JPH0716241B2 - Helical scan video recorder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a helical scan type video tape recorder that repeats still image frame reproduction by intermittently feeding a tape during slow motion reproduction.

[Prior Art] Conventionally, a two-head, helical scan type video tape recorder (hereinafter referred to as a VTR) is based on a start pulse based on a head switching pulse and a tape playback control pulse during slow motion playback. There is a method in which a capstan motor is intermittently driven based on a braking pulse to intermittently feed a tape in a reproducing state, and a still image frame reproduction of an image which is gradually changed is repeated.

By the way, in PAL television broadcasting, for example, a film-recorded movie or the like is broadcast in such a manner that two fields each have the same frame image. When recording this broadcast with a VTR, a vertical synchronization signal at the start of recording is recorded. Recording starts from an odd or even field depending on the.

[Problems to be Solved by the Invention] In the case of the conventional helical scan type VTR, the tape stop position during slow motion playback is fixed by the playback control pulse during playback, and is always from an odd or even field. Since the still image frame reproduction is performed by the two fields, the slow motion reproduction of the tape in which the same image is recorded every two fields and the image changes for each frame like the tape recording the broadcast of the movie etc. However, there are problems described below.

That is, since the order of the two fields in which the same image is recorded differs depending on the tape, the situation in which the two fields of still image frame playback do not become the same image depending on the tape during slow motion playback, that is, the field shift Occurs, and in this case, there is a problem that a still image to be reproduced is blurred and good reproduction cannot be performed.

Therefore, it is conceivable that when the field shift occurs, the timing of the next intermittent feed start pulse is shifted by a half cycle of the head switching pulse and the tape stop position is shifted by one field based on the button operation by the user.

However, even if the generation timing of the start pulse is shifted, the reproduction control pulse is generated by feeding a fixed amount (1 frame) of the tape, so that it cannot be actually shifted by 1 field.

In addition, it is conceivable that a rotation speed detection pulse of the capstan motor is used, the detection pulse is counted to detect the feed of one field of the tape, and the tape stop position is shifted by one field based on this detection. However, when the number of detected pulses in one field does not become an integral multiple due to the difference in television system and the like, it cannot be shifted by one field.

The present invention is a helical scan type VTR capable of performing proper reproduction by shifting the tape stop position by one field regardless of the difference in the television system when a field deviation of two fields to be reproduced in the slow motion reproduction occurs.
The purpose is to provide.

[Means for Solving the Problems] In order to achieve the above object, in the helical scan type VTR of the present invention, the rotation speed detection pulses of the capstan motor are counted and simulated at a timing shifted by one field from the reproduction control pulse. The counter that generates the control pulse, the braking pulse creation circuit that forms the braking pulse based on the pseudo control pulse instead of the playback control pulse when the field deviation of the still image frame playback occurs, and the appropriate timing of the pseudo control pulse generation Pseudo control pulse output that alternately switches the generation timing of the pseudo control pulse to the timing of the count value of the counter before and after the proper generation timing at each generation of the start pulse when the count is deviated from the count timing of the rotation speed detection pulse With circuit That.

[Operation] In the case of the helical scan type VTR configured as described above, when the slow motion reproduction of the tape in which the same image is recorded every two fields, the two field images of the still image frame reproduction based on the tape stop position are the same. If a field deviation occurs, the counter pseudo control pulse, which is one field away from the reproduction control signal, is input to the braking pulse creation circuit.

Then, by the braking pulse based on the pseudo control pulse, the still image frame reproduction in which the subsequent tape stop position deviates by 1 field and 1 field from the position based on the reproduction control pulse is repeated.

Further, by providing the pseudo control pulse output circuit, the generation timing of the pseudo control pulse is alternately changed before and after the proper generation timing for each still image frame reproduction, and the capstan motor is changed due to the difference in the television system. Even when the number of rotation speed detection pulses of 1 field is not an integer and the appropriate generation timing deviates from the counting timing of the integer number of the counter, slow motion reproduction can be performed by repeating reproduction of still image frames shifted by 1 field. .

[Reference Example] FIGS. 1 to 5 showing a reference example will be described.

Figure 1 shows a two-head, helical-scan VTR that records and reproduces PAL video signals. In the figure, (1)
Is an input terminal for the rotation speed detection pulse (hereinafter referred to as FG pulse) of the capstan motor, (2) is an input terminal for a reproduction control pulse (hereinafter referred to as CTL pulse) for each frame of the tape, and (3) is for slow motion reproduction. A normal / special mode signal input terminal, and (4) is a head switching pulse (hereinafter referred to as SW pulse) input terminal.

(5) is a counter that counts FG pulses and outputs a pseudo control pulse (hereinafter referred to as a pseudo CTL pulse). (6) is a switching switch for switching and outputting a CTL pulse and a pseudo CTL pulse according to a mode signal, and (7) is a braking pulse generating circuit to which the output pulse of the switching switch (6) is input.

(8) is an inverter that responds to the SW pulse, (9) is a switching switch that switches and outputs the SW pulse and the inverted SW pulse of the inverter (8) according to the mode signal, and (10) is a switching switch (9). It is a starting pulse generation circuit to which an output pulse is input.

(11) is an OR gate to which the braking pulse of the braking pulse creating circuit (7) and the starting pulse of the starting pulse creating circuit (10) are input, and (12) outputs the output pulse of the OR gate (11) to the drive circuit of the capstan motor. (13) is an output terminal for supplying to the capstan drive circuit, and (13) is an output terminal for supplying a control signal for forward / reverse rotation command of the braking pulse generating circuit (7) to the capstan drive circuit.

(14) is an output terminal that supplies the SW pulse of the input terminal (10) to the video reproduction circuit, (15) is a pseudo vertical synchronization signal generation circuit to which the output pulse of the switching switch (9) is input, and (16) is generated An output terminal for supplying a pseudo vertical synchronizing signal of the circuit (15) to the video reproducing circuit.

Then, the FG pulse of the input terminal (1) is formed based on the output pulse of the rotation speed detection frequency generator of the capstan motor, and the frequency changes according to the rotation speed of the capstan motor.

When the azimuth angles of the pair of video heads of the head cylinder are A and B, the A azimuth track and the B azimuth track are alternately formed on the tape during recording.

Next, the operation during slow motion reproduction will be described.

First, as shown in FIG. 2 (a), the SW pulse of the input terminal (4) is synchronized with the switching of both video heads and is at a high level (hereinafter referred to as H) or a low level (hereinafter referred to as H) every half rotation of the head cylinder. Alternate).

Then, when the normal slow motion playback is set based on the operation of the slow motion playback button or the like, the mode signal of the input terminal (3) becomes L as shown in FIG. 2 (b) and the switching switch (6 ) Is held by the output of the CTL pulse of the input terminal (2), and the switching switch (9) is held by the output of the SW pulse of the input terminal (4).

At this time, the start pulse generation circuit (10) is delayed by a period τa from the trailing edge of every 6 cycles of the input pulse based on the frequency division of the SW pulse of FIG. 2 (c) via the switching switch (9). The starting pulse shown in FIG. 2 (d) is formed.

And the start pulse is OR gate (11), output terminal (1
It is supplied to the capstan drive circuit via 2), the capstan motor is activated and the tape runs, and playback is performed in the tape running state.

Further, the control pulse recorded on the tape is reproduced, and the CTL pulse of FIG. 2 (e) is input to the input terminal (2).

Then, the braking pulse creating circuit (7) has a fixed time constant monostable multivibrator (hereinafter referred to as “monomulti”) which is triggered by the rising edge of the CTL pulse through the switching switch (6) and the output of this monomulti. It has a variable time constant monomulti that is triggered by a falling edge, and forms the braking pulse of FIG. 2 (f) with a delay of a period τb from the rising edge of the reproduction control pulse.

This braking pulse is supplied to the capstan drive circuit via the OR gate (11) and the output terminal (12), and at the same time, a reverse rotation command is issued from the braking pulse creation circuit (7) to the capstan drive circuit via the output terminal (13). The control signal is supplied, the capstan motor is braked in the reverse direction, and the tape running is stopped after feeding the tape for one frame, and the still image frame reproduction is started.

Thereafter, the start pulse based on the SW pulse and the braking pulse based on the CTL pulse are alternately formed, and the tape 1
Frame playback is repeated by repeating frame by frame.

When the head trace during the normal slow motion reproduction is shown by the known track pattern coordinate method, for example, the range of the solid lines A and A'in FIG. 3 (a) becomes the trace range.

The shaded area in FIG. 3 (a) is the reproduction output portion where the track azimuth of the tape and the head azimuth coincide, and the reproduction envelope waveform based on this portion is the reproduction output waveform.
As shown in.

Further, the SW pulse via the switching switch (9) is input to the pseudo vertical synchronizing signal generating circuit (15), and the generating circuit (1
By 5), the pseudo vertical sync signal is formed at the insertion timing of t ₁ and t ₂ in FIG. 2 (g) synchronized with the rising and falling of the SW pulse.

Then, based on the pseudo vertical synchronizing signal of the output terminal (16), vertical pitching of the screen is prevented during reproduction of a still image frame.

Is formed.

Next, when a movie of TV broadcasting is recorded on the tape, if a blur occurs in the still image due to the normal slow motion playback based on the tape stop position and a field shift occurs, button operation or still image frame playback is performed. The mode signal is inverted to the special side, that is, H based on the comparison of the reproduced signals of the two fields.

This inversion is performed almost simultaneously with the formation of the start pulse by, for example, a timing control circuit having a microcomputer configuration.

Then, by inverting the mode signal to H, the switching switch (6) switches to the output of the pseudo CTL pulse of the counter (5), and the switching switch (9) switches to the inverter (8).
Switch to the output of the inversion pulse of.

The counter (5) is reset by the CTL pulse and counts the FG pulse.
Generate a pulse.

Then, the set value is 1 in the tape feed amount from the CTL pulse.
The pseudo CTL pulse is set to be generated before the field, and when the tape is sent by one field by the start pulse, the pseudo CTL pulse of FIG. 2 (h) is transmitted through the switching switch (6) to the braking pulse (7). ) Is supplied to.

Therefore, immediately after the mode signal is switched, a braking pulse is formed in the tape feed state one field before the normal, and based on this pulse, the tape stop position deviates from the position based on the CTL pulse by one field, and the still image frame is reproduced. Done 2
The field is corrected to 2 fields of the same image.

That is, when the mode signal is switched to H, the head trace becomes, for example, within the range of solid lines B and B'in FIG. 3 (a). The state shifts, and the reproduction envelope becomes as shown in FIG.

When the tape running stops, the counter (5) stops counting because the FG pulse is no longer output based on the rotation stop of the capstan motor.

Further, based on the switching of the switching switch (9), the phases of the input pulses of the starting pulse generating circuit (10) and the pseudo vertical synchronizing signal generating circuit (15) are inverted, and the pseudo vertical synchronizing signal is also shifted by one field. .

Then, based on the inverted SW pulse of the inverter (8), the start pulse creation circuit (10) forms a start pulse in the same way as when the SW pulse is input, and this pulse causes the capstan motor to rotate again and the tape to run. To do.

At this time, the CTL pulse is generated earlier than before the switching of the mode switching signal based on the shift of the tape stop position, the counter (5) is immediately reset, and the pseudo CTL pulse is generated when the tape is fed by two fields.

Therefore, the tape is sent from the stop position for one frame and the still image frame reproduction is started again. After that, the start pulse and the pseudo CTL pulse based on the inversion SW pulse are used as a reference until the mode signal is inverted to L. The braking pulses are alternately formed, and the slow motion reproduction is performed with the tape stop position being shifted by one field from the normal slow motion reproduction.

It should be noted that if the generation of the starting pulse is prohibited after the generation of the first braking pulse based on the pseudo CTL pulse, it is possible to reproduce the still image deviated by one field.

[Embodiment] An embodiment will be described with reference to FIGS. 4 and 5.

In FIG. 4, (17) is a capstan motor, (18)
Is a frequency generator that generates an FG pulse, (19) is an amplifier that amplifies the FG pulse, (20) is a control head that outputs a CTL pulse, and (21) is an amplifier that amplifies the CTL pulse.

Reference numeral (22) is a counter corresponding to the counter (5) in FIG. 1, and has a clock terminal (ck) and a reset terminal (r) connected to the amplifiers (19) and (21). (23) is a pseudo CTL
This is a pulse output circuit, which is composed of a flip-flop (24), n equivalent arithmetic gates (hereinafter referred to as EXNOR) (25) consisting of exclusive NOR gates, an ungate (26), and a count value setter (26).

(27) and (28) are the starting pulse generation circuit (10) of FIG.
A starting pulse creating circuit and a braking pulse creating circuit corresponding to the braking pulse creating circuit (7).

(29) is an OR gate corresponding to the OR gate (11) in FIG. 1, (30) is a capstan speed / phase control circuit,
FG pulse via amplifier (19), via amplifier (21)
The CTL pulse and the output pulse of the OR gate (29) are input to form a speed control signal during slow motion reproduction.

(31) and (32) are output gates of the OR gate (29), a diode for adding the speed control signal, (33) is a capstan drive circuit, and the output pulse of the OR gate (29), the diodes (31) and (32) And the control signal for forward / reverse rotation command of the braking pulse creation circuit (28) are input.

During slow motion reproduction, the counter (22) is reset by the CTL pulse of the control head (20) via the amplifier (21) and the FG pulse of the frequency generator (18) via the amplifier (19). Counts and outputs n bits in order from the LSB of the counter (22) according to the count value (q
Each bit output of ₀ ), (q ₁ ), ..., (qn _-1 ) changes.

By the way, in the capstan motor (17), the generator (18), etc., when the counter (22) counts an integer number (predetermined number) of FG pulses, the tape is sent by one field and the pseudo CTL pulse is generated. It is set so as to have an optimum generation timing.

However, when the capstan motor (17), the generator (18), etc. are used for the manufacture of different VTRs such as the television system, the pseudo CTL is used as explained below based on the differences in the standards.
A situation occurs in which the optimal pulse generation timing deviates from the integer FG pulse counting timing.

For example, a capstan motor (17), a generator (18), etc.
When used for the manufacture of VSC of VHS type of NTSC system and PAL system, the number of FG pulses per rotation of the capstan motor (17) is 720, and the frequency of FG pulse in standard mode and triple mode of NTSC system Is set to be 2160Hz, 760Hz,
In the standard mode of PAL system, the frequency of FG pulse is 1513Hz.

In this case, in the NTSC system VTR, the number of pulses corresponding to one field tape feed in standard mode and triple mode is 36 (= 2160/60), 12 (= 720/60), so the counter (22 ) Counts 36 or 12 FG pulses, the pseudo CTL
The optimum pulse generation timing is reached.

On the other hand, in the PAL system VTR, the number of pulses corresponding to the standard mode 1 field tape feed is 30.2 in the calculation.
It becomes 6 (= 1513/50), and the optimum timing of the pseudo CTL pulse deviates from the counting timing of the integer number of FG pulses.

Then, even if the counter (22) generates a pseudo CTL pulse when counting 30 or 31 FG pulses, there arises an inconvenience such as a tape stop position being gradually displaced based on an error from an appropriate generation timing. .

Therefore, in this embodiment, a pseudo CTL pulse output circuit (23) is provided to eliminate the above-mentioned inconvenience.

That is, when applied to a PAL VTR and the optimum generation timing of the pseudo CTL pulse is 30.26 pulses in the number of FG pulses, it will be described below.

First, based on the SW pulse of the input terminal (4) shown in FIG. 5 (a), the start pulse creating circuit (27) forms the start pulse shown in FIG. 5 (b), and this start pulse is generated by the OR gate (2).
9), supplied to the capstan drive circuit (33) through the diode (31), the capstan motor (17) is activated, and the tape runs.

Then, based on the rotation of the capstan motor (17), the FG pulse of FIG. 5 (c) is input to the counter (22), the capstan speed, and the phase control circuit (30) via the amplifier (19).

Also, based on the running of the tape, the fifth via the amplifier (21)
The CTL pulse shown in Fig. (D) is the counter (22), the braking pulse creation circuit (28), the capstan speed, and the phase control circuit (3).
It is input to 0).

Then, the counter (22) counts the FG pulse and
The reset value is reset at the rising edge of the CTL pulse, the count value changes as shown in FIG. 5 (e), and the output terminals q ₀ to (q _n ) change to H and L according to this change.

Also, during slow motion reproduction, the capstan speed / phase control circuit (30) executes only speed control based on the FG pulse, and supplies the speed control signal to the capstan drive circuit (33) via the diode (32) to start. The speed of the later capstan motor (17) is servo-controlled to stabilize the tape running.

Further, the braking pulse generating circuit (28) has a switching switch corresponding to the switching switch (9) in FIG. 1, and the CTL is used during normal slow motion reproduction in which the mode signal of the input terminal (3) is held at L. A control signal for a braking pulse and a reverse rotation command is formed based on the pulse.

Then, the braking pulse via the OR gate (29) is supplied to the capstan speed / phase control circuit (30) and also supplied to the capstan drive circuit (33) via the diode (31).

At this time, the capstan speed / phase control circuit (30) stops speed control, the capstan motor (17) is driven in reverse, and the tape is fed by one frame to shift to still image frame reproduction.

On the other hand, when the mode signal is switched to H, the braking pulse creating circuit (28) selects the output pulse of the pseudo CTL pulse output circuit (23) instead of the CTL pulse via the amplifier (21).

At this time, the proper generation timing of the pseudo CTL pulse is FG
Since it is the timing of counting 30.26 pulses,
The pseudo CTL pulse output circuit (23) outputs a pseudo CTL pulse at the timing described below.

That is, the LSB output terminal (q ₀ ) of the counter (22) changes from L to H when the count value changes from 30 to 31.

The count value setter (26) is set to the output of n-1 bits corresponding to H and L of the output terminals (q ₁ ) to (qn _-1 ) when the count value of the counter (22) is 30. , The output of this n-1 bit is each EXNOR connected to the output terminals (q ₁ ) to (qn _-1 ).
Supply to (25).

The flip-flop (24) latches the inverted output of the output terminal () fed back to the data input terminal (d) every time the start pulse is supplied to the clock terminal (ck), and this inverted output is the fifth output. Invert as shown in FIG.

Then, the inverted output of the output terminal () of the flip-flop (24) is supplied to the EXNOR (25) connected to the LSB output terminal (q ₀ ) of the counter (22), and each EXNOR (25 The set value formed by the n bit of one of the input terminals alternately changes to 30 and 31.

Further, the output of each EXNOR (25) is supplied to the AND gate (26), and the timing at which the AND gate (26) outputs the pseudo CTL pulse of H is set to the first timing every time the tape is intermittently fed by the start pulse. As shown in FIG. 5 (g), when the count value of the counter (22) becomes 30 (= k) and 31 (=
k ₊₁ ) and the timing is changed alternately.

Then, the pseudo CTL pulse of the AND gate (26) is supplied to the braking pulse creating circuit (28), and this creating circuit (28) forms the braking pulse shown in FIG. 5 (h) on the basis of the pseudo CTL pulse. On the basis of the braking pulse and the starting pulse, the slow motion reproduction is performed in the state of being shifted by one field from the normal slow motion reproduction, as in the case of the reference example.

At this time, the pseudo CTL pulse, which is the reference of the braking pulse, alternately changes to the counting timing of the integer number of the counter (22) before and after the optimal generation timing, and therefore the error of the generation timing is based on the tape stop position or the like. Misalignment is prevented.

When manufacturing a NTSC VTR using the capstan motor (17), generator (18), etc., omit the pseudo CTL pulse output circuit (23), and when the count value becomes 36 or 12, for example. The output pulse of the counter (22) is supplied to the braking pulse creating circuit (28) as a braking pulse.

[Advantages of the Invention] Since the present invention is configured as described above, it has the effects described below.

When the field deviation of still image frame playback occurs, the braking pulse creation circuit forms the braking pulse based on the pseudo control pulse of the counter, so the tape stop position based on the braking pulse during slow motion playback is based on the playback control pulse. You can shift one field from the position you set.

Further, by providing the pseudo control pulse output circuit, the generation timing of the pseudo control pulse is alternately changed before and after the proper timing for each reproduction of the still image frame. Good slow motion reproduction can be performed even when the number of rotation detection pulses of the field does not become an integer and the proper timing deviates from the counting timing of an integral number of counters.

[Brief description of drawings]

1 is a block diagram of a reference example, FIGS. 2 (a) to 2 (g) are timing charts for explaining the operation of FIG. 1, and FIGS. 3 (a), (b), and (c) are FIG. 4 is a block diagram of one embodiment of the helical scan type video tape recorder of the present invention, and FIGS. 5 (a) to 5 (h) are for explaining the operation of FIG. It is a timing chart. (5), (22), (34) ... Counter, (7), (28) ...
Braking pulse creation circuit, (10), (27) ... Starting pulse creation circuit, (23) ... Pseudo CTL pulse output circuit.

Claims (1)

[Claims] 1. During slow motion reproduction, a capstan motor is started by a start pulse based on a head switching pulse, the motor is braked by a braking pulse based on a tape reproduction control pulse, and the tape is intermittently fed. In a helical scan type video tape recorder that repeats the reproduction of still image frames, a counter that counts the rotation speed detection pulses of the motor and generates a pseudo control pulse at a timing shifted by one field from the reproduction control pulse; A braking pulse generation circuit that forms the braking pulse based on the pseudo control pulse instead of the reproduction control pulse when a field deviation of image frame reproduction occurs, and an appropriate generation timing of the pseudo control pulse is the rotation speed detection. Pulse integer And a pseudo control pulse output circuit that alternately switches the generation timing of the pseudo control pulse to the timing of the count value of the counter before and after the proper generation timing every generation of the start pulse when the measurement timing deviates from the measurement timing. A helical skiyan-type video tape recorder characterized by being equipped.