JPH09107562A - Method for converting two-dimensional video image into three-dimensional video image and three-dimensional video signal generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the 3-dimensional video signal generator in which an existing 2-dimensional video software is converted into a 3-dimensional video software in a simulating way without the need for a special eyeglass and without production of a 3-dimensional exclusive video image software. SOLUTION: A 2-dimensional video signal from an input terminal 1 is outputted as it is and the other 2-dimensional video signal is delayed in a field memory 5 by a prescribed field and a 3-dimensional video signal is outputted at output terminals 3, 4 in a simulating way. Furthermore, part of the 2-dimensional video signal is given to a motion vector detection circuit 7, from which a motion vector is detected and a CPU 8 controls a memory control circuit 6 depending on the quantity of the motion vector. Thus, the delay of the field memory 5 is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for converting a 2D image into a 3D image for generating 3D image software having parallax from the 2D image software and a 3D image signal generating device.

[0002]

2. Description of the Related Art Conventionally, in order to obtain a three-dimensional image having left and right parallax, a two-dimensional stereoscopic video signal (three-dimensional video signal) obtained by imaging with a dedicated stereoscopic imaging device is recorded by a stereoscopic VTR or the like. It was necessary to reproduce this and reproduce it on a dedicated three-dimensional display or the like.

Therefore, according to this method, existing two-dimensional video software cannot be used, and new three-dimensional video software has to be produced. This has caused an increase in the cost of a stereoscopic image reproduction system. .

On the other hand, there is a method of obtaining a three-dimensional effect by using the relationship between the perceived time and the stimulus intensity (Pulrich effect) in which the light stimulus which is simultaneously turned on feels that the brighter one is lit faster. That is, when there is an object moving in the horizontal direction in a normal video signal (two-dimensional video signal), a stereoscopic effect is generated when the object is observed with glasses having different transmittances on the left and right.

[0005]

However, the above method has a disadvantage that special glasses are required.
The present invention solves the above-mentioned drawbacks, and converts existing 2D video software into 3D video software without the need for special glasses and without producing 3D-only video software. And a 3D video software conversion method.

[0006]

The present invention is a three-dimensional video software conversion method which uses two-dimensional video software and creates three-dimensional video software having a right-eye video and a left-eye video from the two-dimensional video software.

Further, according to the present invention, the right-eye image and the left-eye image are selected by temporarily storing the two-dimensional image software in the memory and selecting the number of delay fields read from the memory according to the speed of the moving portion of the two-dimensional image software. Is a 3D image software conversion method for creating 3D image software having

[0008]

With the above-described means, parallax occurs in the two-dimensional video software due to the relative addition of the time difference or the luminance difference, and the two-dimensional video software is pseudo-converted into the right-eye video signal and the left-eye video signal. The time difference or the brightness difference is controlled according to the amount of movement of the two-dimensional video signal.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the principle of the present invention will be described. FIG.
In a video scene in which the background does not change and the subject moves from left to right as shown in A, when a certain time difference is provided between the reproduced right-eye video and left-eye video as shown in FIG. The position is different by the amount of movement, and this becomes parallax as shown in FIG. The numbers in FIGS. 1B and 1C represent field numbers.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram of a first embodiment of a 3D video software conversion system using the 3D video software conversion method of the present invention, and is a 2D / 3D compatible VTR 11.
2D video software played back on the 3
After being artificially converted into three-dimensional video software by the three-dimensional video software conversion device 12, it is supplied to the 3D monitor 13. If this 3D monitor is a lenticular type display without glasses as described in Japanese Patent Application Laid-Open No. 3-65943, it is possible to use a 3D monitor having a three-dimensional effect even with a two-dimensional video signal without using glasses. A dimensional image can be reproduced in a pseudo manner.

FIG. 3 is a schematic block diagram of the three-dimensional video software conversion device in FIG. 2, and a two-dimensional video signal is input to the input terminal 1. One of the two-dimensional video signals is supplied to the video switching circuit 2.

The other of the two-dimensional video signals is supplied to the field memory 5. The field memory 5 is variably controlled by the memory control circuit 6 in a field unit from a delay amount of 0 to a maximum of 60 fields (about 1 second in the NTSC system). The variable unit may be a small unit of one field or less.

The field memory output is supplied to the video switching circuit 2. This video switching circuit 2
The outputs are connected to an output terminal 3 for outputting a left-eye video signal L and an output terminal 4 for outputting a right-eye video signal R, respectively, and are controlled so that the output state is switched according to the direction of movement of the subject.

The other of the two-dimensional video signals is supplied to the motion vector detecting circuit 7 and, after detecting a motion vector corresponding to the motion between fields, is supplied to the CPU 8.
The CPU 8 extracts a horizontal component from the motion vector and controls the memory control circuit 6 accordingly. That is, when the motion of the subject is large and the motion vector is large, the delay amount of the field memory 5 is controlled to be small. When the motion of the subject is small or the motion vector is small as in slow motion reproduction, the delay amount is reduced. It is controlled to increase. The number of delay fields in the field memory is up to 60 fields, which is equivalent to one second in the NTSC system, which is almost equivalent to a normal video scene. A large-capacity memory of 60 fields or more may be used. Also, for slow-motion playback at very low speed,
What is necessary is just to delay by 00 fields.

Further, the CPU 8 uses the video switching circuit so that the two-dimensional video signal is the left-eye video signal when the direction of the motion vector is from left to right, and the delayed two-dimensional video signal is the left-eye video signal when the motion vector is in the opposite direction. Control 2

Therefore, in a scene in which a subject moves horizontally in a two-dimensional video signal, parallax occurs depending on the speed of movement. The output terminals 3 and 4
If the left and right video signals are supplied to a lenticular type display without glasses as described in Japanese Patent Application Laid-Open No. 3-65943, for example, a stereoscopic image having a partially three-dimensional appearance is pseudo even if it is a two-dimensional video signal. Can be reproduced.

Next, the above three-dimensional image software conversion device
An embodiment in the case of using SI will be described with reference to FIG. The two-dimensional video signal is first separated into a luminance signal Y and color difference signals RY and BY by a YC separation circuit 30, and A / D converted by A / D conversion circuits 31 and 32. The A / D converted signal is input to the 2D / 3D conversion LSI 33.
The luminance signal Y input to the LSI 33 is clamped by the clamp circuit 331 and supplied to the motion vector detection circuit 7, the pass selector S1, the interpolation selector S2, and the external field memory 5. The field memory 5 includes MO1 to MO3 to which data of odd fields are written and ME1 to ME to which data of even fields are written.
3 are connected in parallel, and writing and reading are controlled by the memory control circuit 332.

The motion vector detected by the motion vector detection circuit 7 is supplied to the CPU 8, which in turn controls the memory control circuit 332 based on the horizontal component of the motion vector.
Control.

On the other hand, the color difference signals R-Y and B-Y are clamped by the clamp circuit 333 and converted into a dot-sequential signal in which R-Y and B-Y alternately appear in the dot cycle. This color difference signal is supplied to the pass selector S3, the interpolation selector S4, and the field memory 5.

A total of 12 bits including a luminance signal of 8 bits and a color difference signal of 4 bits are supplied to each of the field memories. Each of the luminance signal outputs YO of the field memories MO1 to MO3 and each of the luminance signal outputs YE of the field memories ME1 to ME3 become one and input to each input terminal of the pass selector S1 and the interpolation selector S2. Each of the color difference signal outputs CO of the field memories MO1 to MO3 and each of the color difference signal outputs CE of the field memories ME1 to ME3 become one and are input to the input terminals of the pass selector S3 and the interpolation selector S4.

Next, the output of the interpolation selector S2 is supplied to the line memory LM1 and the interpolation circuit 334. The luminance signal delayed by 1H (H is a horizontal scanning period) in the line memory is input to the line / field selector S5 together with the luminance signals YO and YE. The output of the selector S5 is supplied to the interpolation circuit 334. This interpolation circuit 33
4 is composed of two coefficient units and one adder for adding these outputs. The interpolation coefficient K is included in the coefficient unit on the selector S2 side, and the interpolation coefficient ( 1-K) is added. The output of the interpolation circuit 334 and the output of the passage selector S1 are respectively the right output selector S
6 and the left output selector S7. The outputs of the selectors S6 and S7 are the first and second parallax adjustment memories SM.
1, SM2 is supplied. This parallax adjustment memory is capable of adjusting the horizontal read position of the output image independently for left and right by ± 48 pixels, and adjusts the amount of parallax arbitrarily to adjust the sense of depth.

The color difference signal processing circuits after the pass selector S3 and the interpolation selector S4 are the same as the luminance signal, and the line memory LM2, the line / field selector S8, the interpolation circuit 334, the right output selector S9, and the left output selector. S10, third and fourth parallax adjustment memory SM3,
SM4 is arranged.

A sync signal is added to the outputs of the first to fourth parallax adjustment memories by a sync signal adding circuit 336 to form a right-eye luminance signal YR and a left-eye luminance signal YL. The signals are encoded into the right-eye color signal CR and the left-eye color signal CL, which are output from the LSI. Among these outputs, YR and CR are A / D converted by a D / A conversion circuit 34 and synthesized by a YC synthesis circuit 35 to become a right-eye video signal R. YL and CL are D
D / A conversion is performed by the / A conversion circuit 36, and the YC synthesis circuit 37
Are combined into a left-eye video signal L.

Next, the operation of the above-mentioned three-dimensional video software conversion device will be described with reference to FIGS. First, the operation of the field memory 5 will be described. As shown in FIG. 5, the write pulses from the memory control circuit 332 are sequentially written into each of the field memories MO1 to ME3 for each field, and the writing is completed in all the field memories after six fields. In this state, the data from the first field to the sixth field are written in each field memory without duplication. Each field memory stores data contents until a write pulse is input. Then, when a write pulse is supplied to MO1 in the seventh field, the data content is rewritten to that of the seventh feed. Thus MO1
ＭＥME3 is cyclically rewritten at different timings every six fields.

On the other hand, the read control is performed as follows. The memory control circuit 332 selects a field memory storing data of a required field based on the number of delay fields determined by the CPU 8 according to the motion of an image, and outputs a read pulse. For example, when the number of delay fields is two and the current field is O3, a read pulse is supplied to MO2 in which data O2 two fields before is stored, and the data O2 becomes MO3.
2 is read.

In the present embodiment, since field memories are connected in parallel and writing is performed to only one of the six at a time, the field memories are connected in series to write to all field memories for each field. Power consumption can be significantly reduced compared to the method of performing.

Next, the operation of each selector will be described for each mode. Note that the following description is for the luminance signal processing circuit, but the color difference signal processing circuit operates in exactly the same manner. All selectors perform a selection operation in response to a control signal from the CPU 8.

The video signal processing circuit including each selector basically has an intra-field interpolation mode and an inter-field interpolation mode. These may be selected manually, but they are automatically selected according to the magnitude of the motion vector. You can also do it. That is, each selector is controlled so as to select the intra-field interpolation mode when the motion vector is smaller than the predetermined threshold value, and to select the inter-field interpolation mode when the motion vector is larger than the predetermined threshold value. When performing further editing, the editing mode is selected.

The operation in each mode will be described below. (Intra-field interpolation mode) In this mode, there are a field in which interpolation is not performed and a field in which intra-field interpolation is performed. That is, when one of the main and sub video signals is an odd field and the other is an even field, there is a vertical shift between the left and right screens when reproduced as it is. An image interpolated vertically in the field based on the delayed image is used. If both the main and sub-picture signals are odd or even fields, no interpolation is necessary.

In this mode, the pass selector S1 always selects the luminance signal Y from the clamp circuit 331 and supplies the undelayed data to the left output selector S6 and the right output selector S7. On the other hand, the interpolation selector S
2 selects one of Y, YO, and YE according to the number of delay fields, as shown in FIG. Further, the field / line selector S5 always selects the output of the line memory LM1.

Accordingly, the interpolation circuit 334 receives the output of the interpolation selector S2 and the output delayed by 1H. The interpolation coefficient of the interpolation circuit 334 is set by the CPU 8. If the output of the interpolation selector S2 is an odd or even field with respect to the output of the selector S1, K = 1, and no interpolation is performed. If the other field is an even field, K = 0.5, and intra-field interpolation is performed.

Accordingly, the interpolated delay output obtained at the output of the interpolation circuit 334 is the selector S6.
And S7. These two selectors constitute the video switching circuit 2 shown in FIG. 3, and complementarily select which of the left and right outputs the signal of the current field and the delay signal depending on the direction of the motion vector.

Then, these outputs are supplied to the parallax adjustment memories SM1 and SM2, respectively, and the parallax amount is adjusted. (Inter-Field Interpolation Mode) In this mode, there are fields where no interpolation is performed, fields where intra-field interpolation is performed, and fields where inter-field interpolation is performed.

Inter-field interpolation is applied to the field immediately after the number of delay fields has changed. That is, when the number of the delayed fields changes, the motion of the delayed image becomes less smooth than that of the image of the current field, so that the motion is smoothed by inter-field interpolation. In other fields, the same operation as in the intra-field interpolation mode is performed.

Even in this mode, the passage selector S1
Always selects the output of the clamp circuit 331. On the other hand, the interpolation selector S2 selects one of Y, YO, and YE as shown in FIG. The line / field selector S5 has YE, YO, the line memory LM1 output LM.
Select one of Interpolation coefficient K of interpolation circuit 334
Is K = 1 if the output of the interpolation selector S2 is both odd or even with respect to the output of the selector S1.
And no interpolation is performed. K in other fields
= 0.5, but if one is an odd field and the other is an even field (E2, E4, E7, E9), intra-field interpolation is performed, and the fields (O2, O3, O4, O5, O7, O8,
In O9), inter-field interpolation is performed.

When intra-field interpolation is performed, the selector S2 selects Y0 and the selector S5 selects LM. When the inter-field interpolation is performed, the selectors S2 and S5 select either YO or YE, respectively, except when converting the number of delay fields from 0 to 1. That is, adjacent fields are selected and supplied to the interpolation circuit 334. Therefore, the output of the interpolation circuit becomes an average of both outputs, and the motion of the image is smoothed.

The operations of the selectors S6 and S7 are the same as the intra-field interpolation mode. (Edit Mode) In the above two modes, the outputs of the selectors S6 and S7 complementarily change the original signal and the delayed signal complementarily depending on the direction of the motion vector. here,
When comparing the original signal and the non-delayed signal (for example, the current field and the output of the interpolation circuit in FIG. 5), the regularity of the field order of the delayed signal in the time axis direction is impaired. In particular, in the process of decreasing the number of delay fields, certain fields are thinned out. For this reason, the delay signal impairs the reproducibility of the original image. Therefore, regardless of which of the left and right outputs is selected, the delay signal is mixed, and it is not preferable to use this output for editing.

That is, at the time of editing, at least one of the outputs must have a signal having the same field order as the original image. When operating the LSI of this embodiment in this editing mode, the output terminal of the field memory and the LS
It is necessary to provide an external selector between the I and the memory input terminal, and it is desirable to increase the number of field memories to about thirteen.

In this mode, the selectors S6 and S7 are fixed and the output of the pass selector S1 is always R output. The selector S1 is always fixed to the input YO, and the selector S2 is fixed to the input YE. The external selector selects a memory output for obtaining a signal of a fixed delay field number for the selector S1 and supplies it to the selector S1, and selects a memory output for obtaining a signal of a variable delay field number according to the movement. And supplies it to the selector S2.

By doing this, when editing,
A signal having the same field order as the original image can always be obtained at one output terminal. Note that the three-dimensional video software conversion device in the above-described embodiment generates a time difference in a two-dimensional video signal as a method for providing left and right parallax. However, if it is configured to generate a luminance difference instead of the time difference. ,
Stereoscopic vision is possible due to the Pulfrich effect.

FIG. 7 shows this embodiment. That is, in this embodiment, an attenuator 9 and a gain control circuit 10 for attenuating the luminance level between 0 db and -10 db are used in place of the field memory 5 and the memory control circuit 6. The attenuator and the gain control circuit are controlled based on the magnitude of the motion vector as in the embodiment of FIG.
That is, when the motion of the subject is large and the motion vector is large, the brightness attenuation of the attenuator 9 is controlled to be small. When the motion of the subject is small or the motion vector is small as in slow motion reproduction, the brightness attenuation is controlled. Is controlled to increase.

The attenuation amount of the attenuator is 0 to -10d.
In addition to b, when used for slower slow-motion playback, an attenuation of several tens of db may be provided. Further, a variable gain amplifier may be used instead of the attenuator.

Further, according to the present invention, even if the existing 2D image software is not converted into 3D image software, a 2D image signal output from a video camera or a CG production device in real time is converted into 3D in real time. It can also be applied when converting to a video signal.

Next, FIG. 8 shows a second embodiment of the three-dimensional video software conversion system to which the present invention is applied. This embodiment is an example in which the three-dimensional video software converter 12 is connected to the input terminal of the 3D monitor 13, and the input signal is compatible with either a two-dimensional video signal or a three-dimensional video signal. That is, 3D input terminals 14 and 15 to which a three-dimensional video signal is input and a 2D input terminal 16 to which a two-dimensional video signal is input are provided, and either one of the two-dimensional video signal or the three-dimensional video signal is input. Is done. Then, the three-dimensional video signals from the input terminals 14 and 15 are supplied to the 3D monitor 13 via the changeover switch S.

On the other hand, the two-dimensional video signal from the input terminal 16 is converted into a three-dimensional video signal by the three-dimensional video software converter 12 to be a 2-channel signal and supplied to the changeover switch S. The changeover switch S is automatically switched according to the type of the input signal. That is, the input three-dimensional video signals from the input terminals 14 and 15 are respectively input to the first video detection circuit 17 to detect the presence or absence of the video signal, and then the logical product of the detection outputs is supplied to the control circuit 19. . The input two-dimensional video signal from the input terminal 16 is input to the second video detection circuit 18 to detect the presence or absence of a video signal.

Then, in the control circuit 19, the output of the first video detection circuit is "present" and the output of the second video detection circuit is "
When "No", the changeover switch S is switched to the a side, and when the output of the first video detection circuit is "No" and the output of the second video detection circuit is "Yes", the switch is switched to the b side.

Therefore, in this embodiment, it is automatically determined whether the input signal is a 2D video signal or a 3D video signal, and when the 3D video signal is input, the 2D video signal is input as it is. Converted to 3D video signal and then 3D
It is supplied to the monitor 13.

Next, FIG. 9 shows a third embodiment of a three-dimensional video software conversion system to which the present invention is applied. This embodiment is an example in which a 3D video software converter 12 is connected to the output terminal of a 2D / 3D compatible VTR 11, and a 2D / 3D compatible VTR is connected.
TR11 has output terminals 20, 21 and a discrimination output terminal 22.
Is provided. The output terminal 20 has a low
The channel is output, and a two-dimensional video signal is output in the 2D mode. In addition, Rch is output to the output terminal 21 in the 3D mode, and nothing is output in the 2D mode. "H" in the 3D mode, 2D
In the mode, an “L” determination output is output. This discrimination output is created by a system controller (not shown) in the 2D / 3D compatible VTR 11 according to the mode, and controls the three-dimensional video software converter 12 and the changeover switch S.

That is, in the 3D mode, the changeover switch S is switched to the a side by the "H" discrimination signal, and in the 2D mode, the power of the three-dimensional image software converter 12 is turned on by the "L" discrimination signal. Together with the changeover switch S
Is switched to the b side, and the three-dimensional video signal converted by the three-dimensional video software converter 12 is output.

Next, FIG. 10 shows a fourth embodiment of a three-dimensional video software conversion system to which the present invention is applied. In this embodiment, the 3D video software converter 12 is connected to the output terminal of the 2D video camera 23.
2D / 3D compatible VTR with video camera 23 output
11 2D input terminal 24. In the 3D mode, the output of the 2D video camera 23 is converted into a three-dimensional video signal by the three-dimensional video software
And 26. The 2D / 3D compatible VTR 11
Selects the input from the input terminal 24 when recording in the 2D mode, and selects the input terminal 2 when recording in the 3D mode.
Select and record the inputs from 5, 26.

In the embodiments of FIGS. 8 to 10, the 3D image software converter 12 and the changeover switch S may be built in the 3D monitor 13, the 2D / 3D compatible VTR 11 or the 2D video camera 23, respectively.

[0052]

As described above, according to the present invention, existing two-dimensional video software can be pseudo-converted into three-dimensional video software, so that existing two-dimensional video software can be converted without producing new three-dimensional video software. Since software can be used, a significant cost reduction can be achieved.

By determining whether the input video soft signal is two-dimensional or three-dimensional, the two-dimensional video soft signal can be automatically converted into a three-dimensional video soft signal.
In addition, by performing intra-field interpolation processing on the main video signal and / or the sub video signal, it is possible to obtain a three-dimensional image in which the left and right images are not displaced vertically and are easy to see.

Also, by performing inter-field interpolation processing on the main video signal and / or the sub video signal, it is possible to obtain a three-dimensional image with smooth motion.

[Brief description of the drawings]

FIG. 1 is a diagram showing the principle of a three-dimensional video software conversion method according to the present invention.

FIG. 2 is a block diagram of a 3D video software conversion system according to an embodiment of the present invention.

FIG. 3 is a schematic block diagram of a three-dimensional video software conversion device according to the present embodiment.

FIG. 4 is a detailed block diagram of a three-dimensional video software conversion device according to the present embodiment.

FIG. 5 is an explanatory diagram of an operation in the intra-field interpolation mode of FIG. 4;

FIG. 6 is an explanatory diagram of an operation in the inter-field interpolation mode of FIG. 4;

FIG. 7 is a schematic block diagram showing another embodiment of the three-dimensional video software conversion device.

FIG. 8 is a block diagram of a 3D video software conversion system according to a second embodiment of the present invention.

FIG. 9 is a block diagram of a 3D video software conversion system according to a third embodiment of the present invention.

FIG. 10 is a block diagram of a 3D video software conversion system according to a fourth embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 5 field memory 6 memory control circuit 7 motion vector detection circuit 8 CPU 11 2D / 3D compatible VTR 12 3D video software conversion device 13 3D monitor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigewa Minechika 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Akihiro Maenaka Keihanhondori, Moriguchi-shi, Osaka 2-5-5 Sanyo Electric Co., Ltd. (72) Inventor Toshiya Iinuma Keihan Hon-dori, Moriguchi-shi, Osaka 2-5-5 Sanyo Electric Co., Ltd. (72) Inventor Yukio Mori Keihan, Moriguchi-shi, Osaka Hon-dori 2-5-5 Sanyo Electric Co., Ltd.

Claims (3)

[Claims] 1. A main video signal serving as a reference and a sub video signal delayed from the main video signal are generated from a two-dimensional video signal, and one of the main video signal and the sub video signal is a left-eye video signal, In the conversion method of outputting the other as the right-eye video signal, the delay amount for detecting the magnitude and direction of the horizontal movement of the video from the two-dimensional video signal and generating the sub-video signal based on the magnitude of the movement. And controlling the video switching means for inputting the main and sub video signals according to the direction of the movement to determine which of the main and sub video signals should be the left-eye video signal or the right-eye video signal. A method for converting a characteristic 2D image into a 3D image. 2. A main video signal serving as a reference and a sub video signal having a luminance difference from the main video signal are generated from a 2D video signal, and one of the main video signal and the sub video signal is a left-eye video signal. In the conversion method of outputting the other as the right-eye video signal, the luminance for detecting the magnitude and direction of the horizontal movement of the video from the two-dimensional video signal and generating the sub-video signal based on the magnitude of the movement. The amount of difference is determined, and the video switching means for inputting the main and sub video signals is controlled according to the direction of the movement to determine which of the main and sub video signals is the left-eye video signal or the right-eye video signal. A method for converting a 2D image into a 3D image. 3. A delay means for delaying an input video signal, the two-dimensional video signal as a main video signal, and the video signal delayed by the delay means as a sub video signal, respectively, and the main and sub video signals are inputted. An image switching unit that outputs one of them as a left-eye image signal and the other as a right-eye image signal, a motion detection unit that detects the magnitude and direction of the horizontal movement of the image from the two-dimensional image signal, and the motion detection. A three-dimensional video signal, comprising: a control means for determining a delay amount by the delay means according to the magnitude of the movement detected by the means, and controlling switching of the video switching means according to the direction of the movement. Generator.