JPH0520473U - Television receiver - Google Patents

Abstract

(57) [Abstract] [Purpose] MUSE when no MUSE signal is received
This is to prevent noise from being mixed by the output from the / NTSC converter. A scanning line number conversion circuit 4 for converting the MUSE signal into the scanning line number of the NTSC signal, and a MUSE signal detection circuit 18 for detecting reception of the MUSE signal.
And the D / A from the clock generation circuit 10 and the frequency divider circuit 11.
The MUS is composed of a switching circuit 17 for outputting or not outputting the clock supplied to the conversion circuits 13, 14, 15 and the synchronization signal from the synchronization separation circuit 12.
When there is no E signal, the switching circuit 17 is turned off so that the clock and the synchronizing signal are not output.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to a television signal converter for converting a television signal into a second television signal having a different aspect ratio.

[0002]

[Prior Art]

 Hi-Vision, the next-generation high-definition television, is being broadcast on satellite broadcasting. This high-definition signal is band-compressed by a band compression technique called MUSE system. The compressed signal (hereinafter referred to as MUSE signal) is broadcast.

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

[0006] Therefore, there is a MUSE / NTSC converter in order to watch this MUSE broadcasting on a normal NTSC television receiver. This MUSE / NTSC converter converts a MUSE signal into an NTSC signal. The operation of the MUSE / NT SC converter is described on pages 31 to 45 of the magazine "TV Technology October 1989" published by Electronic Technology Publishing Co., Ltd.

By the way, when the above-mentioned MUSE / NTSC converter is built into a television receiver capable of receiving NTSC broadcasting, the MUSE / NTSC converter is operated regardless of whether or not MUSE broadcasting is being received. Therefore, there is a drawback that the output from the MUSE / NTSC converter is mixed with the video signal and becomes noise even when the NTSC broadcast is being received.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention is intended to solve the above-mentioned drawbacks, and prevents noise from being mixed by a MUSE / NTSC converter.

[0007]

[Means for Solving the Problems]

 According to the present invention, when the input first television signal of the first system is converted into the second television signal of the second system having a different aspect ratio, the image signal does not appear due to the difference in the aspect ratio. In a television receiver including a television signal conversion device for generating a blanking area, the output from the television conversion device is stopped when the first television signal is not received. And the television receiver.

[0008]

[Action]

 According to the present invention, with the above-mentioned configuration, noise is prevented by not outputting the clock when there is no MUSE signal.

[0009]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a block diagram of an embodiment of the present invention.

In FIG. 1, reference numeral 1 is an analog-digital (A / D) conversion circuit for converting a MUSE signal into a digital signal, and 2 is a MUSE subjected to non-linear emphasis on the transmission side for improving S / N. Non-linear correction circuit for correcting signals, 3 de-emphasis circuit, 4 scanning line number conversion circuit for converting MUSE signal to NTSC signal, 13 analog luminance signal (Y) converted to NTSC signal Digital-analog (D / A) conversion circuits for converting signals, 14 and 15 digital-analog conversion circuits for converting color difference signals (RY, BY) converted to NTSC signals to analog signals, 16 Is an NTSC encoder.

Reference numeral 5 is a timing generation circuit for generating each timing signal, 6 is a phase comparison circuit for comparing the phases of the horizontal synchronizing signals of the MUSE signal, 7 is a voltage controlled oscillation circuit of 32.4 MHz, and 8 is various clocks. A clock generation circuit for generation, 9 is a voltage controlled oscillation circuit of 30.24 MHz, 10 is a clock generation circuit, and 11 is a frequency dividing circuit.

Further, 12 is a sync separation circuit, 17 is a switching circuit that supplies or stops a clock or a sync signal, 18 is a detection circuit that detects a MUSE signal, and 19 is a scanning line number conversion every 5 seconds. The reset pulse generation circuit for operating the circuit 4 determines that there is no MUSE signal even though the MUSE signal is input, and even if the scanning line number conversion circuit 4 does not operate, it does not operate after 5 seconds. A reset signal for causing the scanning line number conversion circuit 4 to operate is generated.

Next, the operation will be described. The MUSE signal is converted into a digital signal by the A / D conversion circuit 1, is input to the scanning line number conversion circuit 4 via the non-linear correction circuit 2 and the de-emphasis circuit 3, and the D / A conversion circuits 13 and 14, It is converted into an analog signal at 15.

Then, the luminance signal is converted by the D / A conversion circuit 13 into an analog signal at the clock (12.12 MHz) of the clock generation circuit 10, and the color difference signal is divided by the D / A conversion circuits 14 and 15 into the frequency dividing circuit 11. It is converted into an analog signal with the clock (7.56MHz).

This clock is created as follows. First, the timing generation circuit 5 creates a gate signal for extracting the horizontal synchronization signal as shown in FIG. 2B, and the phase comparison circuit 6 detects the phase shift of the horizontal synchronization signal A extracted by the gate signal. , B, c, d) are detected, and the respective levels are added to detect the phase shift. If the phases are out of phase, the horizontal sync signal A is located at a position deviated from the gate signal B, and the four points for detecting the level are deviated, so the voltage corresponding to the addition level is input to the voltage controlled oscillator circuit 7. , Will be controlled.

On the other hand, the output from the phase comparison circuit 6 also controls the voltage controlled oscillation circuit 9, and further, the clock generation circuit 10 generates the clock of the D / A conversion circuit 13 described above, and the frequency division circuit 11 outputs D / A. A clock for the A conversion circuits 14 and 15 is made.

By the way, when the MUSE signal is being received, the switching circuit 17 is turned on by the output from the MUSE signal detecting circuit 18 to output a clock and a synchronizing signal to the NTSC encoder 16 for a luminance signal and a color difference. Although the signal and the synchronizing signal are supplied, when there is no MUSE signal, the switching circuit 17 is turned off, and the clock and the synchronizing signal are not output. Therefore, the signal is not supplied to the NTSC encoder 16.

Therefore, the output of the MUSE / NTSC down converter is not affected by noise or the like.

[0019]

[Effect of the device]

 According to the present invention, even when there is no MUSE signal, noise is not added to other signals, and a good video signal can be obtained.

[Brief description of drawings]

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

FIG. 2 is a waveform diagram for explaining the operation of the present invention.

[Explanation of symbols]

 4 Scan Line Number Conversion Circuit 9 Voltage Controlled Oscillation Circuit 10 Clock Generation Circuit 11 Frequency Division Circuit 13 D / A Conversion Circuit 14 D / A Conversion Circuit 15 D / A Conversion Circuit 17 Switching Circuit 18 MUSE Signal Detection Circuit

Claims (1)

[Scope of utility model registration request] 1. When an input first television signal of the first system is converted into a second television signal of the second system having a different aspect ratio, no image signal appears due to the difference in the aspect ratio. In a television receiver including a television signal conversion device that generates a blanking area, when the first television signal is not received,
A television receiver characterized in that the output from the television conversion device is stopped.