KR890003519B1 - Record and playback device - Google Patents

Abstract

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Description

Record and playback device

1 is a diagram showing a recording pattern of a conventional VTR.

2 is a plan view showing a head arrangement of a conventional VTR.

3 is the same front view.

4 is a VTR recording pattern diagram of a conventional example.

5 is a block diagram of a VTR of a conventional example.

6 is a waveform diagram of each corner portion.

7 and 8 are block diagrams showing conventional examples of the time base corrector.

9 is a block diagram of one embodiment of a recording reproducing apparatus of the present invention.

10 is a waveform diagram of each part of the embodiment.

11 is a block diagram of one embodiment of a time base corrector used in the present invention.

12 is a block diagram of a second embodiment of a time base corrector used in the present invention.

* Explanation of symbols for main parts of the drawings

2, 3: video signal 19, 20: composite video signal

4: time base compressor 5, 6: frequency modulator

7, 8: record amplifier 11, 12: regenerative amplifier

13, 14: frequency demodulator 15, 15 ': time base corrector

35, 36: Adder 38: Burst signal generating circuit

The present invention relates to an apparatus for recording and reproducing video signals by time-base compression multiplexing.

At present, the mainstream of the self-recording and reproducing apparatus (hereinafter referred to as VTR) is a helical scan type which forms an image track inclined on a tape by a rotating head.

Especially in home VTR, it is small and high density. For example, in the VHS type VTR, video signals are recorded inclined with respect to a 1/2 inch wide tape with two video heads disposed in a rotational cylinder having a diameter of 62 mm in a 180 ° position relationship with each other. In addition, in the broadcast VTR, the miniaturization and aging are desperately required in the Nuus collection (ENG) portable VTR, and the 3 / 4-inch U-standard VTR has also advanced considerably. In the ENG VTR, high quality image quality is required because of being compact and lightweight and for broadcasting. The 3 / 4-inch U-standard VTR has a cylinder diameter of 110 mm and a tape width of 3/4 inch, which limits the downsizing. Also, as a video signal recording method, the luminance signal is a frequency modulated wave and the low range is removed. Since the method of superimposing the carrier color signal changed in the low range is used, the bands of the luminance signal and the color signal are limited, and the image quality is not necessarily sufficient for broadcasting. 1 shows a recording pattern of an NTSC type 3/4 inch U standard VTR. In FIG. 1, (TW), (TP), and (TS) represent a video track width, a video track pitch, and a space, respectively, and substitutes TW = 85 µm, TP = 137 µm, and TS = 52 µm.

In view of the above, a device is proposed in which a high-quality reproducible image is obtained, which is small in size and light in weight. According to Japanese Patent Application No. 56-4819, this method can be applied to a cylinder diameter and a cassette of the same size as a domestic VTR. It is possible to obtain high quality images, and to be smaller and lighter than conventional ENG VTRs.

FIG. 2 shows a plan view of the head arrangement on the cylinder used in this manner, FIG. 3 shows a front view of the head, FIG. 4 shows an example of the recording pattern by the head, and FIG. The block diagram of the conventional example which is the recording method by the head is shown in FIG. 6 and the waveform diagram of the main part in FIG. 5, and the recording method by FIG.

In FIGS. 2 and 3, (A), (A '), and (B), (B') represent two pairs of heads disposed at 180 ° with the same height on the cylinder circumference. (A), (A '), (B), and (B') in FIG. 4 show the trajectories recorded by the heads (A), (A '), (B), and (B'), respectively. In FIGS. 3 and 4, (TA) and (TB) represent the trek widths of the heads (A), (A '), (B) and (B'), (TP) represents the trek pitch, and (TS ) Represents a space. Now, if the diameter of the cylinder, the number of rotations, the values of X and Y in FIG. 3, the values of (TA), (TB) and (TS), the tape speed, and the angle between the tape and the recording trajectory are properly determined, At the head positions as shown in Figs. 2 and 3, the trajectory can be recorded as shown in Fig. 4. For example, a VTR having a cylinder of the same diameter as that of the VHS system VTR and capable of recording about 20 minutes in a VHS cassette can be configured.

As a method of recording and reproducing a color video signal by the recording / reproducing apparatus as described above, luminance signals (frequency modulation) are used for the heads (A) and (A '), and color signals (frequency) are used for the heads (B) and (B'). Modulation). In this way, the track width of the luminance signal can be increased, and since the color signals are not superimposed, the band can be widened to obtain a high S / N ratio and a high resolution reproduction image. In addition, since the baseband signal (e.g., the B-Y signal of the R-Y signal) can be frequency-modulated also for the color signal, a high S / N ratio reproduction signal can be obtained in the high band.

In the above-described example, a cylinder having the same diameter as that of the VHS system VTR can be used, and recording of about 20 minutes is possible with the VHS cassette, so that a high-quality ENG VTR can be configured with a smaller size and lighter weight than the conventional one.

The recording method of FIG. 5 will be described below with reference to FIGS. 4 to 6. In Fig. 5, reference numeral 1 denotes a Y signal (luminance signal) input terminal, 2 denotes an RY signal input terminal, 3 denotes a BY signal input terminal, 4 denotes a time compressor, and 5 and 6 ) Is a frequency modulator, (7), (8) is a recording amplifier, (9), (10) is a video head, (11), (12) is a regenerative amplifier, (13), (14) is a frequency demodulator, ( 15) and 15 'are time base compensators, and 16 are Y signal output terminals. Reference numeral 17 denotes an R-Y signal output terminal, and 18 denotes a B-Y signal output terminal.

In Fig. 6, (1), (2), and (3) are waveforms of the input Y signal, the RY signal, and the BY signal, respectively. It is a waveform of the axial force signal of the compressor 4, and is a waveform diagram of each numbered part of FIG. The Y signal applied to the Y signal input terminal 1 is modulated by the frequency modulator 5, amplified by the recording amplifier 7, and then recorded on the tape by the head 9. The Y signal has a band of about 4.5 MHz, and in order to record and reproduce this signal with high performance, the frequency shift of modulation is set to be, for example, 5 MHz to 7 MHz. The RY signal and the BY signal applied to the RY signal input terminals 2 and BY signal input terminals 3, R, in the first half 1H of the line 1 like the waveform 19 of FIG. It is synthesized by time-base compression so that it is called -4 signal and RY signal. This signal is modulated by the frequency modulator 6, amplified by the recording amplifier 8, and then recorded by the head 10 on the tape. Since the R-Y signal and the B-Y signal have a band of about 1.5 MHz, the signal obtained by time-compressing each signal by half becomes a band of about 3 MHz. The frequency shift of this synthesized signal is set to 3.5 MHz to 5 MHz, for example. In this manner, the tape pattern in which the Y signal and the color signal are recorded as two pairs of heads having the structure described above is as shown in FIG. In Fig. 4, (A) and (A ') are Y signals, and (B) and (B') are recording trajectories of color signals. As shown in FIG. 4, the width of the track is lower than that of the conventional VHS system VTR for the Y signal, and the band with the low FM carrier frequency is about 3 MHz for the color signal. Can play rain well. At the time of reproduction, the Y signal reproduced by the head 9 is amplified by the reproduction amplifier 11, demodulated by the frequency demodulator 13, and then the time terminal corrector 15 removes the VTR-specific reproduction moment or more from the output terminal. At 16, a reproduction Y signal is obtained. On the other hand, the signal reproduced by the head 10 is amplified by the reproduction amplifier 12, demodulated by the frequency demodulator 14 and then expanded by the time base compensator 15 'and at the same time the abnormality of the abdominal cavity is removed, and the original RY signal And BY signal are separated, and the reproduction RY signal and BY signal are obtained at the output terminals 17 and 18.

In the VTR which performs such a component process, the horizontal synchronizing signal superimposed on a video signal is used for the detection of the abnormality of the reproduction | regeneration instant of a video signal obtained from the magnetic tape.

7 shows an example of a time axis corrector 15 (see FIG. 5). The video signal including the instantaneous abnormality reproduced by the VTR is applied to the input terminal 21, and the horizontal synchronous signal having the transient abnormality information is separated by the horizontal synchronous signal separation circuit 22. A phase-locked loop (23), a low pass filter (24), a voltage variable oscillator (25), and an N divider (26) constitute a PLL (Phase Lock-Loop). The voltage variable oscillator 25 is a circuit for making a memory write clock, and oscillates the output of the horizontal synchronous signal separation circuit 22 at a frequency N times the horizontal synchronous signal.

When the PLL 27 is in the cocked state, since the phase comparison is performed in the phase comparator 23 every one horizontal scanning period, the oscillation of the voltage variable oscillator 25 is performed by the horizontal synchronous signal separation circuit 22. The output is oscillated at the oscillation frequency following the instant of the horizontal synchronizing signal.

In the A / D converter 28, an input video signal is sampled, an analog-to-digital conversion is performed, and the data is written to the memory 29 using a clock that has received a moment or more that is an output of the voltage variable oscillator 25. Based on the clock of the voltage variable oscillator 25, the address made by the write address controller 30 and the write location are determined at once.

On the other hand, the timing of the output from the memory 29 and the projection of the video signal is defined in the airborne signal oscillator 31. That is, in the read address controller 32, the read address determined at one time on the basis of the reference oscillation of the reference signal oscillator 31 is sent to the memory 29, and the data of the place is transferred to the D / A converter 33. After being humanized, the video signal corrected for a moment or more is output to the output stage 34.

8 shows an example of the time base corrector 15 '(see FIG. 5). 8 is substantially the same configuration as FIG. 7, but only output terminals 34, 34 'and D / A converters 33, 33' corresponding to output terminals 17, 18 of FIG. There are two sets. In addition, the D / A converters 33, 33 'and the read address controller 32 shown in FIG. 8 are the reference signal oscillators (the frequency of half of the frequency of the reference signal oscillator 31 of FIG. 31 ') and (Fig. 8). In addition, the memory 29 is composed of two blocks A and B. V / 2 pixels of the first half of the one horizontal scanning period (RY signals) are placed in block A, and the second half of the one horizontal scanning period (BY signals). N / 2 pixels of) are written to block B, and the read from memory 29 simultaneously reads data of blocks A and B at half the frequency of the write clock, and the D / A converter 33, ( 34 '). By the above operation, the output terminals 34 and 34 'obtain the R-Y signal and the B-Y signal from which the time axis is extended and the moment abnormality is removed.

Then, the block of the PLL 27 of FIG. 7 and FIG. 8 contains various problems. The first problem is that since only the horizontal synchronizing signal is used as the clock generation information, both the S / N ratio of the horizontal synchronizing signal portion entering the input stage 21 and the horizontal synchronizing signal separation circuit 22 are used. The accuracy of a) and the like determine the remaining instant abnormality of the time axis correcting apparatus of FIGS. 7 and 8. In general, this type of model is inferior to the remaining moment in the time-base correction device of the color system such as 1-inch VTR which directly records the current. This is because in the time-base correction device of a color system such as a 1-inch VTR, phase information of more than the remaining moment is also used for clock generation clock generation information.

As a second problem, in a model having a time axis stretching device as shown in Fig. 8, the residual instantaneous abnormality indicated by the first problem is that the residual instantaneous abnormality is also extended and enlarged at the same time as the time-base extension of the signal. In addition, since only the horizontal synchronizing signal is present for every 63.5S (NTSC) as the clock generation information, the voltage variable oscillator 25 oscillates itself until the next horizontal synchronizing signal enters the phase comparator 23. For this reason, it is impossible to oscillate the voltage variable oscillator 25 with a clock ideally synchronized with the video signal, and a phase shift occurs, resulting in a speed error. When the time-base compression signal indicated by (19) of FIG. 6 enters the input terminal 21 of FIG. 8, when the RY signal of the waveform 19 starts on the clock phase of the voltage variable oscillator 25 due to the speed error. The BY signal starts and a mismatch occurs, which causes color shift.

An object of the present invention is to reduce abnormality of residual moment and color shift which is a problem of the conventional example.

According to the present invention, a pilot signal having a fixed frequency appropriate to each front porch of a horizontal blanking period of a plurality of video signals is added as a burst signal, and any one of the plurality of video signals is provided only in the horizontal blanking period of one video signal. After the horizontal synchronization signal is added, each of the plurality of video signals is time-base compressed and recorded on the recording medium.

In the present invention, the master clock is made by applying the horizontal synchronization signal reproduced at the time of reproduction to the first PLL, and the master clock is added to the burst signal in the front porch of the plurality of video signals compressed by the second PLL. By matching the phases, a stable write clock is generated by the time-base compression compensator to reduce the problems of the prior art.

As an embodiment of the present invention, two color difference signals (RY signal and BY signal) are time-base compressed and multiplexed by 5/2 times in units of one horizontal scanning period to generate one composite signal, and In the 1/5 horizontal scanning period, the application of the present invention to a time-base compression method in which a voice signal subjected to processing such as time-base compression is superimposed is considered.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail according to an accompanying drawing.

9 is a block diagram showing an outline of the time-base compression method, and the same reference numerals are attached to the parts which perform the same term operation as in FIG. 10 shows an example of the waveform of each point. The numbers given to the waveforms indicate the places in FIG.

The burst signal generating circuit 38 has a predetermined time period (e.g., two color difference signals) in a waveform (burst signal) of a suitable frequency phase locked to the horizontal synchronization signal of the RY signal applied to the input terminal 2. On the front porch of the This burst signal is mixed with the RY signal and BY signal applied to the input terminals 2 and 3 by the mixers 35 and 36, and the waveforms 43 and 44 shown in FIG. And enters the time base compression circuit 4.

Here, there is a blanking period of the video signal in order to multiplex the audio signal in the first half 1H of one horizontal scanning period 1H, and the RY signal obtained by time-compressing the RY signal by 5/2 times in the next 2 / 5H. The remaining 2 / 5H is processed such that a BY signal obtained by time-base compression of the BY signal by 5/2 times is allocated to generate the same waveform as the waveform 19 in FIG. In the mixer 37, the audio signal applied to the input terminal 31 is subjected to, for example, PCM encoding by the audio signal processing circuit 41, and is time-base compressed in the 1 / 5H period of the entire 1H, so that the signal is Multiplexed. In addition, the multiplexed signal is demodulated from the frequency demodulator 14 to the waveform 20 (figure 10) through the system from the frequency modulator 6 to the reproduction amplifier 12, and the time axis corrector 15 ' It is output to the audio signal processing circuit 42. The audio signal processing signal 42 is an inverse circuit of the audio signal processing circuit 42 and the audio signal processing circuit 41. The first terminal 1 / 5H signal of the waveform 20 is restored to the original audio signal, and the output terminal. It is output at 40. On the other hand, in the time axis corrector 15 ', the time axis expansion (time instantaneous) of the magnetic regeneration system is eliminated and the time axis is extended, and restored to two color difference signals (RY signal and BY signal), and output terminal 17 Is output to (18).

However, the frequency of the burst signal is selected to be one of the integers K of the clock frequency used in the time base corrector 15 '.

FIG. 11 is a detailed convex view of the time axis corrector 15 'used in FIG. 9, which is a detailed block diagram of the time axis corrector 15' of the conventional example, modified from FIG. 11 is a first embodiment of the time base corrector in the present invention.

In FIG. 8, the write clock is generated only by the horizontal synchronization signal in the PLL 27. In FIG. 11, the write clock is modified to generate the write clock from the horizontal synchronization signal and the burst signal.

Here, only the generation portion of the write clock will be described. In addition, in FIG. 8 and FIG. 11, the same numbered parts perform the same operation.

If the write clock fc is synchronized with the horizontal synchronization frequency fH, an arbitrary frequency can be selected. However, for simplicity, the write clock fc is an integer J times fH. In addition, in order to set the phase of the write clock fc as the burst signal as in the present invention, the frequency of the burst signal is selected to be 1 / K times the clock frequency.

In addition, the frequency fM of the master clock of the voltage variable oscillator 25 is preferably selected to be an integer i (i≥3) times the frequency fC of the write clock. As for the frequency fM of the clock, fM is fM = i x J x fH.

In FIG. 11, the time-base compressed video signal applied to the input terminal 21 derives the horizontal synchronizing signal from the horizontal synchronizing signal separation circuit 22, so that the frequency fM of the master clock is generated in the PLL 27. .

The PLL 27 is composed of a phase comparator 23, a low pass filter 24, a voltage variable oscillator 25, and a 1 / L divider 35.

Here, since the mast clock frequency fM is fM = xi × J × fH, the constant L of the 1 / L divider is L = i × J.

On the other hand, the video signal applied to the input terminal 21 is also delivered to the burst gate 37 to draw only burst information.

The 1 / i divider 36 divides the frequency (fM = i × J × fH) of the master clock into quarters to generate the frequency (fC = J × fH) of the write clock, There is a possibility that the write clock may generate four-phase write clocks that are out of phase by 90 degrees, and thus it is not determined what phase it will be. Thus, the rise of the burst signal and the 1 / i divider 36 The output is set to the phase closest to the rise of the write clock.

In addition, the phase comparator 38 detects minute phase shift between the information from the burst gate 37 and the write clock, and supplies the phase shift information to the phase shift circuit 39.

In the phase shift circuit 39, the phase shift of the write clock from the 1 / i divider 38 is reversely corrected based on the phase shift information, and the phase of the write clock from the phase shift circuit 39 is always adjusted. It acts to match the phase of the burst.

However, if the following limitations are set for the overlapping burst frequencies, all the burst signals have phase continuity, so that the advantage of simplifying the burst overlapping circuit can be obtained, and the write clock can generate only the burst signal. In this way, the same effects as in the first embodiment (Fig. 11) of the present invention can be obtained. It goes without saying that even in the burst frequency determined as follows, the first embodiment is used as it is. In this case, since the phases of all the burst signals are continuous, even if one burst signal is lacking in a dropout or the like, the previous clock signal is used. If the bay is left as it is, a correct clock signal can be obtained.

1. A plurality of video signals S ₁ , S ₂ ,... Before time-base compression. The frequency of each burst signal to be added is selected by N ₁ x fH (N ₂ , x fH...), Which is an integer N ₁ (N ₂ ,...) Times the horizontal pottery frequency fH.

2. The video signals S ₁ , S ₂ ,. Are K ₁ , K ₂ ,. When multiplexed by time-base compression, the frequency of the burst signal of each video signal fB ₁ = K ₁ × N ₁ × fH fB ₂ = K ₂ × N ₂ × fH... Are the same frequencies, and KB ₁ = K ₁ × N ₁ × fH (KB ₂ = K ₂ × N ₂ × fH) becomes an integer multiple of the horizontal synchronization frequency fH.

3. The burst frequency of fB ₁ = K ₁ × N ₁ × FH (fB ₂ = K ₂ × N ₂ × fH) is selected as the frequency reproduced with good S / N ratio. In the VTR shown in the conventional example, a frequency near 2 MHz is good.

The conditions of 1 and 2 are simplified.

로서 나타내어질 경우, 버어스트 주파수 fB₁(KB₂)이, 수평동기 주파수 fB₁(KB₂)은 m₁,m₂…의 최소공배수(M)의 정수배(n)로서 다음과 같이 나타낼수 있다.Time compression ratio K ₁ , K ₂ . Ratio that does not fall into each other

In this case, the burst frequency fB ₁ (KB ₂ ) is equal to the horizontal synchronization frequency fB ₁ (KB ₂ ), and m ₁ , m ₂ . An integer multiple (n) of the least common multiple (M) of can be expressed as

In other words, the distribution ratio of one horizontal period, that is, the time-base compression ratio K ₁ , K ₂ . Is determined, the least common multiple (M) is estimated at once.

Thereafter, using condition 3 above, the constant n is missing.

In this way, when the burst signal frequency fB at the time-base compression multiple time is obtained, constants N _1, N ₂ ... Which determine the burst frequency added to each video signal before compression are obtained. Is,

Is set.

When the burst frequency is set as described above, all of the added burst signals exhibit phase continuity.

That is, a signal of a single frequency, which is the same frequency as that of the burst signal added at the time-base compression, is assumed here for convenience, for example, with a burst signal added to an RY signal of a certain horizontal scanning period of a composite video signal. When the phase of the single frequency coincides, the burst signal added to the RY signal in any subsequent horizontal scanning period and the burst signal added to the BY signal coincide with the single frequency.

As described above, since the burst signal has a phase continuity, the write clock can be generated only from the burst signal.

As an example, FIG. 12 shows a second embodiment of the present invention.

Only the other places in Fig. 11 will be explained. The composite video signal applied to the input terminal 21 derives the burst signal from the burst gate 37 and enters the phase comparator 23. The other input terminal of the phase comparator 23 receives a signal from the 1 / K door period 35 '. When the PLL 27 'is in the locked state, these two signals become the same frequency, and the phase error signal of the two signals generated by the phase comparator 23 is passed through the low pass filter 24 to the voltage variable oscillator 25. ) Is applied. The voltage variable oscillator 25 receives the signal of the oscillation frequency by this phase error signal, and shows frequency oscillation which is K times the burst signal.

However, in the case of the time-base compression method shown in FIG. 9, the burst signal frequency can be determined as follows using the above-described burst signal conditions.

M = 5 because the B-Y and R-Y signals are 5/2 times the time base and compressed. Next, since the burst frequency at the time-base compression is set around 2 MHz, when n = 27, the burst signal frequency fB = M × nfH = 135fH. In other words, a burst signal of a frequency of 54 fH is superimposed from the third equation before the time base compression multiplexing.

If K of the 1 / K divider is selected to be K = 8, then fc = K × M × n × fH = 1080fH as the write clock frequency fc. Since the horizontal synchronizing frequency fH is fH = 15.75 KHz, it becomes fc = 17 KHz, and since the signal band at time-base compression is about 4 MHx, it can be considered as a suitable sampling block.

By using the write clock generation circuit as shown in the above embodiment, it is possible to obtain the effect of eliminating the residual instantaneous abnormalities which cannot be obtained in the PLL which generates the write clock only by the horizontal synchronization signal.

In addition, since the phase alignment of the write clock is performed by a burst signal superimposed on each time axis compression multiple signal, the phase shift of a plurality of expansion signals generated by a speed error or the like during time axis expansion is also eliminated.

By setting the frequency of the burst signal as in the formulas (1), (2) and (3), the burst portion can simplify the circuit, and the write clock can be easily created only from the burst signal.

In addition, even when a part of the burst signal is interrupted by a dropout or the like, the write clock can be stably created.

In addition, it is apparent that a stable write clock can be obtained even when a burst signal is superposed only on one video signal in any of the time-compression-side multiplexed video signals.

In addition, the present invention is not limited to the time-base compression scheme shown in the embodiment, and the same effect can be obtained by applying to any time-base compression method of any compression ratio.

Claims (8)

In recording a video signal to which a horizontal synchronous signal is added and one or a plurality of other video signals synchronized with the video signal as one composite signal by time-base compression multiplexing, at least one video signal is recorded in a horizontal blanking period. The recording is characterized by superimposing a burst signal of one frequency and generating a clock at the time of reproduction using the burst signal included in the composite signal, and correcting the time axis fluctuations generated during recording and reproduction based on the clock. Playback device. 2. The recording and reproducing apparatus according to claim 1, wherein the frequency of the burst signal added to the composite video signal is 1 which is an integral part of the clock frequency used during reproduction. 2. A plurality of video signals S1, S2... Each "t-2" stage, m1, l1 is an integer that is not divided from each other) times, "t-3" stage m _2, l is ₂ or an integer unless Wu each other) times, ... Time-base compression is recorded in times (including Ki = 1), and m ₁ , m ₂ ,... And a frequency which is the product of the least common multiple (M), the integer (n) and the horizontal synchronizing frequency (FH) of M x n x fH as the frequency of the burst signal. The recording and reproducing apparatus according to claim 1, wherein the plurality of synchronized video signals are a luminance signal and two color difference signals. The recording and reproducing apparatus according to claim 1, wherein the plurality of synchronized video signals are one component of a color difference signal and a luminance signal. The recording and reproducing apparatus according to claim 1, wherein the plurality of synchronized video signals are two color difference signals. The recording and reproducing apparatus according to claim 1, wherein the burst signal is added to a horizontal blanking period of all video signals. The recording and reproducing apparatus according to claim 1, wherein the clock generation is performed by the complex generation from the complex signal and the burst signal.

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