JPH0453101Y2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Industrial Application The present invention relates to a mute circuit for a high-definition video disc player.

(b) Conventional technology MUSE as a method for transmitting high-definition video signals
There is a method.

This MUSE method is described in pages 112 to 116 of the magazine "Nikkei Electronics" published by Nikkei McGraw-Hill on March 12, 1984, and
A preliminary lecture collection for the founding commemorative lecture of the NHK Research Institute of Technology and the NHK Broadcasting Science Research Institute on June 6, 2016, “New Transmission Methods for High-Definition Television,” and Nippon Broadcasting Publishing Co., Ltd., published on April 1, 1984. Pages 103 to 108 of the April issue of the magazine "Radio Science" published by the Association, and pages 19 to 10 of the September issue of the magazine "Television Technology" published by Denshi Gijutsu Publishing Co., Ltd., dated September 1, 1984. Details are disclosed on page 24.

In this MUSE method, the encoder on the transmitting side compresses the band of the high-quality video signal using the TCI multiplex sub-sampling method, converts this band-compressed MUSE signal into a broadcast signal, and transmits it, which is received via a broadcasting satellite. The broadcast signal is sent to MUSE by the receiver.
The signal is demodulated and then input to the MUSE decoder, which decodes the band-compressed signal, where it is decoded and reproduced into the original high-quality video signal.

On the other hand, the applicant had previously proposed Japanese Patent Application No. 1983-47764 regarding a high-quality video disk player that optically records and reproduces MUSE signals. This proposal was made based on the fact that the horizontal synchronization signal of the MUSE signal is not of negative polarity with respect to the video, making synchronization separation difficult, and that it is necessary to remove jitter components at frequencies higher than the horizontal synchronization frequency.
This is a device that plays back optically recorded video disk records by frequency multiplexing a pilot signal with a frequency higher than the horizontal synchronization frequency onto the modulated MUSE signal, and while comparing the phase of the playback pilot signal and a reference signal, the rotation of the video disk record is controlled. and to change the optical path of the pickup.

The playback produced by this video disc player
The MUSE signal is also input to the MUSE decoder described above. This MUSE decoder is input
A/D conversion and A/D conversion of the MUSE signal based on the clock synchronized with the horizontal synchronization signal in the MUSE signal.
It performs all signal processing such as reading and compositing converted data, achieving accurate decoding of high-quality video signals.

(c) Problems to be solved by the invention The clock signal generation circuit in the MUSE decoder mentioned above samples the narrow slope of the horizontal synchronization signal by its frequency-divided output, and adjusts the oscillation frequency according to the sampling output level. It is a control device, and once it goes out of lock, it takes several seconds for it to go back into lock. However, the horizontal synchronizing signal frequency of the reproduced signal is unstable compared to that of the broadcast signal, and the lock state is easily lost, causing the above-mentioned problems.

(d) Means for solving the problem In this invention, the clock oscillation circuit in the MUSE decoder detects the loss of the MUSE signal and oscillates the clock oscillation circuit in order to deal with the momentary interruption of the normal broadcast signal. Considering that the state is fixed, there is a gate signal generation circuit that detects when the reproduction pilot signal frequency is out of a predetermined range and issues a gate control signal, and a reproduction MUSE based on the gate control signal.
The present invention is characterized in that a gate circuit for preventing signal generation is disposed within the video disc player.

(e) Effect Therefore, according to the present invention, the amount of jitter is large.
The MUSE signal is not input, and the MUSE signal in the MUSE decoder is
In the PLL circuit, when the horizontal synchronization frequency deviates by a predetermined amount, the reproduced MUSE signal itself disappears, so the PLL circuit enters a hold state and the oscillation frequency of the PLL circuit does not deviate from the predetermined range.

(F) Embodiment The present invention will be described below with reference to an illustrative embodiment. First, FIG. 1 shows a circuit block diagram of a reproduction signal processing circuit in a high-definition video disc player.

First, in the video disc player, a playback signal obtained by optically reproducing a video disc record by a pickup 1 is amplified by a preamplifier 2 and then input to a limiter circuit 3 and a pilot detection circuit 6. Limiter output plays FMMUSE
The signal is input as a signal to the FM demodulation circuit 4, where it is FM demodulated, the high frequency is suppressed by the de-emphasis circuit 5, and the signal is derived as a reproduced MUSE signal. On the other hand, a pilot detection circuit 6 constituting a low-pass filter
separates the reproduced pilot signal and inputs it to the phase comparator circuit 8. This phase comparison circuit 8 has the output of the fixed oscillation circuit 7 exhibiting a frequency equivalent to the pilot signal as a reference input, and the phase comparison output is inputted as a jitter detection output to the rotation control circuit of the disk motor and the optical path changing circuit of the pickup 1. . At the same time, this phase comparison output is input to the gate control generation circuit 9. This circuit consists of, for example, a high-pass filter, an AM detection circuit, and a Schmitt trigger circuit, and when the fluctuation of the phase comparison output becomes shorter than a predetermined period, that is, when the horizontal synchronization frequency of the reproduced MUSE signal is out of a predetermined range, the high level The gate control signal is generated. This gate control signal is the de-emphasis output, i.e. the regeneration
This is the control input of the gate circuit 10 that inputs the MUSE signal, and when the gate control signal is at a high level,
Cut off the supply of the playback MUSE signal to the MUSE decoder.

FIG. 2 shows a block diagram of a signal processing circuit of a MUSE decoder connected to a high-definition video disc player. The reproduced MUSE signal is sent to the high-definition video signal forming circuit based on the clock signal derived from the clock oscillation circuit 15. is converted into a high-quality video signal. On the other hand, the reproduced MUSE signal is input to the sampling circuit 12. This sampling circuit 12 samples the slope of the synchronizing signal portion of the reproduction circuit MUSE signal using a frequency divided output obtained by inputting a clock signal to a frequency dividing circuit 13. A control signal generation circuit 14, which sequentially receives the sampling output, forms a control signal indicating a phase error from the sampling output. This control signal controls the oscillation of the clock oscillation circuit.

Furthermore, the dropout detection circuit 11 which inputs the reproduced MUSE signal inputs the dropout detection output to the control signal forming circuit 14. This control signal generation circuit 14 functions to old the control signal when a dropout detection output is generated, and the oscillation frequency is fixed during the dropout period.

(g) Effects of the invention Therefore, according to the invention, the MUSE decoder operates stably, and the signal is no longer interrupted for several seconds as in the conventional case, and the effect is great.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a signal processing circuit of a high-definition video disc player according to an embodiment of the present invention, and FIG. 2 is a block diagram of a signal processing circuit of a MUSE decoder. 9...Gate signal forming circuit, 10...Gate circuit.

Claims (1)

[Claim for Utility Model Registration] Playback of a video record made by FM modulating the MUSE signal, which is obtained by band-compressing a high-quality video signal using the TCI multiplex sub-sampling method, and frequency-multiplexing recording together with a constant frequency pilot signal. A high-definition video disc player that uses a high-definition video disc player includes a gate control circuit that generates a gate control signal when a reproduced pilot signal frequency is out of a predetermined range, and an FM demodulated circuit that generates a gate control signal based on the gate signal.
Mute circuits each have a gate circuit that prevents the generation of the MUSE signal.