JPS5941636B2 - Color video signal recording and playback method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for recording and reproducing color video signals, and in particular, it relates to a device for recording and reproducing color video signals, and particularly for recording and reproducing color video signals in which luminance signals and color signals are band-shared so that the recording frequency band is reduced. A signal recording and reproducing method is provided.

In simple color video tape recorders (hereinafter simply referred to as VTRs) that are currently widely used, for example, a luminance signal is converted into a frequency modulation signal that occupies the high frequency side of the recordable band (hereinafter referred to as an FM luminance signal). The carrier color signal is frequency-converted to the lower frequency side of the FM luminance signal and recorded on the magnetic tape as a frequency-multiplexed signal.

Then, during playback, the FM
The luminance signal and the low-band converted carrier color signal are separated by a filter, and the brightness signal is demodulated from the FM brightness signal, and the low-band converted carrier color signal is frequency-converted to the original frequency band. . In such a recording method, as shown in FIG. 1a, the band required for recording and reproduction is considerably wide, which is one reason why the TR becomes expensive. Also,
In the recording method of the above-mentioned simple VTR, both the luminance signal and the carrier color signal are recorded as analog quantities, so they are affected by the noise and nonlinear distortion of the electromagnetic conversion system between the magnetic head and magnetic tape, and the time difference caused by the tape running system. It is well known that it is susceptible to axis fluctuations.

This effect is particularly severe on color signals, and in order to reduce moiré caused by the effects of nonlinear distortion in the electromagnetic conversion system, it is necessary to reduce the recording level of the color signals, and in this case, the recording level of the color signals must be reduced.
/N cannot be obtained sufficiently. Furthermore, due to the influence of time axis fluctuations, the phase of the reproduced carrier color signal fluctuates, causing color unevenness. To prevent this, an expensive automatic phase control circuit is required. AP
The recording and reproducing method according to the present invention, which had drawbacks such as requiring C. As shown in Figure 1b, it is narrower than the conventional one, and since the color signal is encoded and recorded, it is essentially less susceptible to the effects of noise and amplitude fluctuations that occur in the recording and reproducing system. The pulse amplitude recorded in the recording of the digitalized pulse train can be kept constant and does not need to be very large, so the generation of moiré due to cross-modulation with the luminance signal can be kept small to the point where it does not become a problem, and the color signal can be digitally recorded and reproduced. Therefore, by providing a temporary storage circuit on the playback side, it has many features such as being able to easily remove the influence of time axis fluctuations.

Hereinafter, details of the color video signal recording and reproducing method of the present invention will be explained with reference to the drawings. FIG. 2 is a basic configuration diagram showing the principle of the present invention.

A color video signal applied to input terminal 1 is separated into a luminance signal and a color signal by a separator 2, and the luminance signal is sent to a frequency modulator (
It reaches a synthesizer 5 via an FM modulator (hereinafter referred to as an FM modulator) 3. On the other hand, the color signal passes through the code modulator 4 and reaches the combiner 5. The output of combiner 5 is coupled to magnetic head 7. These separators 2
, FM modulator 3, code modulator 4, and synthesizer 5 constitute a recording system 6 and are shown surrounded by a broken line frame. The output of the magnetic head 71 reaches the discriminator 8 and also enters the canceler 9, to which the output of the discriminator 8 is coupled. The output of canceller 9 passes through FM demodulator 10 and reaches combiner 12 . On the other hand, the output of the discriminator 8 passes through the decoder 11 and reaches the mixer 12. The output of combiner 12 is coupled to output terminal 14. Here, a discriminator 8, a canceller 9, an FM demodulator 10, a decoder 11
The mixer 12 and the mixer 12 constitute a regeneration system 13 and are shown surrounded by a broken line frame. The operation in the configuration shown in FIG. 2 will be explained.

A color video signal including a carrier color signal modulated by a luminance signal and a chromaticity signal is applied to the input terminal 1. This color video signal is separated by a separator 2 into a luminance signal and a color signal. The separated luminance signal is subjected to FM modulation by an FM modulator 3 and then given to a synthesizer 5, and the color signal is demodulated into I and Q signals, and the carrier color signal is subjected to low-frequency conversion to undergo code modulation. After converting it into a possible signal, it is encoded by a code modulator 4.
Encoding is performed by code modulating PCM on an analog signal and converting it into a pulse code string, and linear PCM, differential PCM, delta modulation, etc. are used. The color signal converted into a digital pulse train by the code modulator 4 is superimposed on the FM luminance signal by the synthesizer 5. At this time, as shown in Figure 1b, the FM deviation is set so that the spectrum of the FM luminance signal is distributed up to the low range limit that can be recorded and reproduced, and the spectrum of the digitized color signal is Bandwidth will be distributed on the regional side in the form of band sharing. Since the chrominance signal can be code-modulated and converted into a digital signal with an occupied band of about 1.5 MHz, for example, the lower frequency portion 1. 5M[-1z is the band sharing part. As is well known, the frequency spectrum envelope of the luminance signal is 6 dB.
Since the FM luminance signal spectrum can be approximated by a high-frequency attenuated form of
B and below). Therefore, it is sufficient that the digitized color signal can be identified as a digital signal in the reproduction system, and if its superimposition level is approximately 15 dB higher than the FM luminance signal spectrum, the code error rate will fall within the allowable range. In other words, by superimposing the digitized color signal on the low frequency portion of the FM luminance signal in a band-sharing manner, it is possible to identify it in the reproduction system even at a fairly low level. In this manner, the FM luminance signal and the digitized color signal are superimposed and multiplexed in the recording system 6 and recorded on the magnetic tape by the magnetic head 7. In the reproducing system 13, the superimposed signal obtained from the magnetic head 7' is discriminated as a digital signal by a discriminator 8.

This is because, as described above, in the shared band, the level of the digital color signal is sufficiently higher than the level of the FM luminance signal, so the discrimination may be performed, for example, through a low-frequency wave generator. This identified digital color signal is transferred to a canceller 9 on which a superimposed signal is printed.
The digital color signal is canceled out from the superimposed signal, leaving only the FM luminance signal. Here, in order to eliminate the digital color signal, the application level and time adjustment of the digital color signal are important, and these are included in the canceller 9. An FM luminance signal is obtained at the output of the canceler 9, and this is demodulated into a luminance signal by an FM demodulator 10 including an emitter. on the other hand,
The digital color signal identified by the identifier 8 is sent to the decoder 11
is decoded into an analog quantity. The decoder 11 generally includes a DA converter and a low frequency filter, and reproduces an analog signal from a given pulse train. The decoded color signal is mixed with the demodulated luminance signal in mixer 12, and the original color video signal is reproduced at output terminal 14. According to the method for recording and reproducing color video signals with the configuration shown in Fig. 2, since a frequency band for color signals is not required, color video signals can be recorded and reproduced in a narrow band, making it possible to reduce costs. If the same band is used, the band of the luminance signal can be widened and the resolution can be greatly improved. Furthermore, since the luminance signal is recorded after being subjected to FM modulation, a limiter can be used in the reproduction system, and the effects of noise and amplitude fluctuations can be removed to some extent. Furthermore, since the color signal is recorded and reproduced as a pulse train with a constant amplitude, the color signal can be reproduced almost unaffected by noise, amplitude fluctuations, and nonlinear distortion occurring in the recording/reproducing system. Jitter 1 will have the effect that the intervals of the reproduced pulse train will not be constant, but by providing a temporary storage circuit in front of the decoder 11 of the reproduction system 13, a pulse train with equal time intervals can be reproduced. Therefore, color unevenness due to phase fluctuations of color signals can be easily removed. Furthermore, since the superimposition level of the digitized color signal on the FM luminance signal is smaller than in the past, moiré fringes due to non-linear distortion of the electromagnetic conversion system hardly occur. FIG. 3 is a block diagram showing an embodiment in which the principle of the present invention is applied to a helical scan rotary head VTR. A commonly used helical scan rotary head VTR is used by switching between two rotary heads for each field, but only one head is shown in FIG. 3 to simplify the explanation. Blocks that have the same function as those in FIG. 2 are designated with the same numbers. The NTSC color video signal applied to the input terminal 1 is separated into a luminance signal and a carrier color signal by a low-band filter 15 and a band filter 16.

This luminance signal is subjected to low carrier vestigial sideband FM by the FM modulator 3 and then applied to the combiner 5. On the other hand, the carrier frequency of the carrier color signal separated by the band wave filter 16 is 3.
581V11z, and the band is approximately ±500KHz. This carrier color signal is converted by the frequency converter 17 to a carrier frequency of 500 KHz, for example. The low-pass converted carrier color signal is encoded by the encoder 18 into a 3 MB/S digital pulse train, for example. For example, a 3 MB/S digital pulse train is 1.5 MB/S if the NRZ code format is used.
Since it can be transmitted in the MHz frequency band, it is band-limited by a low frequency filter 19 and then added to the synthesizer 5.

A synthesizer 5 superimposes and multiplexes an FM-modulated luminance signal and a digital pulse band-limited to 1.5 MHz, and this signal is amplified by a recording amplifier 20 and supplied to a recording head 7. Therefore, the superimposed FM luminance signal and digital carrier color signal are recorded by the magnetic head 7 diagonally scanning the magnetic tape 21. In the reproducing system 13, the superimposed multiplex signal obtained at the reproducing head 7' is amplified by a reproducing amplifier 22, and after the time difference with the digital color signal is corrected by a delay circuit 23, it is applied to a difference calculation circuit 27 and a low-frequency amplifier. It is also provided to waver 24.

The low frequency filter 24 separates the common band between the digital signal and the FM luminance signal, and in this embodiment, the cutoff frequency is 1.5.
It is MHz. Since most of the high-power portion of the FM luminance signal is attenuated by the low frequency filter 24, only the digital color signal and the low frequency portion of the FM luminance signal appear in the output of the low frequency filter 24. As mentioned above, the low-frequency spectrum of the FM luminance signal is sufficiently smaller than the digital color signal, so the digital color signal is identified by the identification circuit 26 and the self-clock generation circuit 25, and the digital pulse train obtained in the recording system 6 is reproduced. be done. This digital pulse is the DA converter 2
9 and a low frequency converter 30, the signal is restored to a low frequency converted color signal which is an analog quantity, and converted to a high frequency signal by a frequency converter 31, and a carrier color signal of 3.58 MHz, which is the same as the input signal, is reproduced. be done. On the other hand, the digital pulse that is the output of the identification circuit 26 is shaped by a waveform shaping circuit 28 into a waveform necessary for cancellation, and is applied to the difference calculation circuit 27. The difference calculation circuit 27 functions to remove the digital color signal by subtracting the digital color signal shaped by the waveform shaping circuit 28 from the superimposed signal of the FM luminance signal output from the delay circuit 23 and the digital color signal. Therefore, only the FM luminance signal is obtained as the output of the difference calculation circuit, and this is the output of the FM demodulator 1.
0 is demodulated into a luminance signal. The luminance signal and the carrier color signal thus obtained are mixed in a mixer 12 to form the original N
The TSC color video signal is reproduced to the output terminal 14. Third
In the case of the embodiment shown in the figure, all of the many features described in the principle configuration of FIG. 2 can be achieved, so it is extremely valuable when used for color TR.

FIG. 4 shows another embodiment of the present invention, which is an improvement over the embodiment of FIG. 3 so that more stable operation can be performed.

Explanation will be added only to the parts that are different in configuration from FIG. 3.

In the recording system 6, a code converter 32 is connected between the encoder 18 and the low frequency wave generator 19.

The carrier color signal is converted into a digital signal by the encoder 18, but this digital signal is usually, for example, an NRz signal, and the band required for transmission is, in principle, DC transmission starting from 0 Hz. (Actually, even if DC is cut off, transmission is possible with a certain bit error rate.) However, in many cases with rotary head type TRs, the rotary head receives and receives signals via a rotary transformer, so it is necessary to
Low frequencies up to Hz cannot be transmitted.

Therefore, it is desirable to use a digital signal transmission code format that does not require low-frequency transmission (G). An example of such a code format is a bipolar code. This code format uses pulses having three values of positive, 0 and negative as information, and is extremely resistant to DC interruption, so it can be said to be very suitable for this embodiment. The code converter 32 therefore serves to convert the digital color signal into a bipolar code format. A code converter 34, which is provided after the identification circuit in the reproduction system 13, has the opposite function to the code converter 32.

Since the code reproduced by the identification circuit 26 is bipolar, this returns the NRZ code necessary to operate the next DA converter 29. In the reproduction system 13, the equalizer 33 provided after the low frequency filter 24 identifies the digital signal superimposed on the FM luminance signal.
It is effective when used when band limitation by the low frequency filter 24 alone is insufficient. For example, it is composed of a delay circuit and an addition/subtraction circuit, and is used to prevent loss in a pulse waveform transmission system. This functions to recover the components that have been removed and obtain a waveform that can be easily identified.

According to the embodiment of FIG. 4, compared to the embodiment of FIG.
In recording and reproducing digital signals, it is not easily affected by DC interruption, and since the band of the digital color signal superimposed on the FM luminance signal is narrow, the degree of interference exerted on the FM luminance signal is extremely small. As detailed above, the color video signal recording and reproducing method according to the present invention separates a color video signal into a luminance signal and a chrominance signal, and records the code-modulated chrominance signal by superimposing it on the FM luminance signal. It is characterized by identifying a digital color signal from a superimposed signal, reproducing the color signal, canceling the digital color signal component of the superimposed signal with the identified digital color signal, and performing FM demodulation to reproduce a luminance signal. As a result, the luminance signal and color signal can be recorded in a shared band, reducing the bandwidth required for a VTR, and since the color signal is encoded and recorded, noise generated in the electromagnetic conversion system of the head tape can be reduced. It is not affected by distortion or time axis fluctuations, and is also hardly affected by cross-modulation of the luminance signal and carrier color signal.

Therefore, extremely high quality color images can be reproduced, and the effect will be great if used in various color image recording and reproducing devices.

[Brief explanation of the drawing]

FIGS. 1A and 1B are spectral distribution diagrams of recording signals used to explain the present invention, and FIG. 2 is a basic configuration diagram showing the principle of the present invention.
FIG. 3 is a block diagram showing one embodiment of the present invention, and FIG. 4 is a block diagram showing another embodiment of the present invention. 2...Separator, 3...FM modulator, 4
... code modulator, 5 ... synthesizer, 8.
... Discriminator, 9 ... Canceller, 10 ...
...FM demodulator, 11... Decoder, 12...
...Synthesizer, 17...Frequency converter, 19
・・・・・・Low frequency waveform generator, 25・・・Presence clock generation circuit, 28・・・Waveform shaper, 23・・・
...Delay circuit, 31...Frequency converter, 32.
... code converter, 33 ... equalizer, 34
...... code converter.

Claims (1)

[Claims] 1. A superimposing means for separating a color video signal into a luminance signal and a chrominance signal in a recording system, and superimposing a signal obtained by code-modulating the chrominance signal on a signal obtained by frequency modulating the separated luminance signal. and recording the signal superimposed by the superimposing means,
The reproduction system includes identification means for identifying a code-modulated color signal from the superimposed signal, and canceling means for canceling the code-modulated color signal from the superimposition means, and the signal identified by the identification means. A color video signal recording and reproducing method characterized in that the color signal is reproduced by the canceling means, and the signal obtained by the canceling means is FM demodulated to reproduce the luminance signal. 2. Color video signal recording and reproduction according to claim 1, characterized in that the superimposition means in the recording system superimposes the code-modulated color signal on the lower frequency side of the frequency-modulated luminance signal in a band-sharing manner. Method. 3. The color video signal recording and reproducing method according to claim 1, wherein the superimposing means in the recording system superimposes the code-modulated color signal on the frequency-modulated luminance signal through a low-pass filter and records the same. 4. The color video signal recording and reproducing method according to claim 1, characterized in that the signal obtained by code-modulating the color signal in the recording system is converted into a bipolar code and then superimposed on the frequency-modulated luminance signal and recorded. 5. The color video signal recording and reproducing method according to claim 1, wherein the means for identifying the code-modulated color signal in the reproduction system limits the frequency band of the reproduced superimposed signal using a filter and reproduces the color signal. . 6. The color signal according to claim 1, wherein the means for identifying the code-modulated color signal in the reproduction system band-limits the reproduced superimposed signal using a filter and reproduces the color signal through an equalizer. Video signal recording and playback method. 7. The color video signal recording and reproducing method according to claim 1, wherein the identification means in the reproduction system reproduces the color signal by giving timing based on a self-clock generated from the reproduced signal. 8. The color video signal recording and reproducing method according to claim 1, wherein the canceling means in the reproduction system reproduces the luminance signal by calculating the difference between the reproduced superimposed signal and the code-modulated color signal after identification. . 9. The color according to claim 1, wherein the canceling means in the reproduction system reproduces the luminance signal by calculating the difference between the reproduced superimposed signal and a signal obtained by waveform shaping the code-modulated color signal after identification. Video signal recording and playback method. 10. The color video signal according to claim 1, characterized in that in the recording system, a signal obtained by low-frequency conversion of the carrier color signal is code-modulated, and in the reproduction system, the carrier color signal is converted to a high frequency to reproduce the carrier color signal. Recording and playback method.