JPS63260291A - Method and apparatus for converting television signal - Google Patents

Abstract

PURPOSE:To improve compressing efficiency without picture quality deterioration by outputting selectively and alternately a 1st color signal separated and a 2nd color signal whose phase is inverted to the 1st color signal for each scanning line and synthesizing the output with a luminance signal. CONSTITUTION:An NTSC color TV signal inputted from a TV camera 1 is sampled by an AD converter 2 to generate a composite signal P. A YC separation circuit 3 separates the composite signal P into a luminance signal Y and a chrominance signal C. A switch circuit 5 selects the chrominance signal C and a chrominance signal C' being the result of phase inversion of the signal C at a chroma inverter 4 for each scanning line and the result is used as a new chrominance signal C'' and outputted to a YC synthesis circuit 6. The YC synthesis circuit 6 synthesizes a luminance signal Y and the chrominance signal C'' to output a new composite signal P'' to a digital signal processing circuit 7. The signal is converted into the original composite signal P by a YC separation circuit 8, a chroma inverter 9, a switch circuit 10 and a YC synthesis circuit 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal conversion method and apparatus for NTSC color TV signals.

[Conventional technology]

As a conventional example of converting an NTSC color TV signal, a case where the signal is digitized and converted will be described.

The sampling frequency fc when digitizing an NTSC color TV signal is an integer multiple of the color subcarrier frequency fxc fc=n
fsc (n: integer) is often selected, and in particular, the case where n=4 is widely used.

This is because (1) it satisfies the 41-line frequency and is a small value, and (2) the sample points are arranged in a grid field, making digital signal processing easier.

The case where -fc=4fgc will be explained below. In this way, the sampled signal is called a composite signal because it includes both the luminance signal (Y) and the chrominance signal (C).

Figure 2 shows the relationship between the structure of sampling points and the phase of the color subcarrier when an NTSC color TV signal is sampled at fc = 4fsc. The relationship between the sample points of the third and fourth fields and the phase of the color subcarrier is shown, respectively.

As is clear from FIG. 2, in the NTSC system, the phase of the color subcarrier is inverted for each scanning line. Therefore, the distance between samples at which the phases of the color subcarriers are equal becomes different within a field, between fields, or between frames.

The above also applies to the case where analog signals are processed as they are.

[Problem that the invention seeks to solve]

In digital VTRs and the like, signals whose errors cannot be corrected due to dropouts or the like are corrected by replacing them with signals whose color subcarriers are equal in phase and highly correlated. However, as described above, if the sample points where the phases of the color subcarriers are equal are far from the signal to be replaced, there is a problem that the image quality deteriorates because correction is performed using a signal with low correlation.

Furthermore, when data is compressed using correlation between samples, as in predictive encoding, there is a problem that compression efficiency deteriorates because the correlation between samples is low.

An object of the present invention is to provide a method and apparatus for converting an NTSC color TV signal with improved compression efficiency and without any deterioration in image quality during processing such as image modification and predictive encoding as described above. It is in.

[Means for solving problems]

The first invention separates an NTSC television signal into a first luminance signal and a first color signal, and alternately selects and outputs this first color signal and a second color signal obtained by inverting the phase of the first color signal for each scanning line. , the selected first or second color signal and the first luminance signal are combined to convert into a new television signal.

A second invention includes a first circuit that separates an NTSC television signal into a first luminance signal and a first color signal, a second circuit that inverts the phase of the first color signal, and a a third circuit that alternately selects one color signal and a second color signal from the second circuit for each scanning line; and a third circuit that outputs the first or second color signal and the first luminance signal from the third circuit. and a fourth circuit that synthesizes and outputs a new television signal.

[Effect]

By inverting the phase of the color signal, it becomes possible to shorten the distance between samples whose subcarriers of one color have the same phase.

〔Example〕

In the conversion method of the present invention, a composite signal is separated into a luminance signal and a chrominance signal, and the phase of the chrominance signal is inverted for each scanning line by a chroma inverter as shown in FIG. Combine to create a new composite signal. Therefore, as shown in FIG. 3, the phase relationship of the color signals shown in FIG. 2 is such that the minimum distance between samples at which the phases of the color subcarriers are equal becomes short, resulting in a signal suitable for digital signal processing.

After completing the predetermined digital signal processing, the new composite signal is separated into a luminance signal and a color signal, and the fourth
As shown in the figure, the phase of the color signal is inverted for each scanning line using a chroma inverter to convert it to the original color signal, and the luminance signal and color signal are combined to create the original NT as shown in Figure 2.
After being reconverted into an SC color TV signal, it is output to an output device such as a CRT.

The fields shown in FIG. 4 can be identified, for example, from the phase of the color burst. However, in that case, it is necessary to prohibit inversion of the phase of the color signal for each scanning line only for color bursts.

FIG. 1 is a diagram showing a circuit diagram of an embodiment of the device of the present invention. The AD converter 2 samples the NTSC color TV signal input from the TV camera 1 at 4 fsc to generate a composite signal P. The YC separation circuit 3 separates the composite signal P into a luminance signal Y and a color signal C. switch circuit 5
selects the color signal C and the color signal C' obtained by inverting the phase of the color signal C by the chroma inverter 4 for each scanning line, and outputs them to the YC synthesis circuit 6 as a new color signal C'.

The YC synthesis circuit 6 synthesizes the luminance signal Y and the color signal C' and outputs a new composite signal P' to the digital signal processing circuit 7.

A digital signal processing circuit consisting of a digital VTR, predictive encoding, etc. applies various types of processing (for example, recording/reproduction, etc.) to the composite signal P', and outputs the composite signal P1 again. The YC separation circuit 8 receives the composite signal P' and separates it into a luminance signal Y and a new color signal C'. The switch circuit 10 receives the color signal C1 from the YC separation circuit 8.
The color signal C''' whose phase is inverted by the chroma inverter 9 is selected for each scanning line and returned to the original color signal C.YCC division circuit 11 synthesizes the luminance signal Y and color signal C, Convert to original composite signal P. DA converter 1
2 converts the composite signal P to the original analog signal,
Output to an output device such as CRT13.

The television signal converter shown in FIG.
．． Chroma inverter 4, 9. Switch circuit 5, 10, Y
This is a case in which the C synthesis circuits 6 and 11 are configured with digital circuits, but it goes without saying that they can also be realized with analog circuits.

〔Effect of the invention〕

What is the distance between the samples at which the phases of the color subcarriers are equal?

Compared to the distance between samples when an NTSC color TV signal is sampled at a sampling frequency of 4 fsc, the distance is closer within a field or between fields or frames, which is convenient for digital signal processing.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a circuit diagram showing an embodiment of the present invention.
A diagram showing the relationship between the structure of sampling points and the phase of the color subcarrier when an SC color TV signal is sampled at 4 fsc. Figure 3 shows the structure of the sampling point and the phase of the color subcarrier after signal conversion by the device of the present invention. FIG. 4 is a diagram showing an example of controlling the phase of a color signal. 1 ・TV camera, 2-AD converter, 3.8-YC separation circuit, 4,9...Chroma inverter, 5.10...
・Switch circuit, 6, 11...YC synthesis circuit, 7...
・Digital signal processing circuit, 12...DA converter, 13
...CRT. Hair l Figure 21!1 (A) (B) 3rd (!l (c)

Claims (1)

[Claims] 1. An NTSC television signal is separated into a first luminance signal and a first color signal, and this first color signal and a second color signal obtained by inverting the phase of this first color signal are alternately selected for each scanning line. A television signal conversion method comprising: outputting a selected first or second color signal and converting the first luminance signal into a new television signal by combining the selected first or second color signal and the first luminance signal. 2. In claim 1, the new television signal is input, the signal is separated into a second luminance signal and a third color signal, and the third color signal and a fourth color signal whose phase is inverted are obtained. A television signal conversion method characterized in that the signals are alternately selected for each scanning line, and the selected third or fourth color signal is combined with the second luminance signal to convert the signal into the NTSC television signal. . 3. A first circuit that separates the NTSC television signal into a first luminance signal and a first color signal, a second circuit that inverts the phase of the first color signal, and a first color signal from the first circuit. a third circuit that alternately selects the second color signal from the second circuit for each scanning line; and a third circuit that synthesizes the first or second color signal and the first luminance signal from the third circuit and generates a new signal. A television signal conversion device comprising a fourth circuit that outputs a television signal. 4. In claim 3, a fifth circuit receives the new television signal and separates it into a second luminance signal and a third color signal, and inverts the phase of the third color signal. a sixth circuit; a seventh circuit that alternately selects a third color signal from the fifth circuit and a fourth color signal from the sixth circuit for each scanning line; and a third color signal from the seventh circuit; A television signal conversion device comprising: an eighth circuit that combines the fourth color signal and the second luminance signal (and outputs the NTSC television signal).