JPS6087448A - Magnetic tape recording speed automatic discrimination device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is an automatic magnetic tape recording speed system that automatically determines the recorded data speed of a magnetic recording and reproducing device at the time of reproduction and automatically switches to a predetermined mode. Regarding a discrimination device.

[@Ming background]

In a rotating head helical scan type magnetic recording and reproducing device such as a household magnetic recording and reproducing device, some kind of synchronization signal is recorded on the magnetic tape at the time of recording, and at the time of playback, the synchronization signal is reproduced and the cabz tongue or rotary head is The rotational position of the cylinder is adjusted and tracking control is performed by a servo circuit so that the rotary head correctly traces the video signal recording track on the magnetic tape.

The synchronization signal is usually a control signal (CT
A method (CTL method) is used in which a pulse signal having a period equal to that of a vertical synchronizing signal called "L signal" is folded into the end of the tape.

In the servo tracking control method using this control signal, the gap between the C 7' L signals recorded on the tape varies depending on the recording speed. (If the recording tape speed is 4 for long-time recording, the 11" gap in the CTL signal will also be 4.) Therefore, the CTL signal during playback (the frequency of No. ii and the playback f-1
The ratio of the frequency of the signal obtained from the frequency generator attached to the cabstan shaft or cabstan motor shaft representing the speed K corresponds by one step 91 to the gap of the CTL signal or recording tape speed. Moreover, since this ratio is constant regardless of the playback speed, by measuring this ratio, the recording tape speed is automatically determined during playback, and the mode is automatically switched to a predetermined mode (corresponding to the speed during recording). be able to.

The method described above was a method using a CTL signal, but this method uses a synchronization signal (for example, four pilot signals j'+, f2. fs, 1), which is another servo tracking control method. -CT
Since the tracking error signal created from the pilot signal that corresponds to the L signal becomes zero in the just trunking state during standard playback (therefore, the frequency share is also zero, that is, only the DC component), it is not possible to use one side. .

[Purpose of the invention]

An object of the present invention is to eliminate the drawbacks of the above-mentioned prior art, do not require a control signal, and stably determine the recording speed even in playback modes with different playback speeds such as standard, slow motion, search, etc. An object of the present invention is to provide an automatic recording speed discrimination device for a magnetic tape that allows automatic switching.

[Summary of the invention]

In order to achieve the above objects, the present invention focuses on the characteristics of a pilot signal, and in a search mode of relatively high-speed reproduction in which the frequency of the tracking error signal normally used during standard reproduction does not become zero, the frequency of this tracking error signal is By focusing on the repetition frequency component of one specific frequency (for example, fs) of the pilot signal in the double speed standard and 20-motion playback modes in which the frequency of the tracking error signal may be zero. , the recording tape speed can be determined.

[Embodiments of the invention]

' Hereinafter, embodiments of the present invention will be explained with reference to the drawings. FIG. 1 is a block diagram of an automatic magnetic tape recording speed determination device according to an embodiment of the present invention.
1 is a magnetic tape, 2 is a cylinder motor, 3 is one A head of two rotating heads, 4 is the other B head,
5 is a tack head for detecting the rotational phase of the cylinder and generating a head switching signal, 5F30, in the servo circuit 6;
7 is the capstan motor % s is the frequency generator (F
In this embodiment, the capstan shaft is directly driven by the capstan motor 7, so the one-frequency generator 8 is attached to the rotating shaft of the motor 7. When the capstan shaft is driven by a belt, the frequency generator 7 may be mounted on either the capstan shaft or the motor. 9 is a preamplifier for amplifying the video-haired output, 10
is a pantone filter (CBPF) for selectively passing a regenerated pilot signal (plLOT) having four pilot frequencies f, ~ m components, and 11 is a band pass with local oscillation signals from two local frequency generators 12 and 15. Mixers 14 and 15 for mixing the outputs of the filters 10 selectively pass specific pilot frequency differences through rectifiers 16 and 17 respectively to the 5f, component and ftH.
A bandpass filter (3j, BpF and f
, BPF ), 18 is a differential plow amplifier, 19 is an 11-fold amplifier, 20 is a switch controlled by a head switching signal, and 22 and 25 are bandpass filters (BpF2 and EpF 1 ) having constant bands. , 24 , 25
is the zero cross detector, 21 and 26 are the frequency 1/N
A frequency divider that divides the frequency into 1/8 (1/8 in the embodiment).

27, 28.1 is “H” when the search mode command is issued during playback.
The switch controlled by the search command S (first
In the figure, the switch is shown in the state where the search command is °B°, and 29 is the signal fprLor after predetermined processing of the frequency fcya of FG8 and the reproduced pilot signal PILOT.
(The frequency is also expressed by the same fpzLot) This is a frequency ratio discriminator for measuring the ratio and discriminating the recording tape speed'.

In this example, SP (standard play) mode and (,
The case of two types of recording tape speeds in p (angray) mode (Lp is the tape speed of SP) will be explained. In addition, there are four types of bimit frequency bands (6,5fx) for the bimitto system.

m(10,5jz) −f4(9,5jx)'t
t' The method will be explained in which the fields are inserted into the video field 5 y/ in this order. Here, f is the horizontal synchronization frequency.

First, the pattern diagrams in Figures 1 and 2, Figures 3 and 4.
Using the signal waveform diagrams of each part in the figure, determine the recording tape speed in a relatively high-speed playback search mode (search command is °H' in Figure 1), based on the tracking error signal normally used during standard playback. Explain the operation. In Figure 2 the person, jl.

It is shown whether the 12 SM 9 tracks were recorded with the A head or the B head, respectively, on tracks on which pilot signals were recorded in advance. FIG. 2 is a playback pattern diagram in the search mode, assuming that the playback tape speed is the same as that during recording (the search speed may be considered to be 1x speed).

As shown in FIG. 3, the α-Cull frequency from the local frequency generator 12 is generated in synchronization with the head switching signal 5ivso in exactly the same phase as during recording for each field, and is mixed with the reproduced pilot signal PILOT in the mixer 11. . That is, in response to the head switching signal 5rvso shown in FIG. 1, in each field period in which the video heads 3.4 (heads A and B, respectively) alternately scan the magnetic tape 1, during the period in which the head A scans the tape, Local frequency LOCAL
is set to 11 or 8, and during the period when the B head scans the tape, the a-cal frequency is set to h or human, and fx
The main pilot signal PILOT is generated from the local frequency generator 12 in the chronological order of -ft -js-f4.
and are mixed in the mixer 11.

The pilot signal is frequency-converted by the mixer 11 according to the local frequency, and the difference frequency component between the two is converted by the mixer 11.
bandpass filters (including tank circuits) with resonant frequencies of 6 and 5f, respectively.
At step 14, the fI frequency component and the 3f frequency component are extracted.

Then, as described below, the jI frequency component corresponding to the difference between the adjacent pilot signals of the main trunk being scanned by the video head (scanning on the f1 track in FIG. 2) and the 5
The fI acid component 3j' and the difference between the components are taken out by a differential amplifier after being rectified by rectifiers 17 and 16, respectively.

For example, when the video head is in a position where tracking is off to the right as shown in Figure 2, the 0-Cull frequency is f,
, and the h component is the large shaded area on the right (f2-mu ft
r), 5ju component is the small shaded part (f4J'+ = 5
fx), which corresponds to the waveform shown in Figure 3. The above was written with the A head and had 7 tracks, but the track written with the B head, for example, the local track l & on the right, and the track with the number f2, is written once and the third track is written due to the tracking deviation. As shown in the figure, the magnitude relationship of each component is reversed.

Therefore, the fh acid component 5jz component and the 5 inverted by the amplifier 19
A tracking error signal ERROR corresponding to the tracking deviation is created by alternately switching the switches 20 controlled by f, component -jief, and minute ysW50. This tracking error signal is the same as the tracking error signal normally used during standard playback in the 4-frequency pilot system, and the tracking error signal generation section shown in Figure 1 is provided in another system, and the tracking error signal is passed through a below-pass filter to the DC component. Servo control during standard playback is performed by controlling the servo circuit 6 to zero the signal (not shown).

As you can see from the above explanation, if you simply leave the standard servo tracking error signal (only the DC component corresponding to the tracking deviation is output), even if you perform the following steps, the above error signal will be The reproduction pilot signal includes the recording tape speed or SP.

L P pattern information is not included, so frequency power generation a
It is difficult to discriminate based on the frequency ratio with the output frequency fcya of 8.

However, when the playback tape speed is more than twice that during recording, non-zero frequency components appear in the tracking error signal. Assuming that the ratio between the playback tape speed and the recording tape speed (corresponding to the recording pattern) is generally 7L (double speed playback) from the drawing of the egg-chip turn, the tracking error signal has a frequency of l rLl 1 A frequency component is obtained (it can be seen from this equation that only the standard reproduction #\F DC component for n=1 is output).

FIG. 4 shows a signal waveform diagram of each part when the search command S is "H" and Le=9. 9x speed search (sp.

In both LP modes), the frequency of the tracking error signal is 120 Hz, and the pilot signal fP11tlr* shown in FIG. Then, the pilot signal 9fpzuyrt' shown in FIG. 4(4), which is generated by the t frequency divider 26, is set as the regenerated pilot signal fPIll)T after predetermined processing, and fcylj? :'/8 frequency divided fcya' (think of this as fcI'G) and the frequency ratio discrimination circuit 29
Enter. The reason for branching is that the pilot signal fP
ILOT2 period Y Pilot No. 16 fpztor
The frequency divider 21 is used to increase the number of fcFO pulses per cycle and reduce quantization errors. It may be placed in the frequency ratio discriminator 29, which will be described separately if necessary. The frequency ratio is the last term (finia G represents the signal entering the 290 input).

Table 1 shows j'p7Aor*(frequency division)i+tJ) and frequency ratio R in the example.

Table 1 In the example, the output frequency of SP standard playback is 240Hz, so LP putter: /kj' pzror2 = 120Hz when playing back at LP9 times speed
, R = 9 with te, fprtorl = 255Hz when played at LplB (Sp9x speed), R = =
8.48, and similarly for the SP pattern, R = 2
It becomes 0.6-18. In this way, depending on the reproduction speed, green onions with slightly different ratio R become large or small when the ratio R reaches 12 or 13.
The recording pattern is discriminated by the frequency ratio discriminator 29, and the discrimination outputs SP and LP are input to the servo circuit 6 to perform necessary switching processing.

The above is the discrimination operation in the search mode, but the discrimination operation in the standard or slow mode will now be explained with reference to the pattern diagrams in FIGS. 1 and 5 and the signal waveform diagrams of various parts in FIG. 6.・As mentioned above, rL== during resuming
In the case where the state 1 appears, it is difficult to distinguish using the method using the standard servo tracking error signal, and the state 1-
Therefore, in the present invention, attention is paid to one frequency of only the third pilot signal gm, and a method is adopted in which the reproduction pilot signal frequency fPILOT is determined by processing the repetition frequency.

In Fig. 5, h to m are tracks on which pilot signals have been recorded in advance, and the playback speed KCn = 1) is the same as that at the time of recording.
The video head or js is scanned with no tracking deviation.

At this time, in Fig. 1, set the search command S to 'L' (other than search), fix the a-cal frequency to human, and set the search command S to 8fs1.
Focus only on frequency. (The switch 28 is in the lower position.) Along with the scanning of the video head, the
The output of is im , 1 , ji for each field.
A pilot signal having frequency components of , f, . . . appears. Since the local frequency mixed with this pilot signal is The amplitude increases with each cycle, resulting in the waveform shown in FIG. 6 (3). Here, the reason why the h component has a slight amplitude even when the video head scans both tracks in close contact with the track on which the pilot signal fa is recorded is that the frequency component of the pilot signal fa is small at the edge of the video head. (In the example shown in FIG. 5, it is slightly wider than the head width or the recording track width.)

7. As a person, -C chose j=fH.

You can choose the value of f4 according to your needs, and −f
+)s can be made sufficiently low, the bandpass filter 15 shown in FIG. 1 is not necessarily a bandpass filter, but may also be constructed from a lowpass filter (LpF).

Next, in order to detect the vibration of the obtained h component and the repetition frequency of 7, a bandpass filter 26 with a band of 1M feet is installed and the BpFO filter is connected to its output terminal.
Obtained UT Sakata, zero cross detector 25 and PILOT1
The frequency of this jPILOTl, which takes 1, coincides with the repetition frequency of the & component.

Therefore, the frequency component element 8 is expressed as the reproduced pilot signal fpit, or after the PJr constant processing.
The comparator 29 compares the output frequency of the 5PLP with the output frequency of the 5PLP to determine the 5PLP mode. In this case, focusing on one frequency, the repetition frequency component of the amplitude change of the component (h component) of one frequency (f,) is generally 15 (Hz) from the pattern drawing.

Table 2 shows fPILOr and frequency ratio R'? in the embodiment. :
They are shown together as in the case of search.

Table 2 That is, when LP pattern '1LPla semi-replayed (1) jp
nov=15Hz:, R=8 (fcra e=
120Hz).

In this case, R=8-legs regardless of the playback speed.

Similarly, in the SP pattern, R=16 is constant. Therefore, it can be determined whether the ratio R is large or small with the boundary of 12 as the recording speed '4' (29).

Is this the frequency ratio R in search mode?

FIG. 7 shows a graph summarizing how the playback tape speed changes depending on the playback tape speed m (normalized to Lp standard playback speed y, -i). When the above-mentioned LP9x speed (m=9) is used, the LP pattern (○ mark) is R = 9°sp pattern (x mark) is R = 2
It turns out that it is 0.57. The general formula is shown at the top of FIG. From this figure, it is possible to design the optimum boundary for frequency ratio discrimination according to the playback mode.

Generally, when searching, pilot level fluctuations are large due to unstable driving, etc., making detection difficult.

4 frequency component elements 1 to f4 (can also be said to focus on 4 frequencies)
A method using a tracking error signal that makes effective use of all of δ41 is preferable, so a method focusing on four frequencies has been described as the optimal embodiment. However, of course, a method using the first frequency layer is also possible at the time of search, and the present invention A case can be considered in which the switching between search and standard or slow mode is extremely large (in this case, switching between search and standard or slow mode is unnecessary).

In addition, when focusing on 4 frequencies, as described above using Figures 1 and 3, the local frequency applied to the mixer 11 during reproduction\the same chronological order as during recording (abbreviated as order a-cheeseon).
j,→mu→mu→mu...l5J) is switched for each field in synchronization with the head switching signal, and the playback Byron) (2
A tracking error signal is obtained by alternately switching the difference signal between the hW, minute and 3j components (h component - 5f, component) and its inverted signal using the switch 20 controlled by the head switching signal. As described above, the local frequency applied to the mixer 11 during playback is set to <f+→J! during recording. →mu→person... direction) and reverse chronological order (abbreviated as reverse loadage tan, f4→j1→j, -j□-
4-f4... direction) in synchronization with the head switching signal and switching for each field. : Difference signal (f'
There is also a method in which the component -31, component] itself (switched by the switch 20 controlled by srso and tlt) is applied to the bandpass filter 22, and the component -5f, component is tracking in the case of forward rotation. Since a signal substantially similar to the error signal can be obtained, fpztor@ may be created using the reverse rotation method described above.

Next, we will discuss a specific example of the 1-frequency ratio discrimination circuit 29.
The explanation will be given based on the block diagram in Fig. 1 and the signal waveform diagram of each part in Fig. 9.

In FIG. 8, 31 is a four-stage counter, 32 is a delay circuit, -33, 34 is a rising edge detection circuit, 65 is an AND gate, 36 is an SR7 logic flop, and 57 is a D flipflop.

In FIG. 8, when the frequency ratio R"" fcya/fpztur is larger than 12, SP, LPY are set to 'H'. First, fpzrorY is delayed by a delay circuit 32, and then at the rising edge, the counter 31 and the SR flip-flop are One cycle period of fPILOT after resetting P36f
cya count. When focusing on the first frequency, in the case of the LP pattern, the count value of the counter 31 (matching R') is 8, and SET does not become 'B'.

QOUT is also "L", and Sp and Lp outputs are also "L" (Lp mode) (91st left case).

Next, when it changes to the SP pattern during playback (case on the right), the count ability becomes ≦16, and the value of the counter 31 (h - Q + both becomes "Io" (count value = 12) is 5ET - b5
'H' and Q OU 1' is 'E' totx
(1) When fPILOT rises (φ+), the QOUT-11 detection circuit 54 latches the D7 lip 7og 37 and sets SP and LP to 0°, thereby determining the csp mode.

This signal is sent to the servo circuit to automatically switch the playback mode.

Next, among the discrimination methods focusing on one frequency, it is also possible to use a method that does not perform frequency conversion by the mixer 11 in Figure 1, with the aim of simplifying one circuit. - (Only the differences from Figure A1 are shown)
The operation is performed using HR,8A. Figure 10 -
C141 is a band pass filter that extracts only the fs component (other frequencies may be used), and 42 is a rectifier. After extracting the +l fs component with the band pass filter 41 and rectifying it with the rectifier 42, p2
After extracting Bppovryt for iwytam with scvmvm and creating it in fpztor1' with zero cross detector 25, do the same as the previous explanation, and compare sp with fcpa as raw pilot signal fpzLor after P)I constant processing, It is possible to distinguish between r and p modes.

〔Effect of the invention〕

As explained above, the present invention does not require the ffCTL code and uses a pilot signal to perform tracking, and the temperature is stable even when the speed is different, such as standard, sumy mode, search mode, etc. It becomes possible to determine the recording speed and automatically switch to a predetermined mode.

[Brief explanation of drawings]

FIG. 1 shows a diagram of a magnetic tape recording speed IEf+ discriminating device according to an embodiment of the present invention.
The figure is a tape pattern diagram for detailed explanation of the present invention.
Figures 5, 4, and 6 are signal wave forms of each part, Figure 7 is a graph representing the frequency ratio characteristic' (l-), and Figures 8 and 9 are 7° lock diagrams of the frequency ratio discriminator, respectively. 10 is a 10-step diagram for explaining another embodiment. 8... Frequency activation 1 Orange 10.14, 15, 22, 23.41... Band Pass filter 12.13...Local frequency generator 11
... Mixer 16, 17.42 ... Rectifier 18 ...
・Differential amplifier 20.27, 28.30...Switch 24.25...
・Zero cross detector 21.26... Branch station Kyo 29... Frequency ratio discriminator 31
...Counter 32...Delay circuit 56.54...
Rising detector 66... SR flip 70 knob 37... D flip frog 〒2 Figure 1 Direction of the door 〒 5 (2) LOcAL! RT! z f5 fa fa(
5) h cycles. (4) Mh feces 0 □ 〒4 figure ('5) jP engineering L and T2 Shiding 10 pressure... ■ 语 (4) frr
Lo Ding Z' Figure 5 - 1111 Figure 6 (2) LOCAL child 4 fa 9 fi + k rise
54f + (5) f PILo 1 Closed 7 Figures, LF Talents'' 1 bunch of friends: 1, 6 Figures, 9 Figures (+)! rcFcr ---Kita ■ Rou ---
--st----IIIllll----
(g) 5PLP □ LP -+4-5P- Punishment 10 diagram

Claims (1)

[Claims] 1. Means for recording at several recording tape speeds. In the magnetic recording and reproducing main device, which has means for performing servo tracking using pilot signals of several different frequencies recorded in advance on the video track, the signal obtained from the frequency 1t4fi representing the rotational speed of the capstan shaft during playback. % copying includes means for measuring the ratio of the frequency to the frequency of the reproduced pilot signal after predetermined processing, and means for determining the recording tape speed according to the desired reproduction mode and the measured frequency ratio. Automatic recording speed discrimination device for "magnetic tape". 2. Using one specific frequency of the recording pilot signal,
``means for creating a first writer pilot signal after the predetermined processing; and means for creating a second regenerated pilot signal, and switches the regenerated pilot signal after the necessary processing to either the first regenerated pilot signal or the second regenerated pilot signal according to a desired reproduction mode. 3. The magnetic tape recording speed automatic discrimination device according to claim 1, characterized in that the apparatus further comprises means for dividing the frequency of the reproduction pilot signal after the predetermined processing according to the reproduction mode. An automatic magnetic tape recording speed determination device according to claim 1 or 2.