JPH02226880A - Signal multiplexing method - Google Patents

Abstract

PURPOSE:To ensure the reproduction of a digital signal by making a timing of a blanking period of a video signal coincident with a timing of a synchronous pattern of a digital audio signal so as to prevent a side band component of an FM modulation luminance signal from being spread during the blanking period. CONSTITUTION:A digital audio signal is supplied from an input terminal 4 to a POM signal recording circuit 2, which applies processing such as error correction encoding to the digital audio signal. Then a synchronizing pattern is added to the encoded digital audio data and the timing of the synchronizing pattern is made coincident with the timing of the video signal for the blanking period. Thus, the side band component of the FM modulation luminance signal is not spread for the blanking period. Thus, the synchronizing pattern is detected surely to ensure the reproduction of the digital signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal multiplexing method for multiplexing digital signals onto a composite video signal.

[Summary of the invention]

In a signal multiplexing method for multiplexing a digital signal into a composite video signal, the present invention ensures that the digital signal is It is made to be playable.

[Conventional technology]

Conventionally, when recording audio signals on a VTR, the audio signals are recorded on an audio track using a fixed head. However, if the audio signal is recorded in a fixed manner as described above, it is not possible to reproduce the audio signal with high sound quality.

Therefore, a method of FM modulating the audio signal and recording this FM modulated audio signal in the deep part of the tape,
A method has been proposed in which an FM-modulated audio signal is frequency-division multiplexed with a video signal and recorded.

However, this method of FM modulating the audio signal and multiplexing it with the video signal is analog recording, so there is a limit to how high the sound quality can be achieved.

Therefore, in order to make it possible to reproduce audio signals of even higher quality, various methods have been proposed for digitizing and recording audio signals.

For example, in 8 mm Ti, a method has been proposed in which a PCM area is provided on the extension of the video track, and a digital audio signal is time-compressed and recorded in this PCM area.

In addition, for 1/2-inch VTRs, which are already widely used, various methods have been developed to digitize and record audio signals. This is a method in which the day signal is frequency division multiplexed with the video signal and recorded.

[Problem to be solved by the invention]

However, when a digital audio signal is deep-recorded and multiplexed with a video signal in this way, or when a digital audio signal is frequency division multiplexed with a video signal, the sideband components of the FM modulated luminance signal spread during the video period, and the digital audio It may affect the signal. Therefore, if the synchronization pattern of the digital audio signal and the timing of the video signal are arbitrarily set, there is a possibility that the synchronization pattern in the digital audio signal cannot be detected. If the synchronization pattern cannot be detected reliably, the digital audio signal cannot be reproduced.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a signal multiplexing method that can reliably detect synchronization patterns and reliably reproduce digital signals.

[Means to solve the problem]

The present invention provides a signal multiplexing method for multiplexing a digital signal into a composite video signal, in which a synchronization pattern in the digital signal is placed at a position outside the video period in the composite video signal. be.

[Effect]

The timing of the retrace period of the video signal and the timing of the synchronization pattern of the digital audio signal are matched.

During the blanking period, the sideband components of the FM modulated luminance signal do not spread. Therefore, during the blanking period, the sideband components of the FM modulated luminance signal do not jump into the digital audio data band, and the digital audio data can be reliably reproduced. can. Therefore, if the timing of the retrace period of the video signal and the timing of the synchronization pattern of the digital audio signal match, the synchronization pattern of the digital audio signal can be reliably detected and the digital signal can be reproduced reliably.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention.

In FIG. 1, 1 is a video signal recording circuit, 2 is a PCM
This is a signal recording circuit.

The video signal recording circuit l has an input terminal 3, for example, an NT
An SC composite color video signal is provided. In the video signal recording circuit 1, this composite color video signal is separated into a luminance signal and a chroma signal, and the luminance signal is FM-modulated.
The chroma signal is converted to lower frequencies.

A digital audio signal is supplied to the PCM signal recording circuit 2 from an input terminal 4. The PCM signal recording circuit 2 performs processing such as error correction encoding on this digital audio signal.

Then, a synchronization pattern is added to this encoded digital audio data. This synchronization pattern is designed to be inconsistent with the timing of the retrace period (pedestal level period or sync tip level period) in the video signal.

That is, the synchronization signal in the composite color video signal from the input terminal 1 is separated by the synchronization separation circuit 5.

This separated synchronization signal is supplied to the PCM signal recording circuit 2. Based on this synchronization signal, the generation timing of the synchronization pattern is determined.

The output of the PCM signal recording circuit 2 is supplied to a modulation circuit 6. A modulation circuit 6 modulates digital audio data. The output APCM of the modulation circuit 6 is supplied to the multiplexing circuit 7.

On the other hand, the FM modulated luminance signal Y from the video signal recording circuit 1
The FM and low frequency converted chroma signals C are supplied to a multiplexing circuit 7. As shown in FIG. 2, the multiplexing circuit 7 frequency-division multiplexes the FM modulated luminance signal YFM, the low frequency converted chroma signal C, and the digital audio data APCM from the modulation circuit 6. This multiplexed signal is supplied to the rotary heads IOA and IOB via the head changeover switch 9 and recorded on the tape 11.

1. In the above example, the multiplexing circuit 7 frequency-division multiplexes the FM modulated luminance signal YFM and the low-frequency converted chroma signal C and the digital audio data APCM from the modulating circuit 6. The digital audio data APCM may be recorded in the deep part of the tape 11 using a separate head.

In one embodiment of the invention, as described above, the synchronization pattern in the digital audio signal is made to match the timing of the blanking period in the video signal. That is, when a video signal is supplied to the input terminal 3 at the timing shown in FIG. 3A, as shown in FIG. 3B, the digital audio is A synchronization pattern is added to the signal.

In this way, since the synchronization pattern in the digital audio signal is matched with the timing of the blanking period in the video signal, the synchronization pattern in the digital audio signal can be reliably detected during playback.

That is, the multiplexing circuit 7 frequency-division multiplexes the FM modulated luminance signal YFM, the low-frequency converted chroma signal C, and the digital audio data APCM from the modulation circuit 6. The FM modulated luminance signal includes sideband components. In the video signal during the video period, there is a possibility that this sideband component jumps into the band of the digital audio data APCM.

Therefore, if a synchronization pattern in a digital audio signal is present in a video period of a video signal, there is a possibility that the synchronization pattern cannot be detected due to the influence of sideband components in the FM modulated luminance signal. If a synchronization pattern cannot be detected, it is difficult to reproduce digital audio signals.

In contrast, in this embodiment, the synchronization pattern in the digital audio signal is placed in the flyback period.

During the retrace period, the level of the luminance signal is constant, so F
The sideband components in the M-modulated luminance signal do not spread. Therefore, by matching the synchronization pattern in the digital audio signal with the retrace period in the video signal, the synchronization pattern can be reliably detected.

[Effects of the Invention] According to the present invention, the timing of the retrace period of the video signal and the timing of the synchronization pattern of the digital audio signal are matched. During the retrace period, the sideband components of the FM modulated luminance signal do not spread, so the synchronization pattern of the digital audio signal can be reliably detected and the digital signal can be reproduced reliably.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a spectrum diagram used to explain the embodiment of the invention, and FIG. 3 is a timing chart used to explain the embodiment of the invention. Explanation of main symbols in the drawings 1: Video signal recording circuit. 2: PCM signal recording circuit. 5: Synchronization separation circuit, 7: Multiplexing circuit.

Claims (1)

[Scope of Claims] A signal multiplexing method for multiplexing a digital signal into a composite video signal, wherein a synchronization pattern in the digital signal is arranged at a position outside the video period in the composite video signal. Multiplexing method.