JPS58166896A - Recording and reproducing circuit of chroma signal - Google Patents

Abstract

PURPOSE:To improve the S/N of a chroma signal, by emphasizing the chroma signal with addition of an output signal of an amplitude limiter during the recording and then controlling the chroma signal with the characteristics complementary with a recording system at a post stage after a comb-shaped filter during the reproduction. CONSTITUTION:The chroma signal is impressed to an input terminal 44. A recording/reproducing changeover switch 47 is set at the position as shown in the diagram in a recording mode. In this case, a variable amplifier 8 and a wave detecting circuit 12 function as an AC circuit for recording. The chroma signal whose level is controlled by an ACC circuit is fed to a chroma emphasizing circuit 31 after passing through a chroma signal recording circuit to emphasize the chroma signal of a low level and the frequency of the chroma signal is converted into a low level through a chroma signal recording circuit 10 to output the chroma signal. In a reproduction mode, the switch 47 is switched to the position opposite to the positio shown in the diagram. Thus the amplifier 8 and the circuit 12 function as an ACC circuit for reproduction. The chroma signal passed through the ACC circuit receives a compensation from a de-emphasizing circuit 34 provided at a post stage after a comb-shaped filter 27 for the characteristic emphasized by the circuit 31. Then the chroma signal is delivered 46.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a chroma signal recording/reproducing system, and is suitable for reducing noise mixed into low-level chroma signals by 1%.

FIG. 81 shows the configuration of a signal processing circuit of a conventional video tape recorder (hereinafter abbreviated as VTR). First, description 11 will be explained. The signal input from the signal input terminal 1 is divided into a luminance signal and a chroma signal by P, F 2 and B, P, F 7.

The luminance signal is processed by a luminance signal recording processing circuit 3 and a frequency modulation circuit 4.
, H, P, F 5 and is recorded and input to the mixing circuit 6. On the other hand, the chroma signal is processed by A, C, C, (automatic chroma signal side'
The level is set by the control) circuit so that the output signal level is always constant even if the input signal level fluctuates.

After that, the chroma signal recording processing circuits 9, 10 and P,
The chroma' signal converted into a low-pass conversion carrier chrominance signal by F, 11K 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 card 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, Il, P, F, 18 and Ri, P, F
, 24 into a luminance signal and a chroma signal. The frequency-modulated luminance signal is demodulated into a luminance signal by a luminance signal reproduction processing circuit 19, 21 and a demodulation circuit 20,
It is input to the mixing circuit 25 through L, p, 1.22. On the other hand, the low-pass converted carrier color signal passes through an ACC circuit consisting of a variable gain amplifier 25 and a detection circuit 29, and is applied to a chroma signal reproduction processing circuit 26.2B and a comb filter 27. The signal is converted into a signal and 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, a limiter circuit, or a limit 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.
B is an example of an everburst de-emphasis circuit, a pseudo-burst removal circuit, and an HpF.

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 has a 1H delay line (1
(H 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 a problem. In addition, the luminance FM signal and the low-frequency conversion carrier color signal have partially overlapping bands, and crosstalk to the low-frequency conversion carrier color signal caused by the lower side band of the luminance FM signal causes cross color, which poses a problem. Furthermore, the number of deviations of H from the adjacent track (hereinafter αB
(abbreviated as ) is toB or α75H, the I alignment (the recording positions of horizontal synchronization signals are adjacent to each other at adjacent tracks) may be misaligned, causing a problem of burst signals leaking from -tangential tracks. Become.

SUMMARY OF THE INVENTION An object of the present invention is to provide a ROMA signal recording and reproducing circuit for a video tape recorder which eliminates the drawbacks of the prior art and reduces noise mixed into chroma signals.

In order to achieve the above object, the present invention includes an amplitude limiter that limits the amplitude of the chroma signal applied to the input terminal to which the chroma signal is input and the cough input terminal, and the output signal of the skeleton chroma signal and the scissors amplitude limiter. By adding the output signal of the scissor amplitude limiter during recording, the chroma signal is strengthened, and during playback, the chroma signal is added to the output signal of the scissors amplitude limiter. By adjusting and reproducing with certain characteristics, the chromaticity is improved.

An embodiment of the present invention will be explained below with reference to FIGS. 2 and 5. #I2 and FIG. 5 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 for 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, only the chroma signal is extracted from the video signal input from the input terminal 1 through R, p, and F.7. Thereafter, the chroma signal adjusted to a constant level by an ACC circuit comprising a variable gain amplifier 8 and a detection circuit 12 is inputted to a chroma emphasis circuit 31 through a chroma signal recording processing circuit 9. The chroma signal whose low level signal has been emphasized by the chroma emphasis circuit 31 is increased in frequency to the low range by the next chroma signal recording processing circuit 10, and is
, P, F, 11, and is outputted 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. 6 shows a chroma signal regeneration circuit according to the present invention. The signal amplified by the reproducing amplifier is input to the input terminal 33. The chroma signals extracted from L, P, and 124 K are adjusted to a constant pel level by an ACC circuit consisting of a variable gain amplifier 25 and a detection circuit 29, and are subjected to low frequency conversion by a chroma signal regeneration processing circuit 26 and a comb filter 27. The carrier chroma signal is converted to the original chroma signal. After that, the chroma de-emphasis circuit 54 corrects the non-linear characteristics performed by the chroma encoder during recording, and the chroma signal passes through the chroma signal reproduction processing circuit 28 and is sent from the output terminal 55 to a mixing circuit with the luminance signal. Output.

According to this embodiment, the conventional problem of +1) < spurious visit IF generated from the delay-in constituting the L-type filter (the interference of the bar-odd pseudo burst is large in #) (2) the lower band of the luminance FM signal P scalar interference due to crosstalk of band waves (3) Leakage of burst signals or pseudo burst signals from adjacent tracks when H alignment is not performed is suppressed, and there is an effect of improving chroma S cooling.

The first characteristic in FIGS. 2 and 3 is that the chromadier emphasis circuit 34 is provided after the comb filter 27. The reason for this is +11 and (3) of the conventional problems mentioned above.
) to solve the problem. That is, for +11, since burst interference occurs at the output of the comb filter, the de-emphasis circuit 54 must be provided on the output side of the k-comb filter 27 to suppress this.

As for (3), the effect of the de-emphasis circuit 54 cannot be produced unless the crosstalk from adjacent tires is sufficiently suppressed by the comb filter 27. From this fact, the de-emphasis circuit 54 is
It is necessary to provide it on the output side of the

The second feature of FIGS. 2 and 6 is that the input signal (or output signal) level of the Chroma En7 assist circuit 31 and the input signal (or output signal) level of the Chroma de-emphasis circuit 34 are approximately equal. It constitutes a loop. Both the chroma emphasis circuit 31 and the chroma de-emphasis circuit 34 are non-linear circuits, and in order for them to become reverse circuits, the input signal level of the encoder assist circuit 31 and the de-emphasis circuit 34 must be
must be approximately equal to the input signal level.

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 120 and the input signal of the emphasis circuit 310 are almost the same, and the input signal of the detection circuit 290 is The input signals of the de-emphasis circuit 34 and the de-emphasis circuit 34 need to be arranged so that they are approximately equal.

Alternatively, it is also possible to arrange the input signal of the detection circuit 120 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 approximately the same as the output signal of the de-emphasis circuit 34.

In addition, in Fig. 2, the detection loop of the ACC circuit is taken out from before the chroma emphasis circuit.
It can also be taken out after the chroma emphasis circuit. Similarly, the detection loop in FIG. 3 can be taken out after 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 thread path that passes through the limiter circuit 37 and a thread path that retains the original signal, adds and mixes them in the adder circuit 38, and outputs the signals to the output terminal. This is what is output from. Limiter circuit 37
outputs a signal with limited amplitude for large amplitude signals, and the characteristics of the chroma emphasis circuit shown in Figure 4 linearly enhances low level signals and controls large level signals. Become something. The chroma de-emphasis circuit shown in FIG. 5 is a subtractive mixture of the circuit shown in FIG. 4 and has reverse circuit characteristics. The reproduced chroma signal inputted from the input terminal 40 is divided into a thread path passing through the lJi signal 37 and a signal path in which the original signal remains unchanged, subtracted by a subtraction circuit 41, and outputted to an output terminal 42.

Another embodiment is shown in FIGS. 6 and 7. The difference from FIGS. 4 and 5 is that a chroma signal sideband extraction circuit 45 having the characteristics shown in FIG. 8 is provided in the thread path of the +7 miter circuit. 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 side band de-emphasis during recording and side band de-emphasis during playback, it is possible to improve the shift of the chroma signal and obtain a high-quality reproduced image.

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, recording/playback switching screen 5. Chi47 plays a liI 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 AC''C circuit.

The chroma signal adjusted to level I4 by the 4CC circuit is
The signal passes through the chroma signal recording processing circuit 9 and is input to the chroma emphasis circuit 31, where 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. ``Only the chroma signal of the reproduced video 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 passed through the ACC circuit is
Chroma signal reproduction processing circuit 26 and comb filter 27
The low-pass converted carrier color signal is converted into the original chroma signal. Thereafter, the chroma signal corrected in the chroma de-emphasis circuit 34 for the characteristics performed by the emphasis circuit during recording is outputted from the output terminal 46 through the chroma signal reproduction processing circuit 28. By providing the recording/reproduction changeover switch 47 as described above, the ACC circuit can be used for both recording and reproduction.

Figure 10 is an example in which the loop of the ACC detection circuit is different from that in Figure 9.
It returns to the detection circuit 12 after the assist circuit 31.
In the case of reproduction, the signal is returned after the chroma de-emphasis circuit.Although the above chroma en-7 assist and chroma de-emphasis were all explained in terms of carrier color signals, of course they can also be used as low-frequency conversion color signals. It is also possible to perform emphasis and de-emphasis.

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

According to the present invention, the noise mixed in the chroma signal can be reduced, and the chroma quality of the reproduced image can be improved.

%K<The effect of the present invention is extremely large for delay-in spurious interference that constitutes an L-type filter, cross-color interference from luminance FM signals, burst signal leakage from adjacent tracks, and chroma interference of pilot signals for Ar1. .

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

[Brief explanation of the drawing]

wc1 is a configuration diagram of a conventional signal processing circuit, FIG. 2 is a configuration diagram of chroma signal recording processing using the present invention, FIG. 5 is a configuration diagram of chroma signal reproduction processing using the present invention, and FIG. Fifth
The figure shows a chroma emphasis circuit and a chroma de-emphasis circuit, Figures 6 and 7 show another emphasis circuit and de-emphasis circuit, Figure 8 shows sideband emphasis characteristics, and Figure 9 shows a sideband emphasis characteristic. 10 are block diagrams of the present invention in which the ACC circuit is shared between recording and reproduction. 8.25......Variable gain amplifier 12.29
......Detection circuit 61...Chroma-emphasis circuit 64...Chroma-emphasis de-emphasis circuit 27・・・・・・・・・・・・・・・
...Comb-shaped filter 57...
・Limiter circuit 38・・・・・・・・・・・・Addition circuit 41・・・・・・・・・・・・・・・Subtraction circuit 43
・・・・・・・・・・・・Chroma signal sideband extraction circuit 47・−・・・・・・・・・・Record/playback switching circuit +144 Figure 15 Kunige et al. (¥1 Mo+70 Challenge 8 Mouth Color #J1 Report Air No. q Record) O Figure z

Claims (1)

[Claims] In an apparatus for recording and reproducing chroma signals, the recording system is provided with means for dynamically emphasizing at least the chroma signal according to the chroma signal level, and the reproducing system is provided with means for dynamically suppressing at least the chroma signal according to the chroma signal level. 1. A color signal recording and reproducing circuit, comprising a filter, and provided at a subsequent stage of an armpit-shaped filter that suppresses the chroma signal more than the dynamo.