JPS6273894A - Vtr - Google Patents

Abstract

PURPOSE:To correct the time axis fluctuation of a PCM signal by applying time axis compression to a reproduced PCM signal to correct it into substantial time axis length and correcting it while the video signal system is utilized. CONSTITUTION:A signal So is fed to a CCD 161 as a clock through a transistor (TR) Q4 and a PCM side contact P of a switch 92. Thus, when a PCM signal Sp is extracted from a demodulation circuit 15, since the frequency fo of the signal So is changed, the signal Sp is fetched at a low sampling frequency at each field period to the CCD 161 and extracted at a high frequency from the CCD 161, the signal Sd is subjected to time axis compression to form a PCM signal with normal time axis length. Thus, even when a track 2 is elongated due to the elongation of the tape 1, the PCM demodulation without any deteriorated error rate is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to, for example, a VTR with an integrated PCM processor.

[Summary of the invention]

The present invention corrects fluctuations in the time axis length of a PCM signal by reusing a part of the video signal system, for example, in a VTR with an integrated PCM processor.

[Conventional technology]

By combining a PCM processor (PCM digital audio processor) with a VTR, audio signals can be
Recording and reproduction can be performed in the state of a CM signal, and high-quality recording and reproduction is possible.

In this case, during recording, the audio signal is encoded by the PCM processor into a PCM signal conforming to a standard video signal, and includes vertical and horizontal synchronization pulses in addition to PCM data. Then, this PCM signal is V
In the TR, the signal is further converted into an FM signal and recorded on tape.

On the other hand, during playback, the FM signal is played back from the tape in the VTR, and the PCM signal is transmitted from the FM signal to tlKW! This PCM signal is then decoded into the original audio signal in a PCM processor.

(Literature = "Introduction to Digital Audio Technology" published by Ohm Publishing) [Problems to be solved by the invention] By the way, in a general home VTR 2, for example, a Hetaumant VTR, due to the helical scan method, the tape (11 As shown in FIG. 5, one field of the video signal is recorded as one diagonal magnetic track (2) on the tape fl). At this time, the angle θ of the track (2) with respect to the longitudinal direction of the tape (11) is 5 degrees.

For this reason, if the tape (1) stretches due to temperature changes, the trunk (2) will also easily become longer, and the one-field period of the PCM signal played from the track (2) will be longer than the regular one-field period. It ends up being longer than the lead period. In other words, the time axis of the PCM signal is expanded. Therefore, while one rotating head does not play to the end of a track (2), the other rotating head starts playing the next trunk (2) from the beginning.
The error rate of the PCM signal worsens.

This invention attempts to solve these problems.

[Means for solving problems]

For this reason, in the present invention, the reproduced PCM signal is time-axis compressed and corrected to the original time-axis length, and
In particular, the correction is performed using a video signal system.

[Effect]

Time axis fluctuations in the PCM signal due to elongation of the tape (1, 1, etc.) are corrected.

〔Example〕

In FIG. 1, +11 indicates a magnetic tape, and a video signal or a PCM signal is recorded on this tape (1). In this case, when the recording signal of the tape (1) is a video signal, the video signal is recorded in, for example, a heteroformant, that is, the luminance signal S
The sum signal of the FM luminance signal FM modulated by y and the general color feeding signal, which is frequency-converted to a lower frequency band than this FM luminance signal and interleaved with each other every field period, is the field. Diagonal 1 for each period
The magnetic tracks of the book are recorded closely at different azimuth angles. In addition, when the recording signal of tape (1) is a PCM signal, it is a PCM signal of EIAJ format.
The signal Sp is replaced with the luminance signal sy as an F'M signal,
This FM signal is also recorded.

Furthermore, (11) to (25) are video signal reproduction systems, (
31) to (35R) are PCM signal reproduction systems, (91)
.

(92) indicates a mode changeover switch, and these switches (91) and (92) are connected to the VTR side contact ■ when in the video signal reproduction mode, and are connected to the PCM side contact P when in the PCM signal reproduction mode. connected to.

And (11) is a pair of rotating magnetic heads, these heads (11) have mutually different azimuth angles, and have an angular interval of 180 degrees from each other, and are driven by a motor (42) through a rotating shaft (41). It is rotated at a rate of 30 times per second (frame frequency). Also, the tape (1) is 180° with respect to the rotating circumferential surface of the head (11).
It runs diagonally across a wide angle range and runs at a constant speed. Note that, for example, the rotation axis (4
A pickup head (43) is provided opposite to the head (11), and one pulse is taken out as a signal indicating the rotational phase of the head (11) for each revolution of the head (11).

In the video signal reproduction mode, an oscillation signal Ss having a frequency of 3.58 MIIz (color subcarrier frequency) is formed in the crystal oscillation circuit (25), and this signal Ss
is supplied to the frequency dividing circuit (26) and divided into a signal Sv with a frequency of 1159718, that is, a frequency of 6011z (field frequency). Circuit (44)
(The reference signal is divided in half in the servo circuit), pulses from the head (43) are supplied to the servo circuit (44), and the servo output is supplied to the motor (42). The rotational phase of the head' (11) is locked to the signal Sv and kept constant.

Further, the signal Sv from the switch (91) is transmitted to the servo circuit (
Although not shown, control pulses are reproduced from the tape (11) and supplied to the servo circuit (45), and the rotation of the gear bus stun motor is controlled by the servo output. Tracking servo of the head (11) with respect to the trunk of ) is performed.

Therefore, a reproduction signal of the tape (1) is obtained from the head (1), and this signal is supplied to the bandpass filter (13) through the reproduction amplifier (12) to extract the FM luminance signal, and this signal is sent to the limiter. (14) to the FM demodulation circuit (15), and the luminance signal Sy is
j key, and this signal sy is supplied to a noise removal circuit (16).

This removal circuit (16) regards components without vertical correlation in the signal sy as noise components and removes them. That is, the signal Sy from the demodulation circuit (15) is sent to the delay circuit,
For example, a pulse Ps having a frequency of, for example, 10.7 Hz is generated in the crystal oscillation circuit (162) while being supplied as an input signal to the CCD (161).
s is the VTR of the switch (92) (CC through the side contact V)
It is supplied as black and white to D (161) and CCD (16
A luminance signal Sd delayed by one horizontal period is extracted from 1), and this signal Sd and the original luminance signal sy are added to a subtraction circuit (1).
63), and a difference signal Sn between both signals Sd and Sy is taken out. In this case, if there is a vertical correlation between the signals SY and Sd, both signals sy and sd will be equal, so
The signal Sn is a signal component without vertical correlation, ie, is mainly a noise component.

Then, when the signal sy from the summer tone circuit (15) is supplied to the subtraction circuit (165), the subtraction circuit (163)
The noise signal Sn is supplied to the subtraction circuit (165) through the ivy (164), and by subtracting the signal Sn from the signal Sy, a signal sy without noise components is extracted from the subtraction circuit (165). sy is supplied to the adder circuit (17).

Also, the signal from the amplifier (12) is filtered through a low-pass filter (
21) to extract the carrier color signal, this signal is supplied to the frequency converter (22) and
An alternating signal Sc with a predetermined frequency and phase is supplied from the F C/A P C circuit (24) to the converter (22), and the carrier color signal from the filter (21) is converted into a signal with the original color subcarrier frequency and phase. This signal is passed through a C-shaped comb filter (23) and sent to an adder circuit (17).
), and in this adder circuit (17), the carrier color signal is added to the luminance signal Sy from the removal circuit (16) to form the original color video signal, and this signal is sent to the terminal (1
8).

At this time, the horizontal synchronizing pulse and burst signal are extracted from the reproduced luminance signal and carrier color signal,
These signals are supplied to the AFC/APC circuit (24), and the oscillation signal S from the oscillation circuit (25)
s is supplied to the AFC/APC circuit (24) as a reference signal to perform AFC and APC.

On the other hand, in the PCM signal reproduction mode, a master clock MCLK having a frequency of 2.643M1tz is formed in the crystal oscillation circuit (51), and this clock gate C
1 and K are supplied to the frequency dividing circuit (52) and PCM, which will be described later.
The frequency is divided into various clock and timing signals necessary for signal decoding and D/A conversion and supplied to each circuit, and the frequency is also divided into a signal Sv with a frequency of l//14050, that is, a frequency of 60 Hz, This signal Sv is supplied to the servo circuits (44) and (45) as a (1@ signal) through the PCM side contact P of the switch (91), and the drum servo and capstan servo are performed.

Therefore, a reproduction signal of the tape (1) is obtained from the head (11), and a PCM signal S of the EIAJ format is obtained from the demodulation circuit (15) instead of the luminance signal Sy.

Then, this PCM signal sp is supplied to the C0D (161), the time axis is corrected as described later, and then supplied to the decoder (32) through the shaping circuit (31), where error correction and correction are performed. This corrected and modified PCM signal is sent to the D/A converter (33L).
, (33R), the original analog stereo signal is converted to R, and this signal R is passed through a low-pass filter (34L).

(34R) through terminal (351,), (35R)
It is taken out.

In this case, time axis correction in C0D (161) is performed as follows.

As shown in FIG. 2A, for example, the servo circuit (44) extracts a rectangular wave signal Sf that is inverted every field period in synchronization with the rotation of the head (11), and this signal Sf However, capacitor C1゜C2, resistor R1, R
2 and a differentiator circuit (61) having a transistor Q1, and as shown in FIG. be done. This transistor Q2 constitutes a charging/discharging circuit (62) together with resistors R3, R4 and capacitor C3. When pulse Pf is not supplied, transistor Q2 is off, so the voltage Vcc at terminal T1 is applied to resistor R1. , R4, and the terminal voltage thereof gradually rises. When the pulse Pf is supplied, the transistor Q2 is turned on, so the capacitor C3 is discharged, and the terminal voltage thereof rapidly decreases. Therefore, at the midpoint of connection between resistors R3 and R4, there is C
As shown in , a sawtooth wave voltage Es that rises at every pulse PfO time point is obtained.Then, a feedback capacitor C5 is connected to the base-grounded transistor Q3, and a resonance capacitor C4 and a coil L1 are connected. At the same time, a connection point between the capacitor Cs and the coil [51] is connected to the variable capacitance diode D1 through the capacitor C6, thereby forming a VCO (63). Then, the voltage Es is supplied to the diode D1. Therefore, as shown in the second diagram, an oscillation signal So whose frequency fo changes in accordance with the voltage Es is obtained from the oscillation circuit (63). Note that at this time, the voltage E
By selecting s and the values of each element, for example, when the voltage Es is the minimum, fo = 8MIIz, and when the voltage Es is the maximum, fo = 12MIIz.

Then, this signal SO passes through the transistor Q4 and further passes through the PCM side contact P of the switch (92) to the CC
D (161) as its clock. Therefore, when the PCM signal S is output from the demodulation circuit (15), this signal Sp is delayed by the signal So in the CCD (161) and is extracted as the signal Sd. The signal So
Since the frequency fo is changing, for each field period, the signal Sp is transmitted to the CCD (1
131) and CCD (161) at high frequency.
Therefore, the time axis of the signal Sd is compressed and becomes a PCM signal with a regular time axis length. Therefore, deterioration of the error rate during PCMfjt adjustment is eliminated.

Thus, according to the present invention, PCM demodulation can be performed without deterioration of the error rate even if the track (2) is extended due to elongation of the tape (1) or the like. Moreover, in this case, the CCD (161) used when reproducing video signals can be used, so the configuration is simple and costs can be reduced.

In the example shown in FIG. 3, it is possible to cope with the case where the time axis of the PCM signal sp is expanded or contracted due to expansion or contraction of the tape (1).

That is, in the PCM signal reproduction mode, the voltage Es from the charging/discharging circuit (62) is supplied to the switch circuit (64) and also to the inverter (65), where the voltage Es is inverted in level. , this voltage Es is supplied to the switch circuit (64), the voltage E3 or Es is taken out from the switch circuit (64), and this taken out voltage is supplied to the VCO (63) as a control voltage.

Furthermore, the PCM signal sp from the demodulation circuit (15) is supplied to the synchronization separation circuit (71), and the horizontal synchronization pulse ph is extracted as shown in FIG. 4B. In this case, the outputs of the pair of heads (11) are actually switched every field period by the signal SF, that is, every time the signal Sf is inverted, but the outputs of the pair of heads (11) are synchronously separated. Since there is a time delay until circuit (71), Fig. 4 A and B
As shown in FIG.
) By the time point (Tc) when the pulse is switched to the pulse Ph of ),
There is a delay of period Td. Then, if there is no expansion or contraction in the track (2) (therefore, if there is no expansion or contraction in the time axis of the PCM signal signal S, as shown in FIG. th pulse p
h) and the pulse Ph immediately after time Tc, the interval τ is one normal horizontal period. However, the track (
If there is an elongation in track (2), and therefore the time axis of the PCM signal S is elongated, the interval τ will be shorter than one normal horizontal period, as shown in C in the same figure, and there will be a contraction in track (2). , Therefore, when the time axis of the PCM signal S is shortened, the interval becomes longer than one regular horizontal period, as shown in FIG.

Therefore, the pulse ph is supplied to the counter (72) as a count input, and the pulse Pf is supplied to the counter (72) as a count input.
72) as a reset input, and therefore, in the counter (72), the time T when the signal Sf is inverted is
The number of pulses ph from i is (
each inversion of signal Sf). Then, the count value of the counter (72) at this time is determined by the decoder (73).
), and the decoded values are taken out at the Nth and (N+1)th pulse Ph, that is, at the pulse Ph immediately before and the pulse Ph immediately after the time Tc.

And these Nth and (N+1)th pulses p
The decoded output of h is supplied as the reset input and count disable input of the counter (74), and the clock CK is supplied as the count input from the oscillator circuit (75) to the counter (74) to generate the Nth pulse Ph and ( The interval from the N+1)th pulse ph is detected as the number of clocks CK. Then, this detected interval τ is supplied to a discrimination circuit (76), which determines the direction and magnitude of the deviation (length or shortness) of this interval with respect to one regular horizontal period, and a signal indicating the size of the deviation is generated. A control signal for the amplitude of the voltage Es is supplied to the charge/discharge circuit (62), and a signal indicating the direction of the deviation is supplied to the switch circuit (64) as the control signal. Therefore, the tape (
Even if the time axis of the PCM signal sp expands or contracts due to the expansion or contraction in 1), the voltage Es or Es is selected correspondingly, and its amplitude is controlled, so it can correspond to the expansion or contraction of the time axis of the PCM signal S. The oscillation signal S of the VCO (63)
.

The frequency fo of changes, therefore, the PCM signal signal S
Expansion and contraction of the time axis is corrected.

In the above description, instead of providing the oscillation circuit (162), the signal So may be supplied to the C0D (161) and its frequency [0 may be fixed to the frequency of the signal Ps. Also, instead of CCD (161), B
A variable delay circuit such as a BD may also be used.

〔Effect of the invention〕

According to this invention, even if the track (2) is extended due to tape +11 elongation, the error rate does not deteriorate.
fig can be done. Furthermore, in this case, the CCI (161) used when reproducing the video signal can be used, so the configuration is simple and costs can be reduced.

[Brief explanation of drawings]

1 and 3 are system diagrams of an example of the present invention, and FIGS. 2, 4, and 5 are diagrams for explaining the same. (11 is a magnetic tape, (11) to (35R) are playback systems,
(44) and (45) are servo circuits. Agent Sada Ito:,,:,,:,:,,)') Same
Hidemori Matsukuma? Decame kanji mask 2nd picture

Claims (1)

[Claims] An FM luminance signal that is FM-modulated by a luminance signal, and
A signal added to a carrier color signal frequency-converted to a frequency band lower than that of the M luminance signal, or a modulated signal modulated by a PCM signal, is recorded as one diagonal magnetic track for each predetermined period. In a VTR that reproduces the added signal or the modulated signal from a magnetic tape, when the added signal is recorded on the magnetic tape, the FM luminance signal and the frequency-converted carrier are reproduced from the reproduced signal of the rotating magnetic head. The color signal is separated and extracted, the luminance signal is demodulated from the extracted FM luminance signal, the demodulated luminance signal is extracted through a noise removal circuit having a delay circuit of one horizontal period, and the extracted carrier is extracted. converting the frequency of the color signal into the original carrier color signal; when the modulated signal is recorded on the magnetic tape, demodulating the PCM signal from the reproduction signal of the rotating magnetic head; and demodulating the PCM signal. is supplied to the delay circuit, and the delay time of the delay circuit is controlled in accordance with the time axis length of the demodulated PCM signal, and by this control, the PCM signal whose time axis length has been corrected is output from the delay circuit. VTR that I tried to get.