JPH0779481B2 - Disk reproduction demodulation device and MUSE decoder device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc reproducing / demodulating device and a MUSE decoder device for reproducing a bivision (high definition television) band compressed signal.

Conventional technology A high-definition video signal that provides higher definition images than the current standard television system is transmitted by the 27 MHz broadcast satellite.
Muse (MUS) that transmits using one channel of z bandwidth
A band compression transmission method called E) has been proposed (for example, Reference (1): Yuichi Ninomiya “Transmission method for high-definition broadcasting using satellite MUSE”, Nikkei Electronics, 198.
7.11.2 (no.433) p.189-212).

The transmission method shown here compresses a high-definition signal originally having a band of 20 MHz or more to about 8 MHz by sub-Nyquist sampling and transmits it. In the case of a still image, 4 fields, that is, 1 image in 2 frames Complete. Therefore, the image receiving device has a memory for two frames in terms of the transmission signal rate, and it is possible to interpolate the transmitted television signal between the frames to obtain 1
The images are completed.

On the other hand, with this method, high-definition 8
Since it is compressed to about MHz, it is useful not only for satellite broadcasting but also for recording and reproducing, and its application to VTRs, video discs, etc. is considered.

Especially with regard to video discs, high-definition, high-definition, wide and powerful images can be enjoyed easily even in ordinary households, and thus it can be expected to spread quickly. The major difference between this MUSE type video disc and the current type is that the sync signal cannot be easily separated in amplitude from the reproduced signal because the sync signal is positive polarity synchronization. The point is that the sync signal cannot be easily separated and used. Therefore, it has been proposed that a pilot carrier signal is multiplexed with a television FM signal and recorded on a disc, and that the pilot carrier signal is detected and used at the time of reproduction to control the rotation of the disc (for example, reference ( 2): Yuichi Ninomiya “Home Video Disc by MUSE” Technical Report of the Television Society of Japan, Technical Circuit Study Group TEBS 99-4, September 20, 1984).

As described in the above reference (2), the MUSE signal is a method that is established by sub-Nyquist sampling, so if the reproduced signal has time axis fluctuations, that is, jitter, the sample phase shifts and the original signal can be decoded. Jitter correction is necessary because it does not exist.

Problems to be Solved by the Invention As described above, the jitter correction is important in the MUSE type video disc, but from the viewpoint of reproduction signal quality, a digital time base collector (hereinafter abbreviated as TBC) using a digital memory is used. Is effective. On the other hand, MUSE television signals require digital signal processing for demodulation, as explained in the prior art.
In the MUSE decoder, it is converted into a digital signal by the transmission clock of 16.2MHz. Therefore, the MUSE signal digitized by the TBC of the MUSE disk and subjected to the jitter correction is converted into an analog signal and supplied to the decoder, where it is converted into a digital signal again. If analog-digital conversion is performed many times in this way, the signal deteriorates due to a quantization error each time, which is not preferable. Therefore, if the interface between the TBC and the decoder is kept as a digital signal, the deterioration can be prevented.

Playback signal with jitter is the MUSE transmission clock
A method for sampling at 16.2 MHz and performing time base correction has already been proposed (Japanese Patent Application No. Sho 62-95661 filed disk reproduction demodulator). If the TBC device is digitized with the same sampling clock as the MUSE decoder, it is easy to interface with digital signals between the two. However, some MUSE decoders may not have a digital interface function, so it is necessary for the output of the TBC device to have a normal analog output in preparation for such a case. However, since the MUSE signal uses the sample value transmission method as shown in the above reference (1), in order to transmit a complete sample value, the phase characteristic of transmission is linear and the frequency characteristic is symmetrical with the roll-off characteristic. Need to be. In order to realize such characteristics, there is a problem that the circuit configuration on the sending side is complicated and it is not preferable for the TBC of the video disk sprayer.

In view of the problems of the prior art, the present invention provides a disc reproducing apparatus that usually suppresses image quality deterioration by a digital interface and simplifies the circuit configuration on the TBC transmission side when an analog interface is required. Another object of the present invention is to provide a MUSE decoder device that can be used for both a disc reproducing device having a digital interface and a conventional disc reproducing device having only analog output.

Means for Solving the Problems The present invention according to claim 1 is a reproducing means for reproducing a video disk in which an FM modulation signal of a MUSE signal which is a band-compressed high-definition signal, a pilot carrier and the like are recorded, and the reproducing FM. A demodulation circuit that demodulates the MUSE signal from the signal and this
An analog-digital conversion circuit that converts the demodulated MUSE signal into a digital signal with a first clock that is synchronized with the time axis fluctuation of the demodulated signal demodulated by the FM demodulation circuit, and a digital MUSE converted by this analog-digital conversion circuit. A time base collector circuit that absorbs a time axis fluctuation by storing a signal and reading it with a second clock whose time axis is stable, an extraction circuit that extracts a pilot carrier signal from the reproduced FM signal, and the like. And a clock generation circuit configured by a phase locked loop oscillation circuit that generates the first clock signal synchronized with the extracted pilot carrier, and the output signal of the time base collector circuit is a MUSE decoder and a digital MUSE signal. Clock generated by the clock generation circuit when interfacing in the state And MUS transmission clock and a disk reproducing demodulating apparatus being characterized in that so as to generate a clock having a frequency higher than at least MUSE transmission clock when interfacing with the state of the analog MUSE signal.

According to a second aspect of the present invention, when the digital MUSE signal sampled by the MUSE transmission clock is output from the digital signal output terminal, the digital MUSE is output to the clock output terminal.
Output the MUSE transmission clock synchronized with the signal, and at least
When converting a digital MUSE signal sampled with a clock of a frequency higher than the MUSE transmission clock to an analog signal and outputting it to the analog signal output terminal, the MUSE transmission clock is not output to the clock output terminal. It is a disk reproducing and demodulating device.

According to a third aspect of the present invention, there is provided a first input terminal which receives an analog MUSE signal from the outside, and an analog-digital which converts the MUSE signal input to the first input terminal into a first digital MUSE signal. Converter and second digital MU from outside
A second input terminal for receiving the SE signal and a third input terminal for externally inputting a clock equal to the sampling clock of the second digital MUSE signal,
When a clock is input to the input terminal of the
The digital MUSE signal is supplied to the next stage, and when the clock is not input to the third input terminal, it has a changeover switch function that operates so as to supply the first digital MUSE signal to the next stage. It is a featured MUSE decoder device.

According to the present invention, the MUSE signal for performing the digital signal processing of TBC is sampled at the transmission clock of 16.2 MHz in the case of the digital interface and at least higher than the transmission clock in the case of the analog interface, for example, MUSE by the above means. 3 times the signal band of 8.1MHz
It facilitates analog conversion of the TBC output as it does at frequencies such as 24.3MHz.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a disc reproducing / demodulating device of the present invention. In the figure, 1 is a disc reproducing device for obtaining a reproduced FM signal from a disc on which a MUSE video signal is recorded, and 2 is a demodulator for a MUSE signal from the obtained FM signal.
The FM demodulation circuit 3 is an analog-to-digital converter (hereinafter abbreviated as A / D) that converts an analog MUSE signal into a digital signal, and operates with a sampling clock having the same time axis fluctuation (jitter) as the input MUSE signal. . 4 is TBC
And digital with time base fluctuation obtained from A / D3 above.
MUSE with stable time axis is written by writing the MUSE signal to the memory with the same clock as the A / D sampling clock and reading it with a stable clock on another time axis.
You get the signal. It should be noted that this memory has sufficient capacity to operate with clocks of two different frequencies, as will be described later.

The digital MUSE signal obtained in this way is output from the output terminal 14 to the MU
Output to SE decoder etc. At the same time, a clock synchronized with the digital MUSE signal is output from the terminal 17 via the switch 16.

Reference numeral 6 is a pilot carrier extraction circuit for extracting the pilot carrier signal described in the section of the prior art from the signal reproduced from the disc, dividing the frequency, and supplying the next stage, 7 is a frequency division signal of the pilot carrier signal. A phase comparison circuit that compares the phase of a frequency-controlled oscillator output with a frequency-divided signal to be described later and generates a control signal according to the phase difference; 8 is a voltage that changes its oscillation frequency according to the output control signal of the phase comparison circuit 7. Controlled oscillator (hereinafter referred to as VCO), 9 is the V
A frequency dividing circuit that divides the output of CO8 and supplies it to the phase comparison circuit 7. A range 14 surrounded by a dotted line in the figure constitutes a phase-locked loop oscillation circuit (hereinafter abbreviated as PLL). As an example of a concrete numerical value of this PLL, if the pilot carrier signal is 67.5fH (about 2.28MHz, fH is the horizontal synchronizing frequency), divide this by 1/3 to 22.5fH and set it to 22.5fH. This is the first input. On the other hand, the VCO oscillation frequency is 1440fH (48.6MHz), which is divided by 1/64 to 22.5fH.
As the second input of the phase comparison circuit, the PLL is established.

20 is a frequency dividing circuit having two dividing ratios of 1/3 and 1/2.
Dividing the VCO8 oscillation frequency to 1/3 is when using the 16.2MHz clock for the digital interface.
24.3 for analog interface when dividing by 2
It is time to use the MHz clock.

10 is a sync signal detection circuit that extracts a sync signal from the MUSE signal digitized at 16.2 MHz, 11 is a phase detection circuit that detects the sampling phase of the MUSE signal digitized at 16.2 MHz, 12 is the detection of the phase detection circuit An up / down counter that generates a signal for controlling the phase of the sampling clock based on the result, and 13 is a phase shift circuit that changes the phase of the sampling clock based on the control signal of the up / down counter 12. The detailed operation principle from the sync signal detection circuit 10 to the phase shift circuit 13 is described in the section of the problem to be solved by the invention.
Although omitted here since it has been described in Japanese Patent Application No. 62-95661), this operation is effective when the sampling clock of the digital MUS signal is equal to the MUSE transmission clock, that is, 16.2 MHz. Therefore, the dividing ratio of the dividing circuit 20 is 1/3.
Clock phase shift circuit only when outputting 16.2MHz at 1
A switch 21 is provided to bypass the phase shift circuit 13 when the frequency division ratio is 1/2 and the frequency is 24.3 MHz.
However, the same applies if the operation of the phase shift circuit is fixed instead of bypassing.

Reference numeral 19 is a reference oscillator that generates a clock that does not fluctuate with time, and may be supplied from the outside. In this embodiment, an example in which the oscillation frequency is 48.6 MHz which is the same as the VCO 8 will be described. 18
Is a frequency dividing circuit for dividing the output of the reference oscillator 19 and operates in the same manner as the frequency dividing circuit 20.

On the other hand, 15 is a digital MU for analog interface.
A digital-analog converter (hereinafter abbreviated as D / A) for converting an SE signal into an analog signal, 15 is an analog MUSE signal output terminal.

In this embodiment, the frequency dividing circuits 18 and 21 and the switch 16
21 works together, for example, 2 to obtain digital MUSE signal output
The two divider circuits each have a divide ratio of 1/3, and switch 1
6 is closed and 20 is connected to the phase shift circuit 21 side. In addition, when the analog MUSE signal output is obtained, they are in different states.

Next, FIG. 2 is a detailed description of the A / D3 portion of FIG. 1, where 30 is an FM demodulation signal input terminal, 31 is a buffer amplifier, and 32 is a buffer amplifier.
Is a LOW-PASS filter with a 8.1 MHz bandwidth, 33 is a low-pass (LOW-PASS) filter with a bandwidth that can sufficiently cut aliasing noise when digitizing at a frequency of 24.3 MHz in the band of at least 32 filters or more, 34 is a clamp circuit, 35 is a clamp pulse generation circuit, and 36 is a sync signal input for generating a clamp pulse. 37 is a switch that switches according to a digital or analog interface, and is connected to the clamp circuit side at the digital interface and to the other side at the analog interface. 38 is an A / D and 39 is a sampling clock input. Four
0 is the A / D output.

Next, the input portion of the MUSE decoder connected to the present disc reproducing / demodulating device will be described with reference to FIG. In the figure, 50 is an analog MUSE signal input terminal, 51 is an A / D, 52 is a digital MUSE signal input terminal, and 53 is the input digital MUSE.
A clock input terminal synchronized with the signal, 54 is a clock detection circuit that detects whether a regular clock is input to the clock input terminal and supplies the clock input to the MUSE decoding device in the next stage, and 55 is a changeover switch Then, if a clock is detected by the clock detection circuit 54, the digital MUSE signal input is switched to be supplied to the next stage based on the detected clock. Reference numeral 56 is a MUSE decoder device body, a device for restoring the supplied MUSE signal to the original high-definition signal, and 57 is a high-definition signal output terminal.

The changeover switch 55 automatically operates depending on whether or not a clock is input to the clock input terminal as described above, but naturally it is operated by other means, that is, by manual means or the like regardless of clock input. Although it is necessary to have a function as well, description thereof will be omitted here because there is no particular difficulty in its configuration.

EFFECTS OF THE INVENTION According to the present invention, it is possible to effectively use a digital interface that prevents image quality deterioration due to heavy use of analog-digital conversion, and obtain an analog signal output for connection with a device having no such function. It is possible with a simple configuration. Further, when there is a disk reproducing apparatus which outputs a digital interface and an analog output at the same time according to the second aspect of the present invention, it is even possible to connect the digital MUSE signal and the clock signal of the digital interface output to the MUSE decoder apparatus according to the present invention. If
Even if a general user who is unfamiliar with device connection accidentally analog
Even if the MUSE signal is connected at the same time, the MUSE decoder device automatically switches to the high-quality digital MUSE signal input side, which has the advantage of always obtaining a high-quality screen. Also, by having two types of interfaces, digital and analog, the output of the MUSE-BS tuner, etc. of analog output is connected at the same time in addition to the disc playback device, and the input is forcibly switched as in claim 4. It is possible to obtain a very useful effect such that the function of the input selection switch can be equivalently achieved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a disk reproducing / demodulating device of the present invention, FIG. 2 is a block diagram showing the configuration of A / D3 in FIG. 1 in more detail, and FIG. 3 is a block diagram showing an embodiment of the MUSE decoder device of FIG. 1 ... Disk playback device, 2 ... FM demodulation circuit, 3 ... A /
D, 4 ... TBC, 5 ... D / A, 6 ... Pilot carrier extraction circuit, 7 ... Phase comparison circuit, 8 ... VCO, 9 ... Dividing circuit, 10 ... Synchronization signal detection circuit, 11 ...... Phase detection circuit, 12 …… Up / down counter, 13 …… Phase shift circuit, 14
...... Digital MUSE signal output terminal, 15 …… Analog MUSE signal output terminal, 16 …… Switch, 17 …… Clock output terminal, 18 …… Division circuit, 19 …… Reference oscillator, 20 …… Division circuit, 21 ...... Selection switch, 50 …… Analog MUSE signal input terminal, 52 …… Digital MUSE signal input terminal, 53 …… Clock input terminal, 54 …… Clock detection circuit, 55 …… Selection switch.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication H04N 9/896 H04N 5/95 A 7/00 A

Claims (4)

[Claims] 1. An MU which is a band-compressed high-definition signal.
A reproducing means for reproducing a video disc on which the FM modulation signal of the SE signal and the pilot carrier are recorded;
A demodulation circuit for demodulating the MUSE signal from the signal, and an analog-digital conversion circuit for converting the demodulated MUSE signal into a digital signal with a first clock synchronized with the time base fluctuation of the demodulation signal demodulated by the FM demodulation circuit, A time base collector circuit that absorbs fluctuations in the time axis by storing the digital MUSE signal converted by the analog-digital conversion circuit and reading it with the second clock whose time axis is stable, and a pilot carrier from the reproduced FM signal or the like. The time base collector includes an extraction circuit for extracting a signal, and a clock generation circuit configured by a phase locked loop oscillation circuit for generating the first clock signal synchronized with the pilot carrier extracted by the extraction circuit. When the output signal of the circuit interfaces with the MUSE decoder in the state of digital MUSE signal Generating clock of the clock generating circuit is a MUSE transmission clock, also analog
A disc reproducing and demodulating device characterized in that a clock having a frequency higher than at least the MUSE transmission clock is generated when interfacing in the state of the MUSE signal. 2. When the digital MUSE signal sampled by the MUSE transmission clock is output from the digital signal output terminal, the MUSE transmission clock synchronized with the digital MUSE signal is output to the clock output terminal, and at least from the MUSE transmission clock. Also, when the digital MUSE signal sampled with a high frequency clock is converted to an analog signal and output to the analog signal output terminal, the MUSE transmission clock is not output to the clock output terminal. apparatus. 3. A first input terminal for receiving an analog MUSE signal from the outside, and an MU input to the first input terminal.
Analog to convert SE signal to first digital MUSE signal-
A digital converter, a second input terminal for receiving a second digital MUSE signal from the outside, and a third input terminal for receiving a clock equal to the sampling lock of the second digital MUSE signal from the outside , When the clock is input to the third input terminal, the second digital signal is input.
A MUSE signal is supplied to the next stage, and when the clock is not input to the third input terminal, it has a changeover switch function that operates so as to supply the first digital MUSE signal to the next stage. MUSE decoder device to do. 4. In the automatic mode, the changeover switch is actuated depending on the presence / absence of a clock input to the third input terminal,
4. The MUSE according to claim 3, wherein the changeover switch is operated by other means in the manual mode.
Decoder device.