JP2706653B2 - Video signal playback device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a video signal reproducing apparatus, and more particularly to a video signal reproducing apparatus for intermittently driving a magnetic tape to perform slow motion reproduction. <Description of the Related Art> Hereinafter, in this specification, a rotary 2-head helical scan type video tape recorder (VT)
R) will be described as an example. In a conventional VTR, a magnetic tape is intermittently driven using a CTL signal, and still playback is performed in a state where a deteriorated portion of a playback video signal output is located near a vertical blanking (V blanking) portion. I get a good playback image of N. Also, slow motion reproduction is performed by repeating this still reproduction and normal reproduction. Such slow motion reproduction, so-called fine slow reproduction, will be described with reference to FIG. Now from t ₀ to t ₁
Time to, and controlled to accelerate the capstan motor for the tape feed control, the acceleration end time t _1, enters a constant speed state (slower than normal speed). Thereafter, the tape end to Ontoratsuku position The temporal constant relationship and control signals written in each frame l (CTL signal) is detected at the time of recording, a predetermined time after the time t _C that detected the CTL signal feeding the tape at a constant speed until t _2, then from t ₂ to t _3, braked to stop the capstan motor, enters a still reproduction state. After repeating the still reproduction state a plurality of times in accordance with the slow ratio, the above operation is repeated to perform fine slow reproduction. At this time, the tape movement amount from Q0 to Q3 is
The tape movement amount Qc for one frame and before the CTL signal is detected is controlled so as to be centered between Q0 and Q3. The principle of the fine throw reproduction in the tracking method using the conventional CTL signal has been described above. As can be seen from the above description, it can be seen that the CTL signal is a reference signal that is essential for controlling the stop position of the still. In FIG. 1, 1 is a magnetic tape, 2 is a recording track, 3 is a CTL signal, and point A
Indicates a still position. On the other hand, in recent years, with the increase in recording density, a VTR that performs tracking without recording and reproducing the CTL has been proposed and implemented. However, in this type of VTR, the positional relationship between the head and the track cannot be easily found as in the case of using the above-mentioned CTL, and a practically effective slow motion reproduction cannot be performed. <Object of the Invention> The present invention has been made in view of the above background, and provides a video signal reproducing apparatus capable of performing good slow motion reproduction without recording a special control signal in a longitudinal direction of a magnetic tape. The purpose is to: <Description by Example> Hereinafter, the present invention will be described based on examples. The embodiment described below is used as a tracking method.
The present invention is applied to a VTR employing a well-known four-frequency pilot system. FIG. 2 (A) shows the relationship between the head trace trajectory and the track when performing a fine throw in a VTR which performs recording / reproduction with two heads having different azimuth angles, and FIG. 2 (B) shows the relationship at this time. 2 shows a timing chart of each signal inside the VTR. In FIG. 2 (A), t indicates the direction of elapse of time, and x indicates the moving direction of the head. Each track indicated by a parallelogram in the figure is traced as indicated by Tr. In the drawing, f ₁ ~f ₄ shows a pilot signal superimposed on each track. By performing the still reproduction for two frame periods and the normal reproduction for one frame period in this manner, it becomes possible to perform apparently 1/3 times slow motion reproduction. In FIG. 2 (B), (a) shows a 30 Hz rectangular wave signal (30 PG) synchronized with the rotation of the rotary head, (b) shows an envelope waveform of the reproduced video signal, and (c) shows a tracking error signal. . At the time of still reproduction, since the trace locus of the video track and the trace locus of the head are shifted by one track pitch during one field period, the tracking error signal causes one cycle of swell in four fields as shown in FIG. 2 (B). . At this time, if the level of the tracking error signal when the center of the trace locus coincides with the center of the track is called the "Just Track Level", in order to drive out the noise bar from the playback screen, the tracking error signal must be at the Just Track Level. It can be seen that it is only necessary that the time when the time becomes coincident with the head switching timing. Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a diagram showing a schematic configuration of a VTR as one embodiment of the present invention. In FIG. 3, 4 is a magnetic tape, 5a and 5b.
Are rotational playback heads. The heads 5a and 5b have different magnetization directions. Reference numeral 6 denotes a cylinder having rotating heads 5a and 5b, and guides the magnetic tape 4 on the outer peripheral surface thereof. The reproduced signals reproduced by the heads 5a and 5b are converted into continuous signals through a head switching circuit (HSW) and supplied to a video signal processing circuit 14 and an ATF signal generation circuit 15. HSW 9 is controlled by 30 PG obtained by detector 12 and generator 13. After the video signal component is separated by the video signal processing circuit 14, the continuous signal obtained by the HSW 9 is returned to the original signal form (for example, a video signal conforming to the NTSC signal) and output. On the other hand, only four frequency pilot signal components are separated from the continuous signal by the ATF signal generation circuit 15 and the AT signal is generated by well-known signal processing.
An F signal is obtained. The signal processing will be briefly described. A reproduction pilot signal included in a reproduction signal from a head is multiplied by a signal (local pilot signal) having the same frequency as a pilot signal superimposed on a track to be reproduced (main track). Then, the level of a frequency signal having a difference from the pilot signal reproduced from the tracks on both sides adjacent to the main track is compared, a tracking error is detected, and an ATF signal is obtained. The ATF signal thus obtained is supplied to the capstan motor control circuit 8, and the capstan 10 is controlled via the capstan drive circuit 7 during normal reproduction. As is well known, the capstan 10 runs the tape 4 in cooperation with a pinch roller (not shown). This rotation is detected by detector 11
It is assumed that X pulses are generated from the detector 11 per one rotation of the capstan 10, for example.
This is supplied as a so-called capstan FG to the capstan motor control circuit 8 and a variable speed reproduction control circuit 17 described later in detail. The capstan FG is supplied to a capstan motor control circuit 8 to form a speed control loop. The variable-speed reproduction control circuit 17 includes the 30PG, the capstan FG,
Using the ATF signal and the signal obtained from the system controller 16, the capstan during slow motion playback is used.
The speed change reproduction control circuit 17, which is a circuit for controlling the rotation of 10, will be described below using a specific circuit example. FIG. 4 is a diagram showing a specific example of the variable speed reproduction control circuit 17 in FIG. 5 (a) to 5 (i) are timing charts showing waveforms at various parts in FIG. 4. The operation of the circuit shown in FIG. 4 will be described below with reference to FIG. In FIG. 4, reference numeral 20 denotes a terminal to which a clock signal having the same frequency as that of the capstan FG during recording is supplied, and reference numeral 22 denotes an ATF.
A terminal to which a signal (d) is input, 26 is a terminal to which 30PG (a) is input, 28 is a terminal to which a high-level signal (i) is supplied when the capstan is driven, and 30 is a capstan
This is the terminal to which FG is supplied. 32 level when head is Ontoratsuku state (approximately 0 level → 5 shown in FIG. V _J) comparators and threshold value, 34 monostable multivibrator for obtaining pulse (e) which occurs at the rising edge of the comparator , 36 is an inverter, 38
Is an AND gate, 40 is a data generator for generating data corresponding to the number of capstan FGs when a tape is run for 4 track pitches, 42 is a mono-multi, 44 is a ternary counter for counting the rising edge of 30 PG (a). , 46 is a ternary counter
At the output (b) of 44, the data generated by the data generator 40 is loaded, and the counter is counted down by the above-mentioned clock signal. 48 is a cross point between the ATF signal (d) and the just track level. The value (c) is loaded and the counter is counted down by Capstan FG, 50 and 52 are mono-multi, 54 is flip-flop and 56
Is AND gate. Hereinafter, the operation of this embodiment will be described step by step. First, when shifting to the slow motion reproduction mode, the tape is stopped at an arbitrary timing. The ATF signal in this state is in a state like an arbitrary still period (t ₁ ) in FIG. Here, it was previously described that if the crossing point between the tracking error signal and the just track level is made coincident with the rising point of 30 PG, the result becomes a fine still. Also, if normal reproduction is started from this cross point, on-track can be performed. First, when the tape stops, the signal (i) indicating the drive of the capstan becomes low level, indicating that the capstan has stopped. In this state, the counter (A) signal (d) and the point at which the just track level crosses, 48 loads the value of the counter 46. At this timing, the normal reproduction may be started. This timing is delayed by two fields by the monomultis 50 and 52, and is set to the timing of the FF 54 for suppressing the start / stop of the capstan. The counter 46 loads data having the value of the capstan FG corresponding to four track pitches from the data generator 40 at the timing of dividing 30PG by 3 and counts down by the clock signal oscillating at the same frequency as the capstan FG at the time of recording. ing. Therefore, the count value of the counter 46 represents the amount of off-track in the still state with the head switching time being on-track for one head as the number of pulses of the captor FG. Therefore, normal playback is started at the cross timing of the tracking error signal delayed by two fields and the just track level, and the tape is stopped when the tape is sent so that the capstan FG is generated by the value loaded in the counter 48. If you can, you can transfer to Fainstill. To do so, the capstan FG is counted down from the value of the counter 48, the FF 54 is reset by the borrow signal of the counter 48, and the capstan is stopped. The control of the capstan is performed by pulse driving using a clock signal via the AND gate 56, but this method is optional. Figure 5 during t ₁ is still reproduction period, t _2, t ₄ is the normal reproduction period, t ₃ is the Fuainsuchiru regeneration period, in this repeated thereafter, a slow 1/3 speed. According to the VTR having the above-described configuration, it occurs in the immediately preceding still reproduction state. The deviation from the ideal stop position was measured using the 30PG and ATF signals, and tracking was performed for the next still playback, so that good slow motion playback could be achieved without the CTL signal. As a means for obtaining a tracking error signal, a known four-frequency tracking error signal is used. However, it is needless to say that a tracking error signal can be obtained by a simple envelope detection circuit or the like. <Explanation of Effects> As described above, according to the present invention,
A video signal reproducing apparatus capable of performing good slow motion reproduction without recording a special control signal in the longitudinal direction of the magnetic tape was obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for explaining slow motion reproduction in a conventional VTR, FIG. 2 (A) is a view showing a relationship between a head trace trajectory and a track during a fine throw, FIG. 2 (B) is a timing chart of each signal in the VTR at the time of a fine throw, FIG. 3 is a diagram showing a schematic configuration of a VTR as one embodiment of the present invention, and FIG. 4 is a speed change in FIG. FIG. 5 is a timing chart for explaining the operation of the circuit shown in FIG. 4, 1, 4 is a magnetic tape, 2 is a recording track, 5a, 5b are rotary heads, respectively. , 10 is a capstan, 13 is a drum PG generation circuit, 15 is an ATF
The signal generation circuit 17 is a variable speed reproduction control circuit.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Toshiaki Mabuchi               770 Shimonoge, Takatsu-ku, Kawasaki-shi Canon               Tamagawa Works Co., Ltd.                (56) References JP-A-59-229766 (JP, A)

Claims (1)

(57) [Claims] A track formed on a magnetic tape at a predetermined pitch is traced while switching a plurality of rotary heads provided on a rotary cylinder to reproduce a video signal, and a running stop state and a running state of the magnetic tape are alternately performed. A video signal playback device that performs slow motion playback by repeating, a capstan that runs the magnetic tape, and a unit that detects rotation of the rotation cylinder and generates a switching timing signal of the plurality of rotation heads, Means for generating a tracking error signal indicating a deviation between the trace trajectory of the rotary head and the track; and a periodic signal synchronized with the switching timing signal, wherein the rotation of the rotary head is switched from a switching time during one cycle. Section where the value increases or decreases monotonically until the cylinder makes two rotations Means for generating a first signal which is a periodic signal having an interval; and a second signal output when the level of the tracking error signal becomes a level in a state where the track and the trace locus of the rotary head substantially match. Means for generating a signal of the second type, and a next signal of the magnetic tape based on a value of a signal in the section of the first signal extracted at a timing based on the second signal in a stopped state of the magnetic tape. Detecting means for detecting a necessary tape running amount to be run in the running state, and driving for shifting to the next running state, driving the capstan, and running the tape running amount based on the detection output of the detecting means. Means for shifting to the next running state so that the running completion time corresponding to the tape running amount matches the switching timing of the rotary head. And a regulating means for adjusting the drive start timing of the capstan.