JP2675441B2 - Magnetic recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an HDTV (High Definition).
itionTV) signals such as wideband signals and VHS (Video Tape Re
The present invention relates to a magnetic recording / reproducing apparatus for recording / reproducing a video signal to which a reference (color) burst signal is not added, such as a home video recording / reproducing signal of a corder). The present invention relates to a magnetic recording / reproducing apparatus in which the phase is reset to a constant value for recording, and the carrier-reset FM carrier portion is used as a reference burst signal during reproduction for jitter detection.

[0002]

2. Description of the Related Art A video signal reproduced by a magnetic recording / reproducing apparatus has a jitter which is a fluctuation in a time axis, and it is important to correct this jitter in order to secure stability of a reproduced image. . Therefore, in the case of a magnetic recording / reproducing apparatus such as a VTR for broadcasting which directly records and reproduces the NTSC signal by FM-modulating it, a color burst inserted every horizontal scanning period of the video signal. A signal is used as a reference signal, and a jitter detection signal is formed from the time base fluctuation of a specific zero-cross point of this color burst signal to correct the jitter.

On the other hand, in the case of a magnetic recording / reproducing apparatus such as a home VTR which adopts the low frequency conversion color signal recording system, since the color burst signal is not added to the video signal, the horizontal synchronizing signal normally rises. A specific portion of the falling edge or the falling edge is detected as a jitter detection signal, and the jitter is corrected based on this jitter detection signal.

However, noise of irregular phase and voltage level is superposed on the horizontal synchronizing signal, and this noise affects the accuracy of the jitter detection signal formed when a specific portion of the horizontal synchronizing signal is detected. It has become a factor to reduce. Then, the deterioration of the accuracy of the jitter detection signal makes it difficult to sufficiently correct the jitter, and eventually causes the reproduced image to become unstable.

Therefore, in recent magnetic recording / reproducing devices, attention is paid to the fact that the jitter of the reproduced FM carrier is equal to the jitter of the reproduced video signal, and a device for detecting the jitter detection signal from the reproduced FM carrier is detected. There is. On this occasion,
Since the FM carrier is recorded / reproduced in a phase that is completely unrelated to the phase of the video signal, the conventional magnetic recording / reproducing apparatus performs carrier reset for matching the phase of the FM carrier with the phase of the reference frequency signal of the video signal. The FM carrier portion, which is recorded at the leading edge portion of the horizontal synchronizing pulse while being carried out every horizontal period and whose carrier is reset at the time of reproduction, is used as a reference burst signal.

As a result, the conventional magnetic recording / reproducing apparatus is
Since the reference burst signal can be obtained from the reproduced FM carrier, it becomes possible to correct the jitter with high accuracy by the jitter detection signal formed from the reference burst signal as in the case of the direct FM recording type magnetic recording / reproducing apparatus. There is.

[0007]

However, in the above-described conventional magnetic recording / reproducing apparatus, the carrier reset of the FM carrier is performed at the leading edge of the horizontal sync pulse at the time of FM modulation, and therefore the FM carrier is discontinuous at the time of carrier reset. Phase shift will occur.

That is, the discontinuous phase change due to the carrier reset will be described. First, as shown in FIG. 10, when the carrier reset is delayed from the leading edge of the horizontal pulse by a predetermined time τ. , The time at a certain leading edge of the horizontal sync is t ₀ ^′ , the carrier reset time is t ₀ , the time at the next leading edge of the horizontal sync is t ₁ ^′ , and the carrier reset time is t ₁ .

At this time, as shown in FIG. 11, the FM carrier amplitude instantaneous value is F (t), and the video amplitude instantaneous value measured from the tip of the horizontal synchronizing pulse is V (t). V
When the relationship with (t) is expressed as a function of time t, the following relational expression (1) is obtained.

[0010]

(Equation 1)

A is the FM carrier amplitude, V ₀ is the peak value of the video signal measured from the horizontal sync tip, f _TP is the FM carrier frequency at the horizontal sync pulse tip, and Δf is the FM carrier frequency f at the sync pulse tip. It is the frequency shift amount from _TP to the carrier frequency of the video signal peak value V ₀ .

Therefore, the phase difference φ ₁ of the carrier frequency fc at the front end of the horizontal synchronization before and after the carrier reset is expressed by the following equation (2).

[0013]

(Equation 2)

Since the FM carrier frequency f _TP of the horizontal sync pulse tip is an integer multiple of the horizontal scanning frequency f _H , fc (t ₁ −t ₀ ) is an integer, and is omitted in the case of a phase difference. Therefore, the above phase difference φ ₁
Can be expressed by the following equation (3).

[0015]

(Equation 3)

Thus, when the FM carrier shown in FIG. 10 is recorded on a magnetic tape, for example, the magnetization patterns (i), (ii), (iii), (iv), (v), and (vi) shown in FIG. ) ・ (Vii)
(Viii) occurs, but since the video signal integral value measured from the horizontal sync tip changes randomly for each horizontal scanning period, the phase shift amount of the FM carrier at the time of carrier reset is the above-mentioned magnetization pattern (i).・ (Ii) ・ (iii) ・ (iv) ・
It does not change in the order of (v), (vi), (vii), and (viii), but changes randomly in each horizontal scanning period.

Therefore, when the above-mentioned magnetization pattern is read out as an FM carrier and FM demodulated, the phase shift amount of the FM carrier at the time of carrier reset changes randomly, and therefore, as shown in FIG. ii) ・ (iii) ・ (iv) and undershoot (v) ・ (vi) ・
(vii) ・ (viii) will occur. For this reason, when the reproduced video signal is clamped at the synchronous front end, it causes a clamp error.

Next, when the carrier reset time is made to coincide with the leading edge of the horizontal sync pulse, the above-mentioned overshoots (ii), (iii), (iv) and undershoots (v), (vi) are taken.
As shown in FIG. 14, (vii) and (viii) cause excessive distortion at the leading edge of the FM-demodulated horizontal synchronizing pulse, and this excessive distortion is the rise time of the leading edge of the horizontal synchronizing pulse. Therefore, the phase accuracy of the leading edge portion of the horizontal synchronizing pulse is lost.

Further, in this case, since the phases of the FM carriers are aligned at the trailing edge of the horizontal synchronizing pulse, there is no particular problem in normal operation, but the processing operation for correcting jitter is Since it is limited to the trailing edge of the horizontal sync pulse, the correction operation is delayed by the pulse width from the leading edge of the horizontal sync pulse to the trailing edge of the horizontal sync pulse. Further, since the above-mentioned excessive distortion changes the horizontal synchronizing pulse width, it also means that the correlation between the leading edge of the horizontal synchronizing pulse and the trailing edge of the horizontal synchronizing pulse is lost.

As described above, the conventional magnetic recording / reproducing apparatus is
Since the reference burst signal can be obtained from the reproduced FM carrier, it is possible to correct the jitter with high accuracy. However, the FM carrier causes a discontinuous phase change at the time of carrier reset, and therefore, after demodulation. There is a problem of causing excessive distortion such as overshoot or undershoot in the horizontal synchronizing signal.

Therefore, recently, in order to prevent excessive distortion of the horizontal synchronizing pulse portion due to carrier reset,
As shown in FIG. 15, there has been proposed a magnetic recording / reproducing apparatus having a recording system into which a phase compensation pulse can be inserted in the front porch portion of a video signal. That is, as shown in FIG. 16, the recording system of this magnetic recording / reproducing apparatus detects the phase of the FM carrier in the front porch part of the video signal output from the FM modulator, and the phase corresponding to this detected phase is detected. The compensating pulse height is predicted and generated, and is input to the FM modulator and inserted into the video signal.

However, in this magnetic recording / reproducing apparatus, since the phase compensation pulse is immediately inserted after detecting the phase of the FM carrier in the front porch portion, high-speed feedback is required, resulting in an advanced and expensive circuit. Requires configuration. Further, in the above magnetic recording / reproducing apparatus, the phase of the FM carrier in the front porch portion arbitrarily changes for each horizontal scanning period, and the phase of the FM carrier one horizontal scanning period before cannot be used for prediction of the phase compensation pulse. Therefore, it is difficult to predict the amplitude of the phase compensation pulse, and it is difficult to obtain the phase compensation pulse that sufficiently removes the phase distortion in spite of the above-mentioned advanced and expensive circuit configuration.

Therefore, the present invention provides a magnetic recording / reproducing apparatus capable of sufficiently preventing the occurrence of excessive distortion such as overshoot or undershoot in a demodulated horizontal synchronizing signal with a simple circuit configuration. It is an object.

[0024]

In order to solve the above-mentioned problems, the magnetic recording / reproducing apparatus of the present invention carries out carrier reset for matching the phase of the FM carrier of the video signal with the phase of the reference frequency signal every horizontal scanning cycle. A magnetic recording / reproducing apparatus that uses as a reference burst signal the portion corresponding to the horizontal sync pulse tip portion of the FM carrier that has been recorded while being recorded and has been carrier-reset during reproduction is characterized by the following configuration.

That is, in the magnetic recording / reproducing apparatus having the structure of claim 1, the reference frequency signal is set to the FM carrier frequency corresponding to the front porch portion of the video signal, and the front porch reference frequency for resetting the carrier of the front porch portion. Signal and F corresponding to the horizontal sync pulse part of the video signal
The horizontal sync reference frequency signal is set to the M carrier frequency and resets the horizontal sync pulse portion to a carrier. The front porch reference frequency signal and the horizontal sync reference frequency signal have an FM carrier frequency of a horizontal scanning frequency. It is characterized in that it is set to an integral multiple and the phases are matched at the leading edge of the horizontal sync pulse.

According to a second aspect of the present invention, there is provided the magnetic recording / reproducing apparatus according to the first aspect, wherein the generator for generating the horizontal synchronizing reference frequency signal is provided with an AFC circuit.

Further, the magnetic recording / reproducing apparatus having the structure of claim 3 is characterized in that, in the structure of claim 1, the generator for generating the front porch reference frequency signal is provided with an AFC circuit.

According to a fourth aspect of the present invention, there is provided the magnetic recording / reproducing apparatus according to the first aspect, wherein only the latter half of the front porch portion is carrier reset by the front porch reference frequency signal and the horizontal synchronizing reference frequency signal is used. It is characterized in that only the latter half of the sync pulse portion is carrier reset.

Further, in the magnetic recording / reproducing apparatus having the structure of the fifth aspect, the reference frequency signal is set to the FM carrier frequency corresponding to the leading end portion of the horizontal synchronizing pulse of the video signal, and the front porch reset for carrying out carrier reset of the front porch portion. It is characterized in that it is composed of a pulse and a horizontal synchronization reference frequency signal whose FM carrier frequency is set to an integral multiple of the horizontal scanning frequency and whose phase is matched at the leading edge of the horizontal synchronization pulse.

[0030]

According to the above-mentioned constitutions 1 to 5, in the video signal, after the front porch portion is carrier reset by the front porch reference frequency signal or the front porch reset pulse, the horizontal synchronizing pulse portion is horizontally synchronized. The carrier will be reset by the reference frequency signal.

Therefore, in the horizontal sync pulse portion whose carrier is reset by the horizontal sync reference frequency signal, the phases of the front porch reference frequency signal and the front porch reset pulse and the phase of the horizontal sync reference frequency signal in which the front porch portion is carrier reset are set. Since the leading edges of the horizontal sync pulses are matched, there is no phase difference between the FM carrier of the front porch and the FM carrier of the horizontal sync pulse.

Thus, when the recorded video signal is reproduced by resetting the carrier of the front porch portion and the horizontal synchronizing pulse portion, there is a phase difference in the front porch portion of the reproduced video signal. Although excessive distortion will occur in the front porch portion, it becomes possible to prevent excessive distortion from occurring in the horizontal sync pulse portion having no phase difference. The prevention of excessive distortion in the horizontal sync pulse section makes it possible to prevent a clamp error in the horizontal sync pulse section and improve the phase accuracy of the leading edge of the horizontal sync pulse section.

[0033]

[Embodiment 1] The following will describe one embodiment of the invention of claims 1 to 3 with reference to FIGS. 1 to 6.

The magnetic recording / reproducing apparatus according to this embodiment uses an AF
An FM modulator forming a C circuit, a time axis correction circuit having a memory for writing data for time axis correction, a reference frequency sine wave and pulse signal generating means, and a timing signal for resetting the FM carrier phase to the reference phase. Generating means and FM for FM demodulating a reproduced FM carrier during reproduction
A demodulator, a horizontal sync pulse detecting means for detecting and outputting a horizontal sync pulse from the output of the FM demodulator, and a carrier whose phase is reset by the FM modulator using the leading edge of the horizontal sync pulse from the horizontal sync pulse detecting means. Gate means for gating a portion as a burst signal and a predetermined zero-cross point in the burst signal at the leading edge or trailing edge of the horizontal sync pulse from the horizontal sync pulse detection means, and the memory write trigger pulse of the time axis correction circuit is detected. The memory write trigger pulse generating means for outputting is provided, the reproduced FM carrier is added to the FM demodulator through the head amplifier and the equalizer, and the demodulated output video signal is inputted to the time axis correction device. By the combination of the above means, the video signal whose time axis is corrected is reproduced.

Then, the reference frequency sine wave and pulse signal generating means described above is used for recording the first frequency of the FM modulator at the time of recording.
And the second reference frequency are derived from the same original oscillator, are set to integer multiples of the horizontal scanning frequency of the input video signal, respectively, and their reference phases are matched at the leading edge of the horizontal synchronizing pulse.

The timing signal generating means is composed of first timing signal generating means and second timing signal generating means, at least one of which is AFC, and the first timing signal generating means is an FM modulator. The first reference frequency is set to the FM carrier frequency corresponding to the leading edge of the video signal horizontal sync, and the reset pulse is created from a part of the first reference frequency pulse train gated by the horizontal sync pulse. The FM carrier phase corresponding to the pulse front end is reset to the reference phase of the first reference frequency. Also, the second timing signal generating means sets the second reference frequency in the FM modulator to the FM carrier frequency corresponding to the video signal front porch portion, and gates with the horizontal blanking pulse to obtain a second reference frequency pulse train. The reset pulse created from a part of the F
The M carrier phase is reset to the reference phase of the second reference frequency.

Explaining the above-mentioned configuration in detail, the magnetic recording / reproducing apparatus, as shown in FIG. 1, when FM-modulating the video signal, the magnetic recording / reproducing apparatus has a front porch portion and a horizontal synchronizing pulse front edge portion of the video signal. It has an FM modulation circuit that performs a double reset in which the carrier is reset in stages. This FM modulation circuit is provided with a sync separation circuit 1 to which the above-mentioned video signal is input, and this sync separation circuit 1 separates a horizontal sync pulse portion from the video signal and horizontally from this horizontal sync pulse portion. The synchronizing pulse signal a is output.

The sync separation circuit 1 is connected to a sync board clock generator 2, and the sync board clock generator 2 has an original oscillator (not shown). The original oscillator outputs a first reference frequency signal f _TPO and a second reference frequency signal f _FPO that matches the frequency of the color difference pedestal level, and outputs the first reference frequency signal f _TPO and the first reference frequency signal f _TPO . The 2 reference frequency signal f _FPO is set to an integral multiple of the horizontal scanning frequency f _H , and is set so that the phases thereof coincide with each other at the leading edge of the horizontal synchronizing pulse.

Further, the synchronous board clock generator 2 described above is
As shown in FIG. 3, a horizontal new synchronizing pulse signal a ₁ , which is a processing pulse signal necessary for the above-mentioned double reset, a horizontal blanking pulse signal b, a front porch pulse signal e indicating a front porch portion of a video signal, and various types. , And the horizontal new synchronizing pulse signal a ₁ is formed in synchronization with the horizontal synchronizing pulse signal a. Further, the front porch pulse signal e is formed by the falling edge of the horizontal blanking pulse signal b and the falling edge of the horizontal synchronizing pulse signal a.

The various processed pulse signals a ₁ , b, e described above
_.Synchronous board clock generator 2 that outputs f _TPO and f _FPO
Is connected to the frequency error voltage hold circuit 7, the sync pulse front end compatible FM carrier frequency comparison circuit 9, the f _FP gate circuit 3, and the f _TP gate circuit 4, and the f _FP gate circuit 3 is connected to the second reference frequency signal. While f _FPO and the front porch pulse signal e are output, f
_{The TP} gate circuit 4 outputs the first reference frequency signal f _TPO and the horizontal new synchronizing pulse signal a ₁ .

The above-mentioned f _FP gate circuit 3 is connected to the reset pulse synthesizing / processing circuit 5, and while the front porch pulse signal e is being input, the second reference frequency signal f _FPO is _supplied to the front porch carrier. The reset pulse signal c is output to the reset pulse synthesis processing circuit 5.

Further, the reset pulse synthesizing processing circuit 5 of the, f _TP gate circuit 4 is also connected, the f _TP
The gate circuit 4 is adapted to input the first reference frequency signal f _TPO to the reset pulse synthesis processing circuit 5 as the synchronous front end carrier reset pulse signal d. And
The reset pulse synthesizing / processing circuit 5 is connected to an FM oscillator 8 composed of a flip-flop, and the FM oscillator 8 is synthesized with a front porch / carrier reset pulse signal c and a synchronous tip carrier reset pulse signal d. It outputs the pulse signal f.

The FM oscillator 8 oscillates in phase with the input FM carrier reset pulse signal f, and the AFC error adder circuit 6 is connected to the input side of the FM oscillator 8. Output amplifier circuit 1 on the output side
0 and the sync front carrier frequency comparison circuit 9 are connected. Then, the synchronization tip carrier frequency comparison circuit 9
Is connected to the AFC error adder circuit 6 via the frequency error voltage hold circuit 7 and constitutes an AFC circuit.

The operation when the magnetic recording / reproducing apparatus having the above-mentioned structure records / reproduces the video signal having the frequency allocation shown in FIG. 2 will be described.

First, in the video signal of FIG. 2, the FM carrier frequency corresponding to the leading edge of the horizontal synchronizing pulse is f _TP , the FM carrier frequency corresponding to the front porch portion is f _FP , and the FM carrier frequency corresponding to the video signal peak value. Is f _P = (f
_TP + Δf), and the horizontal blanking pulse precedes the front edge of the horizontal sync pulse portion by the front porch period.

When the magnetic recording / reproducing apparatus records the above-mentioned video signal, as shown in FIG.
Will be input to the FM modulation circuit 11. The video signal g input to the FM modulation circuit 11 is input to the sync separation circuit 1 and the AFC error addition circuit 6, and the sync separation circuit 1 extracts the horizontal sync pulse signal a from the input video signal g. Will be output to the synchronous board clock generator 2.

After the horizontal synchronizing pulse signal a input to the synchronizing board clock generator 2 forms a horizontal new synchronizing pulse signal a ₁ phase-synchronized with the horizontal synchronizing pulse signal a,
It is output to the f _TP gate circuit 4. Further, a front porch pulse signal e is output from the synchronous board clock generator 2, and the front porch pulse signal e is f
It will be output to the _FP gate circuit 3.

Further, the synchronous clock generator 2 has an original oscillator (not shown), and this original oscillator has a first reference frequency signal f _TPO and a second reference frequency signal which matches the frequency of the color difference pedestal level. f _FPO is output.
Then, the first reference frequency signal f _TPO is output to the f _TP gate circuit 4 which uses the horizontal new synchronizing pulse signal a ₁ as a gate signal, while the second reference frequency signal f _FPO gates the front porch pulse signal e. F _FP gate circuit 3 for signal
Will be output to

The second input to the above f _FP gate circuit 3
The reference frequency signal f _FPO is the front porch pulse signal e.
Reset pulse synthesis processing circuit 5 while is input
Will be output as a front porch / carrier reset pulse signal c. In addition, the first reference frequency signal f _TPO input to the f _TP gate circuit 4 is used to obtain the sync tip carrier reset pulse signal d, and this sync tip carrier reset pulse signal d is
The optimum number of pulses for carrier reset of the image carrier h is set, and carrier reset is executed with high accuracy. That is, the front porch / carrier reset pulse signal c
And the synchronous tip carrier reset pulse signal d are combined,
After the FM carrier reset signal f is set, the FM oscillator 8
Will be output to

When the FM carrier reset signal f is FM
When input to the oscillator 8, the FM oscillator 8 outputs a video carrier h that is phase-synchronized with the FM carrier reset signal f, and the carrier-reset video carrier h is output to the output amplifier circuit 10 and the sync tip carrier. It is output to the frequency comparison circuit 9. Then, this video carrier h is supplied to the sync tip carrier frequency comparison circuit 9
The FM oscillation frequency is stabilized by the AFC circuit composed of the frequency error voltage hold circuit 7 and the AFC error addition circuit 6, and is output to the recording system in the subsequent stage via the output amplifier circuit 10 and recorded on a magnetic tape (not shown). Will be.

The stabilization of the oscillating frequency by the above AFC circuit is carried out by comparing the frequency of the carrier frequency corresponding to the horizontal synchronizing pulse portion of the video carrier h with the first reference frequency signal f _TPO to determine the error voltage by one line. It may be carried out by holding the minute and feeding it back to the next horizontal synchronizing pulse section, or by comparing the carrier frequency corresponding to the front porch section with the second reference frequency signal f _FPO. It may be implemented.

As a result, the FM carrier whose carrier is reset in the front porch portion is in phase synchronization with the FM carrier corresponding to the horizontal synchronizing pulse portion, does not cause a discontinuous phase difference, and further, before the horizontal synchronizing pulse. It is phase-locked to the edge.

When the image carrier h recorded in this way is reproduced, as shown in FIG. 4, since there is a carrier phase discontinuity point in the front porch portion of the reproduced image carrier, this front Although excessive distortion occurs in the pouch portion, excessive distortion does not occur in the FM demodulation output at the leading edge of the horizontal sync pulse where the carrier phase changes continuously. Therefore, the magnetic recording / reproducing apparatus does not cause a clamping error in the horizontal synchronizing pulse portion when the reproducing video signal is clamped by the synchronous tip clamping method.

The front porch portion may be matched with the color difference pedestal level. As shown in FIG. 5, in the TCI (Time-Compressed Integration) signal,
The color difference pedestal level is the intermediate level (50
%). Therefore, the excessive distortion generated in the front porch does not cause a negative undershoot reaching the level of the horizontal sync pulse, and the transient sync noise is mistaken for the horizontal pulse front edge in the horizontal sync separation circuit. There is no.

Since the above-mentioned carrier reset is executed by the FM carrier reset signal f of FIG. 6 in which the front porch / carrier reset pulse signal c and the synchronous tip carrier reset pulse signal d are continuous, the video signal g is changed. It is suitable for recording without pre-emphasis processing.

[Embodiment 2] Next, as an embodiment of the invention of claim 4, a carrier reset method suitable for the case where the pre-emphasis processed video signal g'is modulated and recorded and the de-emphasis processing is carried out during reproduction is shown in FIG. It will be described based on.

The magnetic recording / reproducing apparatus according to the present embodiment uses the AF
An FM modulator forming a C circuit, a time axis correction circuit having a memory for writing data for time axis correction, a reference frequency sine wave and pulse signal generating means, and a timing signal for resetting the FM carrier phase to the reference phase. Generating means and FM for FM demodulating a reproduced FM carrier during reproduction
A demodulator, a horizontal sync pulse detecting means for detecting and outputting a horizontal sync pulse from the output of the FM demodulator, and a carrier whose phase is reset by the FM modulator using the leading edge of the horizontal sync pulse from the horizontal sync pulse detecting means. Gate means for gating a portion as a burst signal and a predetermined zero-cross point in the burst signal at the leading edge or trailing edge of the horizontal sync pulse from the horizontal sync pulse detection means, and the memory write trigger pulse of the time axis correction circuit is detected. The memory write trigger pulse generating means for outputting is provided, the reproduced FM carrier is added to the FM demodulator through the head amplifier and the equalizer, and the demodulated output video signal is inputted to the time axis correction device. By the combination of the above means, the video signal whose time axis is corrected is reproduced.

Then, the reference frequency sine wave and pulse signal generating means is configured so that the first modulator of the FM modulator is used at the time of recording.
And the second reference frequency are derived from the same original oscillator, are set to integer multiples of the horizontal scanning frequency of the input video signal, respectively, and their reference phases are matched at the leading edge of the horizontal synchronizing pulse.

The timing signal generating means is the third
The timing controller includes a timing signal generation means and a fourth timing signal generation means, and the third timing signal generation means sets the first reference frequency to the FM carrier frequency corresponding to the video signal horizontal synchronization front end in the FM modulator, AF
At the same time as configuring C, a reset pulse created from a part of the first reference frequency pulse train gated only in the latter half of the horizontal synchronizing pulse is used to set the FM carrier phase corresponding to the leading end of the horizontal synchronizing pulse for each horizontal period as the reference phase. It is supposed to be reset to.

Further, the fourth timing signal generating means is
In the FM modulator, the second reference frequency is set to the FM carrier frequency corresponding to the video signal front porch portion, and the reset is made from a part of the second reference frequency pulse train obtained by gated only in the latter half of the front porch portion. The pulse resets the FM carrier phase corresponding to the front porch portion to the reference phase every horizontal period.

The operation of the magnetic recording / reproducing apparatus having the above structure will be described.

First, as shown in FIG. 6, in the pre-emphasis processed video signal g ', sags A and A are generated at the front edge of the front porch and the front edge of the horizontal sync pulse. In the portion where A occurs, the frequency of the FM carrier changes. Therefore, the continuous FM carrier reset signal f (shown in FIG. 6 for reference) described in the first embodiment causes a phase error, so that the change in frequency due to the sag A · A falls within a predetermined range. The FM carrier reset signal f'composed of the front porch / carrier reset pulse signal c'and the sync tip carrier reset pulse signal d'that are output at this stage is formed, and the video carrier h'is formed by this FM carrier reset signal f '. The carrier will be reset and recorded.

When the video FM carrier h'recorded by carrying out carrier reset with the FM carrier reset signal f'is reproduced, the carrier reset part is a horizontal demodulator formed by the sync detection dedicated FM demodulator. It is possible to form the burst gate pulse signal j from the synchronization pulse signal and take out the reference burst signal k with this burst gate pulse signal j.

Further, when the image carrier h ′ recorded by carrying out carrier reset with the FM carrier reset signal f ′ is reproduced and demodulated, excessive sag A · A causes carrier phase discontinuity in the front porch portion. Although the reproduced video signal g ″ before the de-emphasis processing in which the distortion has occurred is obtained, the phase continuity of the video FM carrier h ′ corresponding to the horizontal synchronizing pulse portion of the reproduced video signal g ″ is maintained, Further, since the carrier reset is performed at the stage where the frequency change due to the sag A is suppressed, neither excessive distortion occurs at the leading edge of the horizontal sync pulse nor excessive distortion at the carrier reset start point of the horizontal sync tip. . After that, by performing the de-emphasis processing on the reproduced video signal g ″, the reproduced video signal g ″ ′ in which the sag A · A is corrected and the excessive distortion is reduced can be obtained.

The excessive distortion at the leading edge of the horizontal sync pulse can be more surely prevented by adjusting the phase of the front porch / carrier reset pulse signal and the phase of the sync tip carrier reset pulse signal. In some cases. [Embodiment 3] Next, an embodiment of the invention of claim 5 will be described below with reference to FIGS. 7 to 9.

The magnetic recording / reproducing apparatus according to this embodiment is shown in FIG.
As shown in FIG. 2, the second reference frequency f is used as a signal source for resetting the FM carrier phase corresponding to the video signal front porch unit.
Instead of using _FPO (see FIG. 1), the first reference frequency f
It is designed to substitute _TPO . However,
In this case, it is necessary to reset the FM carrier with a single pulse.

That is, the magnetic recording / reproducing apparatus according to the present embodiment has an FM modulator which constitutes an AFC circuit, a time axis correction circuit having a memory for writing data for time axis correction, a reference frequency sine wave and a pulse. Signal generating means and FM
A timing signal generating means for resetting a carrier phase to a reference phase, an FM demodulator for FM demodulating a reproduced FM carrier at the time of reproduction, and a horizontal synchronizing pulse detecting means for detecting and outputting a horizontal synchronizing pulse from an FM demodulator output, Gating means for gated as a burst signal the carrier portion whose phase is reset by the FM modulator using the leading edge of the horizontal synchronizing pulse from the horizontal synchronizing pulse detecting means, and the leading edge of the horizontal synchronizing pulse from the horizontal synchronizing pulse detecting means or And a memory write trigger pulse generating means for detecting a predetermined zero-cross point in the burst signal at the trailing edge and outputting a memory write trigger pulse of the time axis correction circuit.
The carrier is added to the FM demodulator through the head amplifier and the equalizer, and the demodulated output video signal is input to the time axis correction device, and the time axis corrected video signal is reproduced by the combination of these means. ing.

The reference frequency sine wave and pulse signal generating means is set to an integral multiple of the horizontal scanning frequency of the input video signal in the FM modulator during recording,
In addition, their reference phases are matched at the leading edge of the horizontal sync pulse.

The timing signal generating means is the fifth.
The timing controller includes a timing signal generating means and a sixth timing signal generating means. The fifth timing signal generating means configures an AFC by setting a reference frequency in an FM modulator to an FM carrier frequency corresponding to a video signal horizontal synchronization front end. At the same time, with the reset pulse created from a part of the first reference frequency pulse train gated only in the latter half of the horizontal sync pulse, the FM carrier phase corresponding to the leading end of the horizontal sync pulse is set to the reference phase of the reference frequency for each horizontal cycle. It is supposed to be reset to.

The sixth timing signal generating means is
In the FM modulator, one cycle of the reference frequency is gated by the front porch signal, and at the same time, the phase is delayed to make it match the FM carrier frequency phase corresponding to the video signal front porch part. The FM carrier phase corresponding to the front porch part is reset to the reference phase.

The operation of the magnetic recording / reproducing apparatus having the above structure will be described.

As shown in FIGS. 7 to 9, the gate circuit 2 is connected to the front porch signal e of the synchronous clock generator 2.
0 and the single pulse generation circuit 21 generate the first reference frequency signal f
One cycle of _TPO is extracted to obtain a single pulse signal Cs. Then, this single-shot pulse signal Cs is applied to the delay circuit 22.
Output to the reset pulse synthesizing processing circuit 5 in delayed and, in accordance with the second reference frequency signal f _FPO phase resetting the front porch corresponding carrier phase is preceded by, followed by, resets the horizontal pulse tip corresponding carrier phase. This makes it possible to prevent a discontinuous change in the FM carrier phase of the horizontal pulse front end portion and prevent the occurrence of excessive distortion in the horizontal sync pulse of the FM demodulated output reproduced video signal g ′ ″.

[0073]

As described above, in the magnetic recording / reproducing apparatus according to the first aspect of the present invention, the reference frequency signal is set to the FM carrier frequency corresponding to the front porch portion of the video signal, and the front porch portion is carrier reset. The front porch reference frequency signal includes a pouch reference frequency signal and a horizontal synchronization reference frequency signal which is set to an FM carrier frequency corresponding to the horizontal synchronization pulse portion of the video signal and resets the carrier of the horizontal synchronization pulse portion. The horizontal synchronization reference frequency signal has a configuration in which the FM carrier frequency is set to an integral multiple of the horizontal scanning frequency and the phases are matched at the leading edge of the horizontal synchronization pulse.

As a result, after the front porch portion of the video signal is carrier reset with the front porch reference frequency signal, the horizontal sync pulse portion is reset with the horizontal sync reference frequency signal. The video signal recorded by resetting the carrier with the part does not cause a phase difference due to the carrier reset in the horizontal sync pulse part, and thus it is possible to prevent the occurrence of excessive distortion in the horizontal sync pulse part.
This has the effect of improving the phase accuracy.

Further, as described above, the magnetic recording / reproducing apparatus according to a second aspect of the present invention is the configuration according to the first aspect, in which the generator for generating the horizontal synchronization reference frequency signal is provided with the AFC circuit.

As a result, similar to the effect of the first aspect, since the phase difference due to the carrier reset does not occur in the horizontal synchronizing pulse portion, it is possible to prevent the occurrence of excessive distortion in the horizontal synchronizing pulse portion. Thus, there is an effect that the phase accuracy is improved.

As described above, the magnetic recording / reproducing apparatus according to a third aspect of the present invention is the configuration according to the first aspect, in which the generator for generating the front porch reference frequency signal is provided with the AFC circuit.

As a result, similar to the effect of the first aspect, since the phase difference due to the carrier reset does not occur in the horizontal synchronizing pulse portion, it is possible to prevent the occurrence of excessive distortion in the horizontal synchronizing pulse portion. Thus, there is an effect that the phase accuracy is improved.

Further, as described above, in the magnetic recording / reproducing apparatus of the fourth aspect, in the configuration of the first aspect, only the latter half of the front porch portion is carrier reset by the front porch reference frequency signal, and the horizontal synchronizing reference frequency is set. Only the latter half of the horizontal synchronizing pulse portion is carrier reset by the signal.

As a result, similar to the effect of the first aspect, since the phase difference due to the carrier reset does not occur in the horizontal synchronizing pulse portion, it is possible to prevent the excessive distortion from occurring in the horizontal synchronizing pulse portion. Thus, there is an effect that the phase accuracy is improved.

Further, in the magnetic recording / reproducing apparatus of the fifth aspect, as described above, the reference frequency signal is set to the FM carrier frequency corresponding to the leading end portion of the horizontal synchronizing pulse of the video signal,
From the front porch reset pulse for resetting the carrier of the front porch part and the horizontal sync reference frequency signal in which the FM carrier frequency is set to an integral multiple of the horizontal scanning frequency and the phase is matched at the leading edge of the horizontal sync pulse. It is a structure that has become.

As a result, after the front porch portion of the video signal is carrier reset by the front porch reset pulse, the horizontal sync pulse portion is reset by the horizontal sync reference frequency signal, and the front porch portion and the horizontal sync pulse portion are reset. Since the video signal recorded by resetting the carrier and the carrier does not cause a phase difference due to the carrier reset in the horizontal synchronizing pulse portion, it is possible to prevent the occurrence of excessive distortion in the horizontal synchronizing pulse portion,
This has the effect of improving the phase accuracy.

[Brief description of the drawings]

FIG. 1 illustrates a first embodiment and is a block diagram of an FM modulation circuit.

FIG. 2 is an explanatory diagram showing frequency allocation of a video FM carrier.

FIG. 3 is a waveform diagram showing a signal state of the FM modulation circuit.

FIG. 4 is an explanatory diagram showing frequency allocation of a video FM carrier.

FIG. 5 is an explanatory diagram showing frequency allocation of a video FM carrier.

FIG. 6 illustrates Example 2 and is an explanatory diagram of a reproduced video signal subjected to pre-emphasis processing.

FIG. 7 illustrates a third embodiment and is a block diagram of an FM modulation circuit.

8 is a waveform diagram showing a signal state of the FM modulation circuit of FIG.

FIG. 9 is an explanatory diagram of a reproduced video signal subjected to pre-emphasis processing.

FIG. 10 is an explanatory diagram showing a state of carrier reset.

FIG. 11 is an explanatory diagram showing frequency allocation of a video FM carrier.

FIG. 12 is an explanatory diagram showing a state of a magnetization pattern in which an FM carrier is recorded on a magnetic tape.

FIG. 13 is an explanatory diagram showing the occurrence of excessive distortion of the FM demodulated video signal horizontal pulse portion at the time of carrier reset of the reproduced FM carrier phase.

FIG. 14 is an explanatory diagram showing the occurrence of excessive distortion of the FM demodulated video signal horizontal pulse portion at the time of carrier reset of the reproduced FM carrier phase.

FIG. 15 is an explanatory diagram of a method of inserting an FM carrier phase adjustment pulse into a video signal front porch unit.

FIG. 16 is a block diagram of a recording system of a magnetic recording / reproducing apparatus using pulse generation for FM carrier phase adjustment.

[Explanation of symbols]

1 sync separation circuit 2 sync board clock generator 3 f _FP gate circuit 4 f _TP gate circuit 5 reset pulse synthesis processing circuit 6 AFC error addition circuit 6 7 frequency error voltage hold circuit 8 FM oscillator 9 sync tip carrier frequency comparison circuit 10 output Amplification circuit 11 FM modulation circuit a Horizontal sync pulse signal a ₁ Horizontal new sync pulse signal b Horizontal blanking pulse signal c Front porch / carrier reset pulse signal d Sync tip carrier reset pulse signal e Front porch pulse signal f FM carrier signal reset pulse signal f 'FM carrier signal reset pulse signal f "FM carrier signal reset pulse signal g picture signal h video carrier h ₁ video carrier h ₂ video carrier j burst gate pulse signal k reference burst signal f _TPO first reference frequency Signal f _FPO second reference frequency signal f _Tp horizontal sync pulse tip corresponding FM carrier frequency f _FP Front porch portion corresponding FM carrier frequency Δf frequency change value V ₀ video signal peak value

Claims (5)

(57) [Claims] 1. A horizontal sync pulse front end portion of an FM carrier, which is recorded while performing carrier reset for matching the phase of an FM carrier of a video signal with the phase of a reference frequency signal for each horizontal scanning cycle, and carrier reset during reproduction. In a magnetic recording / reproducing apparatus that uses a portion as a reference burst signal, the reference frequency signal is set to an FM carrier frequency corresponding to a front porch portion of a video signal, and a front porch reference frequency signal for carrier resetting the front porch portion is used. , A horizontal sync reference frequency signal which is set to an FM carrier frequency corresponding to the horizontal sync pulse portion of the video signal and resets the carrier of the horizontal sync pulse portion. The front porch reference frequency signal and the horizontal sync reference frequency signal Means that the FM carrier frequency is horizontal scan Together it is set to an integral multiple of the wave number, a magnetic recording and reproducing apparatus, characterized in that the phase is matched with the horizontal sync pulse leading edge. 2. A magnetic recording / reproducing apparatus according to claim 1, wherein the generator for generating the horizontal synchronizing reference frequency signal is provided with an AFC circuit. 3. The magnetic recording / reproducing apparatus according to claim 1, wherein the generator for generating the front porch reference frequency signal is provided with an AFC circuit. 4. The front porch reference frequency signal resets the carrier of only the latter half of the front porch portion, and the horizontal sync reference frequency signal resets the carrier of only the latter half portion of the horizontal sync pulse portion. Magnetic recording and reproducing device. 5. A horizontal sync pulse front end portion of an FM carrier, which is recorded while performing carrier reset for matching the phase of an FM carrier of a video signal with the phase of a reference frequency signal for each horizontal scanning cycle, and carrier reset during reproduction. In a magnetic recording / reproducing apparatus that uses a portion as a reference burst signal, the reference frequency signal is set to an FM carrier frequency corresponding to the leading end portion of the horizontal synchronizing pulse of the video signal, and a front porch reset pulse that resets the carrier of the front porch portion. , An FM carrier frequency is set to an integral multiple of the horizontal scanning frequency, and a horizontal synchronizing reference frequency signal whose phase is matched at the leading edge of the horizontal synchronizing pulse. .