JPH03102975A - Television signal processor - Google Patents

Abstract

PURPOSE:To obtain a desired frequency characteristic on a CRT even for a signal processed by non-linear processing such as gamma-correction, etc., by providing a circuit to convert an input signal so as to be linear, the circuit to execute desired calculation by its output, and the circuit to execute the non-linear processing equivalent to a transmitting side by its output. CONSTITUTION:A transmitted NTSC signal is separated into a luminance signal Y and a chrominance signal C by a separation circuit 14. The C signal is demodulated into I and Q by a demodulation circuit 15. The signals Y, I, Q are converted by a matrix circuit 19 into R', B', G' signals of red, green and blue gamma-corrected on the transmitting side. These signals are raised to 2.2-th power respectively by using the circuits 21, 22, 23, and are returned once to linear signals R, B, G. The linear signals are applied with interpolation processing by scanning line interpolation circuits 24, 25, 26, and further, are raised to 1/2.2-th power by gamma-correction circuits 27, 28, 29, and are inputted to the CRT 20. Through this configuration, the calculation like the interpolation processing, etc., can be executed on a receiving side without being influenced by the gamma-correction on the transmitting side, and the distortion of luminance, hue and saturation is never caused on the surface of the CRT.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a television signal processing circuit, and in particular, to a television signal processing circuit that receives a transmitted signal after performing nonlinear processing such as gamma correction on the transmitting side. It relates to signal processing circuits that perform linear operations such as filter processing and scanning line interpolation. [Prior Art] Ideally, the relationship between the grid signal voltage of the picture tube and the light emission output (tube surface brightness) should be linearly proportional. However, the actual light output is approximately 2 times the signal voltage applied to the grid.
．． It is proportional to the square. For this reason, if the signal from the camera is directly applied to the picture tube, not only the brightness of the screen but also the hue and saturation in the case of a color picture tube will differ from the actual picture. Therefore, before applying the signal to the picture tube, it is corrected so that the overall characteristic becomes linear by passing it through a circuit such that the output signal voltage is 1/2.2 of the input signal voltage. The relationship between the signal voltage of the picture tube and the light emission output is generally called the gamma characteristic, and in the above case, γ=2.2. Further, the above correction circuit is called a gamma correction circuit.

This gamma correction circuit can be inserted just before applying the signal to the picture tube grid. However, the current television system (NT
In the SC method), it is specified that the signal output of the camera is gamma corrected on the transmitting side. Figure 2 shows the main parts of an example of the structure of a current television transmitter/receiver. First, on the transmitting side, the red, green, and blue signals (hereinafter abbreviated as R, G, and B signals) from the camera 4 are
The signals are input to gamma correction circuits 5, 6, and 7, respectively (generally, gamma correction circuits 5, 6, and 7 are often built into the camera 4). Gamma corrected R', G',
The B' signal is converted into a luminance signal Y, a color signal signal, and Q by a matrix 8. Color signals I and Q are filtered by filter 9
and 10 respectively. 5 MHz and 0
．． Bandwidth limited to 5 MHz. After that, the modulator 11 uses a carrier wave called a color printing carrier wave to generate the I signal and the Q signal.
After the signal is orthogonally modulated into a C signal, it is multiplexed with a Y signal using a multiplexing circuit 12. Finally, by filter l3, 4
．． The band is limited to 2 MHz and transmitted as an NTSC signal (Reference 2 "Color Television",
Chapter 1, edited by Japan Broadcasting Corporation, published by Japan Broadcasting Publishing Association, 19
61). The part surrounded by a broken line in FIG. 2 shows an example of the configuration of a television receiver generally called an IDTV.
The transmitted NTSC signal is interlaced scanned every l scanning lines based on the standard. If an image is displayed using interlaced scanning, the scanning line structure becomes visible, causing deterioration in image quality and causing "flicker".
"Flicker" may occur. To prevent this, in I'D TV, skipped scanning lines that are not transmitted are interpolated and reproduced on the receiving side as sequential scanning signals and displayed. (References Ninikkei Electronics, 1987
October 19th issue, no432, ppl02-105
) In the IDTV 100, first, the transmitted NTSC signal is separated into a Y signal and a C signal by the YC separation circuit 14.

The C signal is demodulated into a power signal and a Q signal using a demodulation circuit 15. The separated and demodulated Y, I, and Q signals are sequentially scanned using scanning line interpolation circuits 16, 17, and 18, and then converted into R', G', and B' signals using a matrix 19, The signal is input to a picture tube 20 which has gamma characteristics. Scanning line interpolation will be explained in detail using Figure 3. FIG. 5(a) shows a case in which a scanning line X that is not transmitted is interpolated and reproduced from upper and lower scanning lines A and B in the same field. In this case, X=(A+B)/2, and the average value of the upper and lower scanning lines is taken. In the same figure (b), from scanning lines C and D of the fields before and after the same position, scanning line
The following shows the case of interpolation playback. in this case. X=(C0D
)/2. The same figure (c) is the same figure (a
) and the interpolation method shown in FIG. 3(b) are adaptively switched depending on the amount of motion k. Preliminary movement amount k (0≦k≦l)
Detected, X=k・(A+B)/2 +(1−k)・(
C+D)/2, when the amount of motion k is large (close to 1), use the intra-field interpolated value in (a) of the same figure, and when the amount of motion k is small (close to 0, that is, stationary), use the intra-field interpolated value. The inter-field interpolated values shown in FIG. 2(b) are output. Such interpolation processing can be considered a type of filter processing.

[Problem to be solved by the invention]

FIG. 4 also shows the input/output characteristics of the gamma correction circuit 5 in FIG. 2, and is a curve of R/=R 1/'°2. For simplicity, the subject is a black and white image (i.e. R=G=B=Y), and the voltage of scanning line A is OV.
(perfect black level) and the voltage of scanning line B is assumed to be IV (perfect white level). Gamma correction (1/2.2 power) is performed on this input signal, and A' = OV,
Transmit as B' = IV. In the HDTV IOO shown in FIG. 2 above, the transmitted scan 1! An interpolated scan line X is created from A' and B'. For example, as shown in Figure 3(a), when outputting the average value of the upper and lower scanning lines, x = (A' + B')/2
=0.5V is the voltage of the interpolation scanning line. However, even if this signal is applied to the picture tube, it will be zero due to the gamma characteristics of the picture tube.
．． The screen brightness is only about 52''40.22, and it is always darker by δ (in this case, 0.5-0.22=0.28>) than the original interpolated value (A+B)/2. General color images (i.e. R-I-G-Ih
In the case of B), there was a drawback that not only the brightness but also the hue and saturation were different from reality. Although the explanation was given using scan line interpolation as an example, similar drawbacks occur when creating new pixels or fields by interpolation. In addition to interpolation, if linear operations such as filter processing and edge enhancer (high frequency emphasis) are performed on signals that have undergone non-linear processing such as gamma correction, the brightness observed on the screen will change to the desired frequency. Unlike the characteristics, the tube surface brightness gain is insufficient in small (i.e., dark) portions of the picture tube input.

Therefore, an object of the present invention is to provide a filter circuit that can obtain desired frequency characteristics (or output voltage) on the picture tube surface even for signals that have been subjected to nonlinear processing such as gamma correction. [Problem to be solved by the invention] The above object is to provide a first signal processing circuit that converts a transmitted signal into a linear signal, and a second signal processing circuit that receives the output of the first signal processing circuit and performs a desired calculation. This can be achieved by using the second signal processing circuit and a third signal processing circuit that receives the output of the second signal processing circuit and performs nonlinear processing equivalent to that on the transmitting side. The transmitted signal is passed through a first signal processing circuit, which has characteristics inverse to the nonlinear processing on the transmitting side, and is once returned to a linear signal. For example, when the nonlinear processing on the transmitting side is gamma correction (Rt == RA/Z-2), R=R'2'2 is output. A second signal processing circuit performs desired calculations (filter processing, interpolation processing, etc.) on this linear signal, and then a third signal processing circuit performs gamma correction again to produce an output signal. Therefore, the desired calculated signal can also be correctly gamma corrected, and the desired frequency characteristics can be realized on the picture tube. [Example] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 shows an embodiment of the present invention. A gamma-corrected signal on the transmitting side is input to a gamma circuit 1 and is once converted into a linear signal. This gamma circuit 1 outputs R=R"・2 for the input R'. The signal processing circuit 2 performs desired calculations (filter processing, interpolation processing) on this linear signal.
After performing this, the signal is output as an output signal through a gamma correction circuit 3 for correcting the gamma characteristics of the picture tube.

Figure 5 shows an example in which the present invention is applied to scanning line interpolation of IDTVIOI. A YC separation circuit 14 is used to separate a luminance signal Y and a color signal C from the transmitted NTSC signal.
The C signal is demodulated into an I signal and a Q signal using a demodulation circuit 15. The separated and demodulated Y, I, and Q signals are converted by a matrix 19 into R', G', and B' signals (red, green, and blue signals gamma-corrected on the transmitting side). These signals are raised to the 2.2 power using gamma circuits 21, 22, and 23, respectively, and are once returned to linear signals R, G, and B. For this linear signal, the scanning line interpolation circuit 24.2
5 and 26 to perform the scanning line interpolation process as shown in FIG.
Enter. FIG. 6 shows another example in which the present invention is applied to scanning line interpolation.

As shown in FIG. 3(a), intra-field scanning line interpolation is often performed for the optical signal and Q signal, which are less noticeable even if their resolution is lower than the Y signal, without using expensive field memory. On the other hand, for Y signals with noticeable resolution reduction and afterimages, motion adaptive scanning line interpolation as shown in FIG. 3(c) is often performed. In FIG. 6, a YC separation circuit 14 is used to separate a luminance signal Y and a color signal C from the transmitted NTSC signal. The C signal is demodulated into a power signal and a Q signal using a demodulation circuit 15. From the point of view of economy, the present invention can also be applied only to the luminance signal Y.

That is, the Y signal is returned to a linear signal by the gamma circuit 30, interpolated by the scanning line interpolation circuit 16, passed through the gamma correction circuit 31, and then input to the matrix 19. ■Signals and Q signals are handled by the scanning line interpolator 17 as before.
and l8 to perform only interpolation processing, matrix 1
Enter 9. In the matrix, R' from Y, I, Q signals
, G'B' signals and input to the picture tube 20. In this case, a black and white image (i.e. R=G=B=Y, I=Q
=O), the same effect as in FIG. 5 can be obtained. Furthermore, if economic efficiency is not considered, the same processing as the Y signal may be applied to the engineering and Q signals. The portion 200 surrounded by the broken line in FIG. 6 will be explained in more detail using FIG. 7.

In the figure, a motion detection circuit 36 is used to generate a motion amount k (0≦k≦1) from an input signal in advance. this is,
It is sufficient to normalize by taking the difference of 1 frame or 2 frames between pixel data at the same position. Furthermore, since the input signal has been gamma-corrected on the transmitting side, it is converted into a linear signal using the gamma circuit 30. From this linear signal, IH (H is horizontal scanning period) delay circuit 32, adder 33 and multiplier 3
4 to create the average value of the upper and lower scanning lines (that is, the intra-field interpolated value). In addition, the 263H delay circuit 3
5 to create an inter-field interpolated value (however, in the figure, the inter-field interpolated value is not the inter-field average value, but the previous value interpolated value. Of course, the average value may also be used).

Using multipliers 37, 38 and adder 39, the intra-field interpolated value and the inter-field interpolated value are mixed according to the amount of motion k to produce interpolated scanning line data. Further, the output of the gamma circuit 30 is used as actual scanning line data, which is switched to interpolated scanning line data by a switch 40 and output. At this time, although it is omitted in the figure, in reality, both the actual scanning line and the interpolated scanning line are converted to double speed (compressing the time axis to 1/2), and the actual scanning line and the interpolated scanning line are converted in one horizontal scanning period. The signals are alternately multiplexed on the time axis and output from the switch 40. After passing this output through the gamma correction circuit 31, it is used as an output signal.

A modification of the configuration shown in FIG. 7 is shown in FIG.

In the figure, a motion detection circuit 36 is used to generate a motion amount k (0≦k≦1) from an input signal in advance. It also converts the input signal into a linear signal. From this linear signal. Using the LH (H is horizontal scanning period) delay circuit 32, adder 33, and multiplier 34, an average value of the upper and lower scanning lines is created, which is then passed through the gamma correction circuit 31 to become an intra-field interpolated value. In addition, the input signal can be changed to 263H as it is.
It passes through a delay circuit 35 to create inter-field interpolated values. In this way, in the case of prior value interpolation, etc., which involves only a delay and does not involve calculation between data, there is no need to consider the influence of gamma correction on the transmitting side. Multiplier 37, 38 and adder 3
9, the intra-field interpolated value and the inter-field interpolated value are mixed according to the amount of motion k to obtain interpolated scanning line data. Further, the input signal is actual scanning line data, which is switched to interpolated scanning line data by a switch 40 and output. At this time, although it is omitted in the figure, in reality, both the actual scanning line and the interpolated scanning line are converted to double speed (compressing the time axis to 1/2), and the actual scanning line and the interpolated scanning line are converted in one horizontal scanning period. The signals are alternately multiplexed on the time axis and output from the switch 40. In the above description, γ=2.2, but the same applies to other values. Furthermore, although the nonlinear processing on the transmitting side has been described as gamma correction of the picture tube, the same applies to any nonlinear processing in which an inverse characteristic exists. Furthermore, although we have explained the case where the desired operation on the receiving side is scan line interpolation, there are also cases where new pixels or fields are interpolated, or other linear operations (for example, edge enhancer or , brightness and contrast adjustment, filter processing for frequency separation, etc.). In other words, once the signal is restored to a linear signal, the desired calculation is performed, and nonlinear processing such as gamma correction is performed again, thereby eliminating distortion of brightness, hue, and saturation on the picture tube surface. [Effects of the Invention] By applying the present invention, desired calculations such as interpolation processing can be performed on the receiving side without being affected by gamma correction on the transmitting side, and brightness, hue, and Since no saturation distortion occurs, the effect of implementing this method is extremely large.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a schematic structure of an embodiment of the present invention, and Fig. 2 is a block diagram showing a schematic structure of an embodiment of the present invention.
- Gamma correction circuit, 4... Camera, 8, 19... Matrix, 9, 10.13... Filter, 11...
Modulator, 12... Multiplex circuit, 14... YC separation circuit, 15... Demodulator, 16, 17, 18, 24, 25.
26... Scanning line interpolation circuit, 20... Picture tube, 32.
35...Delay circuit, 33.39...Adder, 34,
37, 38... Multiplier, 36... Motion detection circuit, 4
0...Switcher, 100, 101, 102...I
DTV. FIG. 6 is a circuit block diagram of an embodiment in which the present invention is applied to interpolation processing, and FIGS. 7 and 8 are circuit block diagrams explaining a part of FIG. 6 in detail. 1, 21, 22, 23,
30... Gamma circuit, 2... Signal processing circuit, 3, 5
, 6, 7, 27, 28, Fig. 3 Fig. 1 Fig. 4 Concave

Claims (1)

[Claims] 1. In a circuit that receives and processes a transmission signal that has been nonlinearly processed on the transmitting side, a first signal processing circuit that converts the transmitted signal into a linear signal; and a first signal processing circuit. A second signal processing circuit receives the output of the second signal processing circuit and performs a desired calculation, and a third signal processing circuit receives the output of the second signal processing circuit and performs nonlinear processing equivalent to that on the transmitting side. A television signal processing circuit. 2. The television signal processing circuit according to claim 1, wherein the nonlinear processing is a process for correcting gamma characteristics of a picture tube of a television. 3. The second signal processing circuit generates a new pixel, scanning line 3.
3. The television signal processing circuit according to claim 1, wherein the television signal processing circuit is a circuit that interpolates and outputs a field or the like. 4. The television signal processing circuit according to claims 1 and 2, wherein the second signal processing circuit is a circuit that emphasizes high frequencies of the signal.