JP2512908B2 - Playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in the following order.

A Industrial field B Outline of invention C Conventional technology D Problems to be solved by the invention E Means for solving problems (Fig. 1) F Action G Example G ₁ Explanation of jumping correction G ₂ Description of Signal Replacement of Unnatural Part H Effect of Invention A Field of Industrial Application The present invention relates to a reproducing apparatus suitable for application to a VTR capable of variable speed reproduction.

B Outline of the Invention The present invention provides a variable-speed reproduction video signal by alternately and continuously reproducing the reproduction video signals from the first and second recording tracks in the same field, and jumping (horizontal synchronization signal interval) at the switching portion. In the reproducing device in which the shift) is corrected by using the delay line, the unnatural part of the corrected variable speed reproduced video signal is replaced with the average level signal of the variable speed reproduced video signal in the previous period. As a result, the image quality is improved at low cost.

C Prior Art Conventionally, a video tape recorder (VTR) has been proposed which uses different rotating magnetic heads in different modes of tape running speed. FIG. 5 shows a rotary head device of such a VTR. In the figure, (1) is a rotating drum, and this rotating drum (1)
Is a pair of magnetic heads H with an angular interval of 180 ° from each other.
_SA and _HSB are installed. Further, a pair of magnetic heads H _LA and H _LB are attached to the rotating drum (1) at an angular interval of 180 °. In this case, the magnetic heads H _SA and H _LB , the magnetic heads H _SB and H _LA are arranged in proximity to each other, and the magnetic heads H _SA and S _SB are arranged to precede each other. The angular interval between the magnetic heads H _SA and H _LB and the angular interval between the magnetic heads H _SB and H _LA are, for example, the angular intervals corresponding to two horizontal periods (2H) in the NTSC video signal.

Further, (2) is a magnetic tape, and the rotary drum (1)
It can be run diagonally around the circumference with a wrap angle of about 180 °. The magnetic heads H _SA , H _LB , H _SB , and H _LA rotate once in one frame, and the magnetic heads H _SA and H _LB scan on the magnetic tape (2) in a certain field. In one field, the magnetic heads _HSB and _HLA scan the magnetic tape (2).

The magnetic heads H _SA and H _SB are magnetic heads used for recording / reproducing in a standard mode (hereinafter referred to as “SP mode”) in which the traveling speed of the magnetic tape (2) is high. Figures 6A and B
Indicates magnetic heads H _SA and H _SB , respectively, and the width thereof is, for example, 18 μm. Also, the magnetic head H _SA
The magnetic gap, and inclined with respect to direction, for example + 10 ° perpendicular to the track, is the so-called + azimuth, whereas the magnetic gap of the magnetic head H _SB is tilted for example -10 ° with respect to a direction perpendicular to the track So-called azimuth.

In the SP mode, the magnetic heads H _SA and H _SB form inclined tracks T _A and T _{B on the} magnetic tape (2) as shown in FIG. In this case, the track pitch is
Since it is 20 μm and the track width is 18 μm, it has a guard band.

The magnetic heads H _LA and H _LB are magnetic heads used for recording and reproducing in a long time mode (hereinafter referred to as “LP mode”) in which the traveling speed of the magnetic tape (2) is slow.
FIGS. C and D show magnetic heads H _LA and H _LB , respectively, and the width thereof is, for example, 13 μm. The magnetic gap of the magnetic head H _LA is tilted, for example, by + 10 ° with respect to the direction orthogonal to the track, so-called + azimuth, while the magnetic gap of the magnetic head H _LB is perpendicular to the direction orthogonal to the track. For example, it is tilted by -10 ° and is called so-called azimuth.

LP mode, the track T _A and is inclined as shown in FIG. 8 in the magnetic tape (2) by a magnetic head H _LA and H _LB
T _B is formed. In this case, the track pitch is 10
The track width is regulated to 10 μm by overwriting, and no guard band is provided.

Also, Figure 9 and Figure 10 shows the positional relationship between the horizontal synchronizing signal H _D of the recording tracks T _A, T _B of the SP mode and LP mode. The horizontal synchronizing signal H _D, the SP mode shift 0.5H is aligned between adjacent tracks, the so-called H line is not established, whereas, in the LP mode aligned in a straight line between the adjacent tracks, and take a H line.

In the one having the rotary head device as shown in FIG. 5, during the picture search (for example, rewinding), the magnetic heads H _SA , H _LB or H _SB , H _LA are
_A plurality of recording tracks T _A , T _B as shown by broken lines in FIG.
Scan across. Then, for example, the magnetic head H _SA , H
_In the one-field period in which the _LB scans, the video signals reproduced by the magnetic heads H _SA and H _LB from the recording tracks T _A and T _{B, respectively,} are sequentially and alternately switched to obtain a variable speed reproduction video signal. In one field period in which H _SB and H _LA scan, the video signals reproduced by the magnetic heads H _LA and H _SB from the recording tracks T _A and T _{B, respectively,} are sequentially and alternately switched to obtain a variable speed reproduction video signal.

In this case, the recording tracks T _A , T _B on the magnetic tape (2)
There if due SP mode, as described above, the position of the recording track T _A, the horizontal synchronizing signal H _D of T _B is 0.5H
The magnetic heads H _SA and H _LB, and the magnetic head
The angular interval between H _SB and H _LA is equivalent to 2H, so 0.5H is applied to the video signal switching part of the variable speed playback video signal.
Jumping occurs, and if left as it is, so-called skew distortion occurs in which the reproduced screen is distorted at this switching portion. FIG. 12A shows such a variable speed reproduction video signal.

Conventionally, it has been proposed to correct such jumping using a delay line. FIG. 13 shows the correction circuit, and the terminal (31) is supplied with the variable speed reproduction video signal as shown in FIG. 12A, and the variable speed reproduction video signal is on the B side of the changeover switch (32). Is supplied to the terminal. Also,
The variable speed reproduction video signal supplied to the terminal (31) is supplied to the delay line (33) having a delay time of 0.5H according to jumping, and the output signal of the delay line (33) as shown in FIG. 12B is It is supplied to the terminal on the A side of the changeover switch (32). A signal P _S as shown in FIG. 12C is supplied to the changeover switch (32), and the signal P _S has a high level “1” and a low level “0”.
At this time, the changeover switch (32) is connected to the A side and the B side, respectively. Therefore, at the terminal (34) derived from the change-over switch (32), a jumping-corrected variable-speed reproduced video signal having a continuous horizontal synchronizing signal is obtained as shown in FIG. 12D.

However, in such a correction circuit, the corrected variable-speed reproduction video signal becomes unnatural for one horizontal period from the time of switching to the output signal of the delay line (33) (see FIG. 12D), which deteriorates the image quality. . For example, black noise appears in the center of the screen due to the horizontal synchronizing signal H _D indicated by the arrow P _1. Further, the signal in the period of 0.5H indicated by the arrow P ₂ is a discontinuous signal, so the screen becomes unnatural at this portion.

In order to solve this drawback, the present applicant has previously filed Japanese Patent Application No. 60-1
In No. 31451, it was proposed to replace the unnatural one horizontal period portion of the corrected variable speed reproduction video signal with the immediately preceding one horizontal period portion. Alternatively, it is conceivable to replace an unnatural one horizontal period portion of the corrected variable speed reproduction video signal with a certain DC level signal.

D Problems to be Solved by the Invention However, the replacement by the immediately preceding horizontal period portion requires a delay line with a delay time of 1H, a volume adjustment gain matching switch, and the like, which is disadvantageous in terms of cost. It was something that Further, according to the method of replacing with a constant DC level signal, when the screen is extremely bright or dark, the line of the constant DC level signal portion becomes very conspicuous, which may rather deteriorate the image quality.

In view of the above point, the present invention aims to improve image quality at low cost.

E Means for Solving Problems (FIG. 1) The reproducing apparatus of the present invention comprises the first and second magnetic heads having different azimuths arranged in close proximity to each other and (H _SA ), (H _LB ),
(H _SB ), (H _LA ), the first switching means (5) for switching the output signal of the first magnetic head and the output signal of the second magnetic head, and the first switching means (5). Demodulation means (8) for demodulating a video signal from the output, and second switching means for switching and outputting the demodulated video signal and the delayed video signal obtained by delaying the demodulated video signal by a predetermined delay time (0.5H) (16), an integrating means (22) for integrating the demodulated video signal to generate an average level signal, and a third switching means (21) for switching between the average level signal and the output of the second switching means (16). ) And the level of the output signal of the first magnetic head and the level of the output signal of the second magnetic head are compared to control switching of the first switching means (5), and a first switching control signal (HCHG) Switching control signal generating means (13), (14) for generating Second switching control signal extended by changeover control signals (HCHG) a delay time (0.5H) (P
Second switching control signal generating means (18) for generating S),
(19), (20) and the third switching control signal (INSP) within one horizontal period (1H) at least the delay time (0.5H) or more from the beginning of the first switching control signal (HCHG) are generated. A third switching control signal generating means (23) is provided, and the reproduced video signal from the first recording track and the reproduced video signal from the second recording track adjacent to the first recording track are alternately switched. When the variable speed reproduction signal is continuously obtained and the control period delay video signal of the second switching control signal (PS) is output from the second switching means (16) in response to the first switching control signal, The switching means (21) outputs the average level signal during the control period of the third switching control signal (INSP).

In the above configuration, an unnatural portion of the corrected reproduced video signal, for example, one horizontal period portion is replaced with the average level signal S _AV of the variable speed reproduced video signal SV ^{* in} the previous period,
Even if the screen is extremely bright or dark, the line of this average level signal S _AV is inconspicuous.

G Example One example of the present invention will be described below with reference to FIG. This example is applied to a VTR having a rotary head device as shown in FIG.

In FIG. 1, reproduction signals obtained from the magnetic heads H _SA and H _SB are supplied to the terminals A and B of the head changeover switch (4S) via reproduction amplifiers (3SA) and (3SB). Further, the reproduction signals obtained from the magnetic heads H _LB and H _LA are supplied to the terminals A and B of the head changeover switch (4L) via the reproduction amplifiers (3LB) and (3LA). These head changeover switches (4S) and (4L) have magnetic heads.
The so-called RF switching pulse SWP synchronized with the rotation phase of H _SA , H _SB , H _LA , and H _LB is supplied as a switching control signal,
These head changeover switches (4S) and (4L) are connected to the A side for one field period during which the magnetic heads H _SA and H _LB scan the magnetic tape (2), and the magnetic heads H _SB and H _LA are connected.
Is B for one field period when the magnetic tape (2) scans
Connected to the side.

The reproduction signals S ₁ and S ₂ output from the head changeover switches (4S) and (4L) are supplied to the A side and B side terminals of the changeover switch (5), respectively. The reproduction signal output from the changeover switch (5) is supplied to the bandpass filter (6) and the highpass filter (7). From the high-pass filter (7), the FM modulation luminance signal Y _FM (for example, sync tip 4.2MHz, white peak 5.4MHz, frequency deviation 1.
2 MHz) is obtained, and this FM modulated luminance signal Y _FM is supplied to the FM demodulator (8). Then, the luminance signal Y obtained from the FM demodulator (8) is supplied to the synthesizer (9). Further, a low-pass conversion color signal (for example, a color subcarrier frequency is 743 kHz) C _L is obtained from the bandpass filter (6), and the low-pass conversion color signal C _L is passed through an ACC circuit (10) to a frequency converter. Supplied to (11). And this frequency converter (11)
The resulting carrier color signal C having a color subcarrier frequency of 3.58 MHz is supplied to the synthesizer (9), and the image signal SV is obtained from this synthesizer (9).

The reproduction signals S ₁ and S ₂ output from the head changeover switches (4S) and (4L) are supplied to the envelope detection circuits (12S) and (12L), respectively, and the detection circuits (12S)
The output signals of (12L) and (12L) are supplied to the comparator (13), respectively. The comparator (13) outputs a high level "1" when the output signal of the detection circuit (12S) is larger than the output signal of the detection circuit (12L), and a low level "0" in the opposite case. The signal S ₃ is output. This comparator (1
The output signal S ₃ of 3) is supplied to the D terminal of the D flip-flop (14).

The luminance signal Y from the FM demodulator (8) is supplied to the sync separation circuit (15), and the sync signal SYNC obtained from this sync separation circuit (15) is supplied to the clock terminal CK of the flip-flop (14). To be done. The signal HCHG obtained at the output terminal Q of the flip-flop (14) is supplied to the changeover switch (5) as a changeover control signal. The change-over switch (5) is connected to the terminals on the A side and the B side, respectively, when the signal HCHG is at the high level "1" and the low level "0".

With the above configuration, during the picture search (for example, rewinding), the magnetic heads H _SA and H _LB are used in one field period.
_{Alternatively} , H _SB and H _LA scan across a plurality of recording tracks T _A and T _B as shown by the broken line in FIG. For example, in the one-field period in which the magnetic heads H _SA and H _LB scan (the changeover switches (4S) and (4L) are connected to the A side), when the recording track T _A is scanned, the reproduction signal from the magnetic head H _SA level with is large, the level of the reproduced signal from the magnetic head H _LB is large when scanning the recording track T _B. Further, during the one-field period in which the magnetic heads H _SB and H _LA scan (the changeover switches (4S) and (4L) are connected to the B side), when the recording track T _A is scanned, the reproduction signal from the magnetic head H _LA is transmitted. As the level increases,
When scanning the recording track T _B , the level of the reproduction signal from the magnetic head H _SB becomes high. Therefore, the reproduction signals S ₁ and S ₂ output from the head changeover switches (4S) and (4L) are as shown in FIGS. 2A and 2B, respectively, and the portions where the respective levels are high are alternated. . As a result, the output signal S ₃ of the comparator (13) becomes as shown in FIG. 2C. Since the sync signal SYNC is obtained from the sync separation circuit (15) as shown in FIG. 2D, the signal HCHG as shown in FIG. 2E is obtained at the output terminal Q of the flip-flop (14). .

The changeover switch (5) is changed over by this signal HCHG. Therefore, during the one-field period in which the magnetic heads H _SA and H _LB scan, the reproduction signals reproduced from the magnetic heads H _SA and H _LB from the recording tracks T _A and T _B are alternately alternated from the changeover switch (5). The one switched to
On the other hand, in one field period in which the magnetic heads H _SB and H _LA scan, reproduction signals reproduced by the magnetic heads H _LA and H _SB from the recording tracks T _A and T _{B, respectively,} are sequentially and alternately switched. .

Therefore, for example, at the time of picture search, the video signal SV obtained from the synthesizer (9) is continuously switched by alternately switching the video signals reproduced from the recording tracks T _A and T _{B as} shown in FIG. 3G. It has been done. The third
FIG. A shows the sync signal SYNC obtained from the sync separation circuit (15), and FIG. B shows the signal HCHG obtained at the output terminal Q of the flip-flop (14).

In this case, as described above, when the recording tracks T _A and T _B on the magnetic tape (2) are in the SP mode,
The positions of the horizontal synchronizing signals H _D of the recording tracks T _A and T _B are shifted by 0.5 H, and the magnetic heads H _SA and H _LB and the magnetic heads H _SB and H
_Since the angular interval with _LA is the angular interval corresponding to 2H,
Recording track of video signal SV obtained from synthesizer (9)
0.5H jumping occurs at the switching part of the video signal reproduced from T _A and T _B.

Explanation of G ₁ Jumping Correction Further, in order to correct this jumping, the video signal SV obtained from the synthesizer (9) is processed as follows. That is, the video signal SV from the synthesizer (9) is supplied to the B side terminal of the changeover switch (16), and the video signal SV has a delay line (17) having a delay time of 0.5H corresponding to jumping. Is supplied to. From this delay line (17)
As shown in FIG. 3H, the video signal SV _D delayed by 0.5H
Is obtained, and this video signal SV _D is A of the selector switch (16).
Is supplied to the terminal on the side.

Further, the signal HCHG obtained at the output terminal Q of the flip-flop (14) is supplied to the inverting circuit (18), and from this inverting circuit (18), the signal ▲ ▼ shown in FIG. 3C.
Is obtained. This signal {circle around ()} is supplied to the OR circuit (19), and this signal {circle over ()} is supplied to the delay line (20) having a delay time of 0.5H. From the delay line (20), a signal ▲ ▼ as shown in FIG. 3D.
_D is obtained, and this signal ▲ ▼ _D is supplied to the OR circuit (19). Therefore, the OR circuit (19) obtains a signal P _S as shown in FIG. 3E, and this signal P _S is supplied to the changeover switch (16) as a changeover control signal. The changeover switch (16) has a high level "1" and a low level "0" for the signal P _S.
, The terminals are connected to the A-side and B-side terminals, respectively.

When the changeover switch (16) is connected to the A side and the B side, the changeover switch (16) outputs the video signals SV _D and SV, respectively. Therefore, from this changeover switch (16), as shown in FIG.
Successive video signals H _D SV ^* is obtained. In this case, one horizontal period (IH) portion of the video signal SV ^* becomes unnatural from the time t ₀ when the changeover switch (16) is changed over from the B side to the A side.

G ₂ Explanation of signal replacement of unnatural part To correct this unnatural part, changeover switch (1
The video signal SV ^* obtained from 6) is processed as follows.
That is, the video signal SV ^* from the changeover switch (16) is supplied to the B side terminal of the changeover switch (21), and the video signal SV ^* is supplied to the integrating circuit (22). From the integration circuit (22), the signal S of the average level of the video signal SV ^*
_AV is obtained, and this signal S _AV is supplied to the terminal on the A side of the changeover switch (21).

FIG. 4 shows an example of the integrating circuit (22). In the figure, (22a) is an input terminal, this input terminal (22a) is connected to the base of an npn-type transistor (22b), and the collector of this transistor (22b) is a power supply terminal (2
2c) is connected. The emitter of this transistor (22b) is grounded through a series circuit of resistors (22e) and (22f), and the connection point of these resistors (22e) and (22f) is connected via a capacitor (22g) for charging. While being grounded, this connection point is connected to the base of the pnp transistor (22h). The collector of this transistor (22h) is grounded,
The emitter is a power supply terminal (22c) through a resistor (22i).
Connected to. Then, the output terminal (22j) is derived from the connection point of the emitter of the transistor (22h) and the resistor (22i).

In the integrating circuit (22), the npn-type and pnp-type transistors (22b) and (22h) are used in combination in order to cancel the offset amount due to the voltage drop between the base and the emitter. Further, if the time constant is too small, the followability is too good to obtain an average level signal, and conversely if it is too large, the followability is poor, so the time constant is set to about several H to several tens H.

The signal HCHG obtained at the output terminal Q of the flip-flop (14) is supplied to the mono multivibrator (23). This monomultivibrator (23) is triggered by the falling edge of the signal HCHG, and a pulse signal INSP having a pulse width of 1H is obtained from the output side thereof as shown in FIG. 3F. The pulse signal INSP from the mono multivibrator (23) is supplied to the changeover switch (21) as a changeover control signal. When the pulse signal INSP is at the high level "1" and the low level "0", the changeover switch (21) is for the A side and the B side, respectively.
Connected to the side.

When the changeover switch (21) is connected to the A side and the B side, the changeover switch (21) outputs the average level signal S _AV and the video signal SV ^{*, respectively} . Therefore, from this the change-over switch (21), third image signal video signal SV ^* unnatural one horizontal period portion is replaced with the average level signal S _AV as shown in FIG. J SV ^** is obtained, It is led to the output terminal (24).

As described above, according to this example, one unnatural horizontal period of the video signal SV ^* after the jumping correction is replaced with the average level signal S _AV of the previous period. The screen of the line of the average level signal S _AV is extremely bright or dark so that it is not conspicuous and the image quality can be improved. In addition, according to this example, the cost can be reduced as compared with the conventional example that requires a delay line with a delay time of 1H, a volume adjustment gain adjuster, and the like.

In the above embodiment has been described the examples where the portion of the video signal SV ^* for one horizontal period is replaced with the average level signal S _AV, 1/2 horizontal period 1 inclusive horizontal period without a one horizontal period In this case, the portion that causes the image quality deterioration can be replaced with the average level signal S _AV , and the image quality can be improved. Further, although the above-mentioned embodiment describes an example at the time of picture search (rewind), even during other special reproduction in which jumping correction is performed and an unnatural portion is generated in the corrected video signal. Of course, similarly, the image quality can be improved.

Further, the above-mentioned embodiment is a VTR having an SP mode and an LP mode.
However, the present invention can be similarly applied to other reproducing apparatuses in which jumping of a variable speed reproduced video signal is corrected by using a delay line.

H According to the present invention described above, the unnatural portion of the variable speed reproduced video signal in which jumping is corrected using the delay line is replaced with the average level signal of the variable speed reproduced video signal in the preceding period. Therefore, the image quality can be improved at low cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIGS. 2 and 3 are diagrams for explaining the operation thereof, FIG. 4 is a block diagram of an example of an integrating circuit, and FIGS. 5 to 13 FIG. 6 is a diagram for explaining a conventional example. (1) is a rotating drum, (2) is a magnetic tape, (4S) (4
L) (5), (16) and (21) are changeover switches, (12S) and (12L) are envelope detection circuits, (13) is a comparator,
(14) is a D flip-flop, (15) is a sync separation circuit,
(17) and (20) are delay lines, (18) is an inverting circuit, (19)
Is an OR circuit, (22) is an integrating circuit, (23) is a monomultivibrator, and (24) is an output terminal.

Claims (1)

(57) [Claims] 1. A first magnetic head and a second magnetic head, which are arranged close to each other and have different azimuths, and a first magnetic head which switches between an output signal of the first magnetic head and an output signal of the second magnetic head. Switching means, demodulation means for demodulating a video signal from the output of the first switching means, and switching and outputting the demodulated video signal and the delayed video signal obtained by delaying the demodulated video signal by a predetermined delay time. Second switching means, integrating means for integrating the demodulated video signal to generate an average level signal, third switching means for switching between the average level signal and the output of the second switching means, Comparing the level of the output signal of the first magnetic head with the level of the output signal of the second magnetic head to generate a first switching control signal for controlling switching of the first switching means. First switching control signal generating means, second switching control signal generating means for generating a second switching control signal obtained by extending the first switching control signal by the delay time, and the first switching control A third switching control signal generating means for generating a third switching control signal for at least the above delay time and within one horizontal period from the beginning of the signal, the reproduced video signal from the first recording track, and the above The reproduced video signal from the second recording track adjacent to the one recording track is alternately switched to be continuous to obtain the variable speed reproduced signal, and the second switching means operates in response to the first switching control signal. Control period of the second switching control signal When the delayed video signal is output, the average level signal is output from the third switching means during the control period of the third switching control signal. Reproducing apparatus according to claim.