CA1114056A

CA1114056A - Television picture special effect system using digital memory techniques

Info

Publication number: CA1114056A
Application number: CA288,013A
Authority: CA
Inventors: Ryosuke Takahashi; Masao Inaba; Masashi Onosato
Original assignee: Tokyo Broadcasting System Inc TBS; Nippon Electric Co Ltd
Current assignee: NEC Corp; Tokyo Broadcasting System Inc TBS
Priority date: 1976-10-05
Filing date: 1977-10-03
Publication date: 1981-12-08
Also published as: DE2744815A1; US4178613A; AU2938977A; JPS5345120A; DE2744815B2; AU517189B2; GB1551463A; DE2744815C3; JPS6211549B2

Abstract

Abstract of the Disclosure When combining two video signals on a television screen it has been common practice to extract from the two video signals only those portions required and display those portions together on the screen. A problem arises if a desired portion of one video signal coincides with a desired portion of the other video signal because, in that case, only one of the two portions can be displayed. The present invention permits this problem to be overcome without changing the camera position or angle or moving the subjects or scenes being shot. One of the video signals is operated on in a special effect device where it is divided into portions shifted apart from each other according to an external control signal. The actual configuration and spacing of the portions can be varied by varying the control signal to en-sure that the various portions of the one video signal do not coincide with desired portions of the other video signal.

Description

~14~6 This invention relates to a television picture special effect system or a video processing system designed to produce special effects on the picture as displayed on a television screen by the use of digital memory techniques.
When two video signals A and B are desired to be displayed simul-taneously on a single television screen, it has been common practice to ex-tract from the signals A and B only those portions required and display such signal portions on the same screen to form a single picture thereon. In this practice, if any wanted portions of respective signals A and B coincide or lie in the same position in the picture frame, only one or the other of the two signal portions can be displayed on the screen. This situation can be readily overcome, if either one of two signals A and B is produced by a local television camera, by shifting the scene or subject being picked up or changing the camera angle or the position in which the camera is set. Gn the other hand, if both signals A and B are fixed signals such as the ones from a video tape recorder, a film projection, a telop, or a fixed camera, either one of the two signals must be omitted.
It is, therefore, an object of the present invention to provide a television picture special effect system which makes it possible to display any desired portion of a video signal in any desired position on the tele-vision screen without necessitating any operation at the source of signal.
According to the present invention, there is provided a special effect system for a television signal, said television signal including horizontal and vertical synchronizing signals, said system comprising: memory means responsive to a write-in address signal for storing said television signal; means responsive to said horizontal and vertical synchronizing signals for producing said write-in address signal; means for producing a read-out address signal, the stored television signal being read out in response to said read-out address signal; means responsive to a control signal for control-ling at least one o~ said write-in and read-out address signals, said control-ling means including means responsive to said control signal for producing a control width signal representing the width of said control signal, and means ,~1 ~ ............. , ., , - : . . :
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With the picture special effect device of the present invention, any desired portion of a video signal can be displayed on the television screen in any desired position therein without necessitating any particular operation at the source of input video signal, since the input video signal is divided into portions shifted apart from each other in the picture frame in accordance with an external control signal.
The features and advantages of the present invention will be under-stood from the following detailed description of a preferred embodiment ofthe present invention in conjunction with the accompanying drawings, wherein:
Figure 1 is a schematic block diagram of a video mixing system according to a preferred embodiment of the present invention;
Figures 2(1), 2(2) and 2(3) diagrammatically illustrate several special effects obtainable on the television screen in accordance with the present invention;
Pigure 3 is a block diagram of special effect device used in the preferred embodiment shown in Figure l; and ~ igures 4(1)-4(4) shows examples of the picture obtained by the

2~ special effect device shown in Figure 3.
Referring to Figure 1, a video mixing system 10 includes a picture special effect device 16 embodying the present invention. As shown, the -~
system 10 includes a television camera 12 which is used to take the picture on a chroma-key screen 11 to produce a video signal A and another television camera 14 used to take the picture on another screen 13 to produce a video signal B. A special effect signal generator 15 produces a special effect signal C as an external control signal to be fed to the special effect de- i vice 16 which produces a video signal D as a split version of video signal A

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from camera 12 in accordance with the special effect signal C. A chroma-key signal generator 17 produces a chroma-key signal upon reception of the video signal D from the special effect device 16. A mixing keyer amplifier 18 receives the video signals B and D and the chroma-key signal from generator 17 and produces a composite video signal E as a desired combination of video signals A and B.
The special effect signal C in the embodiment illustrated is a waveform signal, for example, as indicated in Figure 1 but may also take :
any of other forms as illustrated in Figures 2~2). In this case, where the input video signal A is as illustrated in Figures 2(1), different forms of video signal D as illustrated in Figure 2(3) are obtainable through the special effect device 16 as a split version of the input video signal A in accordance with the respective waveform signals of Figure 2(2), employed as the special effect signal C.
A detailed description of the picture special effect device 16 will now be made with reference to the block diagram of Figure 3.
As illustrated, the device 16 includes an A-D converter 20 for converting the input video signal A to a digital video signal, a memory 30 for storing the digital video signal and a D-A converter for converting the digital video signal as read out from the memory 30 into a corresponding analog video signal D. A write-in address signal generator 50 produces write-in address signals specifying the address in the memory 30 at which the digital video signal is to be written in, horizontal and vertical read-out address signal generators 60 and 70, respectively, produce a horizontal : and a vertical read-out address signal, respectively, specifying the horizon- ~ .
tal and vertical read-out addresses in the memory 30 at which video inform-ation stored therein is to be read out. Horizontal and vertical read-out address controllers 80 and 90 control, respectively, the horizontal and ~: vertical read-out address signals in accordance with the special effect signal C.

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In operation, the input video signal A is converted at the A-D
converter 20 into the digital video signal which is written in the memory 30 under control of write-in address signals ~hich are fed to the memory 30 from the write-in address signal generator 50. As indicated, the signal generator 50 is supplied with remote synchronizing signals, including a horizontal synchronizing signal, a vertical synchronizing signal and a sub-carrier of 3.58MHz, which are in synchronism with the input signal A.
On the other hand, read-out synchronizing signals, for example, local synchronizing signals including a horizontal and a vertical sync signal and a subcarrier which are in synchronism with the video signal B, are supplied to the horizontal and vertical read-out address signal generators 60 and 70. The read-out address signal generators 60 and 70 produce a hori-zontal and a vertical read-out address signal, respectively, in accordance with the local synchronizing signals. The read-out address signals are fed through the read-out address controllers 80 and 90 to the memory 30 whereby the read-out address in the memory is controlled under the effect of the special effect signal C, which is fed to the read-out address controllers 80 and 90 as an external control signal from the special effect signal generator 15 ~Figure 1). If no special effect signal C is fed to the read-out address controllers 80 and 90, the read-out address signals are fed to the memory 30 without being controlled in any manner by the address controllers 80 and 90 so that the digital video signal stored in the memory 30 is read out in synchronism with the local synchronizing signals without being split in the picture frame. The read-out digital video signal is converted by the D-A
converter 40 into a corresponding analog video signal D. The operation of the device 16 without the read-out address controllers 80 and 90 is similar to that of the systems described in the United States Patent Nos. 3,909,839 entitled "PHASE LOCKING SYSTEM FOR TELE~ISION SIGNALS USING DIGITAL MEMORY
TECHNIQUES" and which issued on September 30, 1975 and 4,007,486 entitled "PHASE LOCKING SYSTEM FOR TELEVISION SIGNALS USING A DIGITAL MEMORY TECHN~QUE"

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~14q~56 and which issued on February 8, 1977 both assigned to the assignee of the present invention.
Now, if the special effect signal C (referred to as a key signal hereinafter) is applied from the special effect signal generator 15 to a key signal width calculator circuit 81, which forms part of the horizontal read-out address controller 80, the calculator circuit 81 detects the values of the key signal C at its beginning and end in reference to the value of the horizontal adress signal from the address signal generator 60 to calcul-ate the width of the horizontal key signal for each period of horizontal scan in subcarrier frequency units. The full horizontal width signal from the calculator circuit 81, representing the width of the horizontal key signal, is fed to a value switching unit 83 directly and through a divider 82 which, reducing the value of the width signal to half, produces a half horizontal width signal. The value switching unit 83 is supplied with a value switching signal F and, under the effect of this signal, whether the output signal of the switching unit is of full or half horizontal width is determined. In other words, the switching unit 83 is controlled by the switching signal F so as to output a half horizontal width signal in the case where the picture on the television screen is to be split into portions shifted to the right and left, respectively, while outputting a full horizon-tal width signal in the case where the picture is to be shifted laterally.
The selected horizontal width signal from the value switching unit 83 is fed through a polarity inverter 84 to a horizontal address adder 85 in order to be added with the read-out horizontal address signal. The polarity inverter 84 outputs either the horizontal width signal intact as fed thereto or an inverted horizontal width signal representing the complement of the signal input to the inverter 84, in accordance with a polarity control signal G
supplied from a value comparator 86.
The polarity control signal G is obtained in the following manner.
The key signal C and the read-out horizontal address signal are fed to a key .. . ~
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signal central value calculator 87 where the central value of the key signal C in reference to a predetermined point in the horizontal scan period is calculated in subcarrier frequency units for each period of horizontal scan. The calculator output signal, representing the central value of the horizontal key signal, is fed to the value comparator 86, which is also fed with the read-out horizontal address signal and a control signal H. The comparator 86 produces, in response to the control signal H, polarity control signal G each time the value of the read-out horizontal address signal co-incides with that of the horizontal central value signal.
As long as no polarity control signal G is fed to the polarity inverter 84 and the horizontal width signal is passed therethrough intact to the horizontal address adder 85 to be added with the horizontal address signal, i.e., till the read-out address signal coincides with the central signal, a picture is obtained on the television screen in a position shifted to the left. In contrast, when polarity control signal G is fed to the polarity inverter, the inverted horizontal width signal output therefrom is added with the horizontal address signal i.e., the horizontal width signal is subtracted from the address signal whereby a picture is obtained on the television screen in a position shifted to the right. The added address signal supplied from the adder 85 is supplied through a switcher 88 to the memory 30. The switcher 88 inhibits the transfer of the added address signal only when the key signal C is applied thereto, whereby the stored signal is not read out during the period of the key signal C.
Thus, the picture is displayed on the television screen in a state shifted horizontally in opposite directions to the center of the key signal, as shown in Figures 4(1) and 4(2). In case where the half width signal is selected by the switcher 83, the split picture as shown in Figure 4(1) is obtained. When the full width signal is selected, the shifted picture is . .
obtained as shown in Figure 4(2).

In the case where no control signal H is applied to the comparator '' ~

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86, the signal G is not produced and the width signal selected by the switcher 83 is directly applied to the adder 85. Therefore, the pictures as shown in Figures 4(3) and 4(4) are obtained in accordance with the half- and the full-width signals, respectively.
Description has been made above of the operation required to shift horizontally the pictures as displayed on the television screen. In cases where picture shifting is desired only in horizontal direction, the memory 30 needs to have a capacity sufficient only to cover two successive periods of horizontal scan. In order to shift vertically the picture on the television screen, the vertical read-out address controller 90 is operated and, in this case, the memory 30 must have a capacity sufficient to cover at least one field of scan. The vertical read-out address controller 90 functions in substantially the same manner as the horizontal read-out address controller 80 except for the period of operation. Thus, whereas the horizontal read-out address controller 80 operates periodically at the period of the horizon-tal scan in subcarrier frequency units, the vertical read-out address con-troller 90 operates periodically at the period of field can in units of the period of horizontal scan. Description will be made below of the vertical address controller 90 in detail.
A key signal vertical detector 99 is provided to decide that the key signal C fed thereto is a vertical key signal only when the key signal C extends over the entire length of the period of horizontal scan and to feed such key signal to a vertical width calculator 91 and a vertical central value calculator 97. Then, the vertical width calculator 91, detecting the values of the key signal at its beginning and end, calculates the width of the vertical key signal for each period of vertical scan in units of the horizontal scan. The full vertical width signal, representing the width of the vertical key signal, i.e., its vertical width on the picture screen or frame, is fed to a value switching unit 93 directly and through a divider 92 which, reducing the value of the width signal to half, produces a half vertical width signal. Whether the output of the switching unit 93 is a full or a half vertical width signal is determined by the value switching si~nal F, which is fed to the value switching unit 93. In other words, the switching unit 93 is controlled by the value switching signal F so as to output the half vertical width signal if the picture on the television screen is to be shifted vertically and to output the full vertical width signal if the picture is to be shifted vertically only in one direction.
The vertical width signal thus selected by the value switching unit 93 is fed through a polarity inverter 94 to a vertical address adder 95 to be added with the read-out vertical address signal. The polarity inverter 94 selectively outputs either the vertical width signal as input thereto or its complement or inverted form in accordance with a polarity control -signal I supplied from a value comparator 96.
The polarity control signal I is formed in the following manner.
The key signal C and the read-out vertical address signal are fed to the key signal central value calculator 97, which calculates the central value of the key signal in units of the value of horizontal scan period for each period of vertical scan with reference to a predetermined point in the vertical scan period. The vertical central value signal is fed to the value comparator 96, which is also fed with the read-out vertical address signal.
The comparator 96 produces the polarity control signal I each time the value of the vertical address signal coincides with that of the vertical control value signal.
As long as no polarity control signal I is fed to the polarity inverter 94 and the vertical width signal is passed therethrough intact to the vertical address adder 95 to be added with the vertical address signal, a picture is obtainable on the television screen in a position shifted upward.
In contrast, when polarity control signal I is fed to the polarity inverter 94 and the inverted vertical width signal output therefrom is added with the vertical address signal, a picture is obtained on the television screen in a .

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position shifted downward. In this manner, eventually the picture is dis-played on the television screen in a state divided in*o portions shifted vertically in opposite directions to the center of the vertical key signal.
It is noted that the vertical address controller derives similar effects to the horizontal address controller 80 except for the scanning direction.
In the above embodiment, the switchers 88 and 98 are provided for inhibiting the added address signals for the periods of the key signals.
~lowever, these switchers 88 and 89 may be dispensed with. In such a modification, with the switcher 88 omitted, the output signal D from the special effect device 16 includes a signal portion as shown in dotted lines -in Figure 4(1) or 4(3~. The signal portion may be cancelled by the process in the mixing keyer amplifier 18.
Though an embodiment of the present invention has been described in which address control is effected on the read-out side, it will be apparent to those skilled in the art that the same results can also be ob-tained by controlling the write-in address.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A special effect system for a television signal, said television signal including horizontal and vertical synchronizing signals, said system comprising: memory means responsive to a write-in address signal for storing said television signal; means responsive to said horizontal and vertical synchronizing signals for producing said write-in address signal; means for producing a read-out address signal, the stored television signal being read out in response to said read-out address signal; means responsive to a control signal for controlling at least one of said write-in and read-out address signals, said controlling means including means responsive to said control signal for producing a control width signal representing the width of said control signal, and means for adding said control width signal with at least one of said address signals.

2. A special effect system as claimed in claim 1 wherein said control width signal producing means includes a first generator for producing a full control width signal representing the width of said control signal, and a second generator responsive to said full control width signal for producing a half control width signal representing a half of the width of said control signal.

3. A special effects system in accordance with claim 2, wherein said address signals include both horizontal and vertical address signals and means associated with said horizontal address signals for calculating the width of a horizontal control signal and associated with said vertical address signals for calculating the width of a vertical control signal.

4. A special effects system in accordance with claim 3, wherein said calculating means includes means for reducing the width of said horizontal and vertical control signals from a full width to a half width.

5. A special effects system in accordance with claim 4 further includ-ing means responsive to the full width horizontal control signal for shift-ing laterally on a television screen a displayed television picture and responsive to the half width horizontal control signal for splitting into portions the displayed television picture and for shifting the portions right and left, respectively from each other, on the television screen.

6. A special effects system in accordance with claim 5, further including means responsive to the full width vertical control signal for shifting vertically, on the television screen, a displayed television picture and responsive to the half width vertical control signal for splitting into portions the displayed television picture and for shifting the portions, up and down respectively from each other, on the television screen.

7. A special effects system in accordance with claim 2, wherein said controlling means further includes means responsive to said control signal for detecting a midpoint in time of said control signal in each scanning period, and means responsive to said detecting means for inverting said half control width signal in value to produce an inverted half control width signal complementary to said half control width signal, whereby said inverted half control width signal is added to at least one of said address signals after the detection of said midpoint.

8. A special effects system in accordance with claim 7 wherein said detecting means includes means for calculating a midpoint value of said control signal in reference to a predetermined point in the scanning period, and means for comparing said midpoint value with at least one of said address signals to produce a midpoint pulse when said address signals are coincident with said midpoint value.

9. A special effects system in accordance with claim 7, wherein said controlling means further includes means for selectively applying said full and half control width signals to said inverting means.

10. A special effects system in accordance with claim 7, wherein said controlling means further includes means for inhibiting the supply of the output of said adding means to said memory means in response to said control signal.

11. A special effects system in accordance with claims 8, 9 or 10 wherein said address signal comprises both horizontal and vertical address signals, said control signal comprises horizontal and vertical signal components, and said controlling means includes horizontal controlling means and vertical controlling means responsive to said horizontal and vertical signal components, respectively.