KR100453010B1 - Digital video recording apparatus and method therefor - Google Patents

Abstract

The present invention relates to a digital video recording apparatus, and more particularly, to a storage medium for recording data reduced and output from a codec in units of frames, and extracting image data for a predetermined period from a storage medium to calculate correlation coefficients between screens. A digital signal processor for setting the correlation value for each time zone by using the correlation coefficient, and recording the image data output from the codec at a different image quality and recording rate for each time zone in a storage medium according to the correlation value set by the digital signal processor. By using the central processing unit to record the image data input from the camera at different image quality and recording speed according to the time zone, there is an effect that can increase the amount of image data that can be recorded on the storage medium.

In addition, by varying the image quality and recording speed for each time zone, high-quality recording can be performed in a desired time zone for accurate recording, thereby improving recording efficiency.

Description

Digital video recording apparatus and method {DIGITAL VIDEO RECORDING APPARATUS AND METHOD THEREFOR}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surveillance video recording apparatus, and more particularly, to a digital video recording apparatus and a method for recording at different screen speeds and picture quality according to a change in screens according to time zones based on stored video data.

The unmanned security system is mainly used as a control system that operates by connecting security devices and automation devices installed in large apartment houses or high-rise buildings, and is used to detect intruders who intrude into homes or buildings and detect fires early. It is a system that can be monitored through a monitor displayed at a remote place after connecting a fire detection sensor to a computer in an entrance, a window or an area where a fire is likely to occur, or an area where a fire can be easily detected.

An example of an unmanned security system is the Time Lapse Video Tape Recorder, which is installed in major areas such as banks and museums and is used for long-term surveillance to prevent theft. Instead of recording the transmitted video screen in full frame in real time, one frame is recorded at a predetermined time interval selected from the real-time video screen transmitted while repeating driving and stopping of the recording tape by the capstan motor of the recording unit. Attempt to reproduce the video signal recorded in the recording unit by controlling the capstan motor of the recording unit to advance the tape in the image frame unit to read the video frame recorded on the recording tape, the recording and playback of the video frame is set by the user Depending on the mode at regular intervals As a result, intermittent recording and reproduction of the video signal was performed.

The management operator of the video recording player is very cumbersome because the recording tape needs to be replaced periodically, and there is a problem that a separate external device must be provided in order to perform special functions such as multi-recording and playback screen division.

In order to solve this problem, a digital video recorder (DVR) using a digital recording medium rather than an analog recording tape has been developed, which digitally records an image on a recording medium such as a memory. By reproducing and reproducing, the recorded data can be almost semi-permanently preserved without damaging the recording medium, and it is an expensive device that can perform special functions such as multiple recording and playback screen division without a separate external device.

The digital video recording device used in the unmanned security system records 20 frames per second in the normal recording mode, and the required storage space for recording one frame is 20 kilobytes.

The video data recorded for 24 hours in the digital video recording apparatus may have no change in the screen and a lot of change in the screen, which is defined as correlation. In other words, if the correlation is high, there is almost no change in the screen captured by the camera. If the correlation is low, the screen captured by the camera is large.

However, the conventional digital video recording apparatus is inefficient because it records at the same screen speed and image quality regardless of high and low correlation, and thus has a problem of unnecessary waste of storage capacity.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art, and to determine the degree of correlation between screens according to time zones based on pre-recorded image data, and to record at different screen speeds and image quality as the correlation is high and low. An apparatus and method for data recording are provided.

In order to achieve the above object, the present invention provides a digital video recording apparatus comprising a decoder for digitizing and converting the analog video data input from the camera, the predetermined compression scheme receives the digitized video data from the decoder A codec for reducing and outputting the total amount of data by compression-coding, a storage medium for recording the reduced-output data from the codec on a frame basis, and extracting image data for a predetermined period from the storage medium to obtain a correlation coefficient between the screens. And a digital signal processor configured to set the correlation value for each time zone using the correlation coefficient, and an image output from the codec at a different image quality and recording speed for each time zone according to the correlation value set by the digital signal processor. Data to the storage medium It includes a central processing unit for recording.

In another aspect, the present invention provides a digital video recording method using a key input unit for setting a recording mode for recording video data photographed from a camera, and a storage medium for recording the video data corresponding to the recording mode. Determining whether the recording mode is the intelligent mode; extracting a predetermined amount of image data from the storage medium when the determination mode is the intelligent mode; and using the extracted image data, Calculating a correlation coefficient between screens and setting a correlation value for each time zone using the calculated correlation coefficient; and storing the image on the storage medium at a different image quality and recording speed for each time zone according to the correlation value set for each time zone. Recording the data

1 is a block diagram showing a digital video recording apparatus according to the present invention,

2 is a flowchart illustrating a process of recording image data using the digital imaging apparatus of the present invention.

<Description of the code | symbol about the principal part of drawing>

100: camera 102: decoder

104: codec 106: storage medium

108: video expander 110: encoder

112: playback section 114: digital signal processing section

116: central processing unit 118: key input unit

There may be a plurality of embodiments of the present invention, and a preferred embodiment will be described in detail below with reference to the accompanying drawings. Those skilled in the art will be able to better understand the objects, features and advantages of the present invention through this embodiment.

1 is a block diagram illustrating a digital video recording apparatus according to the present invention, and FIG. 2 is a flowchart illustrating a process of recording image data using the digital video recording apparatus according to the present invention.

As shown in FIG. 1, the digital video recording apparatus includes a decoder 102 for converting analog image data photographed and input from a signal-connected camera 100 into a digital signal, and a digital signal transmitted from the decoder 102 in a wavelet manner. A codec 104 for compressing and encoding a reduced amount of total data, a storage medium 106 for sequentially recording the reduced output image data (in units of frames), and compressed digital image data read out from the storage medium 106. Video decompressor 108 which decodes and decodes the image data of the original size by the wavelet method, a video encoder 110 converting and outputting the decoded and output digital video data into a composite analog video signal (Y / C), and the converted output analog. Playback unit 112 for reproducing the video signal, correlation between screens for each time zone based on the video data stored in the storage medium 106 for a predetermined period Digital signal processor (DSP) 114 for determining the degree of correlation and generating a correlation value, central processing unit 116 for overall control of image data storage and playback of image data of storage medium 106, and recording And a key input unit 118 that can set a mode (normal mode, intelligent mode, high speed mode, etc.) and playback mode.

The codec 104 reduces the video signal digitized by the decoder 102 to a preset wavelet and records the image signal on the storage medium 106 through the central processing unit 116, which is set through the key input unit 118. The recording method is changed according to the recording mode to record the image data photographed from the camera 100 to the storage medium 106.

The digital signal processor 114 extracts the stored image data for a predetermined period (for example, a week) from the storage medium 106 through the central processing unit 116, and extracts the lowest frequency region among the extracted image data. After calculating the correlation coefficient between screens by decoding, the correlation time value (for example, "1" if the correlation is high and "0" if the correlation is low) is set for each time slot. In this case, the set correlation value is a value for recording image data in the storage medium 106 at different screen speeds and image quality depending on the correlation between the screens. After the preset period (for example, one week), the digital signal processor 114 The correlation value set in this way is applied only when the recording mode input through the key input unit 118 is an intelligent mode.

Here, the intelligent mode, which is one of the recording modes, sets the correlation value for each time zone by examining the correlation between screens for each time zone, and is recorded by the camera 100 at different recording speeds and image quality for each time zone based on the set correlation value. In this mode, video data is recorded in the storage medium 106.

In this case, the reason for extracting the data of the lowest frequency region among the image data extracted from the storage medium 106 is that the important information of the image is generally included in the low frequency region, and the amount of the image data of the lowest frequency portion is This is because the load of the digital signal processor 114 may be reduced in high speed calculation because it is about 1/1000 of the amount of data.

The calculation formula for calculating the correlation between the screens extracted by the digital signal processor 114 from the image data is as follows.

Where X and Y are images to be compared, X (i, j) and Y (i, j) are Pixel values at the (i, j) position of each image, and {m} _ {x }, {m} _ {y} is the average of the pixel values of each image. And m and n represent the size of an image.

At this time, if the value of the correlation coefficient {R} _ {xy} is greater than or equal to -1 and less than or equal to 1, and if {R} _ {xy} = 0, there is no correlation between the two images (that is, two The video is very different), If the value is close to 1, the correlation between the two images is high (ie, similar images).

The digital signal processor 114 extracts the image data having a low frequency from the storage medium 106 in which the image data is stored for a predetermined period and calculates a correlation coefficient from Equation 1, using 0.8 as a reference value and calculating the correlation coefficient. If the value is greater than -0.8 and less than 0.8, the correlation between the two images is judged to be low, and the video is recorded at a rate of about 5 frames per second higher than the preset value (20 frames per second), and the calculated correlation coefficient is less than or equal to -0.8. If it is greater than or equal to 0.8, it is determined that the correlation between the two images is high, and the correlation value is set to record at a rate about 5 frames per second lower than the preset value.

As described above, the central processing unit 116, which processes playback and recording, extracts image data of a predetermined period from the storage medium 106, calculates a correlation coefficient, and sets a correlation value using the calculated correlation coefficient. In the following, since the load takes a lot, the digital signal processing unit 114 processes it.

An operation process of the digital video recording apparatus having the above configuration will be described below with reference to FIG. 2.

Before describing the operation of the digital video recording apparatus of the present invention, the amount of video data extracted from the storage medium 106 is recorded as video data recorded for one week in order to set the correlation value to be applied in the intelligent mode. It will be explained on the assumption.

The central processing unit 116 determines whether the recording mode input through the key input unit 118 is the intelligent mode (S201), and when the determination result is not the intelligent recording mode, the recording mode set through the key input unit 118 is determined. In operation S202, the image data photographed from the camera 100 is recorded. For example, the central processing unit 116 records image data captured by the camera 100 at a rate of 20 frames per second in the normal recording mode.

As a result of the determination in step 201, when the recording mode input through the key input unit 118 is the intelligent recording mode, the central processing unit 116 sets a period of time after which the elapsed date is set after setting the intelligent recording mode (for example, For example, it is determined whether one week has passed (S203).

As a result of the determination in step 203, when the preset period has not elapsed, the central processing unit 116 returns to step 202 and stores the reduced image data input through the codec 104 in the normal recording mode (20 frames per second) in the storage medium 106. ).

As a result of the determination in step 203, when the preset period has elapsed, the digital signal processor 114 extracts image data for one week from the storage medium 106 through the central processing unit 116 (S204), and extracts the image data. After extracting the image data of the part with low frequency band, calculate the correlation coefficient to check the correlation between screens, and use the correlation coefficient to obtain the correlation value (1 for high correlation, 0 for low correlation). (S205).

As a method of setting the high and low correlation degree, the correlation coefficient ({R} _ {xy}), which is the correlation coefficient between the screens, can be obtained by comparing the reference value with a preset reference value. If it is less than 0.8, it is determined that the correlation is low and the correlation value is set to 0. If the correlation coefficient is less than or equal to -0.8 or greater than or equal to 0.8, it is determined that the correlation is high and the correlation value is set to 1. .

Thereafter, the central processing unit 116 checks the current recording time for recording the image data transmitted from the camera 100, extracts the correlation value set in the checked recording time zone, and then determines whether the extracted correlation value is 0 or 1. It is determined (S206, S207, S208).

When the correlation value of the determination result of step 208 is 0, the digital signal processing unit 114 sets about 5 frames per second (25 frames per second) faster than the screen recording speed in the normal recording mode, and the central processing unit 116 sets the digital value. The reduced image data output from the codec 104 at the recording speed set by the signal processing unit 114 is recorded in the storage medium 106 (S209).

When the correlation value is 1 as the result of the determination in step 208, the digital signal processor 114 sets the frame rate to about 5 frames per second (20 frames per second) slower than the screen recording speed in the normal recording mode, and the central processing unit 116 sets the digital signal. The reduced image data output from the codec 104 at the recording speed set by the signal processor 114 is recorded in the storage medium 106 (S210).

As described above, the correlation coefficient between the screens is calculated by using the image data stored in the storage medium for a preset period, and the correlation coefficient for each time zone is set by using the calculated correlation coefficient value. By recording the image data input from the camera at the recording speed, there is an effect that can increase the amount of image data that can be recorded on the storage medium.

In addition, by varying the image quality and the recording speed according to the correlation between time zones, high-quality recording can be performed in a desired time zone for accurate recording, thereby improving recording efficiency.

Claims (7)

A digital video recording apparatus comprising a decoder for digitizing and converting analog video data input from a camera, A codec which receives the digitized image data from the decoder and compresses and encodes the data in a predetermined compression scheme to reduce the total amount of data; A storage medium for recording data reduced in size from the codec in units of frames; A digital signal processor for extracting image data for a predetermined period from the storage medium to calculate correlation coefficients between screens and setting the correlation value for each time zone using the correlation coefficients; And a central processing unit for recording the image data output from the codec into the storage medium at different image quality and recording speeds according to the correlation values set by the digital signal processing unit. The method of claim 1, The digital signal processing unit, And the correlation coefficient value is calculated using the image data in a low frequency band among the image data extracted from the storage medium. The method of claim 1, The digital video recording device, A key input unit for setting a recording mode for recording the reduced output data; And the central processing unit records the image data reduced and output from the codec in the storage medium according to the recording mode set by the key input unit. The method of claim 3, wherein The recording mode which can be set by the said key input part is Normal mode, fast mode and intelligent mode; The intelligent mode is, And recording in the storage medium by varying the recording speed and the image quality in the normal mode for each time zone. In the digital image recording method using a key input unit for setting a recording mode for recording the image data taken from the camera, and a storage medium for recording the image data corresponding to the recording mode, Determining whether the recording mode is an intelligent mode; Extracting a predetermined amount of image data from the storage medium in the intelligent mode as a result of the determination; Calculating correlation coefficients between the screens by using the extracted image data, and setting correlation values for each time zone using the calculated correlation coefficients; And recording the image data on the storage medium at different image quality and recording speeds for each time zone according to the correlation value set for each time zone. The method of claim 5, wherein Calculating the correlation coefficient And extracting and calculating image data having a low frequency band from the extracted image data. The method of claim 5, wherein The recording on the storage medium may include: And recording at the storage medium by varying 5 frames per second than a preset recording speed and image quality according to the correlation value.