JPS6153915B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to color television signals, particularly
This invention relates to a method for extracting and separating a carrier color signal from a composite color television signal, such as an NTSC signal, in which the color signal is modulated at a subcarrier frequency and superimposed on a luminance signal.

As a method of separating color signals from a composite color television signal such as an NTSC signal, a carrier color signal (C signal) centered at the subcarrier frequency (f _sc ) is extracted from the NTSC signal using a band pass filter (hereinafter abbreviated as BPF). There is a method for extracting
JP-A-52-84915 (July 24, 1972)). In this case, if the bandwidth of the BPF is narrowed, a part of the color signal component will remain in the luminance signal (Y signal) obtained by subtracting the carrier color signal extracted from the NTSC signal. Furthermore, when the BPF band is widened, the brightness signal band becomes narrower, and the resolution deteriorates.

"Television", Vol. 19, No. 8, pp. 16-23 describes that the NTSC signal is delayed by one horizontal scanning period in a line memory and the luminance signal is obtained using the neighborhood correlation between the scanning lines. ing. There is also a known method that applies this method to calculate a difference signal between scanning lines, inputs this to a BPF, and extracts a carrier color signal.
In this case, the extracted carrier color signal is band-limited not only in the horizontal direction of the screen but also in the vertical direction, so the correct carrier is used in horizontal striped areas (areas where the color changes between scanning lines). The color signal cannot be extracted, and a portion of the carrier color signal remains in the luminance signal. Furthermore, since the resolution in the diagonal direction of the image is removed from the luminance signal, there is a problem in that when the band of BPF is widened, the sharpness of the image is reduced, although not as much as in the case of only BPF described above.

Additionally, the above literature mentions the removal of dot interference using field neighborhood correlation in which the line memory is replaced with a field memory, but there is a problem with delay time accuracy, and the specific calculation method and circuit configuration are was not mentioned. Recently,
With the practical use of semiconductor memories, the problem of delay time accuracy has been solved, and for example, Japanese Patent Application Laid-Open No. 84915/1983 discloses a color signal extraction method using a frame memory. However, since it uses calculations between frames, it is limited to still images and cannot operate correctly on moving images.

FIG. 1 is a circuit diagram specifically configuring a circuit for extracting a carrier color signal from the difference between the previous field and the signal 263H before. In the figure, the NTSC signal input to the input terminal 1 is input to the delay circuit 2 which delays the signal by 263H, and the difference between the signal and the signal delayed by 263H is obtained by the subtraction circuit 3. Since the subcarrier phases of the current scanning line and the signal delayed by 263H are opposite to each other, the output of the subtraction circuit 3 is 2 of the carrier color signal.
A signal with twice the amplitude is obtained. This is done by multiplication circuit 4.
Multiply by 1/2 and use BPF5 to obtain the subcarrier frequency (f _sc )
When a band centered around is extracted, a desired carrier color signal (C signal) is obtained at the output terminal 8. When this is subtracted from the current signal (NTSC signal) by the subtraction circuit 6, a luminance signal (Y signal) from which the carrier color signal has been removed is obtained at the output terminal 7.

This circuit configuration uses adjacent scanning lines on the screen of the previous field, so it
Compared to a method using a 1H delay circuit, the distance between the scanning lines used is halved. Therefore, in the conventional 1H method, there was a problem that oblique components of the luminance signal were removed, but in the configuration shown in Figure 1, the passband in the vertical direction of the screen is twice as wide as in the 1H method. Therefore, very few oblique components are removed, and a high-quality luminance signal can be obtained in a still image. In addition, in the conventional 1H method, deterioration occurs over two scanning lines at horizontal color edges where the color changes rapidly in the vertical direction, but with the configuration shown in Figure 1, the deterioration subsides to one scanning line, and the deterioration occurs in still images. It is possible to obtain a carrier color signal with less color.

With the circuit configuration shown in FIG. 1, high-quality color signal separation is possible for still images, but correct separation cannot be performed for moving images, resulting in an unnatural image being reproduced.

In addition, in the case of applications dedicated to still images, high-quality color signals can be separated, but field memory is required to separate the color signals, making it difficult to realize an economical still image reproduction device. Ta.

The present invention has been made to solve the above-mentioned problems, and in particular, it is an object of the present invention to provide a high-quality color signal separation method that can correctly separate color signals not only for still images but also for moving images. .

To achieve the above object, the present invention separates color signals by using adjacent scanning lines on the screen of an interlaced composite color television signal, that is, scanning lines of adjacent fields. The color signal is separated using adjacent scanning lines of the television signal, and the mixing ratio of both signals is changed by motion information contained in the television signal. As described later, this makes it possible to obtain correct separated signals even in moving images, and furthermore, compared to the conventional method, the band from which luminance signals are removed is narrower, and for color signals, a wider band can be extracted, and luminance signals It is possible to reduce the amount of residual color signals left in the image, and extract high-quality color signals.

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 2 shows the configuration of an embodiment of the present invention which can also correctly operate moving images. In other words, in the conventional example shown in FIG. 1, when the subject moves, the 263H delay circuit 2
Since a signal from a location away by the distance traveled during the field period is output as an output, the extracted color signal is degraded.

The embodiment shown in FIG. 2 solves this drawback.
The NTSC signal input from the input terminal 1 is input to the 263H delay circuit 2 and the 1H delay circuit 9. Next, the signal delayed by 263H is multiplied by _k1 in the multiplication circuit 10,
In addition, the signal delayed by 1H is multiplied by _k2 in the multiplier circuit 11,
By adding both in the adder circuit 12, a signal in which the phase of the subcarrier is reversed is obtained. The subsequent operations of the subtraction circuit 3, multiplication circuit 4, BPF 5, and addition circuit 6 are the same as in the case of FIG. 1, and the extracted and separated luminance signal (Y signal) and carrier color signal ( C signal) is obtained.

In this embodiment, the color signals separated using the scanning lines of adjacent fields shown in FIG. 1 are multiplied by a coefficient _k1 , and the delay circuit 2 in FIG. 1 is replaced with a 1H delay circuit. The same operation is performed as adding a color signal multiplied by a coefficient k ₂ using adjacent phase scanning lines of the same field. That is, in Fig. 1, the input television signal is A, 263H.
Assuming that the delayed signal is B and the characteristic of the filter 5 is BPF, the separated color signal C ₁ is expressed as C ₁ =(A-B)/2·(BPF)k ₁ . Similarly, when the delay time of the delay circuit 2 in Fig. 1 is 1H and its output is C, the separated color signal C ₂ is expressed as C ₂ = (A-C)/2・(BPF)k ₂ .

Therefore, if C ₁ + C ₂ is representatively transformed with k ₁ + k ₂ = 1, C ₁ + C ₂ = 1/2・(BPF) {A−k ₁ B−k ₂ C}, and the configuration shown in FIG. is obtained.

Therefore, compared to a circuit configuration that mixes separated color signals, the number of bandpass filters 5, coefficient circuits 4, and subtraction circuits 3 are reduced by half, making the circuit configuration extremely simple. In addition, by using an adaptive type that detects the movement of the subject and controls the coefficients k ₁ and k ₂ depending on the presence or absence of movement, it can be applied to moving images with even less deterioration.
YC separation becomes possible.

As explained above, according to the present invention, color signals are extracted using both the signal before or after 263H, which is 1 field away from the current scanning line, and the signal 1H away from the same field. For,
Problems with conventional methods using a simple bandpass filter or 1H delay circuit include the residual subcarrier color signal in the luminance signal, the degradation of the resolution of the luminance signal due to the mixing of the luminance signal into the subcarrier color signal, and
The deterioration of horizontal stripes and color edges in the 1H method is reduced, making it possible to perform high-quality YC separation on still images, as well as extracting correct color signals from moving images. It is highly effective when applied to etc.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional carrier color signal extraction circuit which is the premise of the present invention, and FIG. 2 is a block diagram of an embodiment of the color signal separation method according to the present invention. 1, 16...input terminal, 2, 9...delay circuit,
3, 6... Subtraction circuit, 12... Addition circuit, 4, 1
0, 11...Multiplication circuit, 5...BPF, 7, 8...
Output terminal.

Claims (1)

[Claims] 1. A composite color television signal source in which a carrier color signal is superimposed on a luminance signal, and scanning in which an adjacent field is an adjacent scanning line on the image with respect to the scanning line of the current field of the signal source, and the subcarrier phase is opposite to the scanning line of the current field of the signal source. a first delay means for obtaining a line signal, a second delay means for obtaining a signal of an adjacent scanning line in the same field as the current field, and a mixing circuit for mixing the outputs of the first delay means and the second delay means; It is characterized by comprising means for changing the mixing ratio of the mixing circuit based on motion information contained in the signal source, and a circuit for obtaining a difference between the output of the mixing circuit and the signal source signal. Color signal separation method.