JPH0619897B2 - Playback device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing apparatus, and more particularly to a reproducing apparatus adapted to reproduce two kinds of signals having different video frequency bands.

BACKGROUND ART A reproducing apparatus for reproducing a video signal or an audio signal recorded on a disc-shaped recording medium called a so-called video disc has a frequency band of 3.1 to 4.2 MHz (megahertz), for example. In addition to the standard video signal, a so-called high-resolution video signal having a wider frequency band can be recorded / reproduced. However, the signal processing performed when reproducing each of the signals is different from each other, and the conventional reproducing apparatus requires a signal processing circuit corresponding to each of the signals, resulting in a complicated configuration.

Problem to be Solved by the Invention An object of the present invention is to provide a reproducing apparatus having a simple structure and capable of reproducing both standard video signals and high resolution video signals.

Means for Solving the Problems The present invention is (a) a first demodulation circuit 5 for demodulating first and second signals, wherein the demodulated first signal has a frequency band lower than a first frequency f1. The standard video signal 22 having the first audio signal 24 and either the left or right modulated with the second frequency f2 higher than the first frequency f1 as the carrier frequency, and the third frequency higher than the second frequency f2. The second acoustic signal 25 of either the left or the right, which is modulated with f3 as the carrier frequency, and the demodulated second signal has a frequency band higher than the third frequency f3 and lower than the fourth frequency f4. The third high-resolution video signal 23 and the third same as the left or right second audio signal 25 modulated with the fifth frequency higher than the fourth frequency f4 as the carrier frequency.
Such a first demodulation circuit having an acoustic signal 26 and a fourth acoustic signal 27 identical to the left or right first acoustic signal 24 modulated with a sixth frequency f6 higher than the fifth frequency f5 as the carrier frequency. 5 and (b) the output of the first demodulation circuit 5 is given, and the first frequency f
First low-pass filter 6 having cutoff frequency 1
(C) The output of the first demodulation circuit 5 is given, and the fourth frequency f
Second low-pass filter 7 with cutoff frequency 4
(D) The first changeover switch 3 for switching and deriving the outputs of the first and second low-pass filters 6 and 7, and (e) the output of the first demodulation circuit 5 is given, and the third and fourth acoustic waves are given. The first bandpass filter 8 for deriving only the signals 26 and 27, (f) the detection circuit 2 for detecting the output of the first bandpass filter 8, and (g) When the carrier frequency is fc, fc = f2 + f6 = a carrier wave generating circuit 11 for generating a carrier wave satisfying f3 + f5, and (h) third and fourth carrier waves from the first band pass filter 8.
A circuit 10 for obtaining the frequency difference between the acoustic signal and the carrier wave from the carrier wave generating circuit 11, and (i) a second switching for deriving by switching between the output of the first demodulation circuit 5 or the output of the circuit 10 for obtaining the frequency difference. A switch 4, (j) a second bandpass filter 12 for deriving only an acoustic signal of a second frequency f2, (k) a third bandpass filter 13 for deriving only an acoustic signal of a third frequency f3, (l ) A second demodulation circuit 14 that demodulates the output of the second bandpass filter 12, and (m) a third demodulation circuit 15 that demodulates the output of the third bandpass filter 13 are included. When the third and fourth acoustic signals are not detected, the output of the first low-pass filter 6 is derived by the first changeover switch 3 and the output of the first demodulation circuit 5 is derived by the second changeover switch 4. A circuit for deriving the output of the second low-pass filter 7 by the first changeover switch 3 and detecting the difference between the frequencies by the first changeover switch 4 when the detection circuit 2 detects the third and fourth acoustic signals. The reproducing device is characterized by deriving 10 outputs.

Operation According to the present invention, the standard video signal 22 and the high resolution signal 23 are input to the first demodulation circuit 5, and the signal waved by the first band pass filter 8 is detected by the detection circuit 2 in the third and fourth audio signals. If it is not detected as a signal, it is assumed that the first signal is input, the standard video signal 22 of the first signal is derived from the first low-pass filter 6 via the changeover switch 3, and the first and second audio signals are output. The signals 24 and 25 are given to the second and third demodulation circuits 14 and 15 from the respective second and third band pass filters 12 and 13 via the second changeover switch 4, and can be sonicated. When the second signal is input, the bandpass filter 8 supplies the detection circuit 2 with the third and fourth acoustic signals, which are detected, whereby the high-resolution video signal 23 is output to the second lowpass filter 7 and the second lowpass filter 7. A circuit 10 which is derived via the 1 changeover switch 3 and also obtains a frequency difference.
At, the frequency difference between the third and fourth acoustic signals 26 and 27 and the carrier wave from the carrier wave generation circuit 11 is obtained, and the second changeover switch 4 passes through the second and third band pass filters 12 and 13 to obtain the second And applied to the third demodulation circuits 14, 15 and can then be sonicated. By determining the carrier wave frequency fc so that the following expressions 3 to 8 are established, either the left or right acoustic signal 24 or 27 is obtained from the second demodulation circuit 14, and the third From the demodulation circuit 15, the other left or right acoustic signal 25, 26 is obtained.

Embodiment FIG. 1 is a block diagram showing an electrical configuration of a reproducing apparatus 1 according to an embodiment of the present invention. The reproducing apparatus 1 includes a detection circuit 2 as a signal discriminating means and switching switches 3 and 4 as a switching means. The demodulation circuit 5 demodulates the frequency-modulated input signal, and the output terminal of the demodulation circuit 5 has low-pass filters 6 and 7 that pass only signals having frequencies lower than a predetermined frequency, and a predetermined frequency. A bandpass filter 8 that passes only signals within the band,
It is connected to the terminal 4a on one side of the changeover switch.

The output terminals of the low-pass filters 6 and 7 are connected to the terminals 3a and 3b of the changeover switch 3, respectively, and the common terminal 3c of the changeover switch 3 is connected to the video processing circuit 9.
The output side of the bandpass filter 8 is connected to the detection circuit 2 and the balanced modulator 10, and the output from the carrier generation circuit 11 is input to the balanced modulator 10, and its output is the terminal 4b of the changeover switch 4. Connected to. The common terminal 4c of the changeover switch 4 is connected to the bandpass filter 12 and the bandpass filter 13, and the respective outputs of the bandpass filters 12 and 13 are given to the demodulation circuits 14 and 15. The operation of the reproducing apparatus 1 having the above configuration will be described below.

The reproducing apparatus 1 is used when reproducing a video signal and an audio signal recorded on a disc-shaped recording medium called a video disc. Signals such as images and sounds recorded on a video disc are signals that are frequency-modulated by a carrier having a predetermined frequency.

FIG. 2 is a block diagram showing an electrical configuration of the modulator 16 for performing frequency modulation. In the modulator 16,
A right acoustic modulation circuit 18 for frequency-modulating a right channel acoustic signal input from the input terminal 17, and an input terminal 1
The acoustic signal is frequency-modulated by the left acoustic modulation circuit 20 for frequency-modulating the left channel acoustic signal input from the input channel 9. Then, the mixing circuit 21 causes the input terminal 22
The video signal input from the device is mixed with the frequency-modulated audio signal, and the modulation circuit 23 further performs frequency modulation. The signal modulated in this way is subjected to predetermined processing from the terminal 24 by another processing circuit (not shown) and recorded on the video disk. At this time,
The frequency band of the video signal is, for example, 3.1 to 4.2 MHz
There are two different recording methods: a standard video signal as the first signal having a band of 1) and a so-called high resolution signal as a second signal having a band wider than that.

FIG. 3 is a diagram showing the frequency spectrum of the standard video signal, and FIG. 4 is a diagram showing the frequency spectrum of the high resolution signal. A region 22 in FIG. 3 and a region 23 in FIG. 4 show respective video frequency bands,
Regions 24 and 25 in FIG. 3 and regions 26 and 27 in FIG.
Indicate the acoustic frequency bands, respectively.

In FIG. 3, the region 24 shows the left channel acoustic signal frequency-modulated by the carrier frequency 2, and the region 25 shows the right channel acoustic signal frequency-modulated by the carrier frequency 3. The area 26 in FIG. 4 shows the right channel acoustic signal frequency-modulated by the carrier frequency 5, and the area 27 shows the left channel acoustic signal modulated by the carrier frequency 6. In this way, the left channel and right channel acoustic signals of each of the above signals have a left-right inverted relationship in FIGS. 3 and 4. Then, the differences Δ1 and Δ2 (see FIGS. 3 and 4) in the carrier frequencies of the left and right channels of the respective signals are set to be equal. Here, the above Δ1 and Δ2 are values represented by the following first and second equations.

Δ1 = 3-2 (1) Δ2 = 6-5 (2) The video and audio signals thus recorded are read from the video disc by the reading means (not shown) and are input from the input terminal 28 of the reproducing apparatus 1. Is entered. The input signal is demodulated by the demodulation circuit 5. The demodulation process by the demodulation circuit 5 is a demodulation process corresponding to the frequency modulation of the modulation circuit 23 of the modulator 16 described above.

FIG. 5 is a diagram showing the frequency characteristic of the low-pass filter 6, and FIG. 6 is a diagram showing the frequency characteristic of the low-pass filter 7. Cutoff frequency 01 of the low-pass filter 6
Is provided so as to be the same as the maximum value 1 of the video frequency of the standard video signal, and the cutoff frequency 02 of the low pass filter 7 is the maximum value 4 of the video frequency of the high resolution signal.
Is provided to be the same as.

FIG. 7 is a diagram showing frequency characteristics of the bandpass filter 8. The frequency band that can pass through the band-pass filter 8, that is, the region 29 shown in FIG. 7 is provided so as to include only the regions 26 and 27 of the acoustic band of the high resolution signal as shown in FIG.

The output of the demodulation circuit 5 is given to the low-pass filters 6 and 7, the band-pass filter 8 and the terminal 4a of the changeover switch 4 having the above-mentioned characteristics. The low-pass filters 6 and 7 and the band-pass filter 8 pass only signals having frequency components according to their respective characteristics. At this time, if the signal input from the input terminal 28 is a standard video signal, the bandpass filter 8 does not output anything, and if it is a high-resolution signal, its acoustic signal component is the bandpass filter 8 Is output from.

The detection circuit 2 is supplied with the output of the bandpass filter 8, performs a predetermined detection process, and outputs a switching switching signal for changing the switching mode of the changeover switches 3 and 4. In the changeover switch 3, when the switching changeover signal is applied, the common terminal 3c is connected to the terminal 3b, and when the switching changeover signal is not applied, the common terminal 3c is connected to the terminal 3a. On the other hand, also in the changeover switch 4, when the switching switching signal is given, the common terminal 4c is connected to the terminal 4b, and when the signal is not given,
The common terminal 4c is connected to the terminal 4a.

Therefore, when the signal input to the reproducing apparatus 1 is the standard video signal, the video signal of the output of the demodulation circuit 5 is
The signal is supplied to the video processing circuit 9 via the low-pass filter 6, the terminal 3a of the changeover switch 3 and the common terminal 3c, and a predetermined video signal processing is performed. Then, it is given from the terminal 29 to another image display means (not shown), and the image is reproduced. On the other hand, the acoustic signal in the output of the demodulation circuit 5 is
It is applied to the bandpass filters 12 and 13 via the terminal 4a and the common terminal 4c of the changeover switch 4, respectively. The bandpass filter 12 has a characteristic of passing only the signal in the frequency band (region 24 in the third illustration) of the left channel acoustic signal of the standard video signal.
No. 3 has a characteristic of passing only the signal in the frequency band 25 of the right channel acoustic signal of the standard video signal.

Therefore, only the left channel acoustic signal is output from the band pass filter 12, the signal is demodulated by the demodulation circuit 14, and is applied from the terminal 30 to an acoustic output means (not shown). Further, only the right channel acoustic signal is output from the band pass filter 13, and the signal is demodulated by the demodulation circuit 15 and given from the terminal 31 to the acoustic output means. In this way, the acoustic signal is reproduced.

Next, when the signal input to the reproducing apparatus 1 is a high resolution signal, the video signal in the output of the demodulation circuit 5 is the low pass filter 7, the terminal 3b of the changeover switch 3, and the common terminal 3c.
Is supplied to the video processing circuit 9 through the, and video signal processing is performed, and is supplied from the terminal 29 to the video display means.
The video is reproduced in this way. On the other hand, the acoustic signal passes through the bandpass filter 8 and is given to the balanced modulator 10. Further, the balanced modulator 10 is supplied with an output of a carrier wave generation circuit 11 for generating a carrier wave signal having a predetermined frequency c determined as described later.

FIG. 8 is a diagram showing a frequency spectrum of the output of the balanced modulator 10. In the balanced modulator 10, the frequency c
, The frequencies 9 and 10 of which the acoustic carrier frequencies 5 and 6 of each channel are added, and the frequencies of which are subtracted 7,
Frequency modulation using 8 as a new carrier is performed. That is, the frequencies 9, 10, 7, and 8 are values shown by the following third to sixth equations.

9 = c + 5 (3) 10 = c + 6 (4) 7 = c-6 (5) 8 = c-5 (6) Here, for the frequency c, the following formulas 7 and 8 are satisfied. Is set in advance.

7 = 2 (7) 8 = 3 (8) By the modulation operation of the balanced modulator 10 as described above, the acoustic signal frequency-modulated by the carrier frequencies 5 and 6 in the high-resolution signal has a frequency of 8 and 7, It is converted into a signal modulated by the frequencies 3 and 2. In other words, the standard video signal is converted into a signal having the same frequency band as the audio signal, and the left and right channels have the same arrangement relationship.

After such a modulation operation is performed, the output of the balanced modulator 10 is given to the bandpass filters 12 and 13 via the terminal 4b and the common terminal 4c of the changeover switch 4. Then, similar to the case of the standard video signal, the demodulation circuits 14, 15
Sound reproduction is performed from the terminals 30 and 31 via the sound output means.

As described above, in the reproducing apparatus 1 of the present embodiment, the video processing circuit 9 and the demodulation circuit 1 are used regardless of whether it is a standard video signal or a high resolution signal.
4 and 15 can be used in common, and it is not necessary to provide them separately according to each of the above cases, and the circuit can be greatly simplified.

As described above, according to the present invention, it is possible to selectively reproduce the first signal and the second signal having mutually different video frequency bands, and it is possible to greatly simplify the circuit configuration. .

Particularly, according to the present invention, the first bandpass filter 8 and the detection circuit 2 are used for discriminating the first signal and the second signal, and such a configuration is relatively simple, and moreover, the first bandpass filter is used. 8 is used for discriminating the first and second signals, and also has a function of selectively extracting the third and fourth acoustic signals 26 and 27 from the first band-pass filter 8. The configuration can be simplified.

Furthermore, according to the present invention, the output of the detection circuit 2 causes the first
And the second changeover switches 3 and 4 are simultaneously changed over so that the standard video signal 22 and the first and second audio signals 2 are transmitted.
4, 25, and the high-resolution video signal 23 and the third
Also, the fourth acoustic signals 26 and 27 can be derived and reproduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of a reproducing apparatus 1 according to an embodiment of the present invention, FIG. 2 is a block diagram showing an electrical configuration of a modulator 16, and FIG. 3 is a frequency spectrum of a standard video signal. FIG. 4, FIG. 4 is a diagram showing a frequency spectrum of a high-resolution signal, FIG. 5 is a diagram showing frequency characteristics of the low-pass filter 6, FIG. 6 is a diagram showing frequency characteristics of the low-pass filter 7, and FIG. FIG. 8 is a diagram showing the frequency characteristics of the pass filter 8, and FIG. 8 is a diagram showing the frequency spectrum of the output of the balanced modulator 10. 1 ... Reproducing device, 2 ... Detection circuit, 3, 4 ... Changeover switch, 6, 7 ... Low pass filter, 8 ... Band pass filter, 10 ... Balanced modulator, 11 ... Carrier wave generation circuit

Claims (1)

[Claims] 1. (a) A first demodulator for demodulating first and second signals.
In the demodulation circuit 5, the demodulated first signal is modulated using the standard video signal 22 having a frequency band lower than the first frequency f1 and the second frequency f2 higher than the first frequency f1 as a carrier frequency. Or a right first acoustic signal 24 and a left or right second acoustic signal 25 modulated with a third frequency f3 higher than the second frequency f2 as a carrier frequency, The demodulated second signal has a high resolution video signal 23 having a frequency band lower than the fourth frequency f4 higher than the third frequency f3 and a fifth frequency higher than the fourth frequency f4 as a carrier frequency. Or the third same as the second acoustic signal 25 on the right
Such a first demodulation circuit having an acoustic signal 26 and a fourth acoustic signal 27 identical to the left or right first acoustic signal 24 modulated with a sixth frequency f6 higher than the fifth frequency f5 as the carrier frequency. 5 and (b) the output of the first demodulation circuit 5 is given, and the first frequency f
First low-pass filter 6 having cutoff frequency 1
(C) The output of the first demodulation circuit 5 is given, and the fourth frequency f
Second low-pass filter 7 with cutoff frequency 4
(D) The first changeover switch 3 for switching and deriving the outputs of the first and second low-pass filters 6 and 7, and (e) the output of the first demodulation circuit 5 is given, and the third and fourth acoustic waves are given. The first bandpass filter 8 for deriving only the signals 26 and 27, (f) the detection circuit 2 for detecting the output of the first bandpass filter 8, and (g) When the carrier frequency is fc, fc = f2 + f6 = a carrier wave generating circuit 11 for generating a carrier wave satisfying f3 + f5, and (h) third and fourth carrier waves from the first band pass filter 8.
A circuit 10 for obtaining the frequency difference between the acoustic signal and the carrier wave from the carrier wave generating circuit 11, and (i) a second switching for deriving by switching between the output of the first demodulation circuit 5 or the output of the circuit 10 for obtaining the frequency difference. A switch 4, (j) a second bandpass filter 12 for deriving only an acoustic signal of a second frequency f2, (k) a third bandpass filter 13 for deriving only an acoustic signal of a third frequency f3, (l ) A second demodulation circuit 14 that demodulates the output of the second bandpass filter 12, and (m) a third demodulation circuit 15 that demodulates the output of the third bandpass filter 13 are included. When the third and fourth acoustic signals are not detected, the output of the first low-pass filter 6 is derived by the first changeover switch 3 and the output of the first demodulation circuit 5 is derived by the second changeover switch 4. A circuit for deriving the output of the second low-pass filter 7 by the first changeover switch 3 and detecting the difference between the frequencies by the first changeover switch 4 when the detection circuit 2 detects the third and fourth acoustic signals. A reproducing device characterized by deriving 10 outputs.