JPH07114486B2 - Disc player - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc reproducing apparatus for reproducing signals from a disc on which frequency-modulated video signals and audio signals are recorded.

Conventional technology When reproducing a frequency-modulated video signal and audio signal from a recorded disc, generally, there is a fluctuation in the time axis that was not present in the recording signal due to eccentricity of the disc or mechanical vibration. The signal is regenerated. When the reproduced signal has such a fluctuation (jitter) on the time axis, the influence thereof becomes a disturbance of direct synchronization with the video signal and, at the same time, appears as color unevenness when the video signal is a composite signal. On the other hand, since the frequency component of the jitter is demodulated with respect to the audio signal together with the audio signal, the disk rotational frequency and its harmonic components are mixed in the reproduced audio, resulting in annoying noise. For this reason, this type of disc reproducing apparatus has been devised to suppress the above-mentioned adverse effects. Hereinafter, description will be given with reference to FIG. FIG. 4 shows a block diagram of an example of a conventional disc reproducing apparatus. The reproduction signal read from the disc by the reproduction means 1 is separated in the video signal band by the first demodulation means 2, FM demodulated and output as a reproduction video signal. The phase comparison means 3, the loop filter 4, the clock generation means 12 and the frequency division means 8 constitute a phase locked loop (PLL), and generate a clock signal phase-locked with the horizontal synchronizing signal or the burst signal of the reproduced video signal. . Jitter is removed from the reproduced video signal by writing the reproduced video signal in the digital memory 13 in synchronization with this clock signal and reading it with a stable clock that is obtained by the reference clock oscillator 14 and does not fluctuate on the time axis. On the other hand, the second demodulation means 10 separates the audio signal band from the reproduced signal, FM demodulates and outputs the reproduced audio signal, but as described above, this reproduced audio signal contains a noise component due to jitter. . On the other hand, at the input of the clock generating means 12, a signal almost equivalent to the frequency fluctuation component of the reproduced signal, that is, the noise component in the reproduced audio signal appears. Therefore, this noise component is canceled by adding a proper gain to the adding means 11 and adding the gain to the reproduced voice signal. In this way, the influence of the jitter is removed from the reproduced audio signal (for example, Japanese Patent Laid-Open No. 63-121386).

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention A signal processing circuit in a disc reproducing apparatus tends to be steadily integrated and digitized in order to improve performance and reliability and reduce cost. In order to respond to such a tendency, the applicant has previously proposed Japanese Patent Application No. 1-2003 (Japanese Patent Application Laid-Open No. 2-2003).
No. 009) "Phase synchronizer" filed. However, in order to remove the influence of the time-axis fluctuation of the reproduction signal on the reproduction audio signal, it is possible to newly add the means described in the “Prior Art” of the present application to the configuration of the above-mentioned prior application. The characteristic of being suitable for integration and digitization described above is lost.

In view of the above problems, the present invention is a disc reproducing apparatus having a configuration suitable for integration and digitization, capable of removing time-axis fluctuations from a reproduced video signal and removing noises accompanying the time-axis fluctuations from a reproduced audio signal. Is intended to provide.

Means for Solving the Problems In order to solve the above-mentioned problems, a disk reproducing apparatus of the present invention is a reproducing apparatus for reading a signal from a disk in which a video signal and an audio signal are frequency-modulated and synthesized, and outputting a reproduction signal. Means, first demodulation means for separating and demodulating a frequency-modulated video signal from the reproduction signal to output a reproduction video signal, and a phase of the horizontal synchronization signal or burst signal of the reproduction video signal and the internal synchronization signal. Phase comparison means for comparing and outputting a phase difference signal, a loop filter for correcting the frequency phase characteristic of the phase difference signal, a variable frequency oscillating means for generating a signal of a frequency based on the output of the loop filter, and A signal generating means for generating a reference signal of a frequency, a frequency addition of the output of the variable frequency oscillating means and the reference signal are performed, and the addition result is clocked. A frequency converting means for outputting as a clock signal, a frequency dividing means for dividing the clock signal to generate the internal synchronizing signal and supplying it to the phase comparing means, and a frequency converting means for adjusting the frequency of the output signal of the variable frequency oscillating means. Frequency detecting means for outputting a signal
Second demodulation means for separating and demodulating a frequency-modulated audio signal from the reproduction signal to output a reproduction audio signal, and addition means for adding the output of the frequency detection means and the reproduction audio signal at an appropriate ratio. It is equipped.

Effect The present invention can eliminate the influence of jitter from the reproduced audio signal by connecting the video processing circuit and the audio processing circuit with the addition of a small amount of hardware by the above configuration.

Embodiment A disk reproducing apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a disc reproducing apparatus according to an embodiment of the present invention. 5 is a variable frequency oscillating means, 6 is a signal generating means, 7 is a frequency converting means, and 9 is a frequency detecting means. . Also, the reproducing means 1,
The first demodulating means 2, the phase comparing means 3, the loop filter 4, the frequency dividing means 8, the second demodulating means 10 and the adding means 11 are the same as the elements shown in FIG. The operation of reproducing the signal from the disc in the reproducing means 1 and obtaining the reproduced video signal through the first demodulating means 2 is the same as in FIG. The phase comparing means 3, the loop filter 4, the variable frequency oscillating means 5, the signal generating means 6, the frequency converting means 7 and the frequency dividing means 8 constitute a phase locked loop. The operation of the loop is similar to that of FIG. 4 except that the clock generating means 12 is replaced with the variable frequency oscillating means 5, the signal generating means 6, and the frequency converting means 7 as compared with FIG. The means 7 outputs a clock signal which is phase-synchronized with the horizontal synchronizing signal or the burst signal of the reproduced video signal. Although not shown in FIG. 1, the clock signal is given to a digital memory similar to that shown in FIG. 4 as a write clock for the reproduced video signal, and is read out from the digital memory by the reference clock signal so that there is no jitter. The reproduced video signal is output. The frequency detecting means 9 outputs a signal according to the oscillation frequency of the variable frequency oscillating means 5, and operates almost in the opposite manner to the variable frequency oscillating means 5. As a result, a signal which is almost proportional to the input of the variable frequency oscillator 5 is obtained as the output of the frequency detector 9. In the adding means 11, the output of the frequency detecting means 9 is added to the reproduced audio signal obtained by the second demodulating means at an appropriate ratio, and the noise component due to the jitter is canceled out from the reproduced audio signal. It is similar to FIG.

FIG. 2 shows a concrete example of the frequency conversion means 7, 15 is an exclusive OR (EX-OR) gate, and 16 is a bandpass filter. A binary signal from the signal generating means 6 and the variable frequency oscillating means 5 is inputted to the EX-OR gate 15. Since the exclusive OR operation is a multiplication in which the input signal is regarded as a binary signal of (1, -1), beat components of each input frequency appear in the output. The band pass filter 16 extracts only a necessary component from these beat components, for example, the sum component of the fundamental frequencies of the respective inputs. When the output frequency of the variable frequency oscillating means 5 is changed in this configuration, the output frequency of the bandpass filter 16 is changed accordingly, but the value is offset by the output frequency of the signal generating means 6. If the frequency center value of the clock signal to be finally generated is relatively high and the frequency fluctuation width is sufficiently smaller than the center value, the output frequency of the signal generating means 6 should be sufficiently close to this frequency center value. Since the output frequency of the variable frequency oscillating means 5 is relatively low and the variable width can be wide, it can be easily realized by a digital circuit. Although the EX-OR gate is used as the gate means in this example, the gate means is not limited to this, and an AND gate, an OR gate, another gate, or simply an analog switch may be used. Further, the bandpass filter 16 needs to sufficiently attenuate the adjacent unnecessary beat component in order to suppress the jitter of the output signal, and can be configured by a filter having a relatively steep characteristic such as a ceramic filter. .

FIG. 3 shows a concrete configuration example of the frequency detecting means 9, where 17 is a mono-multivibrator and 18 is a low-pass filter.
The mono-multivibrator 17 receives the output of the variable frequency oscillating means 5 and outputs a pulse having a constant width in synchronization with its edge, for example, a rising edge. In this case, the output pulse width of the mono-multivibrator 17 is selected to be smaller than the minimum value of the output signal period of the variable frequency oscillation means 5. The low pass filter 18 smoothes this pulse signal and removes ripple components. As a result, at the output of the low-pass filter 18, a signal which is almost proportional to the oscillation frequency of the variable frequency oscillation means 5 is obtained. Since the frequency of the variable frequency oscillating means 5 can be selected to be relatively low and sufficiently higher than the voice band, the mono-multivibrator 17 can be easily configured using a counter, and the low-pass filter is simple. A filter having a configuration such as R / C may be used.

Although the configuration using the mono-multivibrator as the frequency conversion means is shown here, the configuration is not limited to this configuration as long as it receives the output of the variable frequency oscillation means and outputs a signal corresponding to the frequency. Absent.

As described above, according to the present invention, even when the video signal system is digitized, the addition of a small amount of hardware enables connection with an audio processing circuit to remove the influence of jitter from reproduced audio. It is possible to realize a disc reproducing apparatus suitable for the.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a disc reproducing apparatus according to the present invention, FIG. 2 is a configuration diagram of an example of frequency converting means, FIG. 3 is a configuration diagram of an example of frequency detecting means, and FIG.
FIG. 1 is a block diagram showing the structure of a conventional disc reproducing apparatus. 1 ... Reproducing means, 2 ... First demodulating means, 3 ... Phase comparing means, 4 ... Loop filter, 5 ... Variable frequency oscillating means, 6 ... Signal generating means, 7 ... Frequency converting means, 8
...... Dividing means, 9 ...... Frequency detecting means, 10 ...... Second demodulating means, 11 ...... Adding means.

Claims (2)

[Claims] 1. A reproducing means for reading a signal from a disc on which a video signal and an audio signal are frequency-modulated and synthesized and recorded to output a reproduced signal, and a demodulated frequency-modulated video signal from the reproduced signal. A first demodulation means for outputting a reproduced video signal, a phase comparison means for comparing the phases of a horizontal synchronizing signal or a burst signal of the reproduced video signal and an internal synchronizing signal and outputting a phase difference signal, and the phase difference signal A loop filter that corrects the frequency and phase characteristics of
Variable frequency oscillating means for generating a signal of a frequency based on the output of the loop filter, signal generating means for generating a reference signal of a specific frequency, and frequency addition of the output of the variable frequency oscillating means and the reference signal. Frequency conversion means for outputting the addition result as a clock signal, frequency division means for dividing the clock signal to generate the internal synchronization signal and supplying it to the phase comparison means, and frequency of the output signal of the variable frequency oscillation means. , A second demodulation means for separating and demodulating a frequency-modulated audio signal from the reproduction signal to output a reproduction audio signal, an output of the frequency detection means and the reproduction audio A disc reproducing apparatus comprising: an adding unit that adds signals at an appropriate ratio. 2. The frequency converting means comprises gate means for performing a logical operation of a logical product or an exclusive OR of the output of the variable frequency oscillating means and the reference signal, and a specific frequency range from the output of the gate means. 7. A disc reproducing apparatus according to claim 1, further comprising a band pass filter for extracting the signal of FIG.