JPH0658745B2 - Tape speed switching device for video tape recorder - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high speed mode (SP mode) and a low speed mode (L mode).
The present invention relates to an azimuth recording type helical scan type video tape recorder having at least two pairs of rotary magnetic heads, which are used by switching between P mode and The present invention relates to a device for switching the tape running speed in accordance with.

<Prior Art> Conventionally, in the azimuth recording type helical scan type video tape recorder having at least two pairs of rotary magnetic heads used by switching between a high speed mode (SP mode) and a low speed mode (LP mode), In the high speed mode shown in FIG. 10, the video tape T is run at high speed to record / reproduce a video signal by the high speed rotary magnetic head H having a wide head width, and in the low speed mode shown in FIG. The video tape T is run at a low speed, and the video signal is recorded / reproduced by the low speed rotary magnetic head H'having a narrow head width. Here, the head width of the rotary magnetic heads H and H'is usually set to about 1.5 times the corresponding video track width.

Further, in such a video tape recorder, as shown in FIG. 12, the video tape T has four continuous pilot signals f1, f2, f3, f4, which have sequentially different frequencies.
The low frequency conversion chroma signal S1 and the FM modulated luminance signal component S2 for recording the color video signal on the video tape are recorded, and the four pilot signals f1, f2, f3 and f4 are
As shown in FIG. 10 and FIG. 11, recording is performed while circulating each field. A shaded portion S3 of the FM modulated luminance signal component S2 is an FM carrier frequency shift portion corresponding to the tip of the sync signal and the white peak. In addition, the pilot signals f1, f2, f3, f4
, 6.5f, 7.f, respectively, as shown in FIG.
5f, 9.5f and 10.5f (f is the horizontal scanning frequency of the horizontal scanning signal) are set.

In such a video tape recorder, during normal reproduction, tracking control is performed by detecting the pilot signals of both adjacent tracks as shown in FIG. 14 and comparing the detection levels. However, during video search such as fast forward or rewind, the rotary magnetic head crosses the track, and tracking control like that in normal reproduction is not performed. The noise bar is not fixed and the screen during video search becomes unsightly.

Further, when video signals are recorded on the same video tape in two modes, a high speed mode and a low speed mode, switching of the rotary magnetic head and switching of the tape running speed corresponding to the mode are performed at the time of video search. Therefore, the video search is performed in a mode different from the recording mode, and reproduction output cannot be sufficiently obtained, and the video search screen becomes difficult to see.

<Objects of the Invention> The present invention has been made in view of the above points, and in a video search, a noise bar on the screen is fixed and video signals are transmitted to the same video tape in different running speed modes. An object of the present invention is to improve the screen during video search and make it easier to see by switching the running speeds of the rotary magnetic head and the video tape so as to match the mode at the time of recording when the data is recorded.

<Structure of the Invention> In order to achieve the above object, the present invention has a plurality of pilot signals having at least two pairs of rotary magnetic heads used by switching between a high speed mode and a low speed mode, and sequentially having different frequencies. In the tape speed switching device of the helical scan type video tape recorder of the azimuth recording system for performing tracking control based on the reproduction output of the pilot signal from the video tape recorded individually on the video track, Error signal generating means for generating two error signals based on a reproduction output and a reference pilot signal corresponding to fast forward / rewind,
The error signal is alternately switched every 2 fields and 2
Same as switching means for forming and outputting one discrimination signal and tracking control signal output means for forming and outputting a tracking control signal by sampling and holding two discrimination signals from the switching means at predetermined timings and comparing the levels. In the double-speed video search, either the error signal or the determination signal, which corresponds to fast forward / rewind,
Moreover, different signal cycles are detected, the mode is determined based on the detected cycle, and the rotary magnetic head is switched and the video tape running speed is adjusted so that the mode at the time of recording matches the mode at the time of video search. A discriminating means for outputting a signal for switching is included, and at the time of odd speed video search, tracking control is performed based on the tracking control signal, and the tape speed is switched based on the output from the discriminating means. I am trying.

<Examples> Hereinafter, the present invention will be described in detail based on Examples shown in the drawings. FIG. 1 is a circuit diagram of an embodiment of the present invention. The tape speed switching device according to this embodiment is applied to an azimuth recording type helical scan type video tape recorder. This video tape recorder has first and second rotary magnetic heads H1 and H2 for high speed mode and third and fourth rotary magnetic heads H3 and H4 for low speed mode. The rotary magnetic heads H1 to H4 are mounted in a cylindrical cylinder (not shown) via a head bar. Each rotary magnetic head H is formed in a slit formed around the cylinder.
1 to H4 are arranged so as to be slightly outward from the slits, and the video tape T is wound in the Ω shape.

The rotary magnetic heads H1 to H4 are rotated by the first and second head changeover switches SW1 and SW2.
4 is connected to each input section of the head amplifier 1 for amplifying the output of No. 4. A head switching pulse is given to the head amplifier 1, and in response to the head switching pulse, the first and second head changeover switches SW1, SW
Amplify the output provided via either of the two. Both head changeover switches SW1 and SW2 are adapted to be switch-operated in response to a signal from a discriminating means 5 which will be described later so that the mode at the time of recording and the mode at the time of reproducing coincide with each other.

Also in the video tape recorder of this embodiment, as in the above description, the video tape T has four consecutive pilot signals having sequentially different frequencies as shown in FIG.
f1, f2, f3, f4, the low frequency conversion chroma signal S1 and the FM modulated luminance signal component S2 for recording the color video signal on the video tape are recorded, and the four pilot signals f
1, f2, f3, and f4 are recorded while circulating for each field as shown in FIG. 10 and FIG. The pilot signals f1, f2, f3, f4 are set to 6.5f, 7.5f, 9.5f, 10.5f (f is the horizontal scanning frequency of the horizontal scanning signal), as shown in FIG. ing.

In the tape speed switching device of the video tape recorder of this embodiment, two first and second error signals are generated based on the reproduction output of the pilot signals f1 to f4 and the reference pilot signal of the same frequency as the pilot signals f1 to f4. An error signal generating means 2 to be generated, a switching circuit 3 as switching means for alternately switching the error signals for each field and forming and outputting two first and second discrimination signals S1 and S2, and this switching. Tracking control signal output means 4 for sampling and holding the first and second discrimination signals S1 and S2 from the circuit 3 at predetermined timings, comparing the levels, and outputting the tracking control signal S3 to a servo circuit (not shown); First and second
The mode is determined based on the error signal or the cycle of the first and second determination signals S1 and S2, and the rotary magnetic heads H1 to H1 are arranged so that the mode at the time of recording and the mode at the time of video search match.
And a discriminating means 5 for outputting a signal S4 for switching H4 and switching the traveling speed of the video tape T.

The error signal generating means 2 generates two first and second error signals having frequencies f and 3f based on the pilot signals f1, f2, f3 and f4 from the head amplifier 1 and the reference pilot signal. The error signal generating means 2 is a reference in a predetermined order corresponding to the low-pass filter 6, the mixer 7, the first and second band-pass filters 8 and 9 having band frequencies f and 3f, and the fast-forward / rewind search. The reference pilot signal generating means 10 forms and outputs a pilot signal.

The reference pilot signal generating means 10 selects a signal generating circuit 11 for sequentially generating signals having the same frequency as the frequencies of the pilot signals f1, f2, f3 and f4, and a selection for giving the output of the signal generating circuit 11 to the mixer 7. And a circuit 12. The selection circuit 12 is supplied with a head switching pulse, a video search signal, and a capstan forward / reverse signal corresponding to fast forward / rewind, which will be described later in the order corresponding to normal reproduction, fast forward search, and rewind search. Thus, the reference pilot signal is selectively output to the mixer 7. In the mixer 7, the regenerated pilot signal from the low pass filter 6 and the reference pilot signal from the selection circuit 12 are mixed and a signal having a frequency difference between the two signals, that is, a difference frequency signal is output. Of the difference frequency signals, signals having difference frequencies f and 3f are output from the first and second band pass filters 8 and 9 as the first and second error signals and are given to the switching circuit 3 and the output means 5.

The switching circuit 3 alternately switches the first and second error signals from the error signal generating means 2 for each field in response to the head switching pulse, and switches the two first and second discrimination signals S.
1 and S2 are given to the tracking control signal output means 4 and the discrimination means 5.

The tracking control signal output means 4 detects the first and second discrimination signals S1 and S2, respectively.
3 and 14 and the outputs from both detection circuits 13 and 14 are sampled and held when a gate pulse is given.
A second sample and hold circuit 15, 16; a comparator circuit 17 for comparing the outputs of both sample and hold circuits 15, 16 and outputting a corresponding tracking control signal S3; and a switcher 18 for outputting a gate pulse at the time of video search. Is equipped with. The switch 18 is supplied with a video search signal and a capstan forward / reverse signal, and does not output a gate pulse during normal reproduction, and does not output a gate pulse during video search in response to fast forward / rewind. Is output.

The discriminating means 5 includes the first and second error signals or the first and second discriminating signals S from the error signal generating means 2 or the switching means 3.
First and second changeover switches SW3 and SW4 for selecting either S1 or S2, and first and second detection circuits 19 and 20 for respectively detecting signals given through both switches SW3 and SW4, A comparison circuit 21 for comparing the outputs of the two detection circuits 19 and 20, a waveform shaping circuit 22, and a mode determination at the time of recording based on the cycle of the output waveform from the waveform shaping circuit 22 to match the modes at the video search. Thus, the rotary magnetic head and the microcomputer 23 for outputting the signal S4 for switching the running speed of the video tape. First and second changeover switches SW3, SW
4, a capstan forward / reverse signal is given to the first and second error signals or the first and second error signals in response to fast forward / rewind.
It is configured to select one of the second determination signals.

Next, the operation of the tracking control in the video search of the tape speed switching device having the above configuration will be described.

First, the case of triple speed fast-forward search will be described with reference to FIG. 2A is a diagram showing the positional relationship between the video tape T and the rotary magnetic head, FIG. 2B is a head switching pulse, and FIG. 2C is a reference from the reference pilot signal generating means 10. Pilot signal, Fig. 2 (D) (E)
Is the two first and second error signals f and 3f output from the first and second bandpass filters 8 and 9, and FIG. 2 (F) (G) is
Two first and second discrimination signals S output from the switching circuit 3
1, S2 and FIG. 2 (H) are waveform diagrams respectively showing the gate pulse, and show the case where the mode at the time of recording and the mode at the time of video search are the same. In FIG. 2 (A), the pilot signals f1 to f4 recorded on each video track, the rotary magnetic head, and the running direction of the video tape T are also shown.

In the case of the triple speed fast-forward search, the rotary magnetic head traces over three video tracks for each field. The reference pilot signal from the reference pilot signal generating means 10 sequentially outputs, for each field, pilot signals recorded in the central video track of the three video tracks in the order of f4, f3, f2, f1. To do.
For example, the pilot signal f over the fields a to d
Outputs 3, f2, f1, f4.

The error signal generating means 2 mixes the reproduced pilot signal from the head amplifier 1 and the reference pilot signal with the mixer 7.
, And the first and second bandpass filters 8,
Then, the first and second error signals shown in FIGS. Both error signals are alternately switched by the switching circuit 3 every one field and output as first and second discrimination signals S1 and S2 shown in FIGS. 2 (F) and 2 (G). The first and second discrimination signals have regular periodic waveforms as shown in FIGS. 2 (F) and (G). The first and second discrimination signals S1 and S
2 is sampled and held in response to the timing when the rotary magnetic head traces the center of the video tape, that is, in response to the gate pulse corresponding to the center of the head switching pulse, and the sample and hold outputs are compared to form the tracking control signal. The tracking state is controlled by this tracking control signal, and the noise bar on the screen is fixed so that the video search screen is easy to see.

FIG. 3 is a diagram corresponding to FIG. 2 in the case of a triple speed rewind search. In the case of this triple speed rewind search, the rotary magnetic head traces over seven video tracks for each field. Reference pilot signal generating means 1
The reference pilot signal from 0 is, for each field, the order corresponding to the rewinding of the pilot signal recorded in the central video track of the seven video tracks, which is the reverse of the case of fast forward, that is, Output in order of f1, f2, f3, f4. In this way, the reference pilot signal generating means 10 outputs the reference pilot signals in the order corresponding to fast forward / rewind. During this triple speed rewind search, the output waveforms of the two first and second error signals from the error signal generating means 2 are as shown in FIGS. 3 (D) and (E), and both error signals are output. The output waveforms of the first and second discriminating signals S1 and S2 obtained by alternately switching every one field are regular periodic waveforms as shown in FIGS. 3 (F) and (G). The first and second discrimination signals S1 and S2 are sampled and held by a gate pulse at the timing when the rotary magnetic head traces the central portion of the video tape, and the outputs thereof are compared to form a tracking control signal. The tracking state is controlled by.

FIGS. 4 and 5 are diagrams corresponding to FIG. 2 in the case of 5 × fast forward and rewind search, and the tracking control is performed in the same manner as in the 3 × speed.

In this way, in the tape speed switching device of the video tape recorder of the present invention, in the video search of odd speed,
A reference pilot signal in a sequence corresponding to fast forward / rewind is generated, two error signals are formed based on the reference pilot signal and the reproduction pilot signal, and both error signals are alternately switched for each field. On the screen, the first and second discrimination signals are formed, both discrimination signals are sampled and held by the gate pulse at a predetermined timing, and the tracking state is controlled by comparing the sampled and held levels. The noise bar of can be fixed, and the screen during video search becomes easy to see.

In the case of normal reproduction, tracking control is performed in the same manner as in the conventional case without performing sample hold with a gate pulse.

Next, in the tape speed switching device of the video tape recorder of the present invention, the operation when the tape speed is switched so that the recording mode and the video search reproducing mode match each other will be described. In the present invention, in the discriminating means 5, the first and second error signals or the first and second discriminating signals S
The mode S is discriminated based on the cycles of S1 and S2, and the signal S for switching the rotary magnetic head and the tape running speed is set so that the mode at the time of recording matches the mode at the time of video search.
4 is output.

Here, the quintuple speed search will be described. The case where the signal recording mode and the 5 × speed search mode match is shown in FIGS. 4 and 5 described above. As shown in FIG. 4, the first and second discrimination signals S1, S2
The period of S2 is easier to detect, and the period at this time is 1 V (V: vertical synchronizing signal period).

On the other hand, in the case of the 5 × speed rewind search, it is clear from FIG.
The twelfth error signal is easier to detect the cycle,
The cycle at this time is 0.65V.

Next, the waveforms when the recording mode and the quintuple-speed video search reproduction mode are different are shown. In FIG. 6, recording is performed in the SP mode (high speed mode), and the 5 × fast forward search is performed in the L mode.
FIG. 6 is a waveform diagram when the operation is performed in the P mode (low speed mode), and in this case, as is clear from FIG.
The discrimination signals S1 and S2 are easier to detect the cycle, and the cycle at this time is about 2.7V.

Fig. 7 shows SP mode for recording and L for 5x rewind search.
It is a waveform diagram when it performs in P mode. At this time, as is apparent from FIG. 7, it is easier to detect the cycle of the first and second error signals, and the cycle at this time is about 1.
It is 14V.

Fig. 8 shows the LP mode for recording, and the 5x fast forward search for S.
It is a wave form diagram when it performs in P mode. At this time, as is clear from FIG. 8, it is easier to detect the cycle of the first and second discrimination signals, and the cycle is about 0.45V.
Is.

Fig. 9 shows recording in LP mode and SP in 5x rewind search
It is a waveform diagram when it is performed in the mode. At this time, as is apparent from FIG. 9, the period of the first and second error signals is easier to detect, and the period is 0.325V.

As described above, in the case of fast-forward search, the first and second determination signals S1 and S2 are easier to detect the cycle, and in the case of fast-rewind search, the first and second error signals are shorter than the cycle. Easy to detect. The above cycles are summarized in Table 1.

Next, the operation for detecting the cycle will be described. Since the signal required for mode discrimination in the video search differs depending on the fast-forward search and the rewind search as described above, the discriminating means 5 corresponds to the forward / reverse signal of the capstan, that is, fast-forward / rewind. First and second changeover switch SW
3 and SW4 are switched. The first and second error signals or the first and second discrimination signals provided via the both changeover switches SW3 and SW4 are respectively detected and input to the comparison circuit 21, and both are compared to correspond to the cycle. The signal is output. The reason why the two signals are compared in this way is to ensure that the cycle can be detected even when a phase shift occurs. The output from the comparison circuit 21 is shaped by the waveform shaping circuit 22 into a rectangular wave.
The period of this rectangular wave is read by the microcomputer 23 based on Table 1, and the mode is discriminated by this period.

By the way, when the tape recorded in the LP mode is reproduced by the video search, the signal output is small and the cycle is short, so that the waveform shaping circuit 22 may not have a regular pulse. Therefore, in this embodiment, the microcomputer 23 determines the mode under the conditions shown in Table 2 by using the cycle when the recording mode is the SP mode.

When the conditions in Table 2 are met, the mode of video search for playback is changed. For example, a 5x fast-forward search is performed by S
In the P mode, the LP mode is switched to when the 1V cycle signal disappears.
Further, when performing the fast forward search at 5 times speed in the LP mode, the mode is switched to the SP mode when a signal of 2.7 V cycle starts to be output.

For 3x and 7x speed, fast-forward search is
In the rewind search, the cycle of the first and second error signals is
The mode is determined by detecting the cycles S1 and S2 of the second determination signal, respectively. It should be noted that the cycle for determination, which is input in advance to the microcomputer 23, is appropriately selected according to the double speed.

As described above, in the odd-numbered speed video search, the rotating magnetic field is adjusted so that the recording mode and the video search mode match based on the cycle of the first and second error signals or the first and second determination signals S1 and S2. Since the head is switched and the tape running speed is switched, it is possible to avoid the problem that a sufficient video output cannot be obtained by performing a video search in a mode different from the recording mode as in the conventional case. The screen will be easier to see than before.

<Effects of the Invention> As described above, according to the present invention, tracking control is performed by sampling and holding the first and second discrimination signals at a predetermined timing and comparing the levels thereof at the time of odd speed video search. In addition, the mode at the time of recording is determined based on the cycle of the first and second error signals or the first and second determination signals, and the rotary magnetic head is switched and the tape is run so that the modes at the time of video search are matched. Since the speed is switched, the noise bar on the screen during video search is fixed and the screen is easy to see, and the video search is performed in a mode different from the recording mode as in the past and sufficient playback output is achieved. The screen is easier to see than before.

In particular, in determining the mode, the period of either the error signal or the determination signal is detected depending on whether the search is a fast-forward search or a rewind search. The signal can be used to detect the period, which allows accurate period detection and therefore mode determination.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a positional relationship between a video tape and a rotary magnetic head for triple speed fast-forward search (FIG. 2 (A)) and signals. Waveforms (FIGS. 2 (B) to (H)), FIG. 3 corresponds to FIG. 2 of the 3 × speed rewind search, and FIG. 4 corresponds to FIG. 2 of the 5 × fast forward search. 5 and 5 are diagrams corresponding to FIG. 2 of the 5 × speed rewind search, and FIG. 6 is a video tape and rotary magnetic head when a 5 × speed fast forward search is performed in the LP mode on a signal recorded in the SP mode. Fig. 6 shows the positional relationship (Fig. 6 (A)) and the signal waveform (Figs. 6 (B) to (G)), and Fig. 7 shows the signal recorded in SP mode being rewound at 5 times speed in LP mode. FIG. 8 and FIG. 8 corresponding to FIG. 6 when the search is performed show a signal recorded in the LP mode and a 5 × fast-forward search in the SP mode. 6 corresponding to FIG. 6 and FIG. 9 are views corresponding to FIG. 6 when a signal recorded in LP mode is subjected to a 5 × speed rewind search in SP mode, FIG. 10, and FIG. 11. Is a diagram showing the positional relationship between the video track and the head, FIG. 12 is a diagram showing the frequency distribution of the recording signal, and FIG.
FIG. 14 is a diagram showing the frequency distribution of the pilot signal, and FIG. 14 is a diagram showing the positional relationship between the video tape and the head during normal reproduction. 2 ... Error signal generating means, 3 ... switching circuit, 4 ... Tracking control signal output means, 5 ... Discriminating means, 10 ...
Reference pilot signal generating means.

Claims (1)

[Claims] 1. A video tape having at least two pairs of rotating magnetic heads which are used by switching between a high speed mode and a low speed mode, and a plurality of pilot signals having sequentially different frequencies are individually recorded on video tracks. In a tape speed switching device of an azimuth recording type helical scan type video tape recorder for performing tracking control based on the reproduction output of the pilot signal from the above, a reference pilot signal corresponding to the reproduction output of the pilot signal and fast forward / rewind Error signal generating means for generating two error signals on the basis of
Same as switching means for forming and outputting one discrimination signal, and tracking control signal output means for forming and outputting a tracking control signal by sample-holding two discrimination signals from the switching means at predetermined timings and comparing their levels. In the double-speed video search, the cycle of the signal that is either the error signal or the determination signal that is different from each other is detected according to the fast forward / rewind, and the mode is determined based on the detected cycle. However, it includes a discriminating means for outputting a signal for switching the rotary magnetic head and switching the running speed of the video tape so that the mode at the time of recording and the mode at the time of video search coincide with each other. In addition to performing tracking control based on the tracking control signal,
A tape speed switching device for a video tape recorder, wherein the tape speed is switched based on an output from the discriminating means.