JP2680854B2 - Image signal processing circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to image signal processing of a MUSE television, and more particularly to a noise reducer for a time-compressed time-division multiplexed luminance signal and chroma signal.

[Conventional technology]

As one of high-definition television, MUSE (Multiple S
The ub-Nyquist Sampling Encoding) type television receiver (hereinafter referred to as MUSE decoder) was developed by NHK. In this MUSE method, as described in JP-A-62-53079, a noise reducer control signal is added from the transmitting side, and the MUSE decoder separates this control signal and performs noise reduction.

An example of the noise reducer is shown in FIG. 1 is MU
SE signal input terminal, 2 is an AD converter, 3 is a noise reducer, 5 is a noise reducer control signal detection circuit (hereinafter referred to as NR control circuit), 6 is a synchronization detection circuit, 7 and 8 are subtractors, Reference numeral 9 is a frame memory, 11 is a still image processing signal output terminal, 12 is a moving image processing signal output terminal, and 10 is a coefficient unit for multiplying a certain value. Input from input terminal 1
The MUSE baseband signal is digitally converted by the AD converter 2. This digital signal is guided to the noise reducer 3, the NR control circuit 5, and the synchronization detection circuit 6.
In the noise reducer 3, the data for 4 fields is stored in the frame memory 9, the difference is obtained from the input signal and the signal 4 fields before by the subtractor 7, the noise component is extracted through the coefficient unit 10, and the subtractor 8 is used. By subtracting from the input signal,
Remove noise. The coefficient unit 10 is the NR control circuit 5
By the NR control signal separated by, the noise component is extracted with a coefficient according to the signal.

[Problems to be solved by the invention]

In the MUSE system television signal, the color difference signal is time-compressed, and this and the luminance signal are time-division multiplexed. Therefore, the MUSE decoder performs different signal processing for the color difference signal and the luminance signal. That is, the color difference signal processing includes a time extension process. Considering the Fourier transform H (f) of the signal h (t) here, it is h (t / n) ⇔nH (nf) due to time extension, where ⇔ is the Fourier transform pair n is the time extension amount, and is added on the transmission line. Noise appears at low frequencies and is easily noticeable.

In the above-mentioned conventional example, the same noise reducer is used for the color difference signal and the luminance signal in which the appearance of noise is different as described above, and the noise of the color signal is particularly noticeable in the case of a screen with poor S / N.

An object of the present invention is to provide an image signal processing circuit having a higher noise removal effect by performing noise reduction according to each of color difference signals and luminance signals.

[Means for solving the problem]

The purpose is to detect a NR control signal,
A circuit that generates a signal indicating the timing of the luminance signal and the color difference signal of the television signal (hereinafter referred to as the Y / C pulse signal), and a coefficient multiplier according to the Y / C pulse signal and the NR control signal. And a logic circuit that changes the coefficient to be multiplied.

[Action]

Since the coefficient multiplied by the coefficient unit can be appropriately changed based on each period of the luminance signal and the color difference signal and the NR control signal, more effective noise reduction can be performed.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
In the embodiment of FIG. 1, 4 is a noise detection circuit and 13 is a noise detection circuit.
A Y / C pulse generation circuit, 14 is a Y / C pulse signal, 15 is a logic circuit, and others are the same as in the conventional example of FIG.

A MUSE baseband signal is input from input terminal 1
Converting to a digital signal with the -D converter 2 and guiding it to the noise reducer 3, NR control circuit 5, and synchronization detection circuit 6
This is the same as the conventional example. Horizontal / vertical signals separated by the synchronization detection circuit 6 are also guided to the Y / C pulse signal generator 13,
The Y / C pulse signal 14 that matches the luminance / color difference signal period (Y / C timing) in the noise reducer 3 is generated. Also,
The MUSE baseband signal converted into the digital signal is guided to the noise detection circuit 4 to detect the noise amount.
The detected noise amount and the NR control circuit 5
The NR control signal detected by and the Y / C pulse signal 14
And are guided to the logic circuit 15. The logic circuit 15 outputs a control signal, which is switched at the Y / C timing, from the above three signals to the coefficient unit 10. In the noise reducer 3, as in the conventional example, the image data for four fields is stored in the frame memory 9, and the input digital signal and the frame memory 9 are stored.
The first subtractor 7 calculates the difference from the four-field preceding signal from. This difference is introduced to the coefficient unit 10. The coefficient unit 10 responds to the control signal from the logic circuit 15 with Y /
Multiplying different coefficients at C timing, the noise component of the luminance signal and the noise component of the color difference signal are respectively extracted by this, and output to the second subtractor 8. The second subtractor 8 subtracts the noise component from the input digital signal to perform noise reduction according to the luminance signal and the color difference signal.

FIG. 3 shows an example of the coefficient multiplied by the coefficient unit 10. For example, when the transmitting side adds a 2-bit NR control signal according to the S / N, the NR control circuit 5 detects the 2-bit NR control signal and divides the S / N into four stages to reduce noise. To do. The logic circuit 15 is the Y / C pulse signal 14, for example, 3a, 3b, 3c, 3d for the luminance signal.
Then, for the color difference signal, the coefficient of the coefficient unit 10 is switched according to 3b, 3c, 3d, 3e and S / N. In addition, for example, the noise detection circuit 4
The amount of noise detected in 3b, 3c, 3 for the luminance signal.
d, 3e and 3c, 3d, 3e, 3f for color difference signals, or 3a, 3b, 3c, 3d for luminance signals and 3c, 3d, 3e, 3f for color difference signals Then, the logic circuit 15 outputs a control signal so as to switch the coefficient for four steps of S / N. As in the above example, the noise component extraction amount of the color difference signal is made larger than that of the luminance signal as the S / N becomes worse. By doing this, by performing time extension as described above,
The noise in the high frequency band that is added during transmission falls to the low frequency band and reduces the noise of the color difference signals that was easily noticeable.

As described above, according to the present embodiment, it is possible to switch the noise reduction amount between the luminance signal and the color difference signal, and to perform stronger noise reduction than the luminance signal on the color difference signal in which noise is more noticeable, which is more effective. Noise reduction is possible.

Although not shown, an adder is used in place of the second subtractor 8, the coefficient unit 10 multiplies a negative coefficient to extract a negative noise amount, and this and the input digital signal are combined by the adder. You may add and you may perform noise removal.

FIG. 5 shows another embodiment of the present invention. The present embodiment is different from the embodiment of FIG. 1 in that the second and third coefficient units 16 and 17 are used instead of the coefficient unit 10, and otherwise the configuration is the same as the embodiment of FIG. Yes, the basic operation is the same.

The noise component extraction operation by the logic circuit 15 and the second and third coefficient multipliers 16 and 17 will be described. Based on the noise amount detected by the noise detection circuit 4 and the m-bit NR control signal detected by the NR control circuit 5, the logic circuit 15 outputs a control signal for performing, for example, four stages of noise extraction as a second control signal.
And output to the third coefficient units 16 and 17. At the same time, the logic circuit 15
Receives the Y / C pulse signal 14 and outputs the outputs of the second and third coefficient multipliers 16 and 17, for example, the second coefficient multiplier 16 outputs the luminance signal period,
The third coefficient unit 17 outputs a signal for controlling the color difference signal period to be output. As a result, the second coefficient unit 16 outputs the noise component of the luminance signal, and the third coefficient unit 17 outputs the noise component of the color difference signal. Noise reduction is performed by subtracting these from the input digital signal by the second subtractor 8.

FIGS. 5 and 6 show an example of the coefficients multiplied by the second and third coefficient multipliers 16 and 17. When the noise component is extracted in four stages as in the above example, for example, for luminance signals, 5a, 5b, 5 in FIG.
Using the coefficients of d and 5d, 6a, 6b,
The coefficients of 6c and 6d are used. As a result, noise reduction according to each of the luminance signal and the color difference signal is performed.

As described above, according to the present embodiment, it is possible to extract the noise component according to each of the luminance signal and the color difference signal in which the appearance of noise is different. More effective noise reduction can be performed.

Although not shown, the Y / C pulse signal 14 is output to the logic circuit 1
Instead of leading to 5, it is also possible to lead to the second and third coefficient multipliers 16 and 17 and directly control the outputs of the coefficient multipliers 16 and 17.

Further, in the embodiment of the present invention shown in FIGS. 1 and 4, the noise amount detected by the noise detection circuit 4 and the NR control signal and Y / C pulse detected by the NR control signal detection circuit 5 are included in the logic circuit 15. Only the case where the signal 14 is derived and the logical operation of these three signals is performed to control the coefficient unit 10 or the second and third coefficient units 16 and 17 has been described.
The present invention is not limited to the above configuration, for example, the noise amount and Y /
Signal that is logically calculated from C pulse signal or NR
The coefficient unit 10 or the second and third coefficient units 16 and 17 depending on the signal obtained by logically operating the control signal and the Y / C pulse signal.
The effect of the present invention can be obtained even by controlling.

〔The invention's effect〕

According to the present invention, it is possible to perform noise reduction according to different signal processing performed on each of a luminance signal and a color difference signal, so that noise of the color difference signal is conspicuous even when S / N becomes poor. There is no effective noise reduction.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of a conventional example, FIG. 3 is a diagram showing an example of coefficients multiplied by a coefficient unit in FIG. 1, and FIG. FIG. 5 is a block diagram of another embodiment of the invention, FIG. 5 is a diagram showing an example of a coefficient by which a luminance signal is multiplied in the example of FIG. 4, and FIG. 6 is an example of a coefficient by which a color difference signal is multiplied in the example of FIG. FIG. 1 ... MUSE baseband signal input terminal, 2 ... A / D converter, 3 ... noise reducer, 4 ... noise detection circuit,
5 ... NR control circuit, 6 ... Synchronous detection circuit, 7,8
...... Subtractor, 9 …… Frame memory, 10,16,17 …… Coefficient multiplier, 11 …… Still image processing image signal output terminal, 12 …… Movie processing image signal output terminal, 13 …… Y / C Pulse signal generation circuit, 14 …… Y / C pulse signal, 15 …… Logic circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ichio Nakagawa 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Inside the Home Appliance Research Laboratory, Hitachi, Ltd. (72) Inventor Yuichi Ninomiya 1-10-11 Kinuta, Setagaya-ku, Tokyo No. 72 Broadcasting Technology Research Institute of Japan Broadcasting Corporation (72) Inventor Yoshimichi Otsuka 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside Broadcasting Technology Research Institute of Japan Broadcasting Corporation (56) Reference JP-A-62-53079 (JP, A) JP 62-137994 (JP, A)

Claims (4)

(57) [Claims] 1. An image signal processing circuit for demodulating at least a television signal in which a luminance signal, a time-compressed color difference signal, a synchronizing signal and an NR control signal for controlling a noise removal amount are time-division multiplexed. An A / D conversion circuit for converting the television signal thus converted into a digital signal to output a digital television signal, and a synchronization detection circuit for detecting a synchronization signal from the digital television signal converted and output by the A / D conversion circuit, From the sync signal detected by this sync detection circuit, a Y / C pulse signal generation circuit that generates a Y / C pulse signal indicating the multiplexing period of the time division multiplexed luminance signal and color difference signal, and the digital television signal A frame memory that stores image data for 4 fields,
A subtractor for obtaining the difference between the digital television signal and the digital television signal output from the frame memory four fields before, a coefficient unit for multiplying the difference signal output by the subtractor by a certain value, and outputting A mixer for adding or subtracting the output signal from the coefficient unit and the digital television signal, an NR signal detection circuit for detecting the NR control signal from the digital television signal output from the A / D conversion circuit, and the NR NR detected by the signal detection circuit
From the control signal and the Y / C pulse signal, a logic circuit for individually performing a logical operation in a luminance signal period and a color difference signal period is provided, and a coefficient output from the logic circuit is multiplied by the coefficient unit. An image signal processing circuit for controlling the image signal. 2. An image signal processing circuit for demodulating at least a television signal in which a luminance signal, a time-compressed color difference signal, and a synchronizing signal are time-division-multiplexed, and the input television signal is converted into a digital signal to be digitalized. A / D conversion circuit that outputs a television signal, a synchronization detection circuit that detects a synchronization signal from the digital television signal converted and output by the A / D conversion circuit, from the synchronization signal detected by this synchronization detection circuit, A Y / C pulse signal generation circuit for generating a Y / C pulse signal indicating a multiplexing period of the time-division multiplexed luminance signal and color difference signal, and a frame memory for storing image data of four fields of the digital television signal. A subtracter for obtaining a difference between the digital television signal and the digital television signal output from the frame memory four fields before, and the subtractor Output from the A / D conversion circuit, and a coefficient unit that multiplies the difference signal output from the output by a certain value, a mixer that adds or subtracts the output signal from the coefficient unit and the digital television signal, and the A / D conversion circuit. A noise detection circuit that detects the amount of noise superimposed on a signal from a digital television signal, and the amount of noise detected by the noise detection circuit and the Y / C pulse signal, individually in a luminance signal period and a color difference signal period. And a logic circuit that performs a logical operation,
An image signal processing circuit, wherein a coefficient multiplied by the coefficient unit is controlled by a signal output from the logic circuit. 3. An image signal processing circuit for demodulating at least a television signal in which a luminance signal, a time-compressed color difference signal, a synchronizing signal and an NR control signal for controlling a noise removal amount are demodulated in a time division manner. An A / D conversion circuit for converting the television signal thus converted into a digital signal to output a digital television signal, and a synchronization detection circuit for detecting a synchronization signal from the digital television signal converted and output by the A / D conversion circuit, From the sync signal detected by this sync detection circuit, a Y / C pulse signal generation circuit that generates a Y / C pulse signal indicating the multiplexing period of the time division multiplexed luminance signal and color difference signal, and the digital television signal A frame memory that stores image data for 4 fields,
A subtractor for obtaining the difference between the digital television signal and the digital television signal output from the frame memory four fields before, a coefficient unit for multiplying the difference signal output by the subtractor by a certain value, and outputting A mixer that adds or subtracts the output signal from the coefficient unit and the digital television signal, an NR signal detection circuit that detects the NR control signal from the digital television signal output from the A / D conversion circuit, and the A A noise detection circuit for detecting the noise amount superimposed on the signal from the digital television signal output from the / D conversion circuit, the noise amount detected by the noise detection circuit and the NR control signal detected by the NR signal detection circuit And a Y / C pulse signal, and a logic circuit that individually performs a logical operation in a luminance signal period and a color difference signal period. The signal output, the image signal processing circuit and controlling the coefficient multiplying by the coefficient multiplier. 4. The coefficient unit is replaced with two coefficient units, a first and a second coefficient unit, the noise amount and an NR control signal are guided to the logic circuit, and the first and the first coefficient are output by an output signal of the logic circuit. 2. The coefficients of the two coefficient units of 2 are individually controlled, and the output signals of the first and second coefficient units are switched by the Y / C pulse signal and are guided to the mixer. The image signal processing circuit according to item 3.