JPS6015195B2 - Carrier color signal processing circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Generally, a signal obtained by recording and reproducing a video signal using a VTR (video tape recorder) has a time axis error due to a tape speed error or the like.

In particular, the influence of this time axis error is large on the conveyance color signal, and the correct color image is not reproduced on the monitor screen, but becomes distorted. In this invention, as described above, the processing of the carrier color signal including the time axis error is devised so that the carrier color signal without the time axis error can be obtained.

Hereinafter, an example of a processing circuit for carrier color information according to the present invention will be described as a playback output signal using a so-called direct recording type recorder/player in which the carrier color signal in a color video signal is recorded in its original form without being subjected to low frequency conversion. Let's take the case of processing as an example and explain it with reference to the figure. In addition, in this invention, when the recording/playback device is played back in a normal state, and when the tape is played back in a state where the tape speed is different from the normal state, such as slow motion playback, still playback, or quick motion playback, The playback output is also taken into account, and for this reason switches 1 and 2 are provided in this example.

In FIG. 1, 11 is an input terminal, through which the reproduced color video signal Sv is supplied to the amplifier 12.
The video signal passed through this amplifier 12 is passed through the low pass filter 1.
3 and a bandpass filter 14, the low-pass filter 13 supplies the luminance signal SY, and the bandpass filter 14 supplies the carrier frequency 3. Handling MHZ transport color signal S
c are obtained respectively.

The luminance signal SY is then supplied as is to the synthesizer 16,
On the other hand, the carrier color signal Sc is processed by the processing circuit 15 to correct the time axis error, as will be described later, and is then processed by the synthesizer 16.
is supplied to the synthesizer 16 and combined with the luminance signal SY.
A color video signal with better time axis error correction can be obtained.
This is taken out from the output terminal 17.

The processing circuit 15 operates as follows.

That is, the carrier color signal Sc from the bandpass filter 14 is supplied to the frequency converter 18, and on the other hand, the frequency converter 18 is supplied with the conversion signal SF of 5.01 MHz. 5.01-3. Spots = 1.
A converted carrier color signal Scc converted to 43MHZ is obtained. In this case, the conversion signal SF, which is different between normal reproduction and other reproduction, is formed as follows.

When the color video signal Sv is obtained by normal reproduction, switch 1 is connected to the contact N side,
The 14.3 MHz oscillation signal So from the reference oscillator 19 is combined with the frequency divider 201 and divided into 1/4, and from this, 3. A fractional MHz signal S, is obtained and coupled to the frequency converter 21.

Further, the oscillation signal So from the oscillator 19 is supplied to the frequency divider 22 and divided into 1/10, thereby obtaining a signal S2 of 1.49MH2, which is supplied to the frequency converter 21 and becomes the signal S. After multiplication, a 5.01 MHz signal is obtained from this frequency converter 21, and this is the conversion signal S.
F, is supplied to the frequency converter 18. When the playback output signal is for slow motion playback or still playback, the switch is connected to contact S.

At this time, a horizontal synchronizing signal is extracted from the input color video signal Sv by the horizontal synchronizing signal separation circuit 23, and this signal is sent to the variable frequency oscillator 24 with a center oscillation frequency of 3.58 MHZ.
3., which is synchronized with the horizontal synchronization signal, is supplied to an AFC circuit 27 consisting of a 2/455 frequency divider 25 and a phase comparator 26. A signal S3 of uneven MHZ is obtained, and this signal S3 and the 1.43MHZ signal from the frequency divider 22 are
is supplied to the frequency converter 21 and multiplied by the signal S2, thereby forming a conversion signal SF of 5.01 MHz. In this case, the signal S3 is a signal synchronized with the horizontal synchronization signal and includes a time axis error based on the horizontal synchronization signal of the input video signal, and the frequency converter 18 removes the resulting time axis error.

The reason why the conversion signal SF is formed differently during normal playback and during other special playback is as follows. That is, the carrier color signal in the input video signal in this case has a carrier frequency of 3. Since the frequency is as high as MH2, the time axis fluctuation based on the horizontal synchronization signal is almost visible during normal playback compared to this 3.59MH2 signal. In this case, the period of the horizontal synchronization signal is greatly disturbed, so it is preferable to make a rough correction based on this.

Furthermore, when a signal from the AFC circuit 27 is used during normal reproduction, due to the delay in the AFC circuit 27, the frequency converter 18 has a signal fluctuation that is delayed from the signal at that time. This is because the result is that the carrier color information signal Sc is converted by the signal, which is rather undesirable. In this way, the converted carrier color signal Scc obtained from the frequency converter 18 is supplied to the frequency converter 28, where it is converted by the 5.01 MHZ conversion signal Sp2 having time axis fluctuation, and is converted back to the original signal. carrier frequency 3
．． The signal is returned to the carrier color signal Sc of the mottled MHZ, and the time axis variation is canceled out to remove this time axis variation.

In this case, the conversion signal SF2 having a time axis variation is formed as follows.

That is, the converted carrier color signal Scc is transmitted to the burst gate circuit 29.
From this, an intermittent burst signal SBc of 1.43MH2 (Fig. 2A) is obtained, which is supplied to the open A
The PC circuit 3 is supplied with a burst signal S8.
A continuous wave signal Ss of 1.43 MHz is formed which is synchronized with the phase of c and therefore has a time axis fluctuation based on the burst signal.

That is, the converted burst signal S8c is transmitted to the detectors 300 and 30.
1, and the 1.43 MHZ signal S2 from the frequency divider 22 is supplied to phase shifters 302 and 303, respectively. The phase shifter 303 obtains a signal S having a phase different by 90 degrees from the burst signal.

The signal S2 is then supplied to the detector 30, thereby producing a burst signal S8. is detected and its detection output S
. , (FIG. 2B) is supplied to the sampling and holding circuit 304, where it is sampled by the horizontally periodic sampling signal SP (FIG. 2C), the sampled value is held, and the hold voltage SE,
(FIG. 2D) is supplied to a modulator 305, which modulates the signal S from the phase shifter 302, from which a continuous wave signal SM, (FIG. 2E) is obtained. Further, the signal S22 from the phase shifter 303 is supplied to the detector 301 and becomes a burst signal S8. is detected, and the detection output So2 is
Similarly, the signal S22 is sampled and held in the sampling hold circuit 306, and the signal S22 is modulated in the modulator 307 by the hold output SE2, thereby obtaining the continuous wave signal SM2. A signal obtained by combining the output signals SM and Sw2 is sent to the low-pass filter 308 and the limiter 30.
9, and a continuous wave signal Ss is obtained at the output terminal of the open APC circuit 30. The signal Ss obtained from this open APC circuit 30 is the converted burst signal SBc.
Therefore, it is a continuous wave signal that includes a time axis error based on the burst signal.

The 1.43 MHZ continuous wave signal S8 obtained in this way is supplied to the frequency converter 31, which converts the 3.
．． It is multiplied with the irregular MHZ conversion signal SF3 to form a 5.01 MHZ conversion signal SF2.

In this case, the continuous wave signal Ss is an intermittent burst signal SB
Since it was formed from c, data for time axis fluctuations can only be obtained intermittently. Therefore, the phase variation is the solid line 3 in Fig. 3A.
If the amount of phase fluctuation in one horizontal period is large as shown in
There is no problem with the carrier chrominance signal immediately after the burst signal, but the phase correction error cannot be ignored for the carrier chrominance signal at the end of one horizontal section. In other words, the amount of correction based on the burst signal SBc is
This results in a stepwise pattern as shown by the solid line 4 in FIG. In order to reduce this phase correction error, intermittent data may be linearly approximated to detect a speed error, and this may be added.

That is, as shown by the solid line 5 in FIG. 3B, a slope-shaped correction amount is created in each horizontal section according to the correction error.

If this is added to the stepwise correction amount as shown by the solid line 4 in FIG. , thereby returning the converted carrier color signal Scc to a signal of the original carrier frequency, the carrier color signal Sco becomes a signal with almost all time axis errors removed. Therefore, the conversion signal SF3 has a speed error, and during normal playback, the switch 2 is connected to the contact N and the first
A speed error is detected in the speed error detection circuit 32.

That is, the color video signal Sv from the terminal 11 is supplied to the burst gate converter 321, thereby obtaining the burst signal S8 (FIG. 2F), which is supplied to the phase comparator 323. In this, the phase is compared with the burst signal from the delay circuit 322 one horizontal period before, and the comparison error voltage V, (FIG. 2G) is obtained as the output signal of the circuit 32. This error voltage V, is the slope forming circuit 3.
3 to form a linear slope such that the voltage V is reached at the end of one horizontal section, and the signal SL having this slope (H in FIG. 2) is coupled to the phase modulator 34. .

Then, in this phase modulator 34, the three-wavelength MHZ reference signal S from the frequency divider 20 is phase-modulated by the signal SL, and the modulator 34 has a velocity error component 3. A signal SF3 of the MHZ is obtained. Then, the continuous wave signal Ss is converted by the frequency converter 31,
The conversion signal SF2 is formed by adding the speed error to the time axis error based on the burst signal.

During slow motion playback or still motion playback, switch 2 is connected to contact S.
A slope signal is formed from the speed error output from the speed error detection circuit 35.

This is because the first detection circuit 32 uses an intermittent burst signal of one horizontal period, and the delay amount of the delay circuit is fixed at exactly one horizontal period, but the horizontal period changes during variable speed playback. Therefore, the burst signals to be compared are not at the same phase point of the burst signals, but instead output an erroneous signal, resulting in a disturbance. Therefore, the following detection circuit 35 is used. That is, the output signal S of the open APC circuit 30
s is supplied to the delay circuit 351, from which the signal Sc
o (FIG. 2, 1) is obtained, and the phase comparator 352 outputs the burst signal SBc from the burst gate circuit 29 and the signal Ss. are compared. That is, the burst signal S8c,
1 formed from burst information one horizontal period before this one
The phase of the signal immediately before the burst signal S8c at the end of the continuous wave signal portion of the horizontal section is compared, and the comparison output V
2 is obtained as the output of this detection circuit 35 and is supplied to the slope forming circuit 33. In this case, the second
Since the speed error detection circuit 32 detects the phase error between the burst signal and the continuous wave signal just before it, more accurate detection is possible than the detection in the first speed error detection circuit 32. The phase difference approximated by the slope thus formed is closer to the time axis error of the input signal. - From this, it is conceivable to use the second speed error detection circuit 35 to form the slope signal SL even during normal reproduction.

However, when detecting with the detection circuit 35, the AP
Since the signal obtained through the C circuit 30 is used, the amount of delay is relatively large, but since the detection circuit 32 detects speed errors from the input color video signal Sv, the amount of delay is small, so normal playback is possible. In this case, it is possible to more accurately correct the time axis error by using the detection output from the detection circuit 32 as in this example.

As described above, in the present invention, during normal reproduction, the frequency conversion signal is generated from the first speed error formed based on the burst signal from the first detection circuit 32 and the burst signal before this burst signal. During variable speed playback, a frequency conversion signal is formed from the second speed error formed from the burst signal from the second detection circuit 35 and a continuous wave signal formed based on this burst signal, and thereby the frequency conversion signal is Since the frequency of the color signal is converted, the time axis variation included in the carrier color signal can be effectively removed not only during normal playback but also during variable speed playback.

In the above example, a case was explained in which a reproduced video signal from a recording/reproducing device using a direct recording method is processed. The same applies to the case of

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an example of a carrier color signal processing circuit according to the present invention, FIG. 2 is a waveform diagram for explaining the circuit, and FIG. 3 is a waveform diagram for explaining the operation of its main parts. 14 is a band pass filter, 18, 21, 28, 31 is a frequency converter, 19 is a reference oscillator, 29 is a burst gate circuit, 30 is an open APC circuit as an example of a continuous wave signal forming circuit, 35 is a speed error detection circuit ,．． 33 is a slope forming circuit, and 34 is a phase modulation circuit. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A continuous wave signal forming circuit that forms a continuous wave signal having a time axis error included in a burst signal in a carrier color signal;
a first detection circuit that detects a first speed error based on the burst signal and a previous burst signal; and a second detection circuit that detects a second speed error based on the continuous wave signal and the burst signal. a selection circuit that selects a first speed error during normal playback and a second speed error during variable speed playback; and a circuit that phase modulates the reference signal using the speed error selected by the selection circuit. A carrier color signal processing circuit comprising a circuit for forming a conversion signal for frequency converting the carrier color signal using the phase modulated signal and the continuous wave signal.