JPS5923156B2 - Color television signal recording and playback system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing time axis fluctuation components from a color television signal reproduced by a recording and reproducing apparatus.

When a recording and reproducing device records and reproduces a composite color television signal consisting of a luminance signal and a quadrature two-phase modulated color signal, such as an NTSC color television signal, the time axis generated by the recording and reproducing device Due to fluctuations, the playback signal cannot be directly transmitted to a color television receiver (Color T).
Even if input to V), color synchronization cannot be achieved and correct color reproduction is not possible, or a color killer circuit is activated and no color is reproduced at all.

In order to eliminate such inconveniences, various measures have been devised in the past. Typical conventional measures include the following. (1) A method in which the carrier color signal is demodulated into two baseband color signals (I, Q) and the color signals are transmitted sequentially for each horizontal scanning line (color signal line sequential method).

(2) A method in which a pilot signal is recorded during recording and time axis fluctuations are removed from the color signal carrier wave using a heterodyne method during playback (pilot heterodyne method). (
3) A method in which a continuous signal phase-synchronized with the color burst signal is created by an APC circuit during reproduction, and time axis fluctuations in the color signal carrier are removed by the heterodyne method (APC
heterodyne method).

(4) A method that removes time axis fluctuations by passing the reproduced signal through a variable delay circuit. In the conventional methods described above, the circuit configuration is complicated and expensive depending on the method, the time axis variation correction range is narrow, the responsiveness of time axis variation correction is poor,
Each method has its advantages and disadvantages, including problems such as poor utilization of the transmission band and generation of unnecessary components.

In view of the above-mentioned problems in the conventional method, the present invention
It is an object of the present invention to provide a recording and reproducing method that is not affected by jitter of a recording and reproducing device in recording and reproducing color signals, allows effective use of a transmission band, and has a simple configuration.

The outline of the present invention is to convey color signals 2n-1 to be recorded during recording.
Is the frequency of the wave signal f1=Fc+? FH (Fc: color signal carrier signal frequency, FH: horizontal scanning frequency, n: O, ±1
, ±2, . width demodulation, heterodyne detection of the amplitude demodulated color signal with a signal of frequency F, and passing it through a comb filter to obtain a standard frequency carrier color signal from which unnecessary components have been removed;
By adding the reproduced luminance signal, a composite color television signal is obtained.

In addition, in the case of low-frequency conversion, the color signal carrier ( Is the frequency (Fcl) and frequency 2n-1 wave number higher than that?
A signal separated by FH is obtained and recorded together with the luminance signal.

This 2n-1 when playing? A color signal carrier wave of a standard frequency is obtained by heterodyne detection of a color signal carrier wave that has been low frequency converted by a signal separated by FH.

The present invention will be explained below using Examples. FIG. 1 shows an example of a specific configuration for magnetically recording and reproducing color television signals by applying the present invention.

In FIG. 1, an input terminal 1 receives a composite color television signal.

A signal of frequency F from the oscillator 3 is injected into this input color television signal. The frequency f1 of the oscillator 3 is generally selected.

However, Fc is the color subcarrier frequency (Fc-3.
579545MHz), FH is the horizontal scanning frequency (FH=
-Fc=15.734KHz). On the other hand, the frequency spectrum of the television signal is as shown in Figure 2.
In the brightness signal Y, harmonics of the vertical scanning frequency (60 Hz) are distributed around the harmonic of FH, and the level thereof is extremely small in the high frequency region.

The modulated color signal has large energy in the harmonic component of FH on both sides of Fc with Fc=1FH as the center, and the energy of the harmonic component of 60 Hz is distributed around the harmonic of FH. Now, if we assume n-0 as the injection signal f1 for such a television signal, the result will be as shown in FIG. 2.

Now, to make the explanation easier to understand, if we focus only on the carrier color signal component and remove the 60 Hz harmonic component, the relationship between the carrier color signal and F is as shown in FIG. 3a.

In Figure 3, P. are the components of Fc, P1, P2,
P3...... are upper side wave components, P-1, P-2
, P-3, . . . indicate harmonic components of the horizontal incense frequency of the lower side wave components. The composite color television signal to which the f1 frequency signal has been added in this manner is converted into a frequency modulated wave (FM wave) by the frequency modulator 4, and then transmitted through the recording amplifier 5 to the magnetic head 6 on a magnetic tape. be done.

The FM wave reproduced by the magnetic head 6' is amplified by a preamplifier 7, and a reproduced composite color television signal in which f1 is injected is obtained by a frequency detector 8. The output of the frequency detector 8 is guided to a band pass filter (BPF) 9 and a low pass filter (LPF) 10.
An injected carrier chrominance signal of f1 as shown in FIG. The carrier wave Fc and the injection signal f1 obtained at the output of the BPF 9 are each subjected to frequency fluctuations due to time axis fluctuations proportional to the frequency.

Now, if the rate of frequency fluctuation due to time axis fluctuation is X, the color signal carrier frequency is Fc(1+x), and the attention signal frequency is Fc(1+x).

Each sideband signal of the carrier color signal is also subject to frequency fluctuations at the same rate.

When such a signal is amplitude-demodulated in the circuit 11 using f1 as a carrier, each spectrum is converted as shown in FIG. 3b.

That is, carrier wave F.

(=PO) is -FH(1+x), P-1 is -FH(1
+x), P1 becomes -FlI(1+x), and the following -FH intervals: P-2, P2, P-3, P3, etc.
become that way. The signal of FIG. 3b obtained in this way is converted into a signal f1-FO-
By heterodyning with FH, an upper wave (solid line) and a lower side wave (broken line) are obtained centering on f1 as shown in FIG. 3c.

In this case, the PO of the upper side wave is Fc+-FH, and even if x is now 1%, the deviation from the normal carrier frequency Fc is, and the phase fluctuation of the carrier wave in one horizontal scanning period is.

In addition, in Fig. 3c, P1, P2, P3 on the upper side wave side
......and P-1, P-2, P on the lower side wave side
-3, ...... is the P of the upper side wave. They are arranged at intervals of approximately FH with the center at the center. Also, P-1 on the upper side wave side,
P-2, P-3, ...... and P on the lower side wave side.

．． Pl, P2, P3, ...... are in the middle of the spectrum mentioned above, and the frequency position of NfH (actually N
Each side wave is slightly shifted from fH by the time axis variation X, but if the time axis variation is 1% or less, the deviation can be ignored with respect to FH, and in an actual VTR, the time axis variation can be easily compensated for. 0.1% or less). Therefore, by passing the output of the frequency conversion circuit 12 (FIG. 3c) through a comb filter consisting of a delay line 13 and a subtracter 14 for one horizontal scanning period, the component having a spectrum at the frequency of NfH is obtained. This results in that only the components having energy at the frequency are extracted, and a carrier color signal in which the upper and lower side waves are reproduced as shown in FIG. 3d is obtained at the output of 14.

By adding the output of the comb-shaped filter 1 and the luminance signal in the adding circuit 15, a reproduced composite color television signal with substantially no time axis variation in the color signal carrier wave can be obtained.

In the circuit diagram of FIG. 1, the luminance signal spectrum level in the high frequency region is ignored as it is low, but a comb filter is installed between terminal 1 and adder 2 to remove the luminance signal spectrum in the carrier color signal band. 17, luminance signal interference can also be removed.

Next, let us explain this signal processing method mathematically.

Fc=AsinPltcOsωEt+BcOsP2f
=Ap. ;From 6 patterns Ha one book, ^^Tt book. 6^
6 H A]i1 The adjusted carrier color signal Fc is generally Sincl)Et+C-Sin(ωCt+ψ)...
・・・・・・・・・・・・・・・(1)? Since it can be considered as a harmonic of the horizontal scanning angular frequency ωH, p1−n1
ωH. It can be statistically expressed as p2=N2ωH.

(n1, N2: integers) Therefore, formula (1). ．． :-1, ↓↓R. １；−′−、Bankōichi）． ．． ．．
．． ．． ．． −． ．． ．． ．． ．． JO) When formula (2) is decomposed, it shows that seven rams exist.

Signal detection can now be considered for the carrier color signal expressed by equation (3), but first let's consider the case of synchronous detection.

In the case of synchronous detection, Sin(ω) is expressed in equation 5).

-ωH)T and extract the low frequency component, so the detection output G(t) is the carrier component P in equation (6).

This means that the side wave component is placed at one ωH, and the side wave component is placed at nωH ± one ωH.
This shows that the result will be as shown in Figure b.

is obtained.

That is, it becomes the same as equation (3), and the original signal is reproduced. Now, let's consider the case of diode detection using equation (5).

The DC component K is removed from the signal expressed by equation (6), and a signal 4sin(ω) of frequency Fc--FlI is obtained.

The signal F(t) obtained by balanced modulation with -ωH)t is (7
) is passed through a comb filter as shown in Figure 1, then ω
. The ±nωH component remains, ω. The ±(n+mi1)ωH component is removed and equation (9) is decomposed into terms. However, if the Qω equation is synthesized as a simple harmonic harmonic, then amplitude detection is performed on the l equation to obtain JM2+N2 as an output.

Here here K>A. If K is selected so that B and C are satisfied, the term in the - series can be ignored compared to 1, and V2 can be reduced.

There is no practical problem as long as the value of K is set to twice or more the amplitude of the conveying color signal. Comparing equation (self) and equation (6), if we exclude the DC term (8), the right-hand side of equation (self) is equal to 2 on the right-hand side of equation (6).
The DC term is removed from the equation (self) and 2sin(ω) is obtained as in the previous case.

By heterodyning with -7ωH)t, a component similar to equation (7) is obtained, and by passing this through a comb filter, a component of equation (8) is obtained. That is, the injection signal S
Even if in(ωo-1ωH)t is used as the carrier and detected by diode, K is AlB, . It can be seen that if the value is set sufficiently larger than C, the original signal can be restored within an allowable range of distortion components. Furthermore, in the above explanation, the case where f1=FC--FH was selected as the signal frequency f1 to be injected was explained, but at the same time, n (n=0, 1, ±2, . . .
), it can be proven that a similar transformation holds true.

Regarding time axis fluctuations in recording and playback, for example,
Due to time axis fluctuations, the time axis is t+ compared to the regular time axis t.
If Δt, all ts in equation (5) are replaced with t+Δt and synchronous detection is performed using Ksin(ωc−ωH)(t+Δt), and all ts in equation (6) are replaced with t+Δt.

The carrier in the equation (6) in which t is replaced with t + Δt (-COs (-ωHt + ψ)
The phase fluctuation component Δψ due to the time axis fluctuation of the component) is therefore the frequency fluctuation component Δt.If the time axis fluctuation rate - is 1%, Δf is 40t Hz, and even when this is heterodyned and converted to a high frequency, Δt is As it is, the carrier color signal converted to the standard frequency can sufficiently ignore the time axis fluctuation component even if the time axis fluctuation is up to about 1%.

Next, another specific example of the present invention will be shown.

FIG. 4a shows the frequency spectrum of a standard color television signal, which shows that a wide band of 0 to 4 MHz is required.

As a method of band-compressing and transmitting such a wide band signal, the carrier color signal of 3.58 MHz is converted to around 2.5 MHz by heterodyning, and the signal is interleaved with the luminance signal shown in Fig. 4b. A transmission method (buried chroma method) is known. The application of the present invention to such a buried chroma method will be explained with reference to FIG.

In FIG. 5, 21 is a composite color television signal input terminal, and 22 is an LPF for separating luminance signals in the approximately 3 MHz band.
, 23 is a BPF for separating carrier color signals, 24 is a delay line for one horizontal scanning period, and 25 is a subtracter, and 24 and 25 constitute a comb filter. 26 is a heterodyne circuit, and F of the oscillator 7.

The carrier color signal is set to around 2.5MHz (2M~
2.5M). In this case, F such that the transformed carrier chrominance signal is interleaf with the luminance signal spectrum. is set close to an integral multiple of the horizontal frequency FH. 2.5
A carrier color signal f″c whose frequency has been converted to near MHz (carrier frequency is, for example, F.

-Fc) and the signal F2 from the oscillator 28 in an adder 29. Here, F2 is set as in the previous specific example.

The signal from the adder 29 and the output luminance signal from the LPF 22 are added together by an adder 30, converted into an FM modulated wave by 31, and recorded on a magnetic tape by a magnetic head 33 via a recording amplifier 32.

The EFM wave reproduced by the magnetic head 33' is amplified by the head amplifier 34 and demodulated by the frequency detector 35.

36 is a BPF for extracting the vicinity of the carrier wave, 37 is one horizontal scanning delay line, and 38 is a subtracter. These 37 and 38 constitute a comb filter to remove the brightness spectrum.

For example, by amplitude demodulating the output of the subtracter 38 in the amplitude demodulator 39 while regarding F2 as an AM carrier,
6) Obtain a demodulated wave as shown in equation 6. The output of this demodulator 39 and the output F of the oscillator 27. The carrier wave frequency is converted to a standard frequency by heterodyning with a frequency converter 40, and unnecessary components are removed by a comb filter consisting of one horizontal scanning delay line 41 and a subtracter 42 as in the previous example. to obtain a regular carrier color signal. After passing the output of the frequency demodulator 35 through a delay time adjustment DL (duration line) 43, a subtraction circuit 44 subtracts the carrier color signal output from the subtracter 38 to obtain the carrier color signal from the luminance signal. Remove. Further, a limiter 45 extracts the F2 component, and a subtracter 46
The F2 component slightly remaining in the luminance signal is removed. The luminance signal output from subtractor 46 and the carrier color signal output from subtracter 42 are added together by adder 47, and a reproduced composite color television signal is obtained at output terminal 48.

In this case, since the F2 component set to the -offset frequency is attenuated by 3 dB by the comb filters 37 and 38, it is desirable to increase the level at the time of injection by that much.

In the above description, a case has been described in which a processed color television signal is FM-modulated and stored, but not only FM modulation but also various forms of recording can be considered depending on the characteristics of the transmission system.

FIG. 6 shows another embodiment using low frequency conversion.

In FIG. 6, a composite color television signal is input to input terminal 50. In FIG. This input color television signal is applied to a reduction filter 51 and a bandpass filter 52. The luminance signal is separated by the low-pass filter 51, and the FM
The signal is FM modulated by a modulator 53 and provided to an adder 54.
On the other hand, the carrier color signal of the input color television signal applied to the band filter 52 is separated by the band filter 52 and applied to the adder 53 . This carrier color signal is added to a signal of frequency f1 from an oscillator 55 in an adder 53. The frequency f1 of the oscillator 55 is generally selected.

However, FO is color subcarrier one frequency (Fc-3.
579545MHz), FH is the horizontal scanning frequency (FH=
? FO=15.734KHz). As shown in FIG. 7, the frequency spectrum of the carrier color signal is FO=?
Focusing on FH, 2. The FH harmonic components have large energy on both sides of f0, and the energy of the harmonic components of 60 Hz (field frequency) is distributed around the FH harmonic components.

Now, as an injection signal f1 for such a color signal,
If it is n-0, it becomes as shown in FIG.

For ease of explanation, if the harmonic component of 60 Hz is removed, the relationship between the carrier color signal and F becomes as shown in FIG. 8a.

In Figure 8, PO is F. are the components of P1, P2
, P3, ...... are upper side wave components, P-1, P
-2, P-3, . . . indicate harmonic components of the horizontal scanning frequency of the lower wave measurement components, respectively. In this way, the carrier color signal to which the signal of frequency f1 is added is converted to a low frequency by the frequency converter 56, and is converted into a signal with a spectrum as shown in FIG. Jb.

The frequencies of the respective components are f'1, P'0 . P′
1, ......, P''-1, P''-2, ...
It is converted to... For example, the frequency of P'o is 767 KHz. This low-pass conversion carrier color signal is given to the adder 54, where it is added to the FM-modulated FM luminance signal, resulting in a frequency arrangement as shown in FIG. 9 ((A) is the low-pass conversion carrier color signal, FM modulated luminance signal) is recorded on a magnetic recording medium (eg, magnetic tape) by the recording magnetic head 57.

Next, the recorded signal reproduced by the reproducing magnetic head 57/ is applied to a low-pass filter 58 and a high-pass filter 59.

Next, the FM luminance signal is separated by a range filter 59 and FM demodulated by an FM demodulator 60 to reproduce the original luminance signal and provided to an adder 61 . On the other hand, the low-pass filter 58 provides a low-pass converted color signal into which the f'I signal is injected, as shown in FIG. 8b.

The low-pass converted carrier wave f'c and the injection signal f'I obtained at the output of the low-pass filter 58 are each subjected to frequency fluctuations.

Now, if the rate of frequency fluctuation caused by time axis fluctuation is X, the low-pass conversion color signal carrier frequency is f'c(1+x), and the low-pass conversion injection signal frequency is.

Furthermore, each sideband signal of the low-pass converted carrier color signal is also subject to frequency fluctuations at the same rate.

When such a signal is amplitude demodulated by the amplitude detection circuit 62 using FC as a carrier, each spectrum is converted as shown in FIG. 8c.

That is, the low-frequency conversion carrier wave f'c(-P″o) is 1FH(1
+x), P/-1 is -FH(1+x), 4451P
'1 becomes -FH(1+x), and so on at intervals of -FH, such as 42P,, Pl2, P~3, P'3, . . .

In this way, the obtained spectrum as shown in FIG. The spectrum distribution is the same as when detected. By frequency-converting this signal using the output of the oscillator 55 by the heterodyne detection circuit 63 and passing it through the comb filter 64, only the upper and lower side waves as shown in FIG. 3d are obtained.

In this example, during reproduction, the amplitude detection is performed on the low-pass converted carrier color signal as it is, but since the detected color signal and the lower side wave component of the low-pass converted carrier color signal are in the same frequency band, the detected color signal is not detected. This lower side wave component may leak into the color signal and become a damage prevention signal.

Therefore, as another embodiment, a method may be considered in which the frequency of the low-frequency converted carrier color signal is converted to a high frequency band during reproduction, and then amplitude detection is performed. Further, in this embodiment, the signal f1 having a frequency -FH lower than the color signal carrier frequency Fc is inserted into the carrier color signal at the time of recording, but as another method, the carrier color signal may be converted to a low frequency. , a similar effect can be obtained by inserting a -FH low frequency signal to the low frequency conversion color signal carrier frequency f'o.

As described above, the present invention provides a novel method that can easily reduce the influence of time axis fluctuations that occur when recording and reproducing color television signals to a level that poses no problem in practice.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a diagram showing the spectrum of a color television signal, and Fig. 3 is a diagram showing a spectrum of a color television signal.
4 is a diagram illustrating a frequency spectrum of a color television signal; FIG. 5 is a block diagram illustrating another embodiment of the present invention; FIG. 6 is a diagram illustrating a frequency spectrum of a color television signal; Block diagrams showing still other embodiments of the present invention, FIG. 7, FIG. 8, and FIG. 9 are spectrum diagrams for explaining the operation of the embodiment of FIG. 6, respectively. 1... Human power terminal, 2, 15... Adder, 3... Oscillator, 4... FM modulator,
5, 7... Amplifier, 6,6''... Magnetic head, 8... FM demodulator, 9... Bandwidth amplifier, 10 ...Low frequency amplifier, 11...
... Amplitude demodulator, 12 ... Frequency converter, 13
...Delay circuit, 14...Subtraction circuit.

Claims (1)

[Claims] 1. When recording a color television signal that is a combination of a luminance signal and a phase-modulated carrier color signal, f_1=f_C+ for the color signal carrier frequency f_C to be recorded.
A signal of {(2n-1)/4}f_H (f_H: horizontal scanning frequency, n: 0, ±1, ±2, ......) is added and recorded on the recording medium, During playback, the combined recorded signal f_1 is regarded as a carrier wave, the reproduced carrier color signal is amplitude demodulated, and the amplitude demodulated color signal is expressed as f_1=f_C+
{(2n-1)/4} The signal obtained by heterodyning with the f_H signal is passed through a comb filter to obtain a standard frequency carrier color signal from which unnecessary components have been removed, and then added to the reproduced luminance signal. A color television signal recording and reproducing method characterized in that a reproduced composite color television signal is obtained. 2. A claim characterized in that harmonic components of a luminance signal that is frequency interleaved and entered in a carrier color signal band before recording are removed by a comb filter, and then a signal of frequency f_1 is added and recorded. A recording and reproducing method for color television signals according to scope 1. 3 The amplitude of the signal f_1 to be added is 2 of the carrier color signal amplitude.
Claim 1, which is characterized in that it is set to be more than double
The recording and reproducing method for color television signals described in Section 1. 4. The color television signal recording and reproducing method according to claim 1, wherein a composite color signal obtained by adding the signal f_1 is converted into a frequency modulated wave for recording and reproducing.