JPH0683485B2 - Magnetic recording device and magnetic recording / reproducing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic recording device and a magnetic recording / reproducing device, and in particular, a PAL color video signal is separated into a luminance signal and a carrier color signal, and the luminance signal is a frequency signal. Modulate and convert the carrier color signal to the low frequency range and shift the phase of the color subcarrier, record both of these signals on the magnetic recording medium by frequency division multiplexing.
In the helical scan system VTR that reproduces this, the phase of the color subcarrier of the carrier color signal is changed during recording, and the phase shift of the color subcarrier of the reproduced low-frequency conversion carrier color signal is canceled during reproduction. The present invention relates to a magnetic recording device and a magnetic recording / reproducing device for shifting the phase of a subcarrier.

In a low frequency conversion color recording / reproducing system VTR, two adjacent recording tracks are usually provided with a rotary head having different azimuth angles without a guard band or with a guard band having a small width in order to improve tape utilization efficiency. However, since crosstalk from the adjacent track of the low-frequency low-frequency conversion carrier color signal with little azimuth loss effect deteriorates the image quality, some kind of crosstalk countermeasure processing is performed.

As the crosstalk countermeasure processing, in the VTR which converts the NTSC system color video signal or the PAL system color video signal into the above-mentioned signal form and records and reproduces, the applicant of the present invention has already disclosed in Japanese Patent Publication No.
As disclosed in Japanese Patent Publication No. 9073 and Japanese Patent Publication No. 55-32273, the color subcarrier of the low-frequency conversion carrier color signal, which is an amplitude-modulated wave, is moved by 90 ° in a certain direction every horizontal scanning period (1H). Each time it is recorded, the reproduction carrier color signal is obtained by shifting the color subcarrier by 90 ° in 1H steps in the direction substantially opposite to that at the time of recording, and it is passed through a comb filter to obtain a cross. A so-called PS that obtains a reproduction carrier color signal from which talk is removed.
(Phase Shift) method is known.

In such a PS type VTR, a color subcarrier phase shift circuit is provided in the recording system and the reproducing system, and it is important to set the phase switching timing for each 1H.

[Prior Art] FIG. 3 shows a block system diagram of an example of a carrier color signal recording system of the above-mentioned PS type VTR. In the figure, the PAL system color video signal input to the input terminal 1 is supplied to a bandpass filter (hereinafter referred to as BPF) 2, where the color subcarrier frequency F _S (= 4.43).
The carrier color signal of 3619 MHz) is separated and supplied to the horizontal sync signal separation circuit 3 to separate and extract the horizontal sync signal.

The output carrier color signal of BPF2 is supplied to the frequency converter 4, where it is frequency-converted with the signal of a predetermined frequency from BPF9. On the other hand, the horizontal synchronizing signal is a color subcarrier phase shift circuit 5
A rectangular wave (drum pulse) with a repetition frequency of 25 Hz, which is phase-synchronized with the rotation of the rotary head (not shown) from terminal 6.
Supplied with

The color subcarrier phase shift circuit 5 has a constant phase (for example, 0 ° between 0 ° and 0 °) in the field period in which one of two adjacent tracks alternately formed on the magnetic tape by two rotary heads is formed. And a pulse having a repetition frequency of 40 Fh is generated, and the phase is 0 °, 90 °, 180 ° and 270 during one field period which forms the other track.
Every 1 horizontal scanning period (1H), the pulse is switched cyclically in a fixed direction, and a pulse having a repetition frequency of 40 Fh is generated.

In this way, a pulse in which the constant phase and the phase transition are alternately repeated every one field period from the color subcarrier phase shift circuit 5 is taken out, and the frequency converter 7 outputs the constant frequency (F _S + 1 / 8Fh) from the oscillator 8. ) Signal and frequency converted, then BPF
At 9, the signal of the sum frequency (F _S + 40Fh + 1 / 8Fh) is separated and supplied to the frequency converter 4.

The carrier color signal that has been frequency-converted by the frequency converter 4 and taken out is subjected to a low-frequency conversion carrier color signal of a desired color subcarrier frequency F _C (40Fh + 1 / 8Fh) by a low-pass filter (hereinafter referred to as LPF) 10. It is output via the output terminal 11 so as to be frequency division multiplexed with the FM luminance signal.

FIG. 4 shows a block system diagram of an example of the carrier color signal reproduction system of the PS system VTR. In the figure, the reproduction frequency division multiplex signal consisting of the FM luminance signal and the low frequency conversion carrier color signal that has entered the input terminal 13 is supplied to the LPF 14, where the color subcarrier frequency
The low-pass conversion carrier color signal having a time axis fluctuation of F _C ′ is separated and then supplied to the frequency converter 15, which will be described later.
It is frequency-converted with the signal of frequency (F _S + F _C ′) from BPF25.

The output reproduction carrier color signal of the frequency converter 15 has unnecessary frequency components removed by the BPF 16 and is returned to the reproduction carrier color signal of the original color subcarrier frequency F _S , and then by the comb filter 17 having a 2H delay circuit. The crosstalk component is removed and supplied to the burst sampling circuit 18.

On the other hand, a reproduction output PAL system color video signal is supplied to the input terminal 19, the horizontal synchronizing signal is separated and waved by the horizontal synchronizing signal separating circuit 20, and then supplied to the burst sampling circuit 18 and the color subcarrier phase shifting circuit 5, respectively. It

The phase comparator 21 compares the phase of the color burst signal of the frequency F _C ′ with the time base fluctuation from the burst sampling circuit 18 and the continuous signal of the single frequency F _S without the time base fluctuation from the oscillator 22, An error voltage corresponding to the phase difference is output to variably control the output oscillation frequency of the voltage controlled crystal oscillator (VXO) 23. As a result, the frequency (F _S + 1 / 8F) is output from the VXO23.
h ') and the oscillation signal having the same time-axis variation as the reproduced color video signal is taken out and supplied to the frequency converter 24, where the frequency 40Fh' from the color subcarrier phase shift circuit 5 is obtained.
In addition, the frequency is converted into a pulse having a period in which the phase shifts by 90 ° every 1H every other field.

The signal taken out from the frequency converter 24 is supplied to the BPF 25, where the sum frequency component (F _S + 40Fh ′ + 1 / 8Fh ′), that is, (F _S + F _C ′) is waved, and then the frequency converter 15 is fed. Supplied. In this way, the BPF 16 cancels the time base fluctuation and the phase shift during recording, and the reproduced carrier color signal returned to the original band is taken out, and the comb filter 17 further crosses the adjacent tracks. The reproduced carrier color signal from which the talk has been removed is output to the output terminal 26. The phase shift direction by the color subcarrier phase shift circuit 5 during reproduction is set to cancel the phase shift during recording.

Here, in the color subcarrier phase shift circuit 5, the phase switching timing is conventionally changed from the front porch of the horizontal synchronizing signal so that the color burst signal comes in after the phase is shifted by 90 ° and the transient characteristics become stable. It is set appropriately up to the horizontal sync pulse width portion, and there was no intention to set it at a specific timing.

In the conventional color subcarrier phase shift circuit 5, since the phase shift switching timing is made from the horizontal synchronizing signal, the color burst signal CB is superimposed on the horizontal synchronizing signal HS back porch as shown in FIG. 5 (A). When a color video signal is input, the horizontal synchronizing signal separation circuits 3 and 20 supply the horizontal synchronizing signal HS delayed by the time T _A as shown in FIG. 5B, and the color subcarrier phase shift circuit 5 Since the time T _{C is} delayed to obtain the phase shift switching timing from the horizontal synchronizing signal internally, the output frequency conversion signal (local oscillation signal) of the BPF 9, 25 has a phase of 90 at the position indicated by P in FIG. 5 (D). It was supposed to switch.

The local oscillation signal becomes unstable (so-called phase deviation) in a short period immediately after the switching timing P (FIG. 5C).
The switching timing P and the color burst signal CB are separated from each other as shown in, and further the carrier color signal or the low frequency conversion carrier color signal is supplied to the frequency converters 4 and 15 after being delayed by the time T _B by the BPF 2 or LPF 14. Therefore, there is no influence by the above-mentioned phase deviation.

[Problems to be solved by the invention]

By the way, Japanese Patent Application No. 62-206016 (the title of the invention "magnetic recording device and magnetic recording / reproducing device") previously proposed by the applicant.
In addition to the standard image quality mode in which the band of the luminance signal is a relatively narrow band as described above, it is a VTR that has a high image quality mode for obtaining a high resolution image with the luminance signal in a wide band. In a VTR in which the video signal recorded in the mode can arbitrarily select one of the composite color video signal, the YC separated input luminance signal and the carrier color signal, the carrier color signal contains a high-frequency luminance signal component of a predetermined level or higher. For example, in the horizontal blanking period or the vertical blanking period in order to distinguish during playback whether the video signal recorded in the high image quality mode is a composite color video signal or a YC separated input depending on whether or not it is included, Insert and record a burst-shaped constant frequency pilot signal whose phase is a predetermined value different from the color burst signal, and perform the above identification by the phase value of the pilot signal. There are things I try to do.

That is, especially when a comb filter using a 2H delay circuit is used to obtain a luminance signal in a wide band from a PAL system color video signal, there is a large time difference between the carrier color signals separated by the comb filter, and color blur occurs. I will end up. It is possible to configure the comb filter so that color fringing does not occur, but doing so would make the configuration complicated and expensive. Therefore, when the PAL system color video signal is recorded in the high image quality mode, the luminance signal uses a comb filter and the carrier color signal is separated from the PAL system color video signal using a bandpass filter.

However, since a bandpass filter is used to separate the carrier color signal, the output carrier color signal also has a high-frequency component of the luminance signal in the same band as the carrier color signal, which adversely affects the image quality. Exert. On the other hand, the luminance signal and the carrier chrominance signal input by YC separation have a wide band, but since they are transmitted separately without being band-shared multiplexed, there is no interference between them.

Therefore, in the proposed device of the present applicant, the cutoff frequency of the high-pass filter for separating the FM luminance signal from the reproduced signal is discriminated in the reproducing system by determining which of the two phases the reproduced pilot signal has. , PAL system Color video signal input and composite video signal recorded in high image quality mode is played back to raise it to maximize the effect from the high frequency component of the luminance signal in the low frequency conversion carrier color signal. On the other hand, when reproducing the recorded wideband luminance signal and YC separated input carrier color signal in high image quality mode, lower the cutoff frequency of the above high-pass filter to make the FM luminance signal wideband. Waves are being made to contribute to high image quality.

In addition, the color burst signal of the PAL system color video signal is 1
Since the phase changes alternately with a phase difference of 90 ° for each H (with an offset), the reproduction carrier color signal
The time constant of the APC loop is set to be long so that the APC loop operates at the phase average value. Therefore, it takes time for the APC loop to complete the pull-in operation, and the screen becomes unstable during that time.

Therefore, the above proposed device keeps the phase of the pilot signal constant (however, the value of the phase differs as described above depending on the type of recording input) and uses it in the APC loop to record and reproduce the NTSC color video signal. It also has the feature that the APC loop can be pulled in quickly as in the VTR for use.

However, in the above-mentioned proposed apparatus, the pilot signal frequency is equal to the color subcarrier frequency F _S , and its insertion position is between the color information portion C of the carrier color signal and the color burst signal CB shown in FIG. 5C. Because of the position, the conventional magnetic recording device and magnetic recording / reproducing device have a problem that the phase shift switching timing P affects the frequency conversion by the frequency converters 4 and 15.

The present invention has been made in view of the above problems, and provides a magnetic recording device and a magnetic recording / reproducing device that are capable of performing phase transition processing at an optimum phase shift switching timing and determining the type of high image quality mode. The purpose is to do.

[Means for solving problems]

The magnetic recording apparatus of the present invention includes a circuit for generating a periodic signal that is phase-synchronized with a horizontal synchronizing signal relating to a carrier color signal, and a timing for generating a timing pulse at a predetermined time in the front porch of the horizontal synchronizing signal by the periodic signal A generation circuit,
A 90 ° phase shift processing circuit that generates a frequency conversion signal in which the phase is shifted in a fixed direction by 90 ° for each horizontal scanning period based on the timing pulse, and a sub carrier from a predetermined time in the front porch of the horizontal synchronizing signal. A circuit for generating a recording signal in which a pilot signal for discriminating the type of high image quality mode is multiplexed with a carrier color signal between the start time of a color signal and a low-frequency recording signal based on a frequency conversion signal. And a circuit for magnetically recording the low-frequency converted recording signal obtained by conversion on a magnetic tape.

The magnetic recording / reproducing apparatus of the present invention is, in addition to the configuration of the magnetic recording apparatus described above, a circuit for magnetically reproducing a low-frequency converted recording signal from a magnetic tape to generate a low-frequency converted reproduced signal, and a low-frequency converted reproduced signal. And a circuit for generating a reproduction timing pulse at a predetermined time within a front porch of the horizontal synchronization signal related to the low-frequency conversion reproduction signal by the reproduction periodic signal. , A circuit for generating a reproduction frequency conversion signal in which the phase is shifted in a constant direction by 90 ° for each horizontal scanning period based on the reproduction timing pulse, and a low frequency conversion reproduction signal to a high frequency based on the reproduction frequency conversion signal. It is composed of a circuit for performing a domain conversion to generate a reproduction carrier color signal and a reproduction pilot signal.

[Action]

A pulse is extracted from the timing generation circuit at the timing within the front porch of the horizontal synchronizing signal by the periodic signal and is supplied to the 90 ° phase shift processing circuit.

The 90 ° phase shift processing circuit operates so as to generate a frequency conversion signal in which the phase is shifted in a fixed direction by 90 ° for each horizontal scanning period based on this timing pulse, and also in the front porch of the horizontal synchronizing signal. From the predetermined time to the start time of the sub-carrier color signal, a recording signal is generated by multiplexing a pilot signal for determining the type of the high image quality mode with the carrier color signal and magnetically recorded on the magnetic tape. Acts like.

〔Example〕

FIG. 1 shows a block system diagram of an embodiment of the present invention. In the figure, the horizontal sync signal from the horizontal sync signal separation circuit 3 or 20 that has entered the input terminal 28 is supplied as a control voltage to a voltage controlled oscillator (VCO) 30 through a phase comparator 29, and its output oscillation frequency is Variable control. Assuming that the horizontal synchronizing signal is the PAL system color video signal coming into the input terminal 1 or the reproduced PAL system color video signal output to the output terminal 26, it has a waveform as shown in FIG. The horizontal synchronization signal HS is delayed by time T _A.

The VCO 30 oscillates at a center frequency of 160 Fh, and its output oscillation frequency is divided by the 1/4 frequency divider 31 to 40 Fh, and then further passed through the 1/40 frequency divider 32 to generate the phase comparator 29 and timing. Each is supplied to the circuit 33.

The closed loop of the phase comparator 29, the VCO 30, the 1/4 frequency divider 31, and the 1/4 frequency divider 32 is a known phase locked loop (PL
L), and the 1/40 frequency divider 32 extracts a periodic signal of frequency Fh, which is phase-locked with the input horizontal synchronizing signal.

The output periodic signal Fh of the 1/40 divider 32 is the timing generation circuit.
It is supplied to 33, where it is delayed for a certain time, and FIG. 2 (A)
A timing pulse is output at the timing (indicated by a chain line I in FIG. 2) in the front porch of the input PAL system color video signal or the reproduction PAL system color video signal shown in FIG.
The timing pulse is supplied to the 90 ° phase shift processing circuit 34 together with the drum pulse which is a symmetric square wave of two field period from the input terminal 6 and the signal of the frequency 40Fh from the 1/4 frequency divider 31.

The 90 ° phase shift processing circuit 34 outputs 0 from the signal of 40 Fh, for example.
Frequency with four kinds of phases of ゜, 90 ゜, 180 ゜ and 270 ゜
A circuit for outputting a 40 Fh signal in parallel, a switch circuit for switching and outputting these four types of signals based on the timing pulse to output a predetermined signal, and a switching operation for this switch circuit based on a drum pulse. The control circuit is configured so that the one-field period and the one-field period in which the switching operation is prohibited and the signal of a constant phase is always output alternately appear.

As a result, the output terminal 35 is output from the 90 ° phase shift processing circuit 34.
The frequency is 40Fh, which is always constant, but the phase is 90% every 1H.
A frequency conversion signal is output in which one field period in which the field is switched in a constant direction in increments of ° and one field period in which the phase is always constant is alternately switched for each field.

As a result, not only when the output carrier color signal of BPF2 has the waveform shown in FIG. 2 (C), but also when the reproduced low frequency conversion carrier color signal from LPF14 shows the color information signal as shown in FIG. 2 (D). Part C
Between the color burst signal CB and the color burst signal CB, even in the case of a signal recorded and reproduced by superimposing the pilot signal PL.
Since the phase switching point of the output frequency converting signal is in the front porch shown by the alternate long and short dash line I in FIG. 2, the level unstable portion immediately after the phase switching is the pilot signal PL as shown by e in FIG. 2 (E). Therefore, it is possible to prevent the adverse effect due to the phase switching.

Even if the phase shift switching timing is set at an intermediate position between the pilot signal PL and the color burst signal CB, and the pilot signal PL and the color burst signal CB are set in different phase transition sections, the above operation is performed operably. Same as the example.

However, in this case, considering the standard image quality mode in which the pilot signal PL is not recorded, there is no time margin up to the color burst signal CB input as compared with the embodiment, and the phase deviation at the time of phase shift switching remains, which adversely affects the image quality. give. Also,
In this case, since the pilot signal PL at the beginning of one line and the color burst signal CB are in different phase transition periods,
When detecting the phase of the pilot signal, the circuit configuration such as a phase shifter becomes complicated and the scale becomes large.

On the other hand, according to this embodiment, both the pilot signal PL and the color burst signal come in after the transitional state immediately after the phase shift is switched, so that the frequency conversion can be performed stably and the image quality of color S / N and the like is improved. Is advantageous. Further, since the pilot signal PL and the color burst signal CB are within the same phase transition period, the phase detection can be simple.

Further, as in the present embodiment, it is possible to delay the horizontal synchronizing signal by delaying the periodic signal obtained by the PLL with the timing generating circuit 33.
Accurate phase shift switching timing in the front porch can be obtained more easily than delaying by 1H.

The present invention is a PAL system for recording and reproducing color video signals.
Although it is particularly suitable for application to the S system VTR, it can also be applied to the PS system VTR for recording and reproducing NTSC system color video signals.

〔The invention's effect〕

As described above, according to the configuration of the magnetic recording apparatus of the present invention, the phase transition is switched based on the timing pulse generated at a predetermined time in the front porch of the horizontal synchronizing signal, and the influence of this switching is avoided. Since a pilot signal for determining the type of high image quality mode is multiplexed with the carrier color signal between a predetermined time in the front porch of the horizontal synchronizing signal and the start time of the subcarrier signal, a recording signal is generated. It is possible to stably record not only the carrier color signal but also the pilot signal on the magnetic tape, and as a result, it is possible to provide the magnetic tape capable of reliably discriminating the type of the high image quality mode.

According to the configuration of the magnetic recording / reproducing apparatus of the present invention, in addition to the effect of the magnetic recording apparatus described above, the pilot signal is not affected even by switching the phase transition at the time of reproduction. There is an effect that it can be surely identified.

[Brief description of drawings]

FIG. 1 is a block system diagram of an embodiment of the present invention, FIG. 2 is a signal waveform diagram for explaining the operation of FIG. 1, and FIGS. 3 and 4 are respectively recording system of carrier color signals of PS system VTR and FIG. 5 is a block diagram showing an example of a reproducing system, and FIG. 5 is a signal waveform diagram for explaining the operation of FIGS. 3 and 4. 6 ... Drum pulse input terminal, 28 ... Horizontal synchronization signal input terminal, 29 ... Phase comparator, 30 ... Voltage controlled oscillator (VC
O), 31 …… 1/4 divider, 32 …… 1/40 divider, 33 …… Timing generation circuit, 34 …… 90 ° phase shift processing circuit, 35 ……
Signal output terminal for frequency conversion.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-60-132493 (JP, A) JP-A-55-97785 (JP, A) JP-A-64-49395 (JP, A)

Claims (2)

[Claims] 1. A circuit for generating a periodic signal phase-synchronized with a horizontal synchronizing signal relating to a carrier color signal, and a timing generator for generating a timing pulse at a predetermined time in the front porch of the horizontal synchronizing signal by the periodic signal. A circuit, a 90 ° phase shift processing circuit for generating a frequency conversion signal in which the phase is shifted in a fixed direction by 90 ° for each horizontal scanning period based on the timing pulse, and in the front porch of the horizontal synchronizing signal. A circuit for generating a recording signal in which a pilot signal for determining the type of high image quality mode is multiplexed with the carrier color signal between a predetermined time and the start time of the sub carrier color signal, and the frequency conversion signal. And a circuit for magnetically recording a low-frequency converted recording signal obtained by low-frequency converting the recording signal on the basis of the above. 2. A circuit for generating a periodic signal that is phase-synchronized with a horizontal synchronizing signal relating to a carrier color signal, and a timing generator for generating a timing pulse at a predetermined time in the front porch of the horizontal synchronizing signal by the periodic signal. A circuit, a 90 ° phase shift processing circuit for generating a frequency conversion signal in which the phase is shifted in a fixed direction by 90 ° for each horizontal scanning period based on the timing pulse, and in the front porch of the horizontal synchronizing signal. A circuit for generating a recording signal in which a pilot signal for discriminating the type of the high image quality mode is multiplexed with the carrier color signal between the start time of the sub carrier color signal from a predetermined time, and the frequency conversion circuit. A circuit for magnetically recording a low-frequency conversion recording signal obtained by low-frequency converting the recording signal on the basis of the signal, and a low-frequency conversion by magnetically reproducing the low-frequency conversion recording signal from the magnetic tape. A circuit for generating a reproduction signal, a circuit for generating a reproduction periodic signal phase-synchronized with a horizontal synchronization signal related to the low frequency conversion reproduction signal, and a horizontal synchronization signal related to the low frequency conversion reproduction signal by the reproduction periodic signal Of a circuit for generating a reproduction timing pulse at a predetermined time in the front porch of the vehicle, and for each horizontal scanning period based on the reproduction timing pulse.
A circuit for generating a reproduction frequency conversion signal whose phase is shifted by 90 ° in a fixed direction, and a reproduction carrier color signal and a reproduction pilot for converting the low frequency conversion reproduction signal to a high frequency based on the reproduction frequency conversion signal. A magnetic recording / reproducing apparatus having a circuit for generating a signal.