JPS6023555B2 - SECAM color television signal recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a SECAM color television signal (S
This relates to a recording and reproducing method for ECAM signals, and is designed to reduce the influence of crosstalk from adjacent recording tracks and to enable high-density recording and reproducing.

Recently, for high-density recording, a helical scan type magnetic green video reproduction device (VTR) that utilizes the azimuth effect has been devised.

In this system, the gap directions of the magnetic heads for recording and reproducing adjacent recording tracks are made different from each other, so that even if a part of the adjacent tracks is scanned at the same time during reproduction, no output is obtained from the adjacent tracks due to the azimuth effect. It is something.

On the other hand, in a simple VTR that records and plays back a composite color television signal, the composite color television signal to be recorded as shown in FIG. angularly modulate Y' (for example, FM modulation), and convert the chrominance signal C to a low frequency range (about 600 to 700KH2) to obtain C'
and the FM luminance signal Y'(F
M) is recorded as a child's tatami mat.

Therefore, FM with high recording frequency (short recording wavelength)
The luminance signal can sufficiently eliminate the influence of crosstalk from adjacent tracks due to the azimuth effect, but the chrominance signal converted to low frequency can sufficiently eliminate crosstalk due to the azimuth effect in a configuration where the azimuth acid is small (10 degrees). cannot be expected.

Therefore, in the NTSC system, Mochiseki 50-427
As disclosed in the issue, low frequency converted chrominance signals are frequency interleaved and recorded between adjacent recording tracks, and during playback, the low frequency converted chrominance signals from the adjacent recording tracks are removed by a comb filter. There is.

For SECAM signals, it is difficult to use the above-mentioned cancellation method using a comb filter for the following reasons.

That is, in the SECAM signal, B-Y whose center frequency is 4.29 MHz and 4.40 MHz are added to the high frequency part of the luminance signal Y.
Since the 8MH2 R-Y chroma FM modulated wave signal is multiplied as a line-sequential signal to produce a composite wave signal, it is very difficult to obtain the correlation between carrier waves between adjacent tracks using the method using the comb filter described above. It is difficult to do so. The present invention utilizes the fact that the chrominance signal of the SECAM signal is FM modulated and provides a method for reducing the influence of cross strokes from adjacent tracks with a simple configuration. , an example thereof will be given and explained.

In FIG. 2, reference numeral 1 designates an input terminal for a SECAM signal to be recorded, which is separated into a luminance signal component and a chrominance signal component by a low-pass filter 2 and a bandpass filter 3, respectively.

The separated luminance signal component is subjected to FM modulation by an FM modulator 4 and then guided to an adder 6 via a high-pass filter 5. On the other hand, the chrominance signal is limited in its oscillation and is lowered to, for example, 1/2 by a down-converter 7, then guided to a frequency converter 8, frequency-converted by the output of a carrier wave generator 9, and then down-converted by a low-pass filter 10. A chrominance signal is obtained which has been frequency-converted to a lower frequency band, and this low-frequency converted chrominance signal is added to the adder 6, and the azimuth effect is added to the lower frequency side of the FM modulated luminance signal. To achieve this, the magnetic heads 11 and 11' have different head gap angles to record on the recording medium.

During reproduction, the signals reproduced by the magnetic heads 11 and 11' are separated into an FM modulated luminance signal and a low frequency modulated chrominance signal by a high-pass filter 12 and a low-pass filter 13, respectively.
The FM modulated luminance signal is transmitted through an amplitude limiter 14 and an FM demodulator 15.
, demodulated to the original luminance signal via the low-pass filter 16 and applied to the adder 17.

On the other hand, the low frequency modulated chrominance signal is frequency-converted by the frequency converter 18 and the bandpass filter 19 to high frequency by the output of the carrier wave generator 20, and then doubled by the bandpass filter 21 and the bandpass filter 21. , is restored to the chrominance signal of the original frequency band and applied to the adder 17.

Thus, the original SECAM signal can be obtained from the output terminal 23. In this way, in the present invention, the S to be recorded
Since the chroma FM modulated wave signal of the ECAM signal is down-converted and converted to a low frequency before being recorded, the following advantages arise.

The chroma FM modulated wave signal of the SECAM signal is illustrated as shown in FIG. 3A.

In other words, the center frequency of the R-Y signal is 4.4 MH2
The maximum frequency deviations are 1350KHZ and 1500HZ, and the B-Y signals are 4.29MH2 and 150KHZ, respectively.
The dish HZ, -350 KH2, and during each maximum frequency excursion is 850 KHZ.

Therefore, lowering this chroma FM modulation wave signal by, for example, 1/2 means reducing the maximum frequency deviation to 1/2 (42
arc HZ).

Now, FIG. 3 shows a case where the frequency of the above-mentioned chromatic FM modulation wave is directly converted to a predetermined frequency fc by heterodyning as in the conventional method.

In this case, the effect of removing crosstalk from adjacent recording tracks due to the azimuth effect becomes smaller as the frequency becomes lower (the recording wavelength is larger), so the azimuth effect is sufficient even at the lowest frequency fcL among the frequency deviations in Figure 3. In order to obtain this, it is necessary to make the center frequency fc higher, which narrows the luminance signal band accordingly.

In this regard, in the present invention, as shown in FIG. 3C, even if the frequency is converted to the same center frequency fc, the lowest frequency among the frequency deviations is (fcL+KHZ), as shown in FIG. 'Compare this, old lady. The higher the K, the more effectively the azimuth effect can be obtained. In addition, reducing the frequency middle by downshifting means that the chroma FM modulation band width converted to a lower frequency band becomes narrower (the sideband band width is the same), and the FM modulation luminance signal band width becomes narrower. If the frequency is constant, the center frequency can be set to fc'(fc'>fc) as shown in FIG. 32, and the azimuth effect can be used more effectively.

In the SECAM system, the chrominance signal is FM-modulated, so even if it contains crosstalk from adjacent tracks, it can be removed to some extent by the transmitter of the FM demodulation section of the receiver. Therefore, by converting the carrier chrominance signal to the lower frequency side of the angle-modulated luminance signal using frequency pass-through, and recording and reproducing it with a head having an azimuth angle, crosstalk between adjacent tracks can be reduced to a level that can be practically tolerated. This enables high-density recording. Next, an embodiment that can further reduce crosstalk from adjacent recording tracks will be described.

FIG. 4 shows the recording pattern on the magnetic tape of the same embodiment, where A is the recording locus recorded by the first magnetic head 11 and B is the recording locus recorded by the second magnetic head 11'. In the track, adjacent recording signals have approximately the same order (in the example, the order is shifted by 1.5 horizontal scans), and chrominance signals of the same type among the R-Y and R-B signal components. recorded as being located.

With this configuration, even if adjacent tracks are simultaneously reproduced during playback, the frequencies between the reproduced chroma modulation signal from the adjacent track and the reproduced chroma FM modulation signal from the main track almost match, so that both reproductions can be performed simultaneously. The beat frequency generated between the signals is low, and the influence on the reproduced image is reduced. As is clear from the above description, the present invention separates a SECAM system color television signal into a luminance signal component and a chrominance signal component, angle-modulates the luminance signal component, and performs frequency reduction on the chrominance signal component. The conversion means converts the frequency of adjacent recording tracks so that the frequency is in the same frequency band, and the converted chrominance signal is added to the low frequency side of the angle-modulated luminance signal component to perform azimuth recording. It is something to do.

Therefore, the crosstalk of the chrominance signal component can be reduced by effectively utilizing the azimuth effect, making high-density recording possible.Furthermore, in the present invention, the chrominance signal component is frequency-divided and then frequency-converted to a predetermined frequency. Since it is used to lower the frequency, it can convert the frequency to any frequency band. Furthermore, since the present invention does not change the frequency band of the chrominance signal recorded on adjacent recording tracks, the structure of the frequency conversion means during recording and reproduction is also simplified.

Note that even if some crosstalk from adjacent tracks is mixed into the reproduced chrominance signal, it is removed by means such as a limiter because the chrominance signal of the SECAM system is FM modulated.

[Brief explanation of the drawing]

Fig. 1 is a frequency vector diagram explaining the low frequency conversion recording method of the secondary chrominance signal, Fig. 2 is a block diagram showing an embodiment of the present invention, Fig. 3 is an explanatory diagram of the same operation, and Fig. 4 is a diagram of the present invention. FIG. 3 is a recording pattern diagram of one embodiment of the invention. 1...Input terminal, 2,10...Low pass filter, 3...Band filter, 4...FM modulator, 5... ...Takagi filter, 6...Adder, 7...Downloader, 8...Frequency converter, 1 1, 1 1'... magnetic head. Boar Diagram 1 Diagram N Ship Diagram 3

Claims (1)

[Claims] 1 Separate a SECAM color television signal to be recorded into a luminance signal component and a chrominance signal component, angle-modulate the luminance signal, and convert the frequency of the chrominance signal to a predetermined frequency to obtain the angle-modulated luminance signal. In a recording and reproducing method in which the chrominance signal component is superimposed on the low-frequency side of the chrominance signal component and is recorded and reproduced on a recording medium using magnetic heads having different head gap directions between adjacent recording tracks, the chrominance signal component is lowered by a frequency lowering means and then a frequency converting means is used. The SECAM is characterized in that frequency conversion is performed to the predetermined frequency in the same frequency band with respect to adjacent recording tracks.
Color television signal recording method.