JP2834239B2 - Television receiver - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for receiving a television signal, and more particularly to an apparatus for receiving a television signal band-compressed by multiple sub-Nyquist sampling.

2. Description of the Related Art In recent years, high-definition televisions have been put into practical use. One of the transmission methods is a band compression method called MUSE (Ninomiya et al.
Development of method '' NHK technical research, Vo139, No.2, P18-P53, Showa 6
2) has been proposed. This MUSE method is used between fields,
In this method, the sampling phase is offset between frames and between lines, and the image signal is transmitted by performing a process in which the sampling phase makes one cycle in four fields. The information of the transmitted MUSE signal is stored in a frame memory provided on the receiver side, and information of four fields is sequentially synthesized to reproduce an image of a high-definition television signal. Hereinafter, a conventional example of the MUSE system will be described with reference to the drawings.

FIG. 2 shows an embodiment of a MUSE type receiving apparatus, wherein 1 is an input terminal for inputting a received MUSE type signal, 2 is an input circuit for extracting audio signals and various control signals multiplexed on the MUSE signal, 3 , 4 are both frame memories, 5 is a still image processing circuit, 6 is a moving image processing circuit, 7 is a motion detection circuit that detects a motion area of an image and outputs the motion amount, and 8 is a motion amount from the motion detection circuit 7. Still image processing circuit 5 according to
A mixing circuit for outputting a signal obtained by changing the mixing ratio of the output signal of the moving image processing circuit 6, a delay circuit 9, and a low-frequency component in the output signal of the mixing circuit 8 which is a low-frequency component A low-pass replacement circuit for replacing components, 11 is an output terminal, 12 is a high-pass filter that extracts only high-frequency components, and 13 is a noise detection circuit. For simplicity, the processing of the color signal is omitted, and only the processing of the illuminance signal will be described.

FIG. 3 shows the signal formation of the MUSE system. The color signal is
The time axis is compressed to 1/4 and time division multiplexed with the luminance signal. Further, the audio signal and the control signal are multiplexed within the vertical blanking period.

Such a signal of the MUSE system is supplied to the input circuit 2 via the input terminal 1 to separate a synchronization signal or to extract an audio signal or various control signals. Only the video signal is output from the input circuit 2 and applied to the frame memory 3, still image processing circuit 5, moving image processing circuit 6, motion detection circuit 7, and delay circuit 9. Among them, the signal applied to the frame memory 3 is delayed by one frame, further delayed by one frame in the frame memory 4, becomes a signal delayed by two frames, and the input and output of the frame memory 3 and the output of the frame memory 4, ie, the current , A signal delayed by one frame, and a signal delayed by two frames are applied to the still image processing circuit 5. Here, a process such as interpolation is performed based on information for two frames, that is, four fields, and is input to one end of the mixing circuit 8 as a still image signal.

The output signal of the input circuit 2 applied to the moving image processing circuit 6 is subjected to signal processing such as interpolation in the current field, and is input to the other end of the mixing circuit 8 as a moving image signal. The mixing circuit 8 changes the mixing ratio of the still image signal from the still image processing circuit 5 and the moving image signal from the moving image processing circuit 6 according to the amount of motion of the image. Compare the current and past information using the input and output signals of the frame memory 3 and the output signal of the frame memory 4, that is, the signal of the current frame and the signal delayed by one frame and two frames with respect to the amount of motion of the image. Accordingly, the motion amount is output from the motion detection circuit 7 in pixel units. The output of the mixing circuit 8 in which the ratio between the signal of the still image processing and the signal of the moving image processing is changed according to the amount of motion is input to the low-frequency replacement circuit 10.

On the other hand, a signal from the input circuit 2 passes through the delay circuit 9 and is input to the low-frequency replacement circuit 10. The delay circuit 9 is connected to the input circuit 2 by a time corresponding to the time that the signal is delayed by passing through the still image processing circuit 5 or the moving image processing circuit 6 and the mixing circuit 8.
And the timing of the output of the mixing circuit 8 and the output of the delay circuit 9 coincide when they are input to the low-frequency replacement circuit 10.

The low-frequency replacement circuit 10 replaces the low-frequency component of the output signal of the mixing circuit 8 with the low-frequency component of the output signal of the input circuit 2. The principle will be described below.

The image signal is sub-sampled twice by the encoder on the transmission side and converted into a MUSE signal. The state of the spectrum is shown in FIG. 4. In FIG. 4, (a) shows the spectrum of the original signal. The spectrum of the original signal is first subjected to field offset subsampling, as shown in FIG. 4 (b), and the high-frequency component is folded back into the region of 4 MHz to 12 MHz. Next, by performing frame offset subsampling, the spectrum shown in FIG. 4 (c) is obtained. This is the spectrum of the MUSE signal. However, this is a spectrum in a still image area, and details are described in the above-mentioned reference material (Ninomiya et al., “Development of MUSE method”).

The MUSE signal in FIG. 4 (c) has no aliasing of the high frequency component in the low frequency portion, that is, in the region of 0 to 4 MHz. Therefore, this low-frequency component can be used as it is as a reproduced signal without using any special interpolation processing or the like on the decoder side. Interpolation processing is necessary for components of 4 MHz or higher because there are aliasing components. The signal subjected to the interpolation processing on the decoder side, that is, the output signal of the mixing circuit 8 in FIG. 2, is subjected to the vertical arithmetic processing even for the low-frequency component of 0 to 4 MHz. Therefore, as for the low-frequency component that is not folded in FIG. 4C, a signal that does not pass through the still image processing circuit 5 or the moving image processing 6, that is, a signal that passes through the delay circuit 9 is closer to the original signal. It is. However, when the S / N of the original signal is poor, especially when there is random noise, the signal passing through the delay circuit 9 is more noticeable than the output signal of the mixing circuit 8.

Therefore, the signal output from the input circuit 2 passes through the high-pass filter 12 and the noise detection circuit 13 detects the amount of noise, and according to the amount, mixes the low-frequency replacement signal (low-frequency component of the signal) A signal that controls the amount of replacement of the low-frequency component of the output signal from the circuit 8 with the low-frequency component from the delay circuit 9 and combines the low-frequency component subjected to the low-frequency replacement with the high-frequency component from the mixing circuit 8 Is output from the output terminal 11.

However, in the above configuration, only high-frequency noise such as random noise is detected, and low-frequency running noise such as VTR is not detected but output as it is, and the low-frequency noise is output. However, there is a problem that image quality is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a television receiver capable of reducing low-frequency noise.

Means to solve the problem.

In order to solve the above problems, a television receiver according to the present invention uses a signal of a low-frequency noise detection circuit as a signal for controlling a low-frequency switching amount used in a low-frequency replacement circuit, and a conventional high-frequency noise detection circuit. It is configured to be used together.

Operation With this configuration, even when a signal including low-frequency running noise or the like is input, the noise detection circuit detects the signal and controls low-frequency replacement so that the low-frequency component of the original signal is not replaced.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a television receiver according to an embodiment of the present invention. The ones used in FIG. 1 are almost the same as those in FIG.
An input terminal for inputting a signal from R, 2 is an input circuit, 3 and 4 are frame memories, 5 is a still image processing circuit, 6 is a moving image processing circuit, 7 is a motion detection circuit, 8 is a mixing circuit, and 9 is a delay circuit. , 10 is a low-pass replacement circuit, 11 is an output terminal, 12 is a high-pass filter, and 13 is a noise detection circuit. Reference numeral 21 denotes a low-pass filter connected to the input circuit 2, and reference numeral 22 denotes a low-frequency noise detection circuit connected to an output terminal of the low-pass filter 21. The output of the noise detection circuit 13 and the output of the low-frequency noise detection circuit 22 are connected to the low-frequency replacement circuit 10 through an OR gate 23.
Control signal.

The components other than the low-pass filter 21 and the low-frequency noise detection circuit 22 are exactly the same as those in the conventional example, and only the additional circuit will be described below. A playback signal such as a VTR is input from input terminal 1,
By passing through the input circuit 2 and passing through the low-pass filter 21, the input signal is converted into a low-frequency component of 4 MHz or less. The above-mentioned signal is input to the low-frequency noise detection circuit 22, the low-frequency noise of the running noise in the VTR is detected, and when a certain noise is detected, the low-frequency replacement circuit 10 outputs a signal for prohibiting the replacement of the low-frequency component. Is output. The output signal and the noise detection circuit 13
The signal obtained by calculating the logical sum with the signal of the low frequency band is input to the low band replacement circuit 10. The low-frequency replacement circuit 10 inhibits the low-frequency component of the output signal of the delay circuit 9 from being replaced with the low-frequency signal of the output signal of the mixing circuit 8 by the above signal, and outputs only the output signal of the mixing circuit 8.

According to the present invention as described above, by providing the low-frequency noise detection circuit, low-frequency noise such as running noise such as a VTR can be reduced, and a clearer image can be obtained. Is extremely large.

[Brief description of the drawings]

FIG. 1 is a block diagram of a television receiver according to an embodiment of the present invention, FIG. 2 is a block diagram of a conventional television receiver, and FIG. 3 is a diagram showing a signal format of a MUSE television signal. FIG. 4 shows a signal spectrum of the MUSE system. 1 ... input terminal, 2 ... input circuit, 3 ... frame memory, 5 ... still image processing circuit, 6 ... moving image processing circuit,
7: motion detection circuit, 8: mixing circuit, 9: delay circuit, 10: low-pass replacement circuit, 12: high-pass filter,
13 ... noise detection circuit, 21 ... low-pass filter, 22
…… Low-frequency noise detection circuit, 23 …… OR gate.

Claims (1)

(57) [Claims] 1. An input circuit for inputting an image signal output from a VTR and subjected to band compression processing by multiple sub-Nyquist sampling, and first and second serially connected input circuits for receiving an output of the input circuit. An interpolation processing circuit for performing image interpolation processing on a two-frame memory, the input and output of the first frame memory, and the output of the second frame memory, and a low-frequency component of the output of the interpolation processing circuit A low-frequency replacement circuit that replaces an output of the input circuit with a low-frequency component of a signal that has passed through a delay circuit, a high-frequency noise detection circuit that receives an output signal of the input circuit and detects high-frequency noise,
A low-frequency noise detection circuit that receives an output signal of the input circuit and detects low-frequency noise, wherein the low-frequency replacement circuit receives an output of the high-frequency detection circuit and an output of the low-frequency noise detection circuit. A television receiver for controlling a replacement amount of the low frequency component.