JPS6032390B2 - Image signal interpolation reproduction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application of the Invention The present invention relates to a system for efficiently transmitting or storing scanned image signals such as television signals.

'2} Conventional technology There is a method in which a color television signal is separated into a luminance signal and a chrominance signal and then encoded and transmitted.

Since the color signal only requires 1/4 to 1/8 the bandwidth of the luminance signal, there is almost no deterioration in the reproduced image quality even if the color signal is transmitted intermittently every other scanning line, and highly efficient transmission is possible. It is possible. At this time, the decoding circuit at the receiving end interpolates the color signals of the scan lines that are not transmitted from the color signals that are intermittently transmitted every other scan line to create a color signal for each scan line.

In a normal color television system, a color signal is modulated with a subcarrier signal whose phase differs by 1800 points for each scanning line. Therefore, in the above-mentioned color signal interpolation, it is necessary to create a carrier color signal with inverted polarity. In the interpolation playback method configured in this way, monochrome.

When transmitting a television signal, the high frequency components of the monochrome television signal are transmitted in the color signal channel. Therefore, during reproduction, the polarity of the high frequency components intermittently transmitted every other scanning line is reversed and only a reproduced image with degraded resolution is obtained for interpolation. '3} Object of the Invention According to the present invention, when a monochrome television signal is transmitted, a high-resolution reproduced image can be obtained.

The purpose is to obtain an interpolation reproduction method for color television signals. {4} Examples Hereinafter, the present invention will be explained in detail with reference to examples.

FIG. 1 shows the power spectrum of a television signal. Here, the color signal of the color television signal is modulated at the subcarrier frequency fsc and multiplied by the luminance signal. Figure 1b shows a detailed diagram of this spectrum near fsc.
The luminance signal vector has a peak at a position that is an integral multiple of the horizontal scanning frequency fH. On the other hand, f is (n+0.5)f
H (n is a positive integer, n=227 in the case of the NTSC system), so the peak of the color signal is located exactly at the valley of the luminance signal. FIG. 2 shows this on a two-dimensional frequency axis.

In the figure, the horizontal axis indicates the frequency of the television image in the horizontal direction, and the vertical axis indicates the frequency in the vertical direction. In the case of the NTSC system, the subcarrier frequency fSc is 227.5 times fH in the horizontal direction, and fv (fH
/525) is located at 131.25 (525/4) times. The color signal exists around this subcarrier frequency (region C in the figure). On the other hand, the luminance signal exists in regions A, B, and D, and the one-dimensional frequency spectrum shown in Fig. 1b corresponds to region C (color signal) and regions B and D (luminance signal) in Fig. 2. are doing. In the case of a normal color receiver, regions B and D are not only not used as high frequency components of the luminance signal, but also interfere with the color signal.

Therefore, the vertical band of the color signal is 1/1/2 of the luminance signal.
There is no problem even if it is limited to 2 cliffs. In other words, for the color signal channel, the number of samples in the vertical direction (number of scanning lines) is reduced to 1/1 of the normal number.
It can be made into 2. On the receiving side, the color signal of the scan line that was not transmitted can be reproduced by inverting the polarity of the immediately preceding color signal. At this time, the range of color television signals that can be reproduced is region A and region C in FIG. Next, a case will be considered in which a monochrome television signal is transmitted using a method in which color signal channels are transmitted intermittently every other scanning line.

At this time, in the color signal channel, the high frequency component of the luminance signal is 1
Transmitted every other scan line. In terms of human visual characteristics, the visual characteristics of diagonal patterns are generally inferior to those of horizontal and vertical patterns, and even if the high frequency components of diagonal patterns (areas C and D in Figure 2) are removed, the deterioration in image quality is not noticeable. It is said that Therefore, in the case of a monochrome signal, it is desirable that regions A and B can be reproduced. The present invention provides a system that can realize this, and a specific embodiment is shown in FIG.

In the same figure, the television signal input to the input terminal 1 has a color signal band centered at the subcarrier frequency f which is extracted by the band filter 2, and the color signal band is extracted with a delay time equal to the delay time of the band filter 2. A luminance signal is obtained by subtracting the signal that has passed through the delay element 3 in the subtraction circuit 4. Color signals separated in this way (output of Obijo Filter 2)
repeats opening and closing every horizontal scanning period. The switch 5 performs intermittent transmission every horizontal scanning period. Further, an identification information insertion circuit 6 inserts identification information for identifying at the receiving end whether the information transmitted in this color signal channel is a color signal or a harmonic component of a luminance signal. 0 In the receiver, the color identification circuit 7 first identifies whether the information transmitted in the color channel is color information or a high frequency component of a luminance signal.

The color channel signal is processed by an interpolation circuit 9 that uses the output of a delay circuit 8 having a delay time of one horizontal scanning period, by inverting the polarity in the case of color information and outputting it as is in the case of high frequency components of the luminance signal. Create color signals for scan lines that were not transmitted. Next, the switch 10 is moved up and down in each horizontal scanning period to create a color signal for each scanning line, which is added and synthesized with a separately transmitted luminance signal by an adder circuit 11 to reproduce a television signal. In the embodiments described above, a subcarrier burst is transmitted as the identification information of the signal transmitted in the color channel, and the presence or absence of this burst signal can be determined by the color identification circuit 7 in the receiver.

The above-mentioned function can also be realized by periodically transmitting special identification information in a time-division manner. In the embodiment described above, the color signal modulated by the subcarrier is directly transmitted, but it is demodulated before or after the switch 5,
Baseband color difference signals may also be transmitted. In this case, the interpolation circuit 9 is omitted, and the received color difference signal and the color difference signal delayed by one horizontal scanning period are switched by the switch 10, modulated by the rear subcarrier f, and combined with the rear luminance signal. In this case, the phase of the subcarrier signal of the modulation circuit is controlled by the output of the identification circuit 7. In other words, in the case of color information, the phase remains unchanged (i.e., the phase changes by 18 points per horizontal scanning period), and in the case of high-frequency components of the luminance signal, the phase is shifted by 180 degrees per horizontal scanning period (i.e., the phase changes by 18 steps per horizontal scanning period). (with the same subcarrier phase). In the example shown in Fig. 3, the operation was described using a continuous analog signal system for both the time axis and the amplitude axis, but in order to improve the time axis (phase) accuracy and amplitude accuracy, the entire system or a part of the system is converted to a digital signal system. It can be composed of

In particular, by employing a digital signal system for the delay circuit 8, interpolation circuit 9, etc., the characteristics of the entire system can be improved. Although FIG. 3 shows only the main parts for explaining the operation of an embodiment of the present invention, a buffer memory, a transmission line, a storage device for recording, etc. may be added between the transmitting and receiving ends as necessary. , are not limited to their formal characteristics.

{5} Summary As explained above, according to the present invention, a high-resolution monochrome television signal can be transmitted in a method in which color signals are transmitted intermittently every other scanning line, and a high-efficiency transmission method that can be used for both monochrome and color is realized. realizable.

[Brief explanation of the drawing]

FIG. 1 shows a frequency spectrum diagram of a color television signal, FIG. 2 shows its two-dimensional frequency distribution diagram, and FIG. 3 shows a configuration diagram of an embodiment of the present invention. 1...Input terminal, 2...Obijo filter terminal, 3
...Delay element, 4...Subtraction circuit, 5,
10...Switch, 6...Identification information insertion circuit, 7...Color identification circuit, 8...
・Delay circuit, 9...Interpolation circuit, 11...
-Addition circuit, 12... Output terminal. Figure 1 Figure 2 Tsutomutsu Figure

Claims (1)

[Claims] 1 A scanned image signal such as a television signal is separated into a first component including a low frequency component and a second component including a high frequency component that covers the band of a carrier color signal, and the first component is In a method in which signals of all scanning lines are transmitted and the second component is transmitted or stored every other scanning period, identifying whether the transmitted or stored image is a color image or a monochrome image,
The second component transmitted or stored every scanning period is interpolated as it is for a black and white image, or with its polarity reversed in the case of a color image, and reproduces an image signal to be combined with the first component. An interpolation reproduction method for image signals characterized by: