JPS62217447A - Deciding method for recording speed of tape - Google Patents

Abstract

PURPOSE:To shorten the time required for decision making and to decide a tape standstill state by deciding the number of tracks that a head contacts in the reproduction state of a reproduction pilot and deciding the recording speed of the tape. CONSTITUTION:The reproduction pilot signal obtained by the head 10 is amplified by an amplifier 12 and inputted to BPFs 14, 16, 18, and 20 to extract the 1st - the 4th pilot signals f1-f4. Those signals f1-f4 are detected by detectors 22, 24, 26, and 28, whose outputs are inputted to comparators 30, 32, 34, and 36. Then three of the signals f1-f4 are equal in output level in LP mode, one of the comparators 30-36 is at H, and an OR circuit 38 outputs an H signal. In SP mode, on the other hand, three pilot signals never become equal in output level, so the comparators 30-36 outputs L signals and the circuit 38 also outputs an L signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for determining the tape recording speed of a VTR, generally called an 8 mm video tape recorder (8 mm VTR).

(b) Conventional 8 mm VTR has a normal recording mode (SP mode) and a long recording mode (LP mode).

Compared to the SP mode, this LP mode has a tape speed set to 2, and can record for twice the time on the same tape length.

Further, in the 8 mm VTR, tracking pilot signals (f'l, fsh, f3, f4) are superimposed on the video signal and recorded on each track. This pilot signal can be used for the ATF servo, and its outline can be found, for example, in the magazine "Television Technology September 1985, Volume 406," published by Denshi Gijutsu Publishing Co., Ltd. on September 1, 1985, page 25, 2.
It is shown on page 6.

Discrimination between SP mode and LP mode during playback of this 8mm VTR is done by creating an error signal from the pilot signal completely reproduced from the video head, and detecting the cycle of this error signal to determine SP/LP mode. (See Japanese Patent Application Laid-open No. 71149/1983).

Specifically, if the period of the error signal is 7.5 Hz, it means that a track recorded at SP is being played back at LP tape speed, and if the period of the error signal is 15 Hz, it means L.
This is used to indicate that a track that has finished recording is being played back at a tape speed of SP.

(c) Problem to be solved by the invention In the method of detecting the period of the error signal (7.5Hz or 15Hz>), the time required for speed determination is LP→SP.
The change to SP-+LP is 1-8 ec (47 yield), and during this period, the reproduced image is distorted.

Furthermore, when the tape is stopped, it is impossible to determine whether a track has been completely recorded in SP or a track has been recorded in LP.

(d) Means for solving the problem The number of tracks traced by the rotary head at one time varies depending on the recording mode. Therefore, the state of the regenerated pilot signal is also different. The present invention detects the state of the reproduction pilot signal, and uses the detection result to determine whether the tape is in SP mode or LP mode.
Determine the mode.

(E) Function Since the present invention operates as described above, the number of tracks that the head is in contact with can be determined based on the state of the reproduced pyroft signal. Then, the track width is identified from the number of tracks and the width of the head, and the tape recording speed (SP
mode and LP mode).

1) Embodiment An embodiment of the present invention will be described with reference to FIGS. 1 to 5. This embodiment shows an example in which a rotary erasing head with a width of approximately 2 tracks of 40 μ5 (the track width in the SP mode is 20.5 beats) is used as a head for reproducing a pilot signal.

This rotating erasing head (head>(10) spans approximately 4 tracks when it comes into contact with the tape recorded in SP mode, as shown in Figure 2. Also, as shown in Figure 3, it is recorded in LP mode. When it comes into contact with the tape, it spans about four tracks.

Therefore, when a reproducing function is added to this head (10) to reproduce a low frequency pilot signal, the output level of the pilot signal becomes as shown in FIG. 4 in the SP mode. In addition, in the case of LP mode, it becomes as shown in FIG.

As is clear from FIGS. 3 and 5, the output levels of at least three pilot signals reproduced from the head (10) during LP mode reproduction are substantially equal.

Furthermore, as is clear from FIGS. 2 and 4rM, during SP mode reproduction, the output levels of the two pilot signals reproduced from the head (10) are approximately equal at most. The first embodiment of the present invention has been made in view of this point, and is a circuit that determines that the mode is LP mode when the output levels of at least three types of pilot signals reproduced from the head (10) are equal. be.

In FIG. 1, (10) is a rotating erasing head, (12)
is an amplifier. (14) is the first pilot signal (f,
) is a bandpass filter (BPF) that extracts the <
16), (18), and (20) are BPFs that take out the second, third, and fourth pilot signals (f2, f3, f), respectively. <22>(24) and (26><28) are detection circuits which output signals corresponding to the reproduction levels of the respective pilot signals.

(30) is a comparator, and this comparator (30) outputs a high level signal if the three input signals are approximately the same C. In other words, the comparator (30) When the reproduction levels of the three pilot signals are approximately the same (f+: r24-fs
) to output a high level signal. The comparator (30) converts the three input analog signals into digital values, and detects the highest and lowest values of the three digital values.

Then, when the level difference between the highest value and the lowest value is less than a predetermined level, a high level signal is output. (32)(34)(
36) is also a comparator. (38) is an OR circuit. In other words, the above circuit is used when f'1': f'2': f'3 (7) or f2 "p f3"? When r+(1) or f
3 *r+*f'+ (7) or f' 4 * f
' When +ki t2, it is determined that the mode is LP mode.

The operation of the above circuit will be explained. The pilot signal reproduced by the head (10) is amplified by the amplifier (12) and then input to B P F (14) (16) (18) (20).

B P F (14>(16), (18), and (20) take out the first to fourth pilot signals, respectively. This pilot signal (f+"f+) is sent to the detectors (22), (24), and (26).
) (28>), comparator (30) (32) (3
4) Input in (36).

In the LP mode, the output levels of at least three pilot signals are the same, so the output of one of the at least four comparators becomes high level. Therefore, the OR circuit (3
8) also outputs a high level signal.

In SP mode, the output levels of the three pilot signals will never be the same, so the comparators (30) (32) (
34) (36> outputs a low level signal, and the OR circuit (
38) also outputs a low level signal.

In the above embodiment, the LP mode is determined when the output levels of the three pilot signals are substantially the same. but,
The LP mode may be determined when the reproduction levels of at least three types of reproduced pilot signals are equal to or higher than a certain value.

For example, in the case of FIGS. 3 and 5, f2, r3, and fto are above a certain level. Alternatively, the SP/LP mode may be determined by counting the number of pilot signals below a certain level. Note that when determining the SP/LP mode by determining the magnitude of the reproduced output level of the pilot signal in this manner, there is a drawback that it is difficult to set a reference level for determining the magnitude of the reproduced output level. This is because the reproduction output level of the pilot signal varies depending on the characteristics of the magnetic tape.

A second embodiment of the present invention will be described with reference to FIGS. 6 and 7. This second embodiment does not directly detect the reproduced signal level of the pilot signal, but determines whether the signal is under Moo based on the reference pilot signal (f1 to f4) and the beat signal of the reproduced pilot signal. In Figure 6, (40
) is a reference pilot signal generation circuit. <4
1) is a known ATF servo circuit. (42) is AT
This is a pilot signal selection switch for F servo, and outputs a reference pilot signal of f1→f2→f3→f4 in order for each field. (44) is a head for video reproduction, and (46) is an amplifier. (48) is a low-pass filter, and (50) is a mixer. (52) is a 46kHz bandpass filter, (54) is a 16kHz
z bandpass filter, (56) a comparator for creating a servo error signal, and (58) a servo circuit.

10) is a rotating erase head, (12) is an amplifier, (60)
) is a mixer. (62) is a switch that selectively outputs all reference pilot signals during one field period. (64) (66) (68) (70) are husband k 1
6kHz.

These are 30kHz, 46kHz, and 60kHz band pass filters (BPF). (22)(24)<26)
(28) is a detection circuit, (30)<32)(34)(36
) is a comparator, and (38) is an OR circuit.

(72) is a trigger monomulti, and when a high level signal is inputted, it continues to output that high level signal for two fields.

FIG. 7 is a diagram showing the beat component between the pilot signal completely recorded on the tape and the reference pilot signal. As is clear from this figure, during reproduction in the LP mode of FIG. 3, a beat signal between the HLPs of FIG. 7 is generated. In other words, when fl is selected as the reference pilot signal by the switch (62) in FIG. 6, B P F (
64), (68), and (70) output signals to the comparator (34).
) outputs a high level signal, and the OR circuit (38) also outputs a high level signal. Moreover, the Nana no multi (72) (retriggerable mono multi) holds this high level signal for two field periods.

The reason why the reference pilot signal is held for two field periods is that the reference pilot signal is switched several times within one field period and is not reproduced while the erasing head is not in contact with the tape. In other words, when f2 is selected as the reference pilot signal, the beat component is 46
There are components in , 30, and 16, but the beat component in 16 is generated. The signal level of the beat component becomes smaller.Therefore, there are two types of beat components at this time, 46 and 30, and the OR circuit (38) outputs a D level signal.In this way, the reference pilot signal is During the switching from rI4f2→f3→f4 within the pulse period, three types of beat components are not always generated.

However, three types of beat component forces are generated at least once. Therefore, the OR circuit (38) in FIG. 6 may output a high level signal once every two field periods during LP mode reproduction. Therefore, the monomulti (72) holds this high level output signal for two field periods.

The conditions under which the OR circuit (38) of the circuit shown in FIG. 6 outputs a high level signal are shown below.

The operation of the circuit shown in FIG. 6 will be explained. Switch (62) is 4
Species reference pilot signals (f+, f2, f3,
f) is output at least once per field period.

Therefore, in LP mode B P F (64) (66)
From (6g) and (70), three types of beat components having at least the same level are output. One of the comparators outputs a high level component, and the OR circuit (38) also outputs a high level signal. Then, the monomulti (72) holds this high level signal for a period of two fields. Also, in the case of SP mode,
B P F (64) (66) (6g>(70)) do not simultaneously output three types of beat components of the same level, and the output of the mono multi (72) remains at a low level.

In the above embodiment, f l , f 2 , f 3 , and f' 4 are used as reference pilot signals, but for example, a case where f 2 and f 3 are omitted will be shown. That is, similar beat components are detected for C and 0 of the ■■COs without using f2 and f3. In other words, regarding ■, r first use f'+tljt as a reference pilot and
Detect and store the Hz component.

Next, the 46 kHz component of the beat is extracted using fl as a reference pilot. This 46kHz component and the three stored beat components of 16kHz and 46kHz components are the same.'' Similarly for 0, the 46kHz component of the mixer output when the reference pilot is f and the 46kHz component of the mixer output when the reference pilot is fl and 16kHz
It can also be replaced with the condition that "are at the same level".

If you want to reduce the number of bandpass filters (for example, two, 16kHzBPF and 46k)IzBPF, for [Yes], 'Reference pilot is f4 and the 46kHz component of the mixer output and 16kHz
kHz component and reference pilot are rl and the 16kHz component of the mixer output are at the same level.'' Regarding ■, ``The reference pilot is f4 and the mixer output is 16kHz component is the same level.''
This can also be replaced with the condition that the 6 kHz component and the reference pilot are fl and the 16 kHz component and 46 kHz component of the mixer output are at the same level.

If it is simplified further, it will be as shown in FIG. In other words, as shown in Figure 7, the 16kHz beat component generated when the reference pilot signal is fl is the head (10).
This shows that the track of the pilot signal (f2) is in contact with the track of the pilot signal (f2). Similarly, the 46 kHz beat component indicates that the head (10) is in contact with the track of the pilot signal (r4). Further, the 16 kHz beat component generated when the reference pilot signal is f2 indicates that the head (10) is in contact with the track of the pilot signal (r+). Similarly, the beat component of 46 kHz is shown to be in contact with the track of the pilot signal (f*). In the circuit of Fig. 8, the gates (74), (76) (
78) Open and close (80). In other words, when (fl) is selected as the reference signal, gate (74) < 78
) will be opened. The value that can be input to the sample and hold circuit (82) corresponds to the reproduced pilot signal (f2), and the value that can be input to the sample and hold circuit (86) corresponds to the reproduced pilot signal (f4). Furthermore, when (f2) is selected as the reference pilot signal, the value input to the sample and hold circuit (84) corresponds to the reproduced pilot signal (fl), and the value input to the sample and hold circuit (88) corresponds to the reproduced pilot signal (fl).
) corresponds to the regenerated pilot signal (r+). This sample hold circuit (82) (84) (8
6) (88>) serve as a detection circuit for the track that the head (10) is in contact with.

This sample hold circuit (82) (84>(86)(
The output of the detector circuit (22) (24>(2
6) Corresponds to the output of (2g>).The subsequent stage of this sample and hold circuit performs the same processing as in FIG. 1, so this processing is omitted from the illustration.

In the embodiment, a rotating erasing head was used as the head for reproducing the pilot signal. However, for example,
A tracking head may be used which abuts the tape in advance of the rotating erase head, as shown in US Pat. Also, both a tracking head and a rotating erasing head may be used.

Further, in the above embodiment, the mode is determined based on whether there are three or more pilot signals (or beat components) at the same level, but the present application is not limited to this. For example, the mode may be determined by detecting the ratio of the magnitudes of several types of pilot signals. Note that the specific value of the ratio of the magnitudes of the pilot signals may be appropriately selected depending on the head width.

In addition, in the embodiment shown in FIG. 8, two reference pilot signals, fl and fl, are selected, and the BPF is set to 16, 46, or 2.
It was set to . However, by using four of f1 to f4 as reference pilot signals and memorizing the magnitude of the 16kHz component corresponding to each of r1 to rto, the thickness tolerance of the four memorized beat components is It is also good to compare.

(G) Effects of the Invention According to the present invention, the LP/SP mode (tape recording speed) can be determined in a short period of time.

Also, even when the tape is stationary such as during stills, LP/SP
The mode can be determined.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention. FIGS. 2 and 3 are diagrams showing the contact between the track and the head. FIG. 4 and FIG. 5 are diagrams showing the output level of the reproduced pilot signal. FIG. 6 is a diagram showing a second embodiment of the present invention. FIG. 7 is a diagram showing the beat between the reproduced pilot signal and the reference pilot signal. FIG. 8 is a diagram showing a third embodiment of the present invention. (10)...Rad (head) to rotation erasure.

Claims (1)

[Claims] (1) In a helical scan tape recorder that records in normal recording mode and long-time recording mode, and also performs tracking during playback using multiple pilot signals recorded on the track, playback of the playback pilot from the head. A tape recording speed determination method that determines the tape recording speed by determining the number of tracks that the head is in contact with depending on the state.