JPH0634293B2 - Video disc audio recorder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a recording device for audio signals of a video disc.

<Outline of the Invention> The present invention relates to an audio recording device for FM-modulating an audio signal converted into a digital signal and recording the same on a video disk,
The FM carrier frequency is selected as a specific frequency, and the pilot signal is recorded at the recording start position of the digital audio signal.

<Prior Art> Usually, an analog audio FM recording system is adopted for recording an audio signal on a video disk, and the analog audio signals of the first and second channels are FM-modulated respectively and then recorded on the disk together with the video signal. It is generally recorded, but the signal is lost during playback due to scratches on the disc itself,
Noise may appear in the playback audio. Therefore, a method has been proposed in which an audio signal is converted into a digital signal, further code-modulated, and the digitally coded audio signal is FM-recorded. In this case, the influence of noise due to the loss of the reproduced signal can be reduced, and analog audio This is effective because it can reproduce higher quality audio than the FM recording method.

<Problems to be Solved by the Invention> However, a problem in digitally encoding an audio signal and performing FM recording is that beat interference occurs between the FM modulated wave of the digitally encoded audio signal and the video signal. .

<Means for Solving the Problems> The present invention has been made in view of the above circumstances, and shows that the A / D converting means for converting an input audio signal into a digital audio signal and digital audio recording. Pilot signal generating means for generating a pilot signal, inserting means for inserting the pilot signal at a recording start position of the digital audio signal, “H” of the digital audio signal,
An FM modulation means for setting the FM carrier frequency of the signal level of "L" to the same frequency as the FM carrier frequency of the first and second audio channels adopted in the analog audio FM recording system. Is.

<Operation> In the video disk audio recording apparatus of the present invention, the FM
Since the FM carrier frequency of the digital voice is set to match the FM carrier frequency of the first and second voice channels of the analog voice FM recording system by the modulating means, the first and second voices are originally set. Since the FM carrier frequency of the channel is set to a value at which the beat interference with the video signal does not appear most, the audio beat does not appear on the screen.

In addition, a video disc player capable of reproducing both a video disc on which digital audio is FM-recorded by a frequency relationship in the video disc audio recording device of the present invention and a video disc recorded by an existing analog audio FM recording device. When manufactured, it becomes possible to share a part of the audio signal processing circuit system such as the FM demodulator. Further, in this case, the pilot signal is detected to detect the known analog audio FM recording method and the digital audio FM recording according to the present invention. The system is discriminated, and the operation of the audio signal processing circuit is automatically switched based on the discrimination output, and the discs of both systems can be reproduced.

<Example> The present invention will be described below with reference to an example shown in the drawings. First
The figure shows a schematic block diagram of the recording system of the video disk audio recording apparatus of the present invention.

In FIG. 1, the audio signals of the first and second audio channels respectively input to the input terminals 1 and 2 are analog signals.
It is supplied to the digital modulator 9 which is converted into a digital signal by the digital (A / D) converters 5 and 6. On the other hand, the recording start signal input to the input terminal 3 is supplied to the pilot signal generator 7 and the address signal generator 8. At this time, as shown in FIG. ₁ only "H" (High) or "L" pilot signals maintained (Low) is supplied to the digital modulator 9 is generated. The time width T ₁ is sufficiently longer than the time of digital data, and for example, several hundred msec is suitable. Therefore, this predetermined time T
After the passage of ₁ , the digital voice signals from the A / D converters 5 and 6 and the address signal from the address signal generator 8 are added with error correction codes in the digital modulator 9 and digitally modulated by PCM or the like. After that, it is FM-modulated by the coded digital data which is applied to the FM modulator 10. Here, as the FM carrier frequency of the FM modulator 10, the carrier frequencies of “H” and “L” of digital data are 3.43 MHz and 3.73 MHz which are the FM carrier frequencies of two audio channels of the VHD system.
To match exactly. That is, as shown in FIG. 3, the input digital data string to the FM modulator 10 is
_The spectrum distribution has peaks at ₁ (= 3.43MHz) and ₂ (= 3.73MHz).

On the other hand, the video signal input to the input terminal 4 is supplied to the video signal processing circuit 11, where it is subjected to appropriate signal processing such as chroma low frequency conversion and pre-emphasis, and then supplied to the mixing circuit 12. In the mixing circuit 12, the FM modulator 10
The FM wave of the digital audio obtained from the above and the video signal after the signal processing obtained from the video signal processing circuit 11 are mixed and supplied to the FM modulator 13, where they are modulated into the FM signal to be recorded on the disc. The spectrum of the input / output signal of the FM modulator 13 is shown in FIGS. 4 and 5, respectively.
This is the same as the case of performing FM recording on a disk according to the conventional general analog audio FM recording method.

The above is the outline of the digital audio processing and pilot signal processing operation of the recording system when the audio signal is digitally coded and recorded on the disk by the video disk audio recording apparatus of the present invention.

Next, an example of a video disk reproducing apparatus suitable for reproducing a disk recorded by the video disk audio recording apparatus of the present invention will be described with reference to FIG.

In FIG. 6, the disc recording FM signal is detected by the pickup device 14, amplified by the preamplifier 15, and then supplied to the FM demodulator 16 where it is FM demodulated. This demodulated signal is obtained in a state where the video signal of the luminance signal and the color signal and the audio FM signal are mixed as shown in FIG. The middle video signal component is a low pass filter 17
To a video signal processing circuit, where appropriate signal processing such as dropout compensation, chroma high frequency conversion, time base correction, etc. is performed, and a standard color video signal is derived at a video output terminal 19.

On the other hand, the voice FM signal is separated into two FM carriers ₁ and ₂ via the band pass filters 20 and 21, and is supplied to the FM demodulators 22 and 23 at the next stage and is FM demodulated.
The demodulation output of the FM demodulator 22 is the pilot signal detection circuit 2
4 and the pilot signal is detected by the operation described in detail later. Now, when a pilot signal is detected in the detection circuit 24, each switching circuit 2
The switches 5, 26, 27 are switched to the terminal side, respectively. In this case, the digital audio signal obtained as the demodulated output of the FM demodulator 22 is supplied to the digital audio signal processing circuit 30 via the switching circuit 25, where appropriate digital code demodulation, error detection / correction, D / A conversion and the like are performed. As a result, high-quality audio signals are output to the audio output terminal 3 via the switching circuits 26 and 27.
1, 32.

Next, the pilot signal detection operation will be described in more detail. When a digital audio FM recording disk is reproduced, since the pilot signal is recorded in advance at the recording start position of the digital audio signal, the FM demodulator 22 outputs a digital signal as shown in FIG. It is supplied to the signal detection circuit 24. In this case, the pilot signal maintained at the "H" level for the time T ₁ is derived before the digital voice signal. The pilot signal detection circuit 24 is composed of, for example, a retrigger type one-shot multi circuit 33 and a flip-flop circuit 34 as shown in FIG. 8, and the digital signal shown in FIG. When input, the one-shot multi-circuit 33 is triggered by the rising edge of the pulse. Here, the time width T ₂ of the one-shot pulse is set in advance to the relationship of T ₃ << T ₂ << T ₁ by the resistor R ₁ and the capacitor C ₁ attached to the one-shot multi-circuit 33. To do. Here, T ₃ is the unit pulse width of digital data, which is usually 1
Since it is less than μsec, the one-shot pulse width T ₂ may be selected to be, for example, about 1 msec. At this time, the output of the one-shot multi-circuit 33 is inverted from "H" to "L" only during the pilot signal detection period T ₁ as shown in FIG. 7, and is always "H" during the other period, that is, the digital data period. "Maintained at the level. Then, the output of the one-shot multi-circuit 33 changes from "H" to "L", the flip-flop circuit 34 in the subsequent stage is set at the falling edge, and its output is inverted from "L" to "H" as shown in FIG. , And thereafter maintained at "H" level. As a result, when the pilot signal detection circuit 24 detects the pilot signal recorded at the recording start position of the digital audio signal, the "H" level detection signal is constantly applied to the switching circuits 25, 26 and 27. As described above, the switching element of each switching circuit 25, 26, 27 is switched to the terminal side.

Next, the operation when the analog audio FM recording disk is reproduced in the reproducing apparatus will be described. In this case, the operations of the pickup device 14, the preamplifier 15, the FM demodulator 16, the low-pass filter 18, and the video signal processing circuit are the same as those in the reproducing operation of the digital audio FM recording disk described above. The description is omitted. The demodulation output of the FM demodulator 16 is the bandpass filter 2
It is separated into two FM carriers ₁ and ₂ by 0 and 21, and supplied to the FM demodulators 22 and 23, respectively.
Then, the FM demodulator 22 demodulates the analog audio signal of the first audio channel, and the FM demodulator 23 demodulates the analog audio signal of the second audio channel to derive them. In this case, the demodulated analog audio signal does not include the pilot signal, so that the output of the pilot signal detection loop 24 is always at "L" level, and the switching elements of the switching circuits 25, z26, 27 are It has been switched to the terminal side. Therefore, in this case, the audio signal of the first channel is supplied to the analog audio signal processing circuit 28 via the switching circuit 25, where appropriate signal processing such as de-emphasis and noise reduction is performed, and then the switching circuit 26. Through the audio output terminal 31. Similarly, the audio signal of the second channel is subjected to appropriate signal processing in the analog audio signal processing circuit 29, and then led to the audio output terminal 32 via the switching circuit 27.

<Effects of the Invention> According to the video disk audio recording apparatus of the present invention, when the digital audio signal converted into the digital signal as described above is FM-modulated and recorded on the disk, "H" and "H" of the digital audio signal. Since the carrier frequency of the L ”signal level is set to be the same as the FM carrier frequency of the first and second audio channels adopted in the current analog audio FM recording system, the video signal There is no fear of causing beat interference with.

Further, according to the recording apparatus of the present invention, since the pilot signal is inserted at the recording start position of the digital audio signal, the disk can perform analog audio recording by detecting the presence or absence of the pilot signal. It can be discriminated whether or not it is digital audio recording, and by switching the audio processing circuit, it becomes possible to reproduce the disk of both recording systems.

[Brief description of drawings]

FIG. 1 is a block diagram of a recording system of a video disk audio recording apparatus of the present invention, FIG. 2 is a waveform diagram of a digital audio signal according to a recording system by the recording apparatus, and FIG. 3 is an FM modulator in FIG. 10 is a modulation operation characteristic diagram, FIG. 4 is an input signal spectrum of the FM modulator 13 in FIG.
FIG. 6 is an output signal spectrum of the FM modulator 13, FIG. 6 is a block diagram of a video disc reproducing device for reproducing a video disc recorded by the recording device of the present invention,
FIG. 7 is a signal waveform diagram for explaining the operation of the pilot signal generating circuit in the video disc reproducing apparatus, and FIG. 8 is a concrete circuit configuration diagram of the pilot signal generating circuit. 5, 6 ... A / D converter, 7 ... Pilot signal generator, 8 ... Address signal generator, 9 ... Digital modulator, 10 ... FM modulator.

Claims (1)

[Claims] 1. An FM audio signal converted into a digital signal.
In a video disk audio recording device for modulating and recording on a video disk, A / D conversion means for converting an input audio signal into a digital audio signal, and pilot signal generation means for generating a pilot signal indicating digital audio recording. Inserting means for inserting the pilot signal at a recording start position of the digital audio signal, and FM carrier frequencies of signal levels of “H” and “L” of the digital audio signal are adopted in an analog audio FM recording system. A video disk audio recording device, comprising: an FM modulation unit for setting the same frequency as the FM carrier frequency of the first and second audio channels.