JPS5979689A - Reproducing device of magnetic video signal - Google Patents

Abstract

PURPOSE:To prevent the generation of a flicker phenomenon due to skew distortion by compensating the pulse width varied by the skew distortion. CONSTITUTION:If the 4th pulse of a horizontal synchronizing signal appears faster by the skew distortion, an edge pulse generating circuit 35 generates an edge pulse P5 to reset a pulse generating circuit 31 at the switching of a channel. Consequently, the pulse width t1 of a pulse P3 is synchronized with a pulse P5 and turned to an L level and the pulse width t1 is turned to t1''. Since a pulse P1 resets also a counter 32, no counted output is obtained from the counter 32. On the other hand, the pulse generating circuit 31 is actuated again by the 4th pulse of a horizontal synchronizing signal and the H level part with the time width t1 corresponding to the 4 pulses of the horizontal synchronizing signal appears in the pulse P3 again. Therefore, an upper flicker due to the skew distortion does not appear in a reproduced picture.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for recording magnetic material such as 'fc
The present invention relates to a magnetic video signal reproducing device for reproducing video signals.

2-head helical power scan type magnetic video signal reproducing device f
The circuit system for reproducing video signals includes a luminance signal reproducing system and a transport color signal reproducing system. this house,
The main purpose of the carrier color signal regeneration thread is to separate the 629KH2 color signal component from the nC recorded video signal [for (1), the frequency of the 629KH2'z real carrier wave signal]
3. Returned to 58MH2.

(There is a zinc in the playback signal of the 2-pack 629KH2, so this should be removed.

etc. In order to achieve the above purpose, an automatic phase control circuit (hereinafter referred to as AP
(hereinafter referred to as A) and the wave number control circuit (hereinafter referred to as A).
FOIP! 1 road) and purple.

The AFO circuit consists of a tortoise pressure control oscillator (hereinafter referred to as VCO) that emits a frequency signal 160 times the horizontal synchronization frequency fH, and a tortoise pressure control oscillator (hereinafter referred to as VCO) that emits a frequency signal 160 times the horizontal synchronization frequency fH, and a tortoise pressure control oscillator that emits a frequency signal 160 times the horizontal synchronization frequency fH. It is composed of a detection circuit, etc. that performs digital detection twice every four periods, once for each sense signal.

Regarding the operation of the AFO circuit, when the two magnetic heads are switched during the four digital detection periods described above, skew occurs, and this causes an error in the digital detection output. A signal is generated. This error signal is generated by an AF that does not apply phase synchronization sound due to the horizontal synchronization signal.
In the O method, this is an excessive error signal and becomes a factor that interferes with APO convergence. First, the above error H
The occurrence of the problem appears as a blinker image, making it very difficult to see.

Note that skew distortion refers to the distortion of the screen that occurs due to differences in the elongation and movement of the magnetic tape, differences in cylinder diameter, etc., and the distortion of the screen that occurs due to differences in the angle δ of the video trunk during recording or recording operations. say.

Does the present invention have the above-mentioned defects? The object of the present invention is to provide a magnetic video signal reproducing apparatus 7 which can prevent the occurrence of flickering noise due to excessive error signals of a predetermined detection method during reproduction.

Is the drawing below? One embodiment of the present invention will be explained with reference to the following.

The IT diagram shows the circuit configuration of the main part of a two-handed digital image signal reproducing apparatus (hereinafter referred to as a VTR). The magnetic head 1 is an A channel magnetic head and a magnetic bend 1'UB channel magnetic head. The reproduction signal induced by δf in the magnetic hand 1.1' is the rotary transformer 2.2'? The signal is then supplied to the amplifier circuit 3.3'. The amplified 8fL reproduction signal is
Equalizer 4: Characteristic correction is performed by Cvc. The switch circuit 5.5'VC is supplied with the PG device rotation tBL number 30H2) which is generated by the rotation of the magnetic head I%1'. Then, the output δ from the equalizer 4.4'
The fL reproduction signal is supplied to the mixing circuit 6 through switch circuits 5 and 5'. The mixing circuit 6 continuously outputs *S raw numbers and supplies them to the luminance signal reproducing thread 7 and the conveyed color signal reproducing thread δn. Note that the description of the luminance signal reproducing thread 7 will be omitted.

The amplifier circuit 11 is supplied with a reproduction signal from the mixing circuit 6, and the amplified reproduction signal is supplied to a low-pass filter circuit (hereinafter referred to as LPF) 12. LPF1
2, a converted color signal of 629KH2 is outputted and amplified by the amplifier circuit 13. The conversion color key code of the 8C629KH2 is controlled by the AOO circuit 14 so that the burst signal level is constant, thereby obtaining a reference level. The four signals for the AOOl path 14 are supplied to the first frequency conversion circuit 15, and this output signal includes a time variation (zinc: Δft) during reproduction.

The first frequency conversion circuit 15 is a part of the APou path, and the second frequency conversion circuit 16 is connected to a band pass circuit (hereinafter referred to as BPF) 17'. A frequency sand signal of .2MH2 is supplied. 8tli,
The output signal of the number conversion circuit 15 is supplied to a band pass circuit 18, and a carrier color signal of 3.58 MH2 is output from this BPF 18. The burst signal of 3.58 MH2 extracted by the burst gate circuit 19 contains a jitter component ':+f1. This 3.58 MH2 burst signal is supplied to the phase detection circuit 20. The phase detection circuit 20 is supplied with a 3.58 MH reference frequency signal from the crystal oscillator 21. And the phase detection circuit 20
Error signal corresponding to 3.58MH2♀Δf1]!
+8 is output. The oscillation circuit 21 is a crystal perfector kNL.
, outputs an extremely stable 3.58 MH2 frequency g sound and supplies it to the first input terminal of the frequency conversion circuit 16.

The second input terminal is connected to L/4 frequency divider circuits 37 to 6, which will be described later.
A cycle tBL number signal of 29KH2 is supplied. This 629
The KHz frequency signal is the output of a vacuum side generator (vao) 36 having a frequency mantissa of n7t L 60 times fH, which is controlled by the error signal is.

A frequency signal having a frequency of 4.2MH2±Δf1 is supplied to the frequency conversion circuit 15 via the BPF 17'f. In other words, the jitter component is fed back and its shadow #' is removed.

On the other hand, the 58 MHz frequency signal output from the BPFL8 is in a state in which the burst signal has been increased by 6 dB, so it is compressed back to its original state by the burst compression circuit wr22. The LH delay circuit 23 outputs a continuous carrier color signal close to its original form by combining the LH-delayed 7t# color carrier signal and the non-delayed carrier color signal. This carried color signal is amplified by the color killer amplification circuit 24 and mixed with a luminance signal (not shown) obtained from the luminance signal reproducing thread 7. In addition, Color Killer amplification episode lol! r2
Illustrations of the circuit operation and circuit configuration for 4i driving are omitted.

By the way, what about this invention? A channel switch pulse pl having a frequency of 30H2 as shown in FIG. 6 is supplied to the terminal T of the applied AFO circuit. The switch W is turned on during playback operation. Note that the switch 8W is illustrated as a mechanical structure for convenience of explanation, but
In practice, electronic switches are used. Terminal T! A horizontal synchronizing signal f shown in FIG. 2 is supplied to the horizontal synchronizing signal f shown in FIG. In addition, the second
The figure shows the waveform when no skew distortion occurs due to head switching.

The pulse generating circuit 31 generates a horizontal synchronizing signal fak, a set Hals Pus which is frequency-divided and generated as shown in FIG. 3, a count gate pulse P3 shown in FIG. 4, a gate pulse P4 shown in FIG.
Configure it to get k.

The upper reset pulse P is the horizontal synchronization signal f.
It is output every 8 pulses of H and is supplied to the 1IIVL unit 32. Count gate pulse P3 is horizontal synchronization signal fH
4 pulses are supplied to the gate switch 33. 1 of the horizontal synchronizing signal fH to the gate pulse P4.
Regarding the pulse component, digital-current conversion circuit 3
4. In addition, each of the above-mentioned pulses p! , p3, p4
To describe the positional relationship between the pulses Ps and k, the pulse PI has an advanced phase, the pulse P4 has a delayed phase and nIdle, and the pulses rpIA of each pulse p, , p, may be set arbitrarily.

When the horizontal synchronizing signal f is continuously supplied at approximately equal intervals as shown in FIG.
2, P3, and P are obtained continuously. The output signal of the digital current f circuit 34 and the error signal f' outputted from the phase detection circuit 20 are mixed and supplied to an n% voltage controlled oscillation circuit (hereinafter referred to as ``voo'') 36. vo
036 is 1 when the mixed output MY is at the base forward voltage level.
A frequency signal of 60fl is oscillated. This frequency signal is supplied to the gate switch 33 and the 1/4 frequency dividing circuit 37. L/4 frequency divider circuit 37 to 629 KH2 frequency e
A signal is obtained and supplied to the frequency tfIl number conversion circuit 16. Note that the /4 frequency divider circuit also performs phase-S selection at the same time.

On the other hand, the gate switch 33 receives a pulse p as shown in FIG.
m is supplied, the frequency #! of VOO36 during the H level pulse width tI. ! A signal is provided to a counter 32. VC03 between 1 and h in the counter 32
6 laps tB1. Number #f number is done. The output obtained by counting the number of stitches is supplied to the digital-to-airflow conversion circuit #A634.

An output current as shown in FIG. 11 is obtained from the digital-current conversion circuit 34 in response to the count of the counter 32.

Note that this output 11 stream is obtained during the H level period of the pulse P4. When the horizontal synchronizing signal fH is supplied at approximately equal intervals as described above, the count output of the counter 320 is 640.
If it is within ±2, at this time, the digital military style transformation circuit 34
The output current of becomes zero. Therefore, the oscillation frequency of the VOO 36 is controlled by the error signal output δ from the phase detection circuit 20.

Regarding skew distortion, skew distortion tends to occur when channels 9, such as from HA channel to B channel, are switched. That is, when the channel switch pulse PK switches from the A channel to the B channel as shown in FIG. 6, the horizontal synchronizing signal fH shown in FIG. 2 changes to fH' shown in FIG. Horizontal synchronization signal fH
At ', the first pulse appears early, and the interval between the third and fourth pulses becomes 1. Note that the superior pulse interval may be wider than in the illustrated case.

When the above-mentioned skew distortion appears, the pulse P3 shown in FIG. 4 changes to the pulse P3' shown in FIG. 8.

As a result, the interval between the H-level pulses @tI of the pulse P3 becomes zero, such as the pulse widths t and I of the pulse P3'. If this 11 is left alone, the counting output of the counter 22 will drop to 638 or less, and the digital-to-current converter circuit 3
40 If the output current is -0,3 as shown in FIG.
mA, and error No. 16 will be outputted.

However, by applying the present invention, even if the skew M occurs, the above-mentioned malfunction can be prevented.

In other words, at the time of channel cut-off, the edge pulse generation circuit 35 generates a cut-off edge pulse PIl as shown in FIG.
occurs. This edge pulse P11 is supplied to the pulse-♂ generation circuit 31 δn. After this, the pulse generating port %31 is switched to the reset state by producing an edge pulse P6.

The operation of P3 will be described below.

Edge pulses P and K generate pulses 11iJM31
When is switched to the reset state, the pulse l corner 1't of the pulse P3 falls to the L level in synchronization with the edge pulse P5. Therefore, the pulse width 1 of the pulse P3 is the first
The pulse width tI'' of the pulse P3'' shown in FIG.

Furthermore, since the edge pulse "s Il'l" is also supplied to the Fttv unit 32, the counter 32 is also expected to be in the reset state. Therefore, the elbow number output cannot be obtained from the counter 32.

However, even though the above-described operation is performed by the edge pulse P11, the pulse generating circuit 31 becomes operational again by the fourth pulse of the horizontal synchronizing signal fH'. Then, in the pulse P3'', an H level portion with a time width of 1. corresponding to 4 pulses of the horizontal synchronizing signal fH appears again.
During the time LIIM tt, digital-to-#LK conversion is performed for the same number as in the above case. Then, the output current of the digital current conversion circuit 34 returns to the zero level shown in FIG.

In this way, the silkworm frequency of va036 is stabilized only by APC. Therefore, the frequency conversion circuit 16 is always supplied with a stable frequency signal of 629KH2.

Note that when the skew distortion is L and the time width between the third and fourth pulses of the horizontal synchronizing signal fH' becomes wide, the same circuit operation as in the above case is performed.

Therefore, the starting frequency of V○036 does not vary due to skew distortion.

Therefore, by countering the above-mentioned skew distortion, no upper flicker appears on the playback screen, resulting in a playback screen that is compact and easy to view.

Note that the AFO circuit shown in the above-mentioned implementation column has a so-called V
The present invention is also applicable to the H8 format VTR 1 or the so-called beta format VTR.

[Brief explanation of the drawing]

Is Fig. 1 an implementation sequence of the present invention? Horizontal block diagrams of the magnetic recording/playback i[ shown in Figs. 2, 3, 4, 5, 6, 7, 8, 9, 10, FIG. 1.1 is a waveform diagram for explaining the circuit operation of the magnetic video signal reproducing device. 31... Pulse generation circuit, 32... Counter, 33.
...Gate switch, 34...Digital-current conversion circuit, 35...Edge pulse generation circuit, 36...Voltage controlled oscillator circuit, fH, fH'...Horizontal synchronization signal,
P3, p3', p3''...Count gate pulse,
PL...Channel switch pulse, Pll...Edge pulse.

Claims (1)

[Claims] (2) In a magnetic video signal reproducing device that reproduces a video signal recorded on a magnetic material, an edge pulse generation circuit for detecting the switching pulse of the first and second magnetic heads and adding it to the edge pulse; The first gate pulse for opening/closing the gate switch r and the counter? What is the reset pulse for resetting and the output derivation time of the digital-1L current conversion circuit? A frequency signal R supplied from a first gate pulse for determining a frequency signal r supplied from a pulse generation circuit which outputs full output and is switched to a reset state by the edge pulse, and an oscillation circuit. ``a gate circuit that supplies the counter for the time specified by ``, a #1 device that counts the frequency I8 signal outputted from the gate circuit and is switched to a reset state by the edge pulse, and a #1 count state of the IT counter. 7. A magnetic video signal reproducing device comprising a digital-to-current converter circuit for controlling the perfect image frequency of the oscillation circuit according to the current output r corresponding to the oscillation circuit.