JPH0638181A - Television receiver - Google Patents

Abstract

PURPOSE:To obtain a picture with high picture quality by eliminating a loss of a signal on transmission. CONSTITUTION:The television receiver is provided with a down-converter 1 converting a high definition television signal subject to band compression into a digitized NTSC broadcast signal, an A/D converter circuit 4 converting the NTSC broadcast signal into a digital signal, a switch 3 selecting a signal from the down-converter 1 or a signal from the A/D converter circuit 4, a filter 1b processing the signal from the switch 3, a clock generating circuit 7 able to generate a clock with a different frequency, and a control circuit 8 controlling the changeover of the clock frequency of the clock generating circuit 7 as soon as the switch 3 is selected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television receiver capable of receiving high-definition broadcasting and standard television broadcasting.

[0002]

2. Description of the Related Art Hi-vision, which is a next-generation high-definition television, is being broadcast in satellite broadcasting. This high-definition signal is band-compressed by a band-compression technique called MUSE system. Then, this compressed signal (hereinafter referred to as MUSE signal) is broadcast.

However, since this MUSE broadcasting is incompatible with the current television broadcasting, it cannot be received by the current television receiver.

Therefore, in order to watch this MUSE broadcasting on a normal NTSC television receiver,
There is an E / NTSC converter. This MUSE / NTS
The C converter converts the MUSE signal into an NTSC signal. The operation of the MUSE / NTSC converter is described on pages 31 to 45 of the magazine "TV Technology October 1989" published by Electronic Technology Publishing Co., Ltd.

In order to convert the MUSE signal into the NTSC signal, first, the MUSE signal is reproduced, and then the number of scanning lines is set to 525, so that the MUSE signal must be converted into the time axis. As a result, two clock generation circuits synchronized with the horizontal synchronizing signal of the MUSE signal are required: 960fh (fh: horizontal synchronizing frequency) of the MUSE signal system (1125 system) and 910fh of the NTSC signal system (525 system).

FIG. 2 shows a television receiver incorporating a conventional MUSE / NTSC converter. Figure 2
In, 1 is MUSE / NTSC converter, 2 is N
TSC decoder, 11 is a D / A conversion circuit for converting the signal of the converter 1 into an analog signal, 3 is a switch for switching the output of the converter 1 and the decoder 2, and 10 is a 960f
h clock generation circuit, 13 is a 910fh clock generation circuit, 14 is an A / D conversion circuit for converting into a digital signal, 1
Reference numeral 6 denotes a filter, which is a memory 5 for storing one horizontal scanning period.
And an arithmetic circuit 6.

Next, the operation will be described. MU to input terminal a
The SE signal is input and supplied to the converter 1, and the color difference signals (RY, BY) and the luminance signal (Y) are output. On the other hand, the NTSC signal is input to the input terminal b, is supplied to the encoder 2, and the color difference signals (RY, BY) and the luminance signal (Y) are output.

The output signal from the converter 1 is
After being converted into an analog signal by the D / A conversion circuit 11, it is supplied to the switch 3. The switch 3 is selected as an output signal of the decoder 2, converted into a digital signal by the A / D conversion circuit 14, and then input to the filter 16.

The filter 16 is a filter for cross color removal, and is, for example, 105 of "Digital signal processing of image" published by Nikkan Kogyo Shimbun, July 30, 1986.
The ones described on pages 107 to 107 may be used.

By the way, conventionally, the filter 16 performs digital signal processing, and since the output signal is processed as an NTSC signal, its operation clock is 910 fh. On the other hand, when converting the MUSE signal to the NTSC signal, the operation clock is 960 fh, so the A / D
The conversion circuit 14 is required. Therefore, a circuit 11 for D / A converting the digital signal reproduced from the converter 1 and an A / D converting circuit 14 for converting the signal from the switch 3 into a digital signal are required.

As a result, the MUSE signal must pass through the D / A conversion circuit 11 and the D / A conversion circuit 14,
There was a problem that signal loss would occur.

[0012]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned drawbacks, and it is an object of the present invention to obtain a high-quality image without loss of a signal on transmission.

[0013]

SUMMARY OF THE INVENTION The present invention is an NTSC digitalized version of a band-compressed high definition television signal.
A down converter for converting into a broadcast signal, an analog / digital converting circuit for converting an NTSC broadcast signal into a digital signal, a switch for switching between the signal from the down converter and the signal from the analog / digital converting circuit, and a switch from the switch. A digital signal processing circuit for processing a signal, a clock generation circuit capable of generating clocks of different frequencies, and a control circuit for controlling switching of the clock frequency of the clock generation circuit at the same time as switching of the switch. Television receiver to do.

[0014]

The output signal from the converter is directly extracted as a digital signal, and the output signal from the NTSC decoder is
/ D conversion to digital signal. Then, the switch selects the output signal of the converter and the output signal from the NTSC decoder, and when the clock generation circuit selects the output signal from the converter by the selected signal, the output signal from the NTSC decoder is set to 960 fh. When selected, it switches to 910 fh.

[0015]

FIG. 1 shows an embodiment of the present invention. The same reference numerals as those in FIG. 2 indicate the same configurations, and the description thereof will be omitted.

The difference between FIG. 1 and FIG. 2 is that the A / D conversion circuit 4 is inserted after the decoder 2, and 910 fh and 960 are further added.
A clock generating circuit 7 for generating a clock of fh and a C for generating a signal for switching the clocks of the clock generating circuit 7
The point is that PU8 is added and the D / A conversion circuit 11 and the A / D conversion circuit 14 are eliminated.

The operation will be described below. The signal output from the converter 1 is output to the switch 3 as it is, and the output signal from the decoder 2 is converted into a digital signal by the A / D conversion circuit 4 and supplied to the switch 3.

Then, it is supplied to the filter 16 for cross color removal. At this time, the CPU 8 determines whether the clock supplied to the memory 5 is the output signal from the converter 1 or the decoder 2.
Control to switch. The clock switching is 960 fh for the output signal of the converter 1 and 910 fh for the output signal of the decoder 2.

[0019]

According to the present invention, since the MUSE signal is not converted into an analog signal, loss in signal transmission can be reduced. Further, since the D / A conversion circuit can be eliminated as compared with the conventional case, there is an effect that the circuit configuration becomes simple.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a conventional example.

[Explanation of symbols]

 1 MUSE / NTSC down converter 2 NTSC decoder 3 switch 4 A / D conversion circuit 5 1 line memory 6 arithmetic circuit 7 clock generation circuit 8 CPU

Claims (1)

[Claims] 1. A down converter for converting a band-compressed high-definition television signal into a digitized NTSC broadcast signal, an analog-digital conversion circuit for converting the NTSC broadcast signal into a digital signal, and the down converter Switch for switching the signal from the analog-to-digital conversion circuit, a digital signal processing circuit for processing the signal from the switch, a clock generation circuit capable of generating clocks of different frequencies, and a switch for switching the switch. A television receiver comprising: a control circuit that controls switching of a clock frequency of a clock generation circuit.