JPS58148585A - Sound signal recording system - Google Patents

Abstract

PURPOSE:To reduce the beat interference at reproduction and to make the beat on a reproducing screen inconspicuous, by recording sound signals after superimposing it on a low frequency converted chroma signal and a luminance FM signal. CONSTITUTION:At a frequency band between band CB of a chroma signal separated from a video signal and frequency-converted into a low frequency and a band YB of a luminance FM signal separated from the video signal similarly and FM-modulated, the sound signal is FM-modulated and recorded after being superimposed on the low frequency converted chroma signal and the luminance FM signal. Taking a horizontal synchronizing signal as fH, and m, n as natural numbers, and a carrier frequency of the low frequency converted chroma signal as fH(2n+1)/4, the carrier frequency of the sound FM signal is selected as fH(2m-1)/4 and (m-n) is selected as an even number. Thus, the interference between the luminance FM signal and the low frequency converted chroma signal is made less.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an audio signal recording method, and more specifically, an audio signal is FM modulated into a band intermediate between a band of a low frequency conversion color signal and a band of an FM modulated luminance signal. This invention relates to an audio signal recording method for recording audio signals.

[Technical background of the invention]

In a video recorder (hereinafter referred to as a VTR), video signals are generally recorded using a rotating magnetic head, and audio signals are recorded using a fixed head.

Incidentally, the running speed of the tape in a VTR is slower than that in an audio tape recorder, and there is a natural limit to the improvement in recording and reproducing characteristics of audio signals. Therefore, a method has been considered in which an audio signal is superimposed on a video signal and recorded using a rotating magnetic head. According to such a system, the recording/reproducing frequency characteristics of the audio signal are significantly improved compared to the case of recording with a fixed head, and the sound quality can be improved.

[Problems with background technology]

However, in the audio signal recording method as described above, there is a drawback that interference occurs between the luminance signal and the color signal and the audio signal, and this interference appears as beats on the playback screen.

[Purpose of the invention]

The present invention is based on the above nine points, and includes:
It is an object of the present invention to provide an audio signal recording method in which the frequency of an audio FM signal is set to a predetermined value so as to prevent interference with a luminance signal and a color signal.

[Summary of the invention]

The present invention provides a band for a color signal (low-frequency converted color signal) that is separated from the Eirin signal and frequency-converted to a low frequency band, and a band for a luminance signal (luminance FM signal) that is also separated from the Eirin signal and subjected to FM modulation. When the audio signal is FM-modulated in the middle band of
When the frequency of the carrier wave m-1 of the audio FM signal is selected as □fH, and m -n (m.

(n is a natural number) is an even number to reduce interference with the luminance FM signal and the low frequency conversion color signal.

[Embodiment 1 of the invention The present invention will be explained below with reference to the drawings.

The figure is a diagram showing an example of frequency band characteristics, where CB shows the band of the low frequency conversion color signal and YB shows the band of the luminance FM signal.

AB is the audio F inserted in the middle band between bands CB and YB.
This is the M signal band.

Let us consider the interference of the audio signal recorded in this manner superimposed with the chrominance signal and the luminance signal with the two signals.

First, the interference between the audio FM signal and the low frequency converted color signal will be described. Assuming that the audio FM signal is a single frequency signal with a frequency of f, and the low frequency conversion color signal is a signal with a frequency of fc, the frequency of the unnecessary signal is F! , is the frequency of the difference between the two. That is, f and -fc become unnecessary signal frequencies, and a signal having this frequency causes sibeat.

Furthermore, regarding the interference between the audio FM signal and the luminance FM signal, beats of twice the frequency occur due to cross modulation accompanying edge reproduction and the nature of FM demodulation. In other words, if the brightness [FM signal is fY
Calculating the unnecessary frequency components assuming a single frequency signal with a frequency of 3fy, 3rB, ry±2
Frequency components such as f5°2 fYf fs appear. Of these, all but 3f exist within the FM band, so they cause beat disturbance. Due to the nature of the FM signal, when a signal containing these unnecessary components is demodulated, it becomes an interference signal with a frequency different from that of the FM carrier. Therefore, the interference signal frequencies during demodulation are fY-3fB, 2f8. (fY Sat f8)
becomes. Of these, the 2fs component becomes an interference signal with a constant frequency, so it stands out on the screen.

Therefore, for the low-frequency conversion color signal I/'i(f, -fc)
component becomes the interference signal, and the luminance FM signal' is 2f
The s component becomes an interference signal. Therefore, in order to make the interference less noticeable, fs-fc and 2fs should be made to have a -X odd number relationship from the frequency interleaving relationship. Therefore, the low-pass conversion color subcarrier frequency, c1 & -2n+1, , when closed, the audio F
The carrier frequency fs of the M signal may be selected as m-1 - fH, and m-n may be an even number. That is, is an odd multiple of -fH. Also, since the frequency interleaving relationship m-1 2f, = 2 X -fH m-1 = -fH is satisfied, the beats become less noticeable on the playback screen.

Note that during recording, the phase of the color signal is inverted every IH (H is one horizontal scanning period), and this is done every other track (in other words, whether the phase of the color signal is recorded with inverted every IH or inverted). 1 whether to record with the same phase without
The frequency relationship that removes the crosstalk between adjacent tracks of color signals during playback by switching for each track cannot be applied as is.

That is, it is necessary to change the carrier frequency of the audio FM signal by inverting the phase of the color signal and recording it for each IH. This is because the above-mentioned relationship must hold between the carrier wave frequency on the low-pass conversion color side and the carrier wave frequency of the audio FM signal in the state recorded on the recording medium (magnetic tape in the case of a VTR). .

Furthermore, although the embodiments have been explained with the case of a VTR in mind, the present invention is not limited to this, and the present invention is not limited to this.
Applicable to those that record.

〔Effect of the invention〕

As described above, according to the present invention, by recording an audio signal by superimposing it with a low-frequency conversion color signal and a luminance FM signal, beat interference during playback that occurs is reduced, and the beats on the playback screen are made less noticeable. I can do it.

[Brief explanation of the drawing]

The figure shows frequency band characteristics, where CB is the band of the low frequency conversion color signal, AB is the band of the audio FM signal, and YB is the band of the luminance FM signal. Agent: Patent attorney Kensuke Chika (and 1 other person)

Claims (2)

[Claims] (1) FM audio signal in the band between the color signal band which is separated from the Wk image signal and frequency converted to a low frequency band and the band of the nine luminance signal which is also separated from the Eirin signal and is FM modulated.
An audio signal recording method that modulates and superimposes the modulated signal and supplies it to a recording means for recording, and is characterized in that: . (2) For the nine-color signal that is separated from the video signal and frequency-converted to a low frequency band, the phase is inverted with IH (H is one horizontal scanning period), and this is performed for one track and recorded. For tracks recorded with the phase of the color signal inverted using a magnetic recording/reproducing device that adopts the Phase Invert method, the transmission frequency of the audio FM signal is 2m+1. An audio signal recording method according to claim 1, characterized in that: