JP2515717B2 - Quasi-video interframe coding method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an image transmission system that transmits only a changed portion from a previous screen, and in particular, a characteristic based on a difference between a frequency of a fluorescent lamp used for illumination and a TV frame frequency. It relates to a method suitable for eliminating deterioration.

[Background of the Invention]

Relatively low bit rate (eg less than a few 100 Kb / s,
However, there is an image transmission system that transmits only the changed portion from the previous screen as a system that transmits TV images at a rate of 10 Kb / s or less). For example, "Development of a color still image transmission system that transmits only the change from the previous screen", Nikkei Electronics, 1979.9.3, pp. 68-73).

However, the frame frequency of TV signals is 30Hz, and the frequency of fluorescent lamps is 50Hz in East Japan (its brightness is 100Hz).
Therefore, the average illuminance during one frame period of TV is not constant. Therefore, even with a still image, the signal value changes between frames, and it is determined that “there is motion”.
As a result, the image area to be transmitted is apparently large and the transmission time is increased.

[Object of the Invention]

An object of the present invention is to "behave" even though the image is originally a static image even in a situation where the average illuminance during the frame period of the TV is not constant due to the relationship between the frame frequency and the power supply frequency for illumination. An object of the present invention is to provide an interframe coding method that does not generate a false moving image area that is erroneously determined to be processed as a moving image.

[Outline of Invention]

FIG. 1 shows the relationship between the TV frame cycle and the fluorescent lamp cycle. As you can see from this figure, during 1/10 seconds,
There are 3 cycles of 30Hz TV frame and 5 cycles of 50Hz AC power supply. Then, almost this is repeated thereafter. Therefore, it can be seen that a TV signal under the same lighting condition can be obtained every three frames.

The present invention takes advantage of this. That is,
As the image (frame or field), the moving image area is removed by using only the signal every three frames.

Example of Invention

An embodiment of the present invention will be described below with reference to FIG. Second
In the figure, except for the frequency dividing circuit 1, the conventional configuration itself is obtained. First, the conventional configuration will be briefly described.

The signal obtained from the TV camera 2 is compared with the contents of the frame memory 5 in the change detection circuit 4 only during a period (one frame) in which the gate 3 is closed by a method described later.
There are various possible methods of comparison, but one method is to divide the screen into several blocks and compare whether there is a change for each block. So I won't go into detail).

When it is determined that there is a change, this result is stored in the memory for each block. For this purpose, a separate memory may be provided, or one bit may be stored in an appropriate bit in each block of the frame memory 5. Also, rewrite the image with a new one.

After that, the image of the block which is determined to have this change is read out under the control of the code control circuit 6 and is sequentially transmitted at the bit rate of the transmission path 7.

When the sending of all the changed image areas is completed, the completion signal 8 is issued. Then flip-flop 9 is set. On the other hand, by the output of the timing circuit 10 that detects the frame timing and the AND circuit 11,
The timing circuit 12 is driven to output an output for one frame period for closing the gate 3 as shown in FIG.

 The above is the outline of the conventional method.

The present invention is characterized in that the frequency dividing circuit 1 is inserted. This divides the output of the timing circuit 10 by 3 as shown in FIG. Hereinafter, if the output of this frequency dividing circuit is regarded as the output of the timing circuit 10 and is operated and the timing circuit 12 is driven, it is possible to take out signals of only frames that are an integral multiple of three frames.

The methods that can be considered in the actual configuration are listed below.

(I) Although 30 frames and 60 fields are assumed here, it goes without saying that sequential scanning of 60 frames (non-interlaced scanning) may be performed.

(II) Here, power supply frequency 50Hz, frame frequency 30Hz
As mentioned above, power frequency 60Hz, frame frequency 25H
The case of z can be realized by the same idea.

(III) The control unit, the wire unit and the like can be realized not only by the wired logic but also by program control of a microprocessor or the like.

(IV) Further, it is possible to have two frame memories and the motion determination itself can be program-controlled.

(V) In the NTSC color TV signal, the phase of the color signal is inverted every other frame. For this reason, there is a method of using a TV signal at intervals of 6 frames instead of 3 frames.

〔The invention's effect〕

In the present invention, since the image signals of the frames under the same illumination condition that are periodically generated are inter-frame coded,
By preventing erroneous determination that there is “motion” due to the influence of the periodical fluctuation of illumination, the occurrence of a false moving image area that is processed as a moving image even though it is originally a still image is caused by the erroneous determination. It is possible to remove it. Therefore, even when the illuminance is not constant and changes periodically, the image information to be encoded and transmitted does not increase, and the transmission time can be shortened.

[Brief description of drawings]

FIG. 1 is a timing explanatory view showing the outline of the present invention, and FIG.
FIG. 3 is a block diagram showing the structure of the prior art and the present invention, FIG. 3 is a timing explanatory view in the conventional structure, and FIG. 4 is a timing explanatory view in the present invention. 1 ... Frequency divider circuit, 2 ... TV camera, 4 ... Motion determination circuit, 5 ... Frame memory, 6 ... Encoding control circuit.

Claims (2)

(57) [Claims] 1. A frame or a field in an image signal from a camera affected by a change in illumination condition, which is periodically generated every several frames according to the relationship between an illumination power supply frequency and a frame frequency, under the same illumination condition. Is a quasi-moving frame inter-frame coding method, in which the image signal of is inter-frame coded. 2. When the power frequency for illumination is 50 Hz and the frame frequency is 30 Hz, every 3 frames or fields are used as the frames or fields under the same illumination condition. The quasi-moving image interframe coding method described in the first item.