JPS6372277A - Inter-frame difference transmission system - Google Patents

Abstract

PURPOSE:To attain efficient band compression of a video signal by reading a designated video part as a coordinate reference point and taking difference of the same coordinate of each memory in reading video signals from two frame memories. CONSTITUTION:An analog video signal from a television camera 1 is digitized by an A/D converter 2 and outputted to a changeover switch 3. A write controller 7 controls the changeover timing of the changeover switch 3, outputs a write control signal to frame memories 4, 5 in matching with the changeover timing to apply write alternately at each frame. On the other hand, the analog video signal from the television camera 1 is displayed on a monitor 10 via a video signal processing circuit 9. The operator observes the patternand designates a still picture part by a light pen to read its coordinate reference information, which is given to a controller 8. The read controller 8 reads information from the frame memories 4, 5 based on the coordinate and a signal of moving picture part only is extracted from a subtractor 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an interframe differential transmission method for performing band compression of a video signal in a moving image transmission system.

(Prior Art) Conventionally, a video transmission system for transmitting video images such as a video conference uses a narrowband telephone line or the like as a communication path, so it is essential to significantly compress the signal band during video transmission.

An interframe differential transmission method is generally applied to compress this signal band. This inter-frame differential transmission method removes the still image component included in the video signal by taking the difference between frames of the video signal (moving image) from the television camera, and converts the video signal into only the moving image component. This method performs band compression.

By the way, in the conventional video transmission system as mentioned above,
The WL image device, such as a television camera, was used in a fixed manner, and was intended for use mainly indoors, such as in a video conference. However, when using the above system outdoors, if the imaging device is mounted on a moving object such as a vehicle, boat, or aircraft, II! The field of view of the a-image device may move slightly in response to changes in the attitude of the moving object.

Furthermore, even if the imaging device is not mounted on a moving body, the imaging device may swing due to strong winds and the like, causing slight movement in the field of view. Therefore, even if the image within the field of view is originally a stationary object such as terrain, its position changes from frame to frame due to slight movement of the field of view of the imaging device, making it appear to be a moving object. For this reason, when the inter-frame differential transmission method is applied as a band compression method for video signals, what should be a still image behaves as a moving image, which has the disadvantage that the band compression effect is significantly reduced. Therefore, in order to avoid the above-mentioned drawbacks, a stable platform is used to prevent the imaging from being transmitted to the Ia imaging device to suppress the slight movement of the field of view, but the stable platform has the drawback that it is expensive. Ta.

(Problems to be Solved by the Invention) Conventionally, when performing band compression of a video signal by applying an inter-frame differential transmission method to a video signal obtained from an imaging device, etc.
When the field of view of the imaging device slightly moves, the position of the still image differs from frame to frame, resulting in a drawback that the band compression effect of the video signal is significantly reduced. SUMMARY OF THE INVENTION Therefore, the present invention aims to eliminate the above-mentioned drawbacks, and aims to provide an inter-frame differential transmission method that can efficiently compress the band of a video signal obtained even if the field of view of an image carrier moves slightly. do.

[Structure of the Invention] (Means for Solving the Problems) The present invention includes two image memories each capable of storing at least one frame of video signal, and a video signal from an imaging device that is stored in the image memory for each frame. video signal writing means for writing alternately into each of the two images; designation means for designating a specific still image portion in the video signal; and a still image portion designated by the designation means as a coordinate reference point for the two images A system is adopted comprising a video signal readout means for alternately reading out video signals at the same coordinate point from the memory, and a 'g5i means for calculating the difference between the alternately read out video signals at the same coordinate point.

(Function) In the inter-frame differential transmission system of the present invention, the video signal from the device is alternately written into each of the image memories frame by frame by the video signal writing means. Further, the video signal reading means alternately reads video signals at the same coordinate point from the two image memories, using the designated still image portion as a coordinate reference point. The difference between the video signals at the same coordinate point read from each image memory is taken by the subtracting means, and the still image portion is removed to perform band compression of the video signal.

(Example) An example of the present invention will be described below with reference to the drawings. The figure is a block diagram showing an embodiment of a video signal processing circuit to which the inter-frame differential transmission method of the present invention is applied. 1 is a television camera that is a type of imaging device; 2 is an A/D converter that converts an analog video signal from the television camera 1 into a digital video signal (hereinafter sometimes simply referred to as a video signal);
3 is a changeover switch that switches the video signal from the A/D converter 2 frame by frame and outputs it to frame memories 4 and 5, respectively; 4.5 is a frame memory that holds the video signal for one frame ( 6 is a subtractor that calculates and outputs the difference between the video signals of the same coordinate point read from the frame memories 4 and 5, and 7 is a switch control for the changeover switch 3 and the images in the frame memories 4 and 5. A writing control device 8 performs signal writing control, and coordinates 19 indicate two points specified in the video signals written in the frame memories 4 and 5.
A readout control device alternately reads video signals of the same coordinate points from the frame memories 4 and 5 as points, and 9 processes analog video signals from the television camera 1 and displays them on a monitor 10
A video signal processing circuit 10 is a monitor that displays an analog video signal from the television camera 1 as an image and allows a specific position on the screen to be designated with a light pen or the like.

Next, the operation of this embodiment will be explained. TV camera 1
The analog video signal from is converted into a digital video signal by the A/D converter 2 and output to the changeover switch 3. The write control device 7 controls the switching timing of the changeover switch 3, and also outputs a write control signal to the frame memory 4.5 in accordance with this changeover timing, so that the video signal switched for each frame by the changeover switch 3 is output. is written to frame memories 4 and 5. That is, when a video signal is written to the frame memory 4 for the first frame period, the video signal is written to the frame memory 5 for the next frame period. On the other hand, an analog video signal from the television camera 1 is supplied to a monitor 10 via a video signal processing circuit 9 and displayed as an image. The operator looks at this image and selects a still image portion in which a still object such as a beet is photographed, for example, al, bl in the frame memory 4 and a2 . Designation using the video signal portion corresponding to b2 as the coordinate reference is performed by touching the monitor screen using a light pen or the like. As a result, the coordinate reference information is provided from the monitor 10 to the readout control device @8.

From now on, the read control device 8 controls the frame memory 4,
When the video signals of the same coordinate points of 5 are read out alternately and these video signals are sequentially input to the subtracter 6, the a1. bl
, a2. The video signal portion of b2 is read out as a coordinate reference. Therefore, due to slight movement of the field of view of the television camera 1, the video signal portion a1 in the frame memory 4 moves to the video signal portion a2 in the frame memory 5, and similarly, the video signal portion b1 moves to the video signal portion a2 in the frame memory 5.
However, even if the image signal portion b2 is moved to the video signal portion b2, these video signal portions are read out as the same coordinate point by the readout control device 8 and output to the subtracter 5 at the time of readout. Since the subtracter 5 calculates the difference between the video signals at the same coordinate point in the frame memories 4 and 5, the subtracter 5 erases the video signal portion forming the still image. Therefore, from this subtracter 5, only the inter-frame difference video signal component of the video signal based on the movement of the moving object, that is, forming a moving image, is subtracted by 1, and the band of the video signal is compressed.

According to this embodiment, when reading video signals from the frame memories 4 and 5, the still image portion is read out as a coordinate reference point, so even if the still image position differs between frames due to slight movement of the television camera 1, Since the same coordinate points are used when reading from the memories 4 and 5, the video signal corresponding to the still image can be reliably erased by the subtracter 6, and the band compression of the video signal can be performed efficiently. can. Additionally, the device shown in the figure is less expensive than when using a stable platform, and the above effects can be achieved without increasing cost.

[Effects of the Invention] As described above, according to the inter-frame differential transmission method of the present invention, a video signal is written into two image memories for each frame, and when reading a video signal from the image memory, a specified By reading out the video portion as a coordinate reference point and taking the difference between the read video signals at the same coordinate point in each memory, it is possible to efficiently compress the band of the video signal obtained from the imaging device even if the field of view of the imaging device is m. There are effects that can be achieved.

[Brief explanation of the drawing]

The figure is a block diagram showing an embodiment of a video signal compression device to which the inter-frame differential transmission method of the present invention is applied. 1...TV camera 2...A/D converter 3...
Changeover switch 4, 5...Frame memory 6...Subtractor 7...Fortune reading control device 8...Reading control device 10...Monitor agent Patent attorney Nori Chika
Ken Yudo Sanno -

Claims (1)

[Claims] In an inter-frame differential transmission method in a moving image transmission system that transmits a video signal input from an imaging device, at least one frame of video signal can be stored in each frame.
video signal writing means for alternately writing a video signal from the imaging device into each of the image memories frame by frame; and designating means for designating a specific still image portion in the video signal. , a video signal reading means for alternately reading out video signals at the same coordinate point from the two image memories using the still image portion designated by the designation means as a coordinate reference point; and video signals at the same coordinate point read out alternately. an inter-frame difference transmission method, comprising: subtraction means for calculating the difference between the frames.