JPH06105278A - Recording and reproducing device by movement detection - Google Patents

Abstract

PURPOSE:To ensure a large amount of medium, and to erase the increase of an abnormal picture detecting time by detecting a movement by comparing picture data in a present frame with the picture data in a memory before one frame, and recording the picture data only when they are not matched. CONSTITUTION:A movement detecting circuit 4 detects the movement by comparing the picture data in both a recorded picture frame memory (t) 2 and a recorded picture frame memory (t-1) 3 in a different time. When the movement is detected, and the pictures are transferred to the recorded picture frame memory (t-1) 3, a control circuit 11 transmits a data compression control signal to a data compressing circuit 6, and the data compressing circuit 6 compresses the picture data, and successively the picture data in a compressed data memory 5. A recording and reproducing circuit 8 records the compressed data for (n) frames in a medium 7. Then, at the time of reproduction, the data read from the medium 7 are expanded by a data expanding circuit 10, and the reproduced pictures for the plural frames are successively transmitted to an outputting circuit 12 by each frame, and outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing apparatus for compressing image signals and recording them for a long time.

[0002]

2. Description of the Related Art Image signals and the like can be recorded and controlled on a video tape or an optical disk in frame units. By utilizing this, recording is performed on the medium in frame units at a certain fixed period (every 1 second or 5 seconds, etc.) and is recorded for a long time for monitoring or remote recording.
A conventional apparatus for recording / reproducing for a long time will be described below.

FIG. 8 shows the structure of a conventional long-time recording / reproducing apparatus. 1 is an input circuit for capturing an input image signal, 2
2 is a recording / reproducing circuit for recording and reproducing on the medium 7.
12 is a circuit for outputting an image from the medium 7, and 21 is a recording / recording circuit.
It is a timer control circuit that generates a recording control signal for the reproducing circuit 22 at a certain fixed period.

In the recording / reproducing apparatus configured as above, the recording time of the medium is 60 minutes or 60 minutes × 60 seconds ×
It is assumed that 30 frames (in the case of a general television signal of NTSC) = 108000 frames can be recorded. When the timer control circuit 21 sends a timer control signal to the recording / reproducing circuit 22 once every 5 seconds, for example, the recording / reproducing circuit 22 records one frame at that time. FIG. 9 illustrates a configuration in which an image frame is recorded on the medium at time intervals T from time t. In the above example, T
= 5 seconds, 108000 frames / 5 seconds = 2160
Recording can be continued for 0 frame = about 12 hours.

[0005]

However, in the above configuration, most of the recording frames often record exactly the same image in a state where no abnormality occurs when used for night monitoring or the like. Therefore, in the case of recording for a long time, there is a problem that a large amount of medium is secured and the time required for searching for an abnormal image during reproduction becomes enormous.

The present invention solves the above problems and provides a recording / reproducing apparatus which does not record the same image but records only different images and compresses image data for recording. The purpose is to

[0007]

In order to achieve this object, the present invention relates to an input means for taking in an image signal and an input image data for one frame which is temporally different.
One recording frame memory means, a motion detecting means for detecting a motion from the image data of the two recording frame memories, a control means for generating a plurality of control signals according to outputs from the motion detecting means, and a control means. A signal for compressing the image data from the recording frame memory means, a memory means for storing the compressed image data, and a signal from the control means for recording the data from the data compressing means on a medium. Recording and reproducing means for reproducing data from the medium, a medium for storing the data, data expanding means for expanding the signal from the recording and reproducing means by a signal from the control means, and memory means for storing the expanded data, Playback frame memory means for storing the playback image from the data expansion means, and output image data of the playback frame memory means And force means, is intended to comprise.

[0008]

According to the present invention, a motion is detected by sequentially inputting an input image into a memory in frame units and comparing the current frame image data with the image data in the recording frame memory one frame before. The image is recorded only when it is determined that there is motion. Further, the image to be recorded is compressed by using image compression in the spatial axis direction, image compression by entropy coding, compression by discrete cosine transform, etc.,
A device for recording / reproducing.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the structure of a recording / reproducing apparatus according to an embodiment of the present invention. The same parts as those in FIG. 8 showing the conventional example are designated by the same reference numerals and described. FIG. 2 is a diagram showing the overall flow.

When an image is input to the input circuit 1 as an input signal, it is stored in the recorded image frame memory (t) 2 frame by frame as a unit of image (process 31 in FIG. 2). The motion detection circuit 4 detects the motion by comparing the image data of both the frame memory for recording image (t) 2 and the frame memory for recording image (t-1) 3 at different times (the process of FIG. 2). 32).

An example of a method of detecting a motion will be described with reference to FIG. An image at the current time t is stored in the recorded image frame memory (t) 2. Further, it is assumed that the frame memory for recording images (t-1) 3 stores an image of one frame before the current time t. Representation of a block of an image in the frame memory is x-axis in the horizontal direction and y-axis in the vertical direction. The pixel configuration of the image block (x, y) of the frame memory at time t is 8 pixels with i = 0 to 7 in the horizontal direction and pixels with j = 0 to 7 in the vertical direction. Similarly,
The pixel block of the frame memory one frame before the time t has the same configuration. Horizontal i of block (x, y) at time t
= 2, the value of the pixel of vertical j = 5 is P (t, x, y, 2,
5). If this is expressed using i, j, P (t, x,
y, i, j). The value at the same point in time (t-1) is similarly represented by P (t-1, x, y, i, j). The motion amount M is defined by (Equation 1) using the above expression.

[0013]

[Equation 1]

In summary, the difference between each 64 pixels of the (x, Y) block at time t and time (t-1) is first calculated. Next, the (x, y) block at time t and the time (t
-1) (x-1, y-1) block, (x, y-1)
Block, (x + 1, y-1) block, (x-1,
y) block, (x + 1, y) block, (x-1, y)
+1) block, (x, y + 1) block, (x + 1,
y + 1) Differences are similarly obtained between blocks. The amount of movement for each of these 9 blocks is obtained. If both image data are the same, this motion amount is calculated by using both (x,
From the (y) block, ΣP (t, x, y, i, j) -P (t-1, x, y, i, j) = 0. When the amount of movement is 0 or a small value, it is determined that there is no movement. The reason why 9 blocks are also calculated is that it is determined that there is no motion even if only one pixel moves for a fine motion.

First, the recorded image frame memory (t) 2
Image is captured only in the frame memory (t
-1) If there is no image in 3, it is naturally determined that there is movement (process 33 in FIG. 2). Control circuit 11
Then, when this motion detection signal is received from the motion detection circuit 4, the image data of the recording image frame memory (t) 2 is transferred to the recording image frame memory (t-1) 3 (process 34 in FIG. 2). The image data of the next frame is sequentially taken into the recorded image frame memory (t) 2. If the image data in both frame memories is the same, the amount of motion is 0 and no motion is detected (process 33 in FIG. 2).
Therefore, this image data is not transferred. If,
When different image data is taken into the recording image frame memory (t) 2, the amount of motion does not become 0 or a small value, so this image data is transferred.

When the motion is detected and the image is transferred to the recording image frame memory (t-1) 3, the control circuit 11 sends a data compression control signal to the data compression circuit 6. The data compression circuit 6 compresses the image data and sequentially stores it in the compressed data memory 5 (process 35 in FIG. 2). An example of the data compression method is shown in FIGS. FIG. 4 shows a technique called discrete cosine transform, which transforms from the spatial coordinate system to the frequency coordinate system in (Equation 2).

[0017]

[Equation 2]

In this example, the image data of FIG.
The value has a change from 0 to 149, but after conversion in FIG.
(B) has values from 15 to 120 and other values (-2,
-1, 0, 1). (-2, -1, 0, 1)
The numerical value of is a small numerical value, and these are converted to such an extent that they can be approximated by 0. FIG. 5B is shown in FIG.
Is a value obtained by dividing the numerical value of by 12. Here, the numerical value is a change from 1 to 10 and the rest is 0, and the data amount can be compressed. In FIG. 6, when the data is scanned in a zigzag manner instead of in the horizontal and vertical order, the number of consecutive 0s increases, so it is possible to treat the value 0 as 11 in a batch and reduce the number of data. it can. In addition, when the numerical value is represented by the binary system of the digital value, the frequently used numerical value can be replaced with a short code to reduce the data amount. In the example, if the value 5 is replaced with 2 and the value 10 is replaced with 3, the numerical value of each data is from 0 to 3, and all each data can be represented by 2 bits (generally called entropy coding). .

When the image data of one frame is compressed to 1 / n as in the example of the above method, it is possible to record an image of n frames in the area for recording one frame on the medium. The compressed image data is the compressed data memory 5
, The control circuit 11 sends a recording / reproducing control signal, and the recording / reproducing circuit 8 stores the compressed n in the medium 7.
Data for the frame is recorded (process 36 in FIG. 2). FIG. 7 shows an example of the structure of an image frame recorded in this way.

The operation during reproduction will be described. At the time of reproduction, a reproduction signal is sent from the control circuit 11 to the recording / reproduction circuit 8 as a recording / reproduction control signal. The compressed image data is read from the medium 7. Next, the control circuit 11 sends a data expansion control signal to the data expansion circuit 10. The data read from the medium 7 is decompressed by the data decompression circuit 10 and sequentially stored in the decompressed data memory 9 (process 37 in FIG. 2). The decompressed data is sequentially transferred and stored in the reproduced image frame memory 13 frame by frame (process 38 in FIG. 2). Images for playback of multiple frames are
Each frame is sequentially sent to the output circuit 12 and output (process 39 in FIG. 2).

As described above, according to this embodiment, it is possible to record only a frame having a motion and a plurality of these frames on the medium for recording one frame, which is the conventional time, and to record for a long time. It is a recording / reproducing device. If the medium has a margin, images for a plurality of frames may not be recorded at the same time but may be recorded for each one frame as in the conventional case.

[0022]

As described above, according to the present invention,
Most of the recording frames often record the exact same image in a state where no abnormality occurs when used for applications such as nighttime monitoring. Therefore, the input image is sequentially captured in the memory in frame units, the motion is detected by comparing the current frame image data with the image data in the memory one frame before, and the same image is not recorded,
Only different images are recorded. Further, the image to be recorded is recorded by compressing the image using image compression in the spatial axis direction, image compression by entropy coding, compression by discrete cosine transform, and the like. Therefore, in the case of recording for a long time, a large amount of medium is secured and the time required for searching for an abnormal image at the time of reproduction does not become enormous, and its practical effect is great.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing the operation of the recording / reproducing apparatus in the embodiment.

FIG. 3 is a schematic diagram showing an example of a method for detecting a motion in the embodiment.

FIG. 4 is a schematic diagram showing an example of a data compression method in the embodiment.

FIG. 5 is a schematic diagram showing an example of a data compression method in the embodiment.

FIG. 6 is a schematic diagram showing an example of a data compression method in the embodiment.

FIG. 7 is a schematic diagram showing a configuration for recording compressed data of n frames on a medium in the embodiment.

FIG. 8 is a block diagram showing the configuration of a conventional long-time recording / reproducing apparatus.

FIG. 9 is a schematic diagram showing a configuration in which a frame is recorded every time T from the time when an image frame is present on a medium in the conventional example.

[Explanation of symbols]

 1 Input Circuit 2 Recorded Image Frame Memory (t) 3 Recorded Image Frame Memory (t-1) 4 Motion Detection Circuit 5 Compressed Data Memory 6 Data Compression Circuit 7 Medium 8 Recording / Playback Circuit 9 Expanded Data Memory 10 Data expansion circuit 11 Control circuit 12 Output circuit 13 Frame memory for reproduced image

Claims (1)

[Claims] 1. Input means for taking in an image signal, two recording frame memory means for storing inputted image data for one frame which is different in time, and image data of the two recording frame memory means. Motion detecting means for detecting motion from the motion detecting means, control means for generating a plurality of control signals by the output from the motion detecting means, and image data from the frame memory means for recording is compressed by a signal from the controlling means. Data compression means, memory means for storing the compressed image data, a medium for storing the data, data from the data compression means on the medium by a signal from the control means, and data from the medium Recording / reproducing means for reproducing the data, and a data expansion means for expanding the signal from the recording / reproducing means by the signal from the control means. Means, memory means for storing the decompressed data, reproduction frame memory means for storing the reproduced image from the data expansion means, and output means for outputting the image data of the reproduction frame memory means. Recording / playback device with characteristic motion detection.