. 1, the data compression unit 16 compresses captured image data according to a JPEG (Joint Picture Engeering Group) standard, which is one of the standards for compression encoding. The compression ratio at this time is basically 1/20, and is recorded without compression when an accident occurs.

Since the JPEG compression coding method basically compresses based on the correlation of data in an image, it is difficult to expect a compression ratio of more than a certain limit.

Surveillance systems are characterized by the fact that most surveillance cameras are used fixedly. This means that the contents of the photographed screen are almost the same as the previously photographed screen except for the sudden situation. According to the present invention, the screen used as the background of the surveillance space is stored in advance, and only the difference screen between the photographed screen and the background screen is recorded / reproduced.

2 is a flowchart showing one embodiment of a recording method according to the present invention. First, the background screen of the surveillance space is extracted and stored in the memory and the recording medium (step 200). The stored background screen is an uncompressed screen. The wallpaper stored in the memory is used to generate the difference screen, and the wallpaper recorded on the recording medium is used for reproduction and search.

Shoot the surveillance space. (Step 210)

The difference screen is extracted by comparing the photographed screen and the background screen stored in the memory (step 220).

If no sudden situation occurs in the monitoring space, there will be no difference screen. If an unexpected situation occurs, the difference screen will be a screen showing the contents of the unexpected situation. For example, if an intruder occurs in the surveillance space, the difference screen will be changed by the intruder.

The difference picture is compressed and coded (step 230). If a sudden situation does not occur, the difference picture is almost nothing, and thus is greatly compressed by compression coding. In addition, even if a sudden situation occurs, only the difference component from the background screen is compressed, so that the compression is much larger than when compression-coding the photographed picture as in the prior art.

The compression encoding process 230 may be omitted. For example, compression encoding may not be performed when the capacity of the hard disk is large enough to avoid compression encoding, or when an unexpected situation occurs.

Record the compressed difference screen (step 240).

At this time, the background screen is first recorded on the recording medium, and the difference screen sequentially compressed is recorded. During playback, the original screen is played using the background screen and the compressed difference screen.

3 is a flowchart showing one embodiment of a reproduction method according to the present invention.

First, the background screen recorded on the recording medium is read out and stored in the memory (step 300). The background screen stored in the memory is synthesized with a later read difference screen and used to reproduce the original screen.

The difference screen recorded on the recording medium is read out (step 310). The difference screen may be sequentially read out according to the order of recording, and the screen shot by a camera having a predetermined time or a predetermined number using identification information. Only may be read.

It is determined whether the difference screen is a compressed screen (step 320).

If the difference picture is a compressed picture, decompression coding is performed (step 330).

The synthesized screen is generated by combining the restored difference screen and the background screen stored in the memory (step 340).

The generated synthesized screen is converted into an analog signal and provided to a monitor or television receiver (step 350).

4 is a block diagram showing an apparatus suitable for the recording / reproducing method shown in FIG. 2 and FIG. In the apparatus shown in FIG. 4, blocks performing the same functions as those of FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 4, reference numeral 40 is a first memory for storing a background screen, and 42 is a difference screen between a background screen stored in the first memory 40 and a screen captured by the frame capturing unit 14. It is a subtractor. 44 is a second memory for storing the background screen read from the recording medium, and 46 is an adder for combining the background screen stored in the second memory 44 with the difference screen provided by the data restoring unit 21. to be.

The screen data is represented by a matrix having N pixels in the horizontal direction and M pixels in the vertical direction. The subtractor 42 compares screen data of the same position on the screen and outputs the difference value. This process is repeated from the upper left pixel to the lower right pixel.

The adder 46 also adds and outputs screen data at the same position on the screen. This process is repeated from the upper left pixel to the lower right pixel.

The operation of the apparatus shown in FIG. 4 will be described. When the background screen in which only the monitoring target exists in the surveillance space is photographed, the frame capturing unit 14 captures it. The captured background screen is stored in the first memory 40 and the hard disk. Thereafter, the screen shot of the surveillance space is compared with the background screen, and only the difference screen is extracted. The extracted difference screen is compressed by the data compression unit 16 and sequentially described on the hard disk. When there are several surveillance spaces, the first memory 40 is divided by the required number, and the background screen of each surveillance space is stored in the divided spaces.

At the time of searching, a background screen is first read from the hard disk and recorded in the second memory 44. Here, the first memory 40 and the second memory 44 may be implemented as the same memory. That is, the common memory may record the background screen used during storage and refer to it when searching.

The difference screens matching the search conditions are read out and restored through the data restoring unit 22. The restored difference screen is synthesized with the background screen recorded in the second memory 44 by the synthesizer 46 to restore the original screen.

As described above, the recording method of the surveillance system according to the present invention can significantly reduce the screen data to be recorded by storing the difference screen between the background screen of the surveillance space stored in advance and the photographed screen, thereby effectively reducing the recording capacity of the recording medium. It has the advantage of being available as.

Claims (6)

A recording method of a surveillance system for recording a screen shot in a surveillance space on a recording medium, the method comprising: digitally converting a screen shot of a background of a surveillance space and storing the screen in a memory and a recording medium as a background screen; Converting the captured screen of the surveillance space into a digital signal; Detecting a difference screen having a difference component between the digitally converted screen and a background screen stored in the memory; And sequentially recording the difference screen on the recording medium. The recording method as claimed in claim 1, further comprising compression encoding the difference picture. A recording method of a reproducing monitoring system recorded on a recording medium, comprising the steps of: reading a background screen recorded on a recording medium and storing the background screen in a memory; Reading out the difference screen recorded on the recording medium; And generating a composite screen by synthesizing the read difference screen and the background screen stored in the memory. The method of claim 3, further comprising: determining whether the difference screen read out from the recording medium is a compressed screen; And performing back compression coding on the compressed screen. A recording apparatus for recording a screen shot through a surveillance camera, comprising: an analog to digital converter for digitally converting a screen generated by the surveillance camera; A first memory configured to store a background image digitally converted by the analog to digital converter; A comparator for comparing the screen digitally converted by the analog to digital converter and a screen stored in the first memory to detect a difference screen; A second memory for storing a difference screen provided by the comparator; And a recording unit for sequentially recording the difference screen stored in the second memory after recording the background screen stored in the first memory on a recording medium. A reproducing apparatus for reproducing a screen shot from a recording medium on which a screen shot by a surveillance camera is recorded, the reproducing apparatus comprising: a reading unit configured to read a background screen and a difference screen recorded on the recording medium; A first memory configured to store a background screen provided by the reader; A second memory configured to sequentially store the difference screen provided by the reader; A synthesizer for synthesizing the background screen provided from the second memory and the difference screen provided from the second memory in the first memory; And a digital-to-analog converter for converting the synthesized screen provided from the synthesizer into an analog signal and outputting the analog signal.