JPS63245087A - Signal separating circuit - Google Patents

Abstract

PURPOSE:To reduce the circuit scale of a motion adaptive luminance/ chromaticity separating circuit by shifting the frequency of an input composite television signal and compressing the band by subsampling thereafter and separating a chromaticity signal in this state. CONSTITUTION:The input composite television signal has the frequency shifted by a carrier signal C having integer-fold horizontal synchronizing frequency and is subsampled by a subsampler 36 to compress the band of the composite television signal. The chromaticity signal is separated from the composite television signal in this band compressed state, and this separation output is returned to a signal having the original band by an interpolation processing IPF 43, and thereafter, the frequency is shifted by the carrier signal C to return the frequency position of the separated chromaticity signal to the original position. Since the chromaticity signal is separated from the band-compressed composite television signal, the capacity of a frame memory is considerably reduced. Thus, the circuit scale is reduced.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) This invention is a method for frequency multiplexing a plurality of signals, such as a composite television signal in which a luminance signal and a chroma signal are frequency multiplexed. The present invention relates to a signal separation circuit for separating a composite television signal into each signal.

(Prior Art) Current color television broadcasting systems use a composite television signal in which a color subcarrier (chromaticity signal) modulated by a chromaticity signal is superimposed on a luminance signal as a television signal. For this reason, the receiver uses luminance/chromaticity (hereinafter referred to as Y/
C) separation is required. However, when this is done, image quality deterioration such as cross color and dot crawl occurs due to incomplete separation. Furthermore, recently, comb filters with good separation performance have been used for Y/C separation.

However, even if this comb-shaped filter is used, the resolution in the diagonal direction cannot be sufficiently increased.

In order to improve these problems, in recent years, a Y/C separation circuit has been developed that detects movement information of a pattern and changes parameters of filter characteristics.

The Kono circuit is described in the literature (SMPTE journal M
ay1984, pages 470 to 476). The circuit described in this document performs Y/C separation on still images by calculation between frames, and performs Y/C separation on moving images by calculation between lines. It has the configuration shown in the figure. That is, the composite television signal applied to the input terminal 11 is sent to the subtracter 12,
The signal is supplied to an inter-line arithmetic unit 13, an inter-frame arithmetic unit 14, and a motion detector 15. The outputs of the line-to-line arithmetic unit 13 and the inter-frame arithmetic unit 14 are output from gain control circuits 16 and 17, respectively.
are supplied to the adder 18 via the adder 18, and are combined.

This composite output is led out to an output terminal 20 as a chromaticity signal C via a horizontal band filter 19 and is also supplied to a subtracter 12 . Therefore, in the subtracter 12, the luminance signal Y
is separated and led out to the output terminal 21.

Here, the motion detector 15 detects a motion signal corresponding to the motion of an image from the composite television signal, generates a control signal corresponding to the motion according to this detection output, and thereby the gain control circuit 17 It controls the gain of 18 degrees. In other words, in the case of a still image, the signal is as shown in Figure 7 (A).
As shown in the figure, since the luminance signal component Y1 and the chromaticity signal component C1 do not spread in the time direction, the chromaticity signal C1 can be separated by calculating the difference between frames. On the other hand, in the case of a moving image, the signal spreads in the time direction, as shown in FIG. 7(8), but does not spread in the vertical direction.

Therefore, in this case, the chromaticity signal C1 can be separated by calculating the difference between lines.

Utilizing this principle, the circuit of FIG. 6 increases the gain of the gain control circuit 17 and decreases the gain of the gain control circuit 16 in the case of a still image. On the other hand, in the case of a moving image, control is performed in the opposite manner to that in the case of a still image.

However, such a motion adaptive Y/C separation circuit requires a frame memory with a large capacity to separate still images, resulting in a problem that the circuit scale becomes large.

(Problems to be Solved by the Invention) As mentioned above, the conventional motion adaptive Y/C separation circuit developed to increase the resolution in the diagonal direction requires a large capacity frame memory to separate still images. Therefore, there was a problem that the circuit scale became large.

SUMMARY OF THE INVENTION An object of the present invention is to provide a signal separation circuit that can reduce the capacity of a frame memory and reduce the circuit scale of a motion adaptive Y/C separation circuit.

[Structure of the Invention] (Means for Solving the Problems) To achieve the above object, the present invention frequency-shifts an input composite television signal with a carrier signal having a frequency that is an integral multiple of the horizontal synchronization frequency, and then By sampling, the band of this composite television signal is compressed. Then, the chromaticity signal is separated from the composite television signal in this band-compressed state, the separated output is returned to a signal with the original band through interpolation processing, and then the signal is separated by frequency shifting using the carrier signal. The frequency position of the chromaticity signal is returned to its original position.

(Function) According to the above configuration, since the chromaticity signal is separated from the band-compressed composite television signal, the capacity of the frame memory can be significantly reduced.

This makes it possible to reduce the circuit scale.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

In FIG. 1, an input terminal 31 receives a composite television signal. This input composite television signal is applied to a subtracter 32 and a bypass filter 33.

The cutoff frequency of the bypass filler 33 is set to 2MH2. Therefore, a composite television signal in which a luminance signal Y of 2MH7 or more and a chromaticity signal C are mixed is obtained from the bypass filter 34.

The output signal of the bypass filter 33 is input to a multiplier 34, and the output signal is inputted to a multiplier 34, and a carrier signal C given from a carrier generator 35 is input to the multiplier 34.
The frequency is shifted by Here, the frequency of the carrier signal C is the horizontal synchronization frequency f1. an integer multiple of I, and 2
It is set to a value close to MHz, for example 12BfH.

The output of the hanging sieve 34 is given to a sub-sampling circuit 36,
Data is thinned out. The output of the sub-sample circuit 36 is input to an inter-line arithmetic unit 37, an inter-frame arithmetic unit 38, and a motion detector 39, similar to the circuit shown in FIG. The output signals of the inter-line arithmetic unit 37 and the inter-frame arithmetic unit 38 are mixed by a mixing circuit including gain control circuits 40, 41 and an adder 42. As a result, the chromaticity signal @C is separated. The mixing ratio in this case is determined by the motion detector 39
It is determined according to the amount of movement of the image detected in .

The separated chromaticity signal C is passed through an interpolation filter (IPF) 43
, and is converted into a chromaticity signal C having the sampling frequency before being input to the sub-sampling circuit 36. The output signal of the interpolation filter 43 is given to a multiplier 44, and the same carrier signal C as the carrier signal C used in the multiplier 34 is used.
After the wave is detected by a horizontal band pass filter (BP
F) given to 45.

The output signal of the bandpass filter 45 is applied to an output terminal 46 as a separated output of the chromaticity signal C, and is also applied to the subtracter 32. The subtractor Ii[32 obtains a luminance signal Y by subtracting the chromaticity signal C from the input composite television signal applied through the input terminal 31, and provides it to the output terminal 47.

The above operation will be explained in the frequency domain. The spectrum of the input composite television signal is as shown in FIG. The bypass filter 33 cuts off the low-frequency component YL of the luminance signal Y indicated by diagonal lines in FIG. 2, and outputs the chromaticity signal C and the high-frequency component YH of the luminance signal Y of 2 MHz or more. When the output signal of the bypass filter 33 is detected using the carrier signal C, a spectrum as shown in FIG. 3 is obtained.

The sub-sampling circuit 36 converts an input signal having a spectrum as shown in FIG. 3 into data of a low sampling frequency without folding, as shown in FIG. Here, if the sampling frequency of the input signal to the sub-sampling circuit 36 is 4 fsc, and the sub-sampling circuit 36 converts it to 2 rsc, the line memory in the inter-line arithmetic unit 37 and the frame memory in the inter-frame arithmetic unit 38 You can cut your customer base in half.

Thereafter, the chromaticity signal C is separated while the sampling frequency is lowered. This chromaticity signal C is returned to the original sampling frequency by an interpolation filter (IPF) 43. Thereafter, the chromaticity signal C is detected by the same carrier signal C as the previous carrier signal C, and then passed through the bandpass filter 45 to be returned to the original frequency position as shown in FIG. . Then, by subtracting the chromaticity signal C having the spectrum shown in FIG. 5 from the composite television signal having the spectrum shown in FIG. 3, a luminance signal Y is obtained.

As described above, this embodiment aims at band compression of the input composite television signal by frequency shifting the input composite television signal and then subsampling the input composite television signal.
In this state, the chromaticity signal C is separated from the composite television signal. Therefore, according to this embodiment, the capacity of the frame memory can be reduced by the amount of band compression, and the circuit scale can be reduced.

Furthermore, since the sampling frequency of the composite television signal can be lowered by subsampling, the memory can be driven at a lower speed, and circuit design becomes easier.

Although one embodiment of this invention has been described in detail above, this invention is not limited to this embodiment, and it goes without saying that various other modifications can be made without departing from the gist of the invention. It is.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a signal separation circuit that can reduce the capacity of a frame memory and reduce the circuit scale.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.
Figures 2 to 5 are diagrams shown to explain the operation of the circuit in Figure 1, Figure 6 is a block diagram showing the configuration of a conventional Y/C separation circuit, and Figure 7 is shown in Figure 6. FIG. 3 is a diagram shown to explain the operation of the circuit. 31...Input terminal, 32...Subtraction circuit, 33...
Bypass filter, 34.44... Multiplier, 35...
・Carrier generator, 36... Subsample circuit, 37
... Inter-line arithmetic unit, 38... Inter-frame arithmetic unit, 3
9...Motion detector, 40.41...Gain control circuit,
42...Adder, 43...Interpolation filter, 45...
-Band pass filter, 47.46...output terminal. ///
pFigure 2 Figure 3fsc 2fsc (Hz) fs
c 2fsc ()lz3Fig. 4 Fig. 5
figure

Claims (1)

[Claims] Carrier signal generation means for generating a carrier signal having a frequency that is an integral multiple of the horizontal synchronization frequency, and a first signal and a second signal using the carrier signal output from the carrier signal generation means. a first frequency shifting means for frequency shifting the sampling output of a composite television signal frequency-multiplexed; a subsampling means for subsampling the frequency shift output of the first frequency shifting means; frame time direction filter calculation means for filtering the subsample output in the frame time direction; vertical filter calculation means for filtering the subsample output of the subsample means in the vertical direction; The first signal is adjusted by changing the mixing ratio of the calculation output of the frame time direction filter calculation means and the calculation output of the vertical filter calculation means according to the amount of image movement indicated by the image movement signal. a first signal separating means for separating; an interpolation filter means for returning the sampling frequency of the first signal output from the mixing means to the frequency before subsampling by the subsampling means; and a carrier signal generating means. a second frequency shift means for frequency shifting the output of the interpolation filter means using the output carrier signal; and combining the frequency shift output of the second frequency shift means and the sampling output of the sampling means. A signal separation circuit comprising: second signal separation means for separating the second signal.