JPS5941672Y2 - Video signal reproducing device - Google Patents

Description

[Detailed description of the invention] The present invention relates to a video signal reproducing device, at least a part of which is a video signal reproducing device.
It is an object of the present invention to provide a reproducing device that can substantially eliminate vibrations in moving images when reproducing color video signals recorded every other field.

In general, at least part of the video signal is recorded every other field, for example, in a VTR (VTR) that records only the even or odd fields of a color video signal and plays it back.
The DTV (hereinafter referred to as double trace VTR) consumes only one magnetic tape compared to a normal full field VTR, and has the advantage that the recorded tape can be made smaller, lighter, and lower in cost.

As shown in FIG. 1A, the color video signal reproduced by a full-field VTR has field number 1 shown on the horizontal axis.
, 2, 3, 4, 5, and 6 color video signals are sequentially reproduced.

On the other hand, when a color video signal reproduced by a DTV is recorded with only odd fields, for example, as shown in Figure 1B, even field information is missing, so the odd field information is repeated twice and the monitor television is reproduced. It was being played.

However, regarding the video on the playback screen of the conventional DTV mentioned above, the psychological inertia of the human eye that follows the movement causes vibrations back and forth between the position of the video and the time lapse of time. When the field frequency of the color video signal is 60Hz, the width of the difference between the expected position and the actual reproduced image position is perceived as 3011z flicker. be done.

Needless to say, this width is proportional to the speed of the moving image, and is zero for still images.

Note that no flicker occurs in the brightness of the entire screen.

That is, conventional DTV playback images have flickering due to frame-by-frame playback, which has the disadvantage of making the eyes and head tired and uncomfortable.

The present invention eliminates the above-mentioned drawbacks and will be described with reference to its preferred embodiment with reference to FIGS. 2 and below.

FIG. 2 shows the relationship between the field number of a video signal and the playback order for explaining the apparatus of the present invention.

The essence of the flicker in a moving image on a DTV playback screen lies in the fact that every other field is played back twice, as in the conventional method, and is not caused by a reduction in information by half.

As evidence of this, even if a video signal with a field frequency of 60 Hz is recorded every other field and the information is halved, if the same field is not repeated during playback and only 30 fields are played back per second, the brightness of the entire screen will be 30 Hz. flicker
However, the vibration in the video disappears and the video moves smoothly.

Therefore, as a countermeasure against video flicker in DTv playback images,
It is better not to repeatedly play back the same field of video.

Therefore, focusing on this point, for example, if only odd fields are recorded, the even numbers in the playback order will be as shown in Figure 2.
The lost even field can be compensated for by reproducing the sum of the signals of the odd fields before and after the even field that lacks information, and by synthesizing the average value image using the human visual psychological integration effect. Now (for example (1+
3)/2=2. (3+5)/2=4 etc.).

For odd numbers in the playback order, only signals in fields with matching numbers are played back.

As a result, even fields are synthesized by linear approximation (an approximation in which the movement of a moving image per second is linear), but it is extremely close to the same playback method as the full-field VTR shown in Figure 1A. Become.

It has been experimentally confirmed that the device of the present invention virtually eliminates vibrations in moving images.

3A and 3B are a plan view and a front view, respectively, showing the relationship between the rotary head and the drum in one embodiment of the device of the present invention.

In the figure A, 1 is a drum, which rotates, for example, in a counterclockwise direction.

On this drum 1, video heads H2 and R3 are provided at positions adjacent to each other at 180 degrees on the circumference of the drum 1 in a design similar to that of a normal full-field VTR.

Additionally, video heads H1 and R7 are each mounted on drum 1 according to conventional DTV design guidelines.

That is, the video head H1 is provided adjacent to the video head H2 in the head rotation direction (180-α)0, and is provided adjacent to the video head H3 on the drum circumference α0.

Now, assuming that the radius of the drum 1 is R1 and the length of the heads H1 and R3 on the drum circumference is a, the above angle α becomes α=100 (rad) (1).

Further, the rotating surface of the video head H1 is the same as that of the video head H2.
and the length P as shown in Figure 3B for the rotating surface of H8.
Only a low height position is considered.

As a result, the track pitch becomes P. Further, as shown in FIG. 4, if θ is the angle formed between the tape running direction of the magnetic tape 3 as shown by arrow 4 and the video head rotating direction as shown by arrow 5, then the above length a becomes.

However, as will be described later, T is the center delay variation (unit: μ5ec) of the variable delay line (hereinafter abbreviated as VDL) that delays the playback output of the video heads H1 and R2, and the number of scanning lines is 52.
It is assumed that five lines record a video signal with a field frequency of 60 Hz.

Therefore, from the above equations (1) j (2) and (3), the above angle α becomes.

As a result, video heads H1 to H3 exhibit relative positions as shown in FIG. This shows the case where each pulse is reproduced simultaneously.

Since the magnetic tape 3 is attached to the drum 1 having the video heads H1 to H3 over an angular range of over 1800 degrees, the video head H2 is attached to the magnetic tape during the next half rotation of the drum from the state shown in FIG. 3, and only video heads H1 and R3 simultaneously trace respective adjacent video tracks.

Then, in the next half rotation, video heads H1 and R
3. Unable to trace magnetic tape 3, video head H
2 traces the track that the video head H3 has been tracing so far.

In this way, since video heads H1 and H8 always trace adjacent video tracks simultaneously, the amplitude of their playback outputs is set to 7 and added together, while the amplitude of the playback output of video head H2 remains unchanged. Possibly the second
Regeneration as shown in the figure can be performed.

In addition, in FIG. 3A, 2 and 2' are magnets provided on the drum 1 adjacent to each other by 180 degrees on the circumference of the drum 1 as shown in the figure, and are pulsed once per half rotation of the video head by the magnetic head. (drum pulse).

However, with only the mechanical configuration shown in FIGS. 3A and 3B, the phase of the reproduced output video signal of the video head H1,
The phases of the reproduction output video signals of the video head H3 do not match each other, and therefore these two signals cannot be added together as they are.

That is, tension unevenness in the width direction of the magnetic tape 3,
Variations in tape tension during recording or playback, wow, etc.
This is because flutter, jitter, etc. occur.

Therefore, it is necessary to take the following electrical means to align the phases of the output video signals of the video heads H1 and H3.

FIG. 5 shows a block system diagram of a device capable of solving the above problem.

In this figure, the same parts as in FIGS. 3A and 3B are given the same reference numerals, and their explanations will be omitted.

In FIG. 5, ESWl is an electronic switch having fixed contacts X and y, and its movable contacts are alternately switched for each field by drum pulses from the magnetic head H4.

First, when the video heads H1 and H8 play back adjacent video tracks simultaneously, the electronic switch ESW
I was closed connected to fixed contact X.

As a result, the video signal of field number 3, for example, reproduced by the video head H1 is supplied to the video detection circuit 6, where it is detected and then supplied to the synchronization separation circuit 7 and VDL 12, respectively.

The horizontal synchronization signal separated and extracted by the synchronization separation circuit 7 is supplied to a phase comparator 10.

On the other hand, the video signal of field number 5, for example, reproduced by the video head H3 is supplied to the video detection circuit 8, and after being detected there, is supplied to the synchronization separation circuit 9 and the adder 14, respectively.

The output horizontal synchronization signal of the synchronization separation circuit 9 is sent to the phase comparator 1.
0, and here the phase is compared with the horizontal synchronization signal from the synchronization separation circuit 7.

A phase comparison error voltage extracted from the phase comparator 10 according to the phase difference between the two horizontal synchronizing signals is supplied to a variable delay line control circuit 11.

The output signal of the variable delay line control circuit 11 is supplied to the VDL 12 as a control signal to control the amount of delay of the kVDL 12.

That is, the delay amount of the VDL 12 varies depending on the output of the variable delay line control circuit 11 around a certain constant delay T (same as T shown in equations (3) and (4) above).

Here, the delay amount T is selected as the center value of the variation range of VDL12.

As a result, the output reproduced video signal of the video detection circuit 6, which is the input of the VDL 12, is 1. The VDL 12 always makes the phase of the video signal coincide with the phase of the reproduced video signal output from the video detection circuit 8, and the VDL 12 supplies the signal to the adder 14, where it is added to the reproduced video signal output from the video detection circuit 8.

The output signal of this adder 14 is the electronic switch ESW.
It is taken out from the output terminal 15 through I.

Next, when only the video head H2 reproduces the video track of the magnetic tape 3, the electronic switch ESWI is switched to the fixed contact y side by the drum pulse.

At this time, only the video signal of field number 5, for example, reproduced by the video head H2 is transmitted to the video detection circuit 13.
and the electronic switch ESW1, and are taken out from the output terminal 15.

In this way, a video signal obtained by adding the video signals reproduced from video heads H1 and H3, respectively, and a video signal reproduced from video head H2 are alternately reproduced for each field.

This DTV reproduced video signal is projected (displayed) on a monitor television as a video signal whose jitter has been corrected and vibration of the moving image and flicker of the brightness of the entire screen have been substantially eliminated.

In the above embodiment, the lower H1 and H of the video paddle are set so that b in equations (2) and (3) is zero, that is, the delay amount T=0.
3 is mechanically arranged, and a video detection circuit 8 and an adder 14
A fixed delay line having a delay amount T' may be inserted between the two.

FIG. 6 shows a block diagram of the first embodiment of the device of the present invention.

In this figure, the same parts as in FIG. 5 are given the same reference numerals, and their explanations will be omitted.

In this embodiment, a color video signal is separated into a luminance signal and a carrier chrominance signal, the luminance signal is frequency modulated (FM), and the carrier chrominance signal is frequency-converted to a band lower than the frequency modulated luminance signal band. This method reproduces a color video signal in which only the odd or even fields are recorded by multiplexing the signals.

In FIG. 6, ESW1, ESW2. The ESW 3 is an electronic switch having fixed contacts X and y, respectively, and is configured to be switched in conjunction with a drum pulse from a magnetic head H4.

The color video signal reproduced by the video head H1 is
The signal is supplied to a luminance signal detection circuit 16 consisting of a high-pass filter, a limiter, an FM demodulator, etc., where the reproduced FM luminance signal is separately detected and converted into a reproduced luminance signal, which is then supplied to the VDL 18 through a low-pass filter 17. , are supplied to the synchronous separation circuit 7.

Further, the reproduced color video signal is supplied to a low-pass filter 20, where the reproduced low-pass converted carrier color signal is separated, and then supplied to the VDL 21.

On the other hand, the reproduced color video signal from video head H3 is
The signal is supplied to a luminance signal detection circuit 23 having the same circuit configuration as the luminance signal detection direct path 16.

The reproduced luminance signal from the luminance signal detection circuit 23 is passed through a low-pass filter 25 that removes carrier components and then sent to a sync separation circuit 9.
and an adder 28, which will be described later.

Here, the VDLs 18 and 21 used in this embodiment are analog shift registers (semiconductor element delay circuits) that have a relatively low clock frequency and sample and hold inputs, such as BBD (packet brigade device). It is.

Therefore, in this embodiment, if the reproduced color video signals of video heads H1 and H3 are demodulated into standard color video signals such as N780 type and then added to the above VDL, vD
Only one L is required, but the color subcarrier frequency (for example, 3.58M
Hz) and the clock frequency to the VDL (e.g. 5-7M
(about Hz) causes a signal beat, so dedicated VDLs are used for the luminance signal and the carrier color signal, respectively.

Further, as shown at 21 in FIG. 6, the carrier color signal VDL is supplied with a reproduced low-pass converted carrier color signal, and the cutoff frequency of the low-pass filter 22 provided on the output side of the VDL 21 is equal to the clock frequency. The difference between the color subcarrier frequency and the color subcarrier frequency that is being low-pass-converted is made equal to or less than the difference.

Note that the low-pass filter 17 is provided to prevent signal components higher than the sampling frequency determined by the clock frequency from entering the VDL 18 and creating a bead that is converted to a low frequency by the clock pulse.

As a result, as in the first embodiment, the delay amounts of the VDLs 18 and 21 are variably controlled by the output clock pulses of the variable delay line control circuit 11, and the phase with the reproduced color video signal from the video head H3 is controlled. The matched reproduced luminance signal and reproduced low-pass converted carrier color signal are applied to the adder 28 and the fixed contact X of the electronic switch ESW2, respectively, through low-pass filters 19 and 22 provided for removing clock components. .

An adder 28 adds together the reproduced luminance signal output from the low-pass filter 19 and the reproduced luminance signal output from the low-pass filter 25, and this signal is supplied to an adder 48, which will be described later.

Furthermore, the output reproduced low-pass conversion carrier color signal of the low-pass filter 22 is connected to the electronic switch ESW, which is connected in a closed manner to the fixed contact X.
2, the level fluctuation is corrected by an ACC (automatic chroma control) circuit 29, and then the signal is supplied to a frequency converter 30, which will be described later.
The output signal frequency is converted back to the carrier color signal having the original color subcarrier frequency (for example, 3.58 MHz).

The reproduced carrier color signal extracted from the frequency converter 30 is supplied to an adder 32 after unnecessary components are removed by a bandpass filter 31 .

The output signal of this adder 32 is applied to a burst extraction circuit 33 and a movable contact piece of an electronic switch ESW4.

By the way, in this embodiment, the well-known APC (Automatic Phase Compensator) is used to stabilize the amplitude and phase of the reproduced low-pass converted carrier color signal of the DTV and return it to the carrier color signal having the original color subcarrier frequency. ) circuit (hereinafter referred to as color processor) 3
There are 8.

That is, the output reproduced carrier color signal of the bandpass filter 31 is
After a color burst signal of, for example, 3.58 MHz is extracted by a burst extraction circuit 33, its phase is compared with a continuous wave of 3.58 MHz from a crystal oscillator 34 by a phase comparator 35.

The output phase comparison error voltage of the phase comparator 35 is supplied to a voltage controlled oscillator (VCO) 36 with a center frequency of 7 kHz to control its oscillation frequency.

The output oscillation frequency of this VCO 36 is determined by the frequency converter 37
Here, the signal is frequency-converted to the oscillation frequency from the crystal oscillator 34, and a signal having a frequency equal to the sum of the two human frequencies (for example, about 4.3 MHz) is supplied to the frequency converters 30, 40.

The output signals of the frequency converters 37 and 45 change to follow the time axis fluctuations of the reproduced low-pass converted carrier color signal, and in the frequency converters 30 and 40, a difference signal between the reproduced low-pass converted carrier color signal and the reproduced low-pass converted carrier color signal is generated. Therefore, the above-mentioned time axis fluctuation can be removed and the reproduced low frequency converted carrier color signal can be returned to the original carrier color signal.

The carrier color signal returned to its original frequency is transferred to the electronic switch ES
The signal is supplied to the adder 48 via the X contact of W4, where it is added to the sum signal of the luminance signals reproduced by the video heads H1 and H3, and band sharing multiplexing is performed.

The output signal of this adder 48 is a reproduced video signal of the sum of the odd fields before and after the even field, which does not record the luminance signal, for example, by the electronic switch E.
The color signal taken out from the output terminal 50 through the SWI is taken out from the output terminal 50 as a reproduced color signal of the recorded odd field, similar to the conventional DTV shown in FIG. 1B.

Next, during a period in which only the video head H2 traces the video track of the magnetic tape, the color video signal reproduced by the video head H2 is filtered by the low-pass filter 27 to remove the low-pass conversion carrier color signal. After that, it is supplied to the color processor 38 through the electronic switch ESW2, where its phase and amplitude are stabilized, and after being returned to the carrier color signal having the original color subcarrier, it is further supplied to the movable contact of the electronic switch ESW4. Supplied in pieces.

On the other hand, the reproduced color video signal from the video head H2 is supplied to the luminance signal detection circuit 26, where the luminance signal is reproduced, and then supplied to the adder 49 via the low-pass filter 47 that removes the carrier component. electronic switch ESW
It is added to the reproduced carrier color signals from 4 and band-sharing multiplexed.

The reproduced standard color video signal taken out from the adder 49 is guided to the output terminal 50 through the electronic switch ESW1.

FIG. 7 shows a block system diagram of a second embodiment of the device of the present invention.

In this figure, the same parts as in FIG. 6 are given the same reference numerals, and their explanations will be omitted.

Note that the head H4 is omitted.

In this embodiment, for example, a CCD (charger) is used as a variable delay line.
The present invention is characterized in that it uses a semiconductor element delay circuit that can use a relatively high clock frequency of about 10 to 20 MHz, such as a coupled device, and that a reproduced standard color video signal is input to this delay circuit.

Now, when video heads H1 and H3 are simultaneously tracing adjacent video tracks, video head H3
The processing of the output signal is exactly the same as in the second embodiment.

On the other hand, the low-pass converted carrier color signal of the color subcarrier frequency fc from the low-pass filter 20 obtained from the video head H1 is supplied to the frequency converter 53, where it is frequency-converted by the oscillation frequency f9 from the oscillator 52. The frequency fc+fo is approximately equal to the color subcarrier frequency (for example, 3.58 MHz) of the standard color video signal.

The output of this frequency converter 53 is multiplexed with the reproduced luminance signal from the luminance signal detection circuit 16 by an adder 54, and is converted into a reproduced standard color video signal and passed through a low-pass filter 55 to the VDL.
(here, for example, a CCD) 56.

The reproduced standard color video signal output from the VDLS 6 is extracted from the reproduced carrier color signal by a bandpass filter 57, and then supplied to a frequency converter 58, where the oscillator 5
Output oscillation frequency f from 2.

The signal is frequency-converted into a reproduced low-pass converted carrier color signal having a color subcarrier frequency fc.

The output of this frequency converter 57 is applied to the fixed contact X of the electronic switch ESW2.

Furthermore, the period during which only the video head H2 is tracing the video track is exactly the same as in the second embodiment.

In FIG. 1, 51 is a low-pass filter that removes carrier components from the output of the luminance signal detection circuit 16.

This embodiment can be configured with only one variable delay line compared to the second embodiment.

FIG. 8 shows a block system diagram of a third embodiment of the device of the present invention.

In the figure, the same parts as in FIG. 7 are given the same reference numerals, and their explanations will be omitted.

This embodiment uses the VDL 56 described above, and is characterized in that its input is a mixed signal of a frequency modulated luminance signal reproduced by a video head and a low-frequency conversion carrier color signal.

That is, this embodiment is similar to the second and third embodiments described above regarding the output processing of the video heads H2 and H3.

On the other hand, the output of the video head H1 is directly supplied to the VDL 56 through the low-pass filter 55, while the sync separation circuit 5
9.

The horizontal synchronization signal taken out from the synchronization separation circuit 59 is phase-compared with the horizontal synchronization signal from the synchronization separation circuit 60, which is separated from the playback output of the video head H8, by the phase comparator 10.

Here, the synchronization separation circuits 59 and 60 are circuits that extract horizontal synchronization signals directly from frequency modulated luminance signals, but the applicant previously filed a utility model registration application dated February 4, 1975 for this circuit. It is possible to use the ``synchronization signal separation circuit in video signal recording and playback devices'' proposed in .

Note that the upper limit frequency of the FM signal reproduced from the video head H1 reaches 5 MHz, but by using a VDL that can use a clock frequency of 14 MHz or higher, for example, the beat between the carrier of the FM signal and the clock frequency can be lowered to a lower frequency. It can be removed by filter 17.

This embodiment has a frequency converter 53 compared to the third embodiment.
and 58, since the oscillator 52 can be omitted and only one VDL is required compared to the above-mentioned embodiment, the circuit configuration is simpler, and since the FM luminance signal before detection is passed through the VDL,
The S/N of the reproduced luminance signal is good.

As described above, the video signal reproducing apparatus according to the present invention is an apparatus for reproducing a color video signal recorded by sequentially forming a video track for one field on a recording medium every other field. a first reproducing means for repeatedly reproducing a video track twice for each field; a second reproducing means for reproducing the video track every other field; and a second reproducing means for reproducing the video track twice by the first reproducing means. adding means for respectively adding together the luminance signal of one later field of the same field and a color video signal reproduced by the second reproduction means one track ahead of the first reproduction means; The first reproduction means alternately switches the color video signal of the first field of the color video signal reproduced twice by one field period, and the reproduced color video is determined from the output of the switching means. Since the signal is obtained, it is possible to almost eliminate vibrations in moving images that are perceived as flicker, and it is also possible to repeatedly reproduce two fields of the same signal for only the carrier color signal in the same way as before. It has the advantage that it is possible to obtain a reproduced color video signal with less brightness flicker and can be constructed at low cost.

[Brief explanation of the drawing]

1A and 1B are diagrams each showing an example of the relationship between the field number and playback order of the playback video signal of a conventional device, and FIG. 2 is a diagram showing the field number and playback order of the playback video signal for explaining the present invention. FIGS. 3A and 3B are a plan view and a front view, respectively, showing the relationship between the rotary head and the drum in an embodiment of the present invention, and FIG. 4 is an embodiment of the present invention. Figure 5 is a block diagram of a device for obtaining assumptions to solve problems; Figure 6 is a block diagram of the first embodiment of the present invention. , FIG. 7 is a block diagram of the second embodiment of the present invention, and FIG. 8 is a block diagram of the third embodiment of the present invention. 6.8...Video detection circuit, 7,9,59,60
......Synchronization separation circuit, 10, 35, 43...
...Phase comparator, 11...Variable delay line control circuit, 12,18°21.56...Variable delay line, 1
6, 23, 26... Luminance signal detection circuit, 17,
19,20,22゜25.27,47,51.55...
...Low pass filter, 34...Crystal oscillator,
30, 37, 53, 58... Frequency converter, 5
2...Oscillator, ESWl. ESW2, ESW4...Electronic switch.

Claims (1)

[Scope of utility model registration request] In an apparatus for reproducing a color video signal recorded by sequentially forming a video track for one field on a recording medium every other field, the same video track is
a first reproducing means for repeatedly reproducing the video track twice for each field period; a second reproducing means for reproducing the video track every other field; and the same field played twice by the first reproducing means. adding means for respectively adding together the luminance signal of the latter one field and the color video signal reproduced one track ahead of the luminance signal by the second reproduction means; The method comprises means for alternately switching the color video signal of the first field of the twice reproduced color video signal for each field period, and the reproduced color video signal is obtained from the output of the switching means. A video signal reproducing device characterized by: