JPH0193971A - Pilot signal control circuit for video disk recorder - Google Patents

Abstract

PURPOSE:To prevent the degradation of the phase characteristic of a reproducing pilot signal by a noise at a reproducing time by executing the multiple recording of the reproducing pilot signal of large amplitude, whose rising and falling are sharp, in a PCM sound data multiplexing period to have a large noise component. CONSTITUTION:A control pulse generating circuit 4, which generates a control pulse in a vertical blanking period or the PCM sound multiplexing period, and a signal level emphasizing circuit 10, which synchronizes to this control pulse and emphasizes the level of a pilot signal, are added to a conventional video disk recorder. Accordingly, the level of the pilot signal, which is multiplexed in the vertical blanking period or the PCM sound multiplexing period, is emphasized. Thus, without degrading the SN ratio of reproducing PCM sound data, the level of a second lower side band component to be mixed to the reproducing pilot signal can be relatively suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a pilot signal level control circuit for a video disc recorder.

(b) Conventional technology A so-called MUSE signal (hereinafter referred to as a band-compressed video signal) obtained by band-compressing a high-quality video signal using a multiplex sub-Nyquist sampling encoding method is FM-modulated, and a fixed-frequency pilot signal is frequency-multiplexed. Regarding the optical video disc recorder for recording
It is disclosed in Publication No. 179 (G11B20/12).

This conventional technology suppresses the level of high-frequency components when time-division multiplexing PCM audio data compressed on the time axis during the vertical blanking period of a band-compressed video signal.
FM modulation is performed with a limit of Q)%, and the noise component generated near the reproduced pilot signal, that is, the @2 lower sideband component of the FM modulated output of PCM audio data, is suppressed.

(c) Problems to be solved by the invention However, as mentioned above, even if the level of PCM audio data is suppressed, the S/N ratio of the reproduced pilot signal obtained from the bandpass filter is It was observed that significant deterioration occurred. Therefore, it is conceivable to further suppress the level of the PCM audio data, but since suppression deteriorates the SN ratio of the reproduced PCM audio data itself, there is a limit to the suppression of the PCM audio data. Therefore, in the present invention, without deteriorating the S/N ratio of the reproduced PCM audio data, the 'second
The purpose is to relatively suppress the level of the sideband band.

In view of the above-mentioned points, the present invention provides a control pulse generation circuit that generates a control pulse during a vertical blanking period or a PCM audio multiplexing period, and a control pulse generation circuit that generates a pilot signal in synchronization with the control pulse. To add a signal level emphasis circuit that emphasizes the level of
→It is characterized by 碕.

(E) Effect Therefore, according to the present invention, the vertical blanking period or P
The level of the pilot signal multiplexed during the CM audio multiplexing period is emphasized.

(f) Example Hereinafter, a description will be given according to an embodiment of the wood-based 8At shown in the drawings.

As shown in FIG. 1, in this embodiment, the audio signal is input to the IA 6th rank video signal area compression encoder fil (MUSE encoder), and the audio signal is input to the PCM encoder (2).
is being entered. The band compression encoder uses Dowa's multiple sub-Nyquist sampling encoding method to band compress a high-quality video signal, and generates Dowa's band compression video signal (M
USE Shin Ji+) has been formed and derived. In addition, the PCM encoder converts the audio signals of the left and right channels into 3 channels each.
Convert to 14-bit data at a sampling frequency of 2 Kbit, then convert to 10-bit data by bit compression to form 640 Kbit/sec data, and convert 640-bit data to Radio Council's A mode signal every 1 msec. 1024 by doing
PCM audio data of bit/m5ec is formed and derived. This PCM1 voice data is stored in memory (3). On the other hand, from the band pressure encoder (11), a frame pulse (FP) which has a high level during the frame synchronization pulse multi-M period, and a line pulse (LP) which becomes high level during the multi-frame period of the horizontal synchronization signal are derived. Both of these pulses are input to the control pulse generation circuit IjIr+4). This control pulse generation circuit (4) generates a frame pulse (
FP) 'ilJ set input, line pulse (LP)
is used as a counting input to form and derive control pulses during the PCM audio data multiplexing period during the vertical blanking period.

Note that this control pulse applies from the 6th line to the 43rd line, and
During the period up to 5th grade, you will reach a high level. The memory (3
) is derived by compressing the PCM voice and data in the time axis during the control pulse generation period and outside the line pulse generation period. The next-stage time-division multiplexing circuit (6) time-divides the time-axis compressed PCM audio data and data such as address codes generated at data generation times @ +61 during the band compression video (number a) and the vertical blanking period. The level of PCM audio data during multiplexing is 60g6 in the entire range.
shall be suppressed.

The time division multiplexed output is input to an FM, 9.11 circuit (7) with a frequency shift range of 12 to 16 MHz. This FM
The modulated output is input to the next-stage Hibamasa multiplex circuit (8). On the other hand, the circuit (9) for the eight pilot signals generates the 64.8MHz master signal required for the band compression encoder (l).
A pilot signal of 2.278 MHz is derived by dividing the frequency by t-9/256. This pilot signal is input to the same wave number multiplexing circuit (8) via the level emphasizing circuit rto+. The output of the level emphasizing circuit (lO) is 26% higher than the FM modulation output during periods other than the control pulse generation period.
The level is set as low as ~29 dB, and the level is emphasized by +3 to 6 dB during the control pulse generation period. The multiplexed outputs obtained as a result of frequency multiplexing are input to an optical recording means (stream) to form recording tracks on a video disk record.

This optical recording means (Kawa has a recordable frequency of at most 17M)
Hz, and the upper sideband is hardly recorded.

When playing back the uninvented video disc record formed through the above-described procedure or its reproduction disc record, the video disc player separates the playback pilot signal by a bandpass filter, and separates the playback pilot signal during the multiplexing period of PCM audio data. Since the reproduced pilot signal has a large amplitude, the rise and fall near the 0-cross point are steep, and the waveform has a waveform in which the 0-cross point is difficult to displace due to noise. Therefore, if a limiter for limiting the amplitude is provided after the bandpass filter to limit the amplitude of the regenerated pilot signal and the timing of the O-cross point is detected, the phase of the regenerated pilot signal can be detected correctly. It goes without saying that a gain control circuit for keeping the reproduced signal amplitude constant may be provided in place of the limiter.

(g) According to the effect of the invention, and according to the non-invention, in order to multiplex record a large amplitude reproduced pilot signal with steep rises and falls during a multiplexing period of PCM audio data with many noise components, one cycle is required for reproduction. However, the phase characteristics of the reproduced pilot signal do not deteriorate due to noise, and the effect is great.

[Brief explanation of the drawing]

Figure 1 is a circuit block diagram showing an embodiment of the invention, Figure 2 is a circuit block diagram showing an embodiment of the invention.
The figures show the main signal waveform diagrams. Appearing person: Sanyo Electric Co., Ltd. agent Patent attorney Takuji Nishino (1 other person)

Claims (1)

[Claims] (1) PCM audio data is time-axis compressed and multiplexed in the vertical blanking period of the compressed video signal, which is obtained by band-compressing the high-quality video signal using the multiplex sub-Nyquist sampling encoding method, and then FM modulated and recorded. In a video disc recorder that frequency-multiplexes pilot signals to form a recording signal, optically modulates a laser beam with the recording signal, and forms a recording track on a disc record surface, the PCM audio data multiplexing period is or a video disc recorder comprising a control pulse generation circuit that generates a control pulse during the vertical blanking period, and a signal level emphasis circuit that emphasizes the signal level of the pilot signal in synchronization with the control pulse. Pilot signal control circuit.