JPH0555948B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a video disc audio reproducing apparatus for reproducing audio signals recorded on a video disc.

(Prior art) Conventionally, there have been video discs in which analog audio signals are recorded with FM modulation, video discs in which audio signals are converted to digital signals and then FM modulated, and digital audio signals and analog audio signals are mixed. There are video discs etc. that were recorded. Conventionally, these video discs have been individually played back by playback devices suitable for each recording method.

(Object of the Invention) An object of the present invention is to provide a video disk audio playback device that detects the types of each of the video disks described above and plays back analog audio and digital audio appropriately according to the detected type of video disk. shall be.

(Structure of the Invention) The video disk audio playback device of the present invention converts the audio signal into a digital signal and then performs FM modulation and records the video disk and analog audio signal.
A playback device for playing back a video disc recorded with FM modulation and a video disc recorded with a mixture of digital and analog audio signals, comprising an analog audio processing circuit and a digital audio processing circuit, detecting means for detecting pilot signals recorded at the start and end portions of the digital audio processing circuit; and detecting means for detecting the pilot signals recorded at the start and end portions; and switching means for switching to the analog audio processing circuit side when a pilot signal recorded in the analog audio processing circuit is detected.

(Operation) The pilot signal recorded at the start and end portions of the digital audio signal is detected by the detection means. The switching means selects the digital audio processing circuit when it detects the pilot signal recorded at the beginning of the digital audio signal, and the analog signal processing circuit when it detects the pilot signal recorded at the end of the digital audio signal. Switch the signal appropriately.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

First, before explaining the audio playback device, we will explain recording system signal processing for digitizing and recording audio and recording pilot signals at the beginning and end of the digitized audio signal, as shown in Figures 4 to 8. Explain with reference to.

In FIG. 4, which shows the recording system signal processing block, an analog audio signal _S1 of channel 1 inputted from terminal 1 is converted into a digital audio signal S2 by an analog-to-digital converter (A/D converter) _6.
and output to the digital modulator 7.

Analog audio signal S ₃ of channel 2 input from terminal 2 is converted into digital audio signal S ₄ by analog-to-digital converter 8 and output to digital modulator 7 .

On the other hand, a recording start signal _S5 for a disk (not shown) inputted from the terminal 3 is inputted to a pilot signal generator 9 and an address signal generator 10, respectively.

In the pilot signal generator 9, as shown in FIG. 5, the recording start signal _S5 becomes "H" for a time _T1 .
A pilot signal _S6 indicating the start of digital audio recording A is generated at the same level. In addition, when recording a mixture of digital audio and analog audio on an audio channel, digital audio recording A
The level was set to "L" for a time T ₂ from the end of the
A pilot signal _S7 indicating the end of digital audio recording A is generated. These pilot signals S ₆ and S ₇ are output to a digital modulator 7. In addition, time
The widths of T ₁ and T ₂ are set to be sufficiently long compared to the time of the digital data string, for example, several hundred milliseconds. Further, in this example, the pilot signal _S6 indicating the start of digital audio recording is set to the "H" level, and the pilot signal _S7 indicating the _end is set to the "L" level. ₇ may be set as "H" level.

The address signal generator 10 extracts the address signal _S8 from the recording start signal _S5 . This address signal _S8 is output to the digital modulator 7.

The digital audio signals S ₂ , S ₄ and address signal S ₈ inputted to the digital modulator 7 are subjected to digital modulation such as addition of an error correction code after a time T ₁ has elapsed based on the pilot signal S ₆ . The signal is then subjected to FM modulation by the FM modulator 11 at the next stage and output to the mixer circuit 12.

At this time, the FM carrier frequency is selected so that the "L" level and "H" level of the digital data match the carrier frequencies f ₁ and f _{2 of channel 1 or 2} in the case of conventional analog audio recording. That is, as shown in Figure 6,
Input digital data string 15 to FM modulator 11
has a bimodal spectrum distribution 16 with peaks at carrier frequencies f ₁ and f ₂ , which prevents beat damage to the video signal.

On the other hand, the video signal _S9 input from terminal 4 is
After the video signal processing unit 13 performs video signal processing such as color converter and pre-emphasis, the signal is output to the mixer circuit 12.

The mixing circuit 12 mixes the FM wave of the digital audio signal and the video signal.
Digitally recorded FM signal S ₁₀ with FM modulator 14
The signal is modulated and output to terminal 5.

Output of mix circuit 12 and FM modulator 14
The signal spectrum distribution of each output signal is as shown in FIGS. 7 and 8, which is the same as in the case of conventional analog audio.

Next, an audio reproducing apparatus for a video disc on which audio signals are recorded by the above-described signal processing will be described with reference to FIGS. 1 to 3.

Note that the description of the video processing section and tracking servo system will be omitted here.

The recording FM signal _S11 detected from the video disc (not shown) by the pickup circuit 20 is
Properly amplified by preamplifier 21, and then sent to FM demodulator 2
2, and after the video signal and the FM signal of the audio channel are mixed and reproduced, the video signal processing circuit 23, the first bandpass filter 24, and the second bandpass filter 2
5, respectively.

The video signal S ₁₂ input to the video signal processing circuit 23 is subjected to dropout correction, color converter, and time base correction, and then reproduced as a standard color video signal and outputted to the terminal 26.

The FM signal S ₁₃ of the audio channel input to the first bandpass filter 24 is separated here into a signal S ₁₄ of the FM carrier frequency f ₁ , which is demodulated by the FM demodulator 27 at the next stage and sent to the selector switch 28 and the pilot. Each signal is output to the signal detection circuit 31. In addition, the FM signal S ₁₃ of the audio channel input to the second bandpass filter 25 is separated here into a signal S ₁₅ of FM carrier frequency f ₂ , demodulated by the next stage FM demodulator 29, and analog audio processing is performed. The signal is output to the circuit 30 and is reproduced there.

In addition, in this example, digital audio recording is shown in the case where the FM carrier frequency f ₁ of the audio channel is demodulated and reproduced, but the same is true when the FM carrier frequency f ₂ of the audio channel 2 is demodulated and reproduced. Only the relationship between the "H" level and "L" level of the signal is reversed.

The pilot signal detection circuit 31 detects the demodulated
Receiving the signal _S16 of the FM carrier frequency _f1 , the pilot signals _S5 and _S7 respectively recorded at the start and end parts of the digital audio recording A are detected and switched to the respective changeover switches 28, 34, and 35. Outputs control signal _S17 .

Here, the control signal _S17 output from the pilot signal detection circuit 31 will be explained.
The pilot signal detection circuit 31 is comprised of a retrigger type one-shot multivibrator 40 and a flip-flop 41, as shown in FIG.

Figures 2a, b, and c show timing charts of the pilot signal detected by this pilot signal detection circuit 31, and Figure 2a shows the timing chart of the FM demodulator 27 when digital audio recording and analog audio recording are mixed. The output waveform of is shown. That is, as explained in the recording system signal processing, T ₁ is added to the beginning of digital audio recording A as a pilot signal.
A signal of "H" level is recorded for a time of T2, and a signal of a "L" level is recorded for a time of _T2 at the end of digital audio recording A. Now, when a signal having the waveform shown in FIG. 2a is input from the terminal 42, the retrigger type one-shot multivibrator 40
The output (Q) rises at the rising edge of the input waveform, and the resistance
The "H" level is maintained from the rising edge for a pulse width of time constant T _w determined by R ₁ and capacitor C ₁ . Here, the time constant T _w needs to be set shorter than the time T ₁ and sufficiently longer than the data pulse width.
In this example, it is set to about 1 msec. Therefore,
The signal output from the output (Q) of the one-shot multivibrator 40 temporarily goes to the "L" level during the above-mentioned time _T1 , but is retriggered and remains at the "H" level in the digital audio recording section A. ,
The waveform falls to the "L" level during time _T2 (see Figure 2b).

Therefore, from the flip-flop 41,
The switching control signal _S17 rises at the first falling edge of this output waveform and falls at the subsequent falling edge.
See Figure c].

The changeover switches 28, 34, and 35 switch the analog audio processing circuits 30, 32 in response to the changeover control signal _S17 from the pilot signal detection circuit 31.
and the digital audio processing circuit 33. That is, the switching control signal
When _S17 is at “L” level, FM demodulator 27
A signal S ₁₄ from the input signal S 14 is input to the analog audio processing circuit 32 via the changeover switch 28 . The audio signal reproduced here is output to the terminal 36 via the changeover switch 34, and the audio signal reproduced by the analog audio processing circuit 30 is outputted to the terminal 37 via the changeover switch 35. . Furthermore, when the switching control signal S ₁₇ is at "H" level, the signal S ₁₄ from the FM demodulator 27
is input to the digital audio processing circuit 33 via the changeover switch 28. The digital audio processing circuit 33 performs digital code demodulation, error detection,
It performs processing such as error correction and digital-to-analog conversion, and outputs high-quality reproduced audio signals to terminals 36 and 37 via switch switches 34 and 35, respectively.

(Effects of the Invention) The video disk audio reproducing apparatus of the present invention includes a detection means for detecting a pilot signal recorded at the start and end portions of digital audio, and a detection means for detecting a pilot signal recorded at the start portion by the detection means. When a signal is detected, it switches to the digital audio processing circuit side,
Since the configuration is equipped with a switching means that switches to the analog audio processing circuit side when a pilot signal recorded in the end section is detected, the switching operation to each audio processing circuit can be quickly and reliably performed in accordance with the recording signal to the disk. This is something that can be done.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention, in which FIG. 1 is a schematic block diagram of a video disk audio reproducing device, FIG. 2 is a timing chart of a pilot signal detection circuit, and FIG. 3 is a pilot signal detection circuit. Circuit configuration diagrams, Figures 4 to 8 show an example of signal processing for recording on a disk, Figure 4 is a schematic block diagram of signal processing, and Figure 5 shows the relationship between digital audio signals and pilot signals. Figure 6 shows the FM modulation spectrum of the audio channel, Figure 7 shows the signal spectrum of the output of the mix circuit, and Figure 8 shows the signal spectrum of the output of the FM modulator. 24... First band pass filter, 25... Second band pass filter, 27, 29... FM demodulator, 28, 34, 35... Changeover switch, 30,
32...Analog audio processing circuit, 31...Pilot signal detection circuit, 33...Digital audio processing circuit.

Claims (1)

[Claims] 1 FM after converting an audio signal to a digital signal
A playback device that plays back video discs recorded with modulated signals, video discs recorded with FM modulation of analog audio signals, and video discs recorded with a mixture of digital audio signals and analog audio signals, and which plays analog audio signals. a detection means having a processing circuit and a digital audio processing circuit and detecting a pilot signal recorded at a start part and an end part of the digital audio; and a detection means for detecting a pilot signal recorded at the start part by the detection means A video disk audio reproducing device characterized in that it is provided with a switching means that switches to the digital audio processing circuit side when a pilot signal recorded in the end section is detected, and switches to the analog audio processing circuit side when a pilot signal recorded in the end section is detected. .