JP2002290912A - Digital recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a digital recording and reproducing device that can minimize the deterioration of compressed picture quality even in a recording mode high in compression ratio and reduced in the number of the constituting pixels of a screen for recording for a long period and can effectively use a limited recording medium, even in the case of recording when inputting an alarm signal. SOLUTION: The digital recording and reproducing device is provided with a band control means for separating an inputted analog video signal into a luminance signal and a chrominance signal and controlling the information quantity of the luminance signal, a compression/expansion processing means for converting the luminance signal having the information quantity controlled and the chrominance signal a digital signals and compressing or expanding it and a recording medium for recording compressed data. In the device, the information quantity of the compressed data compressed by the compression/ expansion processing means is changed and the information quantity of the luminance signal is also controlled in a recording means. After detecting an alarm signal, recording in a high picture quality recording mode is performed. When a residual capacity becomes small, the mode is switched to a normal recording mode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital recording / reproducing apparatus suitable for recording video from a surveillance camera for a long time in a video monitoring system mainly for monitoring.

[0002]

2. Description of the Related Art In a surveillance camera system used in a convenience store or a financial institution, a period during which a surveillance image is recorded may be full business hours or 24 hours.
There is a demand for continuous operation for a long time. Recently, digital recording / reproducing devices that can record digital video using a hard disk recorder or the like have appeared.
Since the capacity of the amount of information that can be recorded on the recording medium is limited, the recording time is also limited when recording with a large amount of information for high image quality. In response to such a digital recording / reproducing apparatus, the amount of data to be recorded is being increased by increasing the capacity of a recording medium, but compared to analog equipment such as a time-lapse VTR using a conventional tape, it is still more comprehensive. Recording time is short. For this reason, a recording mode such as increasing the compression ratio of digitized data or reducing the number of pixels constituting the screen is used to reduce the amount of information of compressed data, or reduce the recording data rate and record for a long time. And respond to it.

In a digital recording / reproducing apparatus, the capacity of a recording medium is not sufficient for the amount of data to be recorded, and is limited. Therefore, when recording for a long time, the compression ratio of digitized data is increased. A recording method for reducing the amount of data to be recorded, such as reducing the number of pixels constituting the screen, is employed. In this case, however, the recording data rate (the amount of information) can be reduced, so that long-time recording is possible. On the other hand, the resolution decreases due to the decrease in the number of pixels constituting the screen or the image quality deteriorates significantly due to a high compression ratio. However, it is difficult to check the video during playback.

[0004] As a method of improving this, only when an abnormality is detected upon receiving an abnormality detection signal (alarm signal) from the outside, recording is performed by reducing the image compression ratio or increasing the number of pixels constituting the screen. There is a function to increase the rate to increase the amount of information and record more details. A related apparatus of this type is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-27952.

[0005]

SUMMARY OF THE INVENTION The first of the above conventional methods is described below.
In order to change the amount of information of compressed data,
In the case of the method of changing the information amount by changing the number of pixels forming the screen, no consideration has been given to limiting the band of the analog luminance signal in accordance with the number of pixels. As a second problem, the recording is performed in a normal recording mode in which the information amount of the compressed data which is normally suitable for long-time recording is small, and when an external abnormality detection signal (alarm signal) is received, the image compression is performed. In the case of the function of recording an image with a large amount of detailed information by increasing the recording rate by reducing the rate or increasing the number of pixels constituting the screen, the capacity of the recording medium is limited. If the capacity of the recording medium becomes full halfway, no consideration is given to the fact that recording cannot be performed.

[0006]

In order to solve the above-mentioned problems, according to the present invention, a YC separating means for separating an input analog video signal into a luminance signal and a chrominance signal, and controlling the information amount of the luminance signal. Band control means, A / D conversion means for converting a luminance signal and a chrominance signal whose information amount is controlled from an analog signal to a digital signal, and compression / expansion processing means for compressing or expanding the digital signal converted by the A / D conversion means And a recording medium for recording the compressed data compressed by the compression / expansion processing means, and control means for controlling the compression / expansion processing means and the band control means according to the recording mode. According to the recording mode, the information amount of the compressed data compressed by the compression / expansion processing means is changed and the information amount of the luminance signal is controlled. I have.

In the present invention, a plurality of band limiting units are provided as the band control unit, and a band limiting unit corresponding to a predetermined recording mode is selected. Further, according to the present invention, there is provided an alarm signal detecting means for detecting an alarm signal indicating an abnormality inputted from the outside, and when an alarm signal is detected during recording, the image quality is higher than the current one and the information amount of the compressed data is larger. The control is performed so as to switch to the image quality recording mode and to select the band limiting unit corresponding to the high image quality recording mode. Thereby, the band is limited by the band limiting unit so that the input analog video signal has the same band as the recordable frequency band determined by the number of pixels constituting the screen in each recording mode, and unnecessary information amount is reduced. By dropping, it is possible to minimize the deterioration of the image quality due to compression in the video compression processing means in the subsequent stage.

Further, in the present invention, when the capacity of the recording medium becomes small during recording in the high image quality recording mode by an alarm signal, control is performed so as to switch to a normal recording mode in which the information amount of compressed data is small. I have to.
This allows the system control means, such as a microcomputer, to calculate the remaining capacity of the recording medium during recording in the high-quality recording mode, and when the remaining capacity decreases, the compression rate at which the number of pixels constituting the screen is reduced during recording. The control for switching to the high recording mode enables recording of an abnormal image for a longer time. In the present invention, the information amount of the compressed data corresponding to the recording mode is changed by changing the number of pixels constituting the screen. With this, when an abnormality detection signal (alarm signal) is received from the outside during recording, the remaining capacity of the recording medium is calculated, and when the remaining capacity becomes small, the recording mode is switched in the middle to continue the recording for a long time. It is possible to provide a digital recording / reproducing apparatus which can be changed to record for a long time.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described.
This will be described below with reference to the drawings. According to FIGS. 1 to 3,
A digital recording / reproducing apparatus according to a first embodiment of the present invention will be described. FIG. 1 is a diagram showing a configuration of a digital recording / reproducing apparatus according to a first embodiment of the present invention. The schematic operation will be described with reference to FIG.

In FIG. 1, reference numeral 1 denotes YC separation means for separating a luminance signal (Y signal) and a chrominance signal (C signal) from an input analog video signal, and 2a and 2b denote a plurality of bands for limiting the band of the Y signal. Limiting means 3, band limiting switching means for switching a plurality of band limiting means, AD conversion means 4a, 4b for converting an analog signal to a digital signal, and 5 for processing for compressing or expanding data of a digitized video signal. Means for performing video compression / expansion, 6
Temporary storage means for temporarily storing data for arithmetic processing in the decompression process; 7 is a recording medium such as a hard disk drive; and 8a and 8b are digital signals reproduced when a digital signal recorded on the recording medium 7 is reproduced. Is an analog signal, 9 is an alarm signal detecting means for detecting an abnormality detection signal (alarm signal) notifying an abnormality from outside the device, and 10 is a control means for controlling the entire system.

Here, band control means for controlling the information amount of the luminance signal is constituted by using the band limit means 2a and 2b and the band limit switching means 3 and 2a is a band for a high image quality recording mode. Limiting means 2b is a band limiting means for the normal recording mode. Reference numeral 4a denotes an AD converter for the luminance Y signal, 4b denotes an AD converter for the color C signal, 8a denotes a DA converter for the luminance Y signal, and 8b denotes a DA converter for the color C signal.

First, the recording operation will be described. The input analog video signal is separated by a YC separation unit 1 into a luminance signal (hereinafter, referred to as a luminance Y signal) and a chrominance signal (hereinafter, referred to as a color C signal). Here, for the YC-separated luminance Y signal, in a recording mode corresponding to long-time recording, as a method of reducing the information amount of compressed data for recording, a method of reducing the number of pixels constituting the screen is used. The frequency band of the image that can be displayed on the screen is narrow, and the frequency component higher than the frequency band that can be displayed on the screen becomes an operation including an extra amount of information during the data compression processing, which is one of the causes of the image quality deterioration. Therefore, the image compression / decompression means is controlled by the control means in accordance with the recording mode so that the frequency band of the separated luminance Y signal becomes a displayable frequency band of the currently selected recording mode. By controlling the limit switching means 3, the corresponding band limiting means 2a or 2b is selected to limit the band, and the subsequent AD conversion means 4a
Output to

The color C signal YC separated by the YC separation means 1 is output to an AD conversion means 4b. The luminance Y signal and color C signal digitized by the A / D converters 4a and 4b are input to the video compression / expansion unit 5 and subjected to compression processing. At this time, in the calculation processing for performing the compression processing,
Data and the like during the calculation are temporarily stored in the temporary storage unit 6. The video data compressed by the video compression / expansion means 5 is recorded on a recording medium 7 such as a hard disk.

Here, switching is made so as to use the band limiting means 2a in the high-quality recording mode and to use the band limiting means 2b in the normal recording mode. The high-quality recording mode is a recording mode for recording a high-quality image when an abnormality occurs, and a recording mode in which image quality is emphasized.The normal recording mode is a recording mode for long-time recording. is there. Here, as a method of reducing the information amount of the compressed data for recording, a method of reducing the number of pixels forming the screen is used. However, a method of reducing the information amount of the compressed data such as a method of increasing the compression ratio is used. I don't care.

Next, the reproducing operation will be described. At the time of reproduction, video data is read from a recording medium 7 such as a hard disk, and the video data expanded by the video compression / expansion means 5 is converted into analog signals by DA conversion means 8a and 8b. And a color C signal.

The characteristics of the plurality of band limiting means 2a and 2b will be described with reference to FIGS. FIG. 2 shows a comparison between the frequency band of the input video signal and the frequency band in the recording mode in which the number of pixels constituting the screen is reduced in order to cope with long-time recording. FIG. 3 shows band limiting means 2a, 2
4 shows a frequency band of the luminance Y signal after band limitation by b and a recordable frequency band in a normal recording mode for coping with long-time recording.

When performing long-time recording, recording is performed in a normal recording mode in which the number of pixels constituting the screen is reduced and the compression ratio is set high. There are a plurality of recording modes depending on the number of constituent pixels and the compression ratio, and the user can select the recording mode in consideration of the total recording time. Here, the case where the number of band limiting means is two and the recording mode is also two modes has been described, but a plurality of band limiting means and a plurality of recording modes may be provided.

Next, a digital recording / reproducing apparatus according to the second and third embodiments of the present invention will be described with reference to FIG. FIG. 4 is a flowchart showing the processing of the second and third embodiments.

As a second embodiment of the present invention, FIG. 4 shows a case where the alarm signal detecting means 9 detects an abnormality detection signal (alarm signal) from outside the apparatus during recording in the normal recording mode (step 401). (Step 402, ye
s) The system control unit 10 switches to the high image quality recording mode for recording a detailed image with a large number of pixels and a large amount of information constituting the screen (step 403), and at the same time, the band limitation switching unit 3 switches the high image quality recording mode. (Step 40)
4) Perform control and record in the high image quality recording mode (step 405). When the alarm signal detection means 9 does not detect the abnormality detection signal (alarm signal) in step 402 (n
In step o), the flow returns to step 401 to continue the recording in the normal recording mode. Thereby, when an alarm signal is detected, it is possible to record in a high image quality mode for recording a detailed image having a large number of pixels and a large amount of information constituting a screen.

Next, a third embodiment of the present invention will be described with reference to FIG. Error detection signal (alarm signal)
During recording after the alarm signal detecting means 9 receives the alarm (Step 405), the system control means 10 such as a microcomputer calculates the remaining capacity of the recording medium 7 (Step 406), and the remaining capacity of the recording medium that can be stored is small. If the number of pixels constituting the screen is reduced (step 407, yes), the mode is switched to the normal recording mode in which the number of pixels constituting the screen is reduced (step 408). Normal image quality band limiting means 2b
(Step 40409), and the abnormal image can be recorded in the normal recording mode for a longer time (step 410). Step 40
If it is determined in step 7 that the remaining storage capacity of the recording medium is not equal to or smaller than an arbitrary set value (no), the process returns to step 405 to continue recording in the high image quality mode. As a result, even when the remaining storage capacity of the recording medium becomes small, an image at the time of abnormality can be recorded in the normal recording mode for a longer time.

As described above, according to the embodiment of the present invention, even in the recording mode in which the number of pixels constituting the screen is reduced and the compression ratio is increased for long-time recording, the frequency that can be displayed by the band limiting means 3 is increased. By performing a band limiting process suitable for the band on the input video signal, it is possible to prevent the video data compressed and expanded by the video compression / expansion means 5 from including an unnecessary high-frequency information amount, and to minimize the necessary information amount. By doing so, image quality degradation during compression can be reduced. Further, during recording at the time of an alarm when an abnormality detection signal (alarm signal) is detected by the alarm signal detecting means 9 from outside the device during recording, the system control means 10 such as a microcomputer calculates the remaining capacity of the recording medium 7. When the remaining capacity becomes small, the control is performed to switch to a high compression rate recording mode in which the number of constituent pixels of the screen is reduced during recording at a certain remaining capacity, so that an abnormal image (at the time of an alarm) can be further improved. Recording becomes possible for a long time.

[0022]

According to the present invention, it is possible to reduce the number of pixels constituting a screen for long-time recording, and to minimize the deterioration of image quality after compression in a recording mode with a high compression rate. In addition, a digital recording / reproducing apparatus that can effectively use a limited recording medium can be provided by controlling the recording mode to be switched according to the remaining capacity of the recording medium when recording when an abnormality detection signal (alarm signal) is input.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a digital recording / reproducing apparatus according to one embodiment of the present invention.

FIG. 2 is a diagram illustrating a frequency band of an input video signal and a reproducible frequency band in a recording mode corresponding to long-time recording according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a frequency band of an input video signal after band limitation by a band limitation unit according to an embodiment of the present invention, and a reproducible frequency band in a recording mode for coping with long-time recording. .

FIG. 4 is a flowchart illustrating a process when an alarm signal is detected according to the second and third embodiments of the present invention.

[Explanation of symbols]

1 ... YC separating means, 2a, 2b ... band limiting means, 3 ... band limiting switching means, 4a, 4b ... AD converting means, 5 ...
Video compression / expansion means, 6 temporary storage means, 7 recording medium, 8a, 8b DA conversion means, 9 alarm signal detection means, 10 system control means.

Continued on the front page (72) Inventor Koji Nozato 1410 Inada, Hitachinaka-shi, Ibaraki Prefecture Digital Media Products Division, Hitachi, Ltd. (72) Tatsuya Iizuka 1410 Inada, Hitachinaka-shi, Hitachi, Ibaraki Digital Media Hitachi, Ltd. Product Division F term (reference) 5C053 FA02 FA23 GB21 KA01 KA12 KA24 KA25 5C055 AA03 CA03 FA22 GA41 HA00 HA35 5D044 AB05 AB07 BC01 CC05 DE44 EF05 GK08 GK10

Claims (6)

[Claims] 1. A YC separation unit for separating an input analog video signal into a luminance signal and a chrominance signal; a band control unit for controlling an information amount of the luminance signal; AD conversion means for converting the color signal from an analog signal to a digital signal, compression / expansion processing means for compressing or expanding the digital signal converted by the AD conversion means, and compression by the compression / expansion processing means A digital recording / reproducing apparatus comprising: a recording medium for recording compressed data; and control means for controlling the compression / decompression processing means and the band control means according to a recording mode. Digital recording and reproduction characterized by changing the information amount of compressed data compressed by processing means and controlling the information amount of a luminance signal. apparatus. 2. The digital recording / reproducing apparatus according to claim 1, wherein said band control means has a plurality of band limit means, and is configured to select said band limit means corresponding to a predetermined recording mode. A digital recording / reproducing apparatus characterized by the above-mentioned. 3. The digital recording / reproducing apparatus according to claim 2, further comprising an alarm signal detecting means for detecting an alarm signal indicating an abnormality inputted from the outside, wherein when the alarm signal is detected during recording, A digital recording / reproducing apparatus which switches to a high-quality recording mode which has a higher image quality than the current one and has a larger amount of information of compressed data, and controls to select the band limiting means corresponding to the high-quality recording mode. 4. The digital recording / reproducing apparatus according to claim 3, wherein the information amount of the compressed data is reduced when the remaining capacity of the recording medium is reduced during recording in the high-quality recording mode by the alarm signal. A digital recording / reproducing apparatus which controls to switch to a low normal recording mode. 5. The digital recording / reproducing apparatus according to claim 1, wherein the information amount of the compressed data corresponding to the recording mode is changed by changing the number of pixels constituting a screen. A digital recording / reproducing apparatus characterized in that: 6. The digital recording / reproducing apparatus according to claim 1, wherein said band control means has a plurality of band limit means and a band limit switching means, and said band control means corresponds to a predetermined recording mode. A digital recording / reproducing apparatus characterized in that it is configured to be switched and selected by the band limitation switching means.