JPH02290397A - Recorder for chroma signal - Google Patents

Abstract

PURPOSE:To reduce other signal component mixed in a chroma signal by increasing the characteristic of an emphasis circuit as a contour component of a chrominance carrier signal is parted from a center frequency and as a level of a contour component is larger. CONSTITUTION:Only a chroma signal in a video signal inputted from an input terminal 1 is extracted by a BPF 7 and the level of the signal is adjusted to be constant with an ACC circuit comprising a variable gain amplifier 8 and a detection circuit 12. The chroma signal passes through a chroma signal recording processing circuit 9 and the chroma signal whose low level signal is emphasized at a chroma emphasis circuit 31 is subjected to low frequency conversion at a chroma signal processing circuit 10 and outputted to a mixing circuit with a luminance signal from an output terminal 32 as a low frequency conversion chrominance carrier signal via an LPF 11. On the other hand, the input signal to an input terminal 33 is converted into an original chroma signal via an ACC circuit comprising an LPF 25, a variable gain amplifier 25 and a detection circuit 29, a reproduction processing circuit 26 and a comb-line filter 27 and the nonlinearity characteristic is corrected by a CDEE circuit and the resulting signal is outputted via a reproduction processing circuit 28.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing device for color video signals, and is particularly suitable for suppressing other signal components mixed in as sideband components, that is, contour components of a carrier color signal. The present invention relates to a chroma signal recording device.

Figure 1 shows the configuration of the signal processing circuit of a conventional video tape recorder (hereinafter abbreviated as VTR). First, let's talk about records. The signal input from the video signal input terminal 1 is sent to the L.
P. F2 and B. P. The signal is divided into a luminance signal and a chroma signal by F7.

The luminance signal is processed by a luminance signal recording processing circuit 3 and a frequency modulation circuit 4.
, H. P. The signal is recorded by F5 and input to the mixing circuit 6. On the other hand, the chroma signal is generated by A, C, which is composed of a variable gain amplifier 8 and a detection circuit 12. C. The (automatic chroma signal control) circuit sets the level so that the output signal level is always constant even if the input signal level fluctuates. Thereafter, the chroma signal recording processing circuits 9 and 10 and the L. P. The chroma signal converted into a low-pass conversion carrier color signal by Fil is input to the mixing circuit 6, where it is superimposed on the frequency-modulated luminance signal. The recording video signal output from the mixing circuit 6 is amplified by a recording amplifier circuit 13 and recorded on a magnetic tape 15 via a video head 14. Note that the chroma signal recording processing circuits 9 and 10 are, for example, all or part of a frequency conversion circuit, a burst emphasis circuit, and a pseudo burst addition circuit.

Next, playback will be explained. The signal reproduced from the magnetic tape 15 via the video head 16 is transmitted to the reproduction amplifier circuit 1.
7 and amplified with H.7. P. F18 and L. P. The signal is divided into a luminance signal and a chroma signal by F24. The frequency-modulated luminance signal is processed by the luminance signal reproduction processing circuit 19.21
and is demodulated into a luminance signal by the demodulation circuit 20, P,F
22 and input to the mixing circuit 23. On the other hand, the low-frequency conversion carrier chrominance signal passes through an ACC circuit consisting of a variable gain amplifier 25 and a detection circuit 29, and then passes through a chroma signal reproduction processing circuit 26,'
28 and a comb filter 27 , the low-pass conversion carrier color signal is converted into a chroma signal, and the signal is input to the mixing circuit 23 . The luminance signal and the chroma signal are mixed in the mixing circuit 23 and outputted from the output terminal 30 as a reproduced video signal.

The luminance signal reproduction processing circuit 19 is, for example, a dropout canceller circuit or a limiter circuit, and the luminance signal reproduction processing circuit 21 is a luminance signal de-emphasis circuit. Generally, the limiter circuit needs to be in the circuit 19. Further, the chroma signal reproduction processing circuit 26 is a circuit including at least a frequency conversion circuit, and the chroma signal reproduction processing circuit 26 is a circuit that includes at least a frequency conversion circuit.
8 is, for example, a burst de-emphasis circuit, a pseudo-burst removal circuit, and an H PF.

In a conventional VTR having the circuit configuration as described above, the characteristics of the comb filter provided on the reproduction side play an important role. In other words, the comb filter is a 1H delay line (
(IH refers to the horizontal scanning period), but in reality, spurious signals are generated from the delay line and appear as disturbances on the screen, causing problems. In addition, the luminance FM signal and the low-frequency conversion carrier color signal have partially overlapping bands, and crosstoe caused by the lower side band of the luminance FM signal to the low-frequency conversion carrier color signal causes cross color, which poses a problem. Furthermore, the number of deviations of H from the adjacent track (hereinafter α
(abbreviated as H) is 1.0H or 0.75H, the I-i arrangement (the recording positions of horizontal synchronization signals are adjacent to each other between adjacent tracks) is shifted, and burst signals may be generated from adjacent tracks. It becomes crooked.

SUMMARY OF THE INVENTION An object of the present invention is to provide a chroma signal recording device that eliminates the drawbacks of the prior art and reduces other signal components mixed into the chroma signal.

In order to achieve the above object, in the present invention, an emphasis circuit is provided in a chroma signal recording system for emphasizing the contour component of a carrier color signal. The emphasis characteristic of this emphasis circuit is set so that it increases as the contour component moves away from the center frequency, and further increases as the level of the contour component increases.

An embodiment of the present invention will be explained below with reference to FIGS. 2 and 3. 2 and 3 show the configuration of a chroma signal recording and reproducing circuit according to the present invention. The difference from the conventional example shown in FIG. 1 is that a chroma emphasis circuit 31 and a chroma de-emphasis circuit 34 are provided. In other words, during recording, a non-linear circuit called a chroma emphasis circuit is provided to enhance low-level signals during recording, and during playback, a chroma de-emphasis circuit is used, which has a complementary relationship with the input-to-output characteristics of the non-linear circuit in the recording system. By providing a circuit, nonlinear characteristics during recording are removed and the original signal is restored.

In FIG. 2, among the video signals input from the input terminal 1, B. P. F. 7, only the chroma signal is extracted. Thereafter, the chroma signal adjusted to a constant level by an ACC circuit consisting of a variable gain amplifier 8 and a detection circuit 12 passes through a chroma signal recording processing circuit 9 and is input to an evening ROMA emphasis circuit 31. The chroma signal whose low-level signal is emphasized by the chroma emphasis circuit 31 is frequency-converted to a low frequency signal by the next chroma signal recording processing circuit 1o, and the L
．． P. F. 11, and is output as a low frequency conversion carrier color signal from an output terminal 32 to a mixing circuit with a luminance signal. The above is the chroma signal recording circuit according to the present invention.

FIG. 3 shows a chroma signal reproducing circuit. The signal amplified by the reproducing amplifier is input to the input terminal 33. L. P
．． The chroma signal extracted by the F24 is adjusted to a constant level by an ACC circuit consisting of a variable gain amplifier 25 and a detection circuit 29, and is converted from the low-pass converted carrier color signal to the original by a chroma signal regeneration processing circuit 26 and a comb filter 27. Converted to chroma signal. Thereafter, the chroma signal corrected for the nonlinear characteristics performed by chroma emphasis during recording is processed by the chroma de-emphasis circuit 34.
The signal passes through the chroma signal reproduction processing circuit 28 and is output from the output terminal 35 to a mixing circuit with a luminance signal.

According to this embodiment, (1) cross-color interference due to crosstalk from the lower sideband of the luminance FM signal, which has been a problem in the past, (2) < spurious interference (especially Burst and pseudo-burst interference is large) (3) Burst signals from adjacent tracks when H alignment is not formed or! Leakage of 0-like burst signals is suppressed, which has the effect of improving chroma S/N.

The first characteristic of FIGS. 2 and 3 is that the chroma de-emphasis circuit 34 is provided after the comb filter 27. The reason for this is due to (2) and (3) of the conventional problems mentioned above.
This is to solve the problem. That is, regarding (2), since the burst disturbance depends on the output of the comb filter, the only way to suppress this is to provide the de-emphasis circuit 34 on the output side of the comb filter 27.

Regarding (3), the effect of the de-emphasis circuit 34 cannot be produced unless crosstalk from adjacent tracks is sufficiently suppressed by the comb filter 27. For this reason as well, it is necessary to provide the de-emphasis circuit 34 on the output side of the comb filter 27.

The second feature of FIGS. 2 and 3 is that the ACC loop is designed so that the input signal (or output signal) level of the chroma emphasis circuit 31 and the output signal (or input signal) level of the chroma de-emphasis circuit 34 are approximately equal. It is composed of

Both the chroma emphasis circuit 31 and the chroma de-emphasis circuit 34 are non-linear circuits, and in order for each to become an inverse circuit, the input signal level of the emphasis circuit 31 and the output signal level of the de-emphasis circuit 34 need to be approximately equal. .

Since the ACC circuit operates so that the input signal level of the detection circuit 12.29 is constant, it is arranged so that the input signal of the detection circuit 12 and the input signal of the emphasis circuit 31 are almost the same. It is necessary to arrange so that the input signal and the output signal of the de-emphasis circuit 34 are approximately equal.

Alternatively, it is also possible to arrange the input signal of the detection circuit 12 to be approximately the same as the output signal of the emphasis circuit 31. In this case, the arrangement may be such that the input signal of the detection circuit 29 is almost the same as the input signal of the de-emphasis circuit 34. Although the detection loop of the ACC circuit is taken out before the chroma emphasis circuit in FIG. 2, it can also be taken out after the chroma emphasis circuit. Similarly, the detection loop in FIG. 3 can be taken out before the chroma de-emphasis circuit.

Examples of the chroma emphasis circuit and chroma de-emphasis circuit described above are shown in FIGS. 4 and 5. The chroma emphasis circuit shown in FIG. 4 divides the chroma signal input from the input terminal 36 into a path through which it passes through the limiter circuit 37 and a path where the original signal remains unchanged. These are added and mixed in an adder circuit 38 and outputted from an output terminal. The limiter circuit 37 outputs a signal whose amplitude is limited in response to a large amplitude signal, and the characteristics of the chroma emphasis circuit shown in FIG. will be restricted. The chroma de-emphasis circuit shown in FIG. 5 is a version of the circuit shown in FIG. 4 which has negative feedback type reverse circuit characteristics. The reproduced chroma signal inputted from the input terminal 40 is subtracted from the signal fed back from the output terminal 42 through the limiter 37 by the subtraction circuit 41, and is outputted to the output terminal 42. That is, assuming that the transfer function of the limiter circuit 37 in FIG. 4 is Hl(ω), the transfer function R(ω) of the chroma emphasis circuit is expressed by the following equation.

R(ω)=1+H■(ω) Furthermore, the transfer function P(ω) of the chroma de-emphasis circuit shown in FIG. 5 is expressed by the following equation.

P(ω)=1/ (1+H1(ω)} Therefore, if the transfer functions H1(ω) of the limiter circuits for emphasis and de-emphasis are equal, the overall transfer characteristic of emphasis and de-emphasis is R(・)・P(・)= {1+H・(・)}/(1+H,
(,.,))=', the nonlinear characteristics caused by the emphasis circuit are corrected by the de-emphasis circuit, and the original signal can be almost completely restored.

Other examples are shown in FIGS. 6 and 7. The difference from FIGS. 4 and 5 is that a chroma signal sideband extraction circuit 43 having the characteristics shown in FIG. 8 is provided in the limiter circuit path. In other words, emphasis is applied only to the sideband of the chroma signal. The sideband of the chroma signal is a high frequency band with a low level, and is susceptible to noise. Therefore, by performing sideband emphasis during recording and performing sideband de-emphasis during reproduction, the S/N of the chroma signal can be improved and a reproduced image of high quality can be obtained.

In FIG. 6, the input terminal 36 has a carrier color signal (first
Figure 1 (a)) is input and the side band is removed @N4
Supplied to 3. The side band extraction circuit 43 is the eighth
Since it has the frequency characteristics shown in the figure, the center frequency is suppressed from the carrier color signal shown in FIG. 11(a), and only the contour component of the carrier color signal is extracted as shown in FIG. 11(b).

As is clear from FIG. 11(a), the contour component becomes larger when the level change of the carrier color signal is larger. The limiter circuit 37 limits the large amplitude exceeding a predetermined limit level in the contour component of the carrier color signal shown in FIG. 11 (opening), and outputs a signal as shown in FIG. 11 (c). This A3 is converted into the original carrier color signal (Fig. 1-1 (A)) by the adder circuit 38.
, and a signal as shown in FIG. 11 (2) is obtained at the output terminal 39. In this emphasis circuit, the large amplitude contour component is level-limited by the limiter circuit 37 and added to the original carrier color signal, so the emphasis effect on the contour component remains constant from the depth of the contour component to the limit level. The emphasis effect decreases as the contour component increases beyond the limit level.

FIGS. 9 and 10 show a case where the chroma processing circuit of the present invention is used for both recording and reproduction. In FIG. 9, the recording/reproduction changeover switch 47 plays an important role. First, recording will be explained. Of the video signals, only the chroma signal is input to the input terminal 44. During recording, the recording/reproducing switch 47 is in the position shown, and the variable gain amplifier 8 and the detection circuit 12 operate as a recording ACC circuit. Level by ACC circuit! The I1 adjusted chroma signal is passed through the chroma signal recording processing circuit 9 to the rechroma emphasis circuit 3.
1, and low level signals are emphasized. The chroma signal is further frequency-converted to a lower frequency band by the chroma signal recording processing circuit 10 and outputted to the output terminal 45. Next, reproduction will be explained. Of the reproduced video signals, only the chroma signal is input to the input terminal 44 which is common to recording. During reproduction, the recording/reproduction changeover switch 47 is switched to the opposite position from that shown, and the gain amplifier 8 and the detection circuit 12 operate as an ACC circuit for reproduction. The chroma signal that has passed through the ACC circuit is converted by the chroma signal reproduction processing circuit 26 and the comb filter 27 from a low frequency conversion carrier color signal to the original chroma signal. Thereafter, the chroma signal, which has been corrected by the chroma de-emphasis circuit 34 for the characteristics performed by the emphasis circuit during recording, passes through the chroma signal reproduction processing circuit 28 and is output from the output terminal 46. By providing the recording/playback switch 47 as described above, recording and playback ACC can be achieved.
The circuit can be used for multiple purposes.

FIG. 10 shows an example in which the loop of the ACC detection circuit is different from that shown in FIG. 9. In the case of recording, the loop is returned to the detection circuit 12 after the chroma emphasis circuit 31, and in the case of reproduction, the chroma emphasis circuit is returned to the detection circuit 12. The signal is returned from before the de-emphasis circuit.

Although the above chroma emphasis and chroma de-emphasis have been explained using carrier color signals, it is of course possible to perform emphasis and de-emphasis using low-frequency conversion color signals.

Also, the emphasis may be only on the chroma sideband.

According to the present invention, it is possible to reduce the noise mixed in the chroma signal, thereby improving the chroma S/N of the reproduced image.

In particular, spurious interference in the delay line that constitutes a comb filter, cross-color interference from luminance FM signals, VI
Burst signal leakage from J track and AT
The effect of the present invention on chroma interference of the pilot signal for F is extremely large.

Furthermore, according to the present invention, the recording emphasis circuit and the reproducing de-emphasis circuit can be easily reversed, resulting in extremely good restorability.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional signal processing circuit, Fig. 2 is a block diagram of chroma signal recording processing using the present invention, Fig. 3 is a block diagram of chroma signal reproduction processing using the present invention, and Fig. 4 is a block diagram of a conventional signal processing circuit. , FIG. 5 is a block diagram showing a chroma emphasis circuit and a chroma de-emphasis circuit, FIGS. 6 and 7 are block diagrams showing another emphasis circuit and a de-emphasis circuit,
Figure 8 is a characteristic diagram showing the sandband emphasis characteristics.
9 and 10 are configuration diagrams showing an example in which the ACC circuit is shared between recording and reproduction, and FIG. 11 is a waveform diagram showing signal waveforms at various parts in FIG. 6. 8, 25... Variable gain amplifier, 12.29... Detection circuit, 31... Chroma emphasis circuit, 34... Chroma de-emphasis circuit, 27... Comb filter, 37... Limiter circuit, 38... Addition circuit, 41... Subtraction circuit, 43... Chroma signal sideband extraction circuit, 47
... Recording/playback switching circuit. Fig. Z Fig. q Fig. I2 Fig./2 Fig. Fig. Fig. A Fig. Color temperature/j

Claims (1)

[Claims] 1. A chroma that converts the frequency of a carrier color signal into a frequency band that is on the lower side of a frequency modulated luminance signal and that can be interfered with by the lower frequency components of the frequency modulated luminance signal and records it on a recording medium. The signal recording device is provided with an emphasis circuit that nonlinearly emphasizes the carrier color signal, and the amount of emphasis by this emphasis circuit is, for input signals of the same level, from the center frequency in the frequency band of the carrier color signal. 1. A recording device for a chroma signal, which increases as the distance increases, and for input signals of the same frequency, the lower the level, the higher the chroma signal becomes. 2. Claims characterized in that the emphasis circuit includes a limiter circuit for a transfer function H(ω) (ω is the angular frequency of the carrier color signal) and has a comprehensive characteristic of the transfer function 1+H(ω). 2. The chroma signal recording device according to item 1.