CA1328920C - Recirculating special effects video framestore - Google Patents

Abstract

ABSTRACT
A video special effects processor including a recirculating frame store is disclosed. The framestore is constructed of two field stores (86, 94) each with a recirculating path (72, 96; 78, 100). The special effects processor includes two field interpolaters (64) and the signals are recirculated at field rate, rather than frame rate, to allow full resolution alternate field interpolation, and to prevent inter-field flicker.

Description

1 32~q20 This invention relates generally to the recirculation of video data through a video framestore to create a variety of special effects. Thi~ invention further relates to the combining of new Yideo data with recirculating video data, on frame or alternate field interpolation basis. This invention further relates to the use of a recirculating frame store in a video combiner system.

E~ACRGROUND OF THE INVENTION
In composing a television production, there is an ever increasing need for variety of special effects. The phrase, special effects, is used to broadly define the selective altering and/or manipulating of video data to create a visual effect to attract the attention of the viewer. 5pecial effects are used in a variety of vidèo production situations.

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` - ~ 32~920 2- ~ av-3358 Cl There ~re ~ number o~ aev~ce~ th~t c~eate these special e~ect~. Video ~itchers are one device that can produce 6peci~1 effect~. ~he 6peciAl effect6 produced by video switc~er are m~st comm~nly u~ed while ~w~tch$ng ~etween video sources. Common switcher 6pecial effects include dissolves ~nd wipes. An example of a video switcher that can produce a variety of di~801ve~ ~nd wipe6 is the AVC
video ~witcher of Ampex Corpo~ation.
Another device for producing special effects is the digital special effects 6ystem, æuch as the AD0 digital special effects æystem of Ampex Corp~ration. Digital special effects systems can perform a number of special effects such as video frame enlargement and reduction, frame movement, frame rotation in 2 and 3 dimensions, and perspective manipulation. Each of these effects can be combined with other special effects to form even more complex effects.
The output from a digital special effects system commonly includes not only an output video signal, but also a corresponding key signal. The key signal indicates the level of the video signal, that is the ratio of the gain of the video signal relative to its original gain in the corresponding video signal. Xey signals can be created by a variety of video devices.
There are two types of key signals. The first is a bi-state key signal, which simply indicates whether the corresponding part of the video signal is to be retained.
If the corresponding part of the video signal is to be retained, the key signal has a value of one, and if it is not to be retained, then the key signal has a value of zero.
A more generally useful type of key signal is a linear key signal. Instead of having just two possible values, the linear key can have any value from zero to one.
Thus, the value of a linear key can be used to partially reduce the level of a video signal. When viewed on a video monitor, a corresponding video image woula exhibit a level ~ 32892~ -3- C ~V-3~58 Cl of tran~parency corre6ponding to the ~alue of the key ~isn~l. . .
- ~he llnear key i6 one method to ~llow two videG
~ign~ls to be ~dded, If two vldeo ~lgn~ls were ~imply ~dded, their combined dynamic range would be twice the ~mount that could be ~andled by the video 8y6tem. In order to add two video 6ign~1s, their dyn~mic range must be reduce 6uch that when ~dded, their total dynamic r~nge i~ equal to the maximum dynamic range or less. Process~ng the Yideo ~ignals with l~near keys i~ one method to effect this dynamic range reduction.
A key signal is used to process a video signal. A
video signal is processed by a key ~ignal by multiplying the key signal with the video signal. Parts of a video signal which are processed with a corresponding part of a key signal which has a value of zero, will result in keyed video signal that has a signal level of zero. Conversely, when processed with a key signal of one, the keyed video signal will be left unchanged. When processed with some intermediate value of a linear key, the signal level of the video signal is reduced by that amount, effectively resulting in the video signal appearing transparent, if viewed on a video monit~r.
Two or more keyed video ~ignals can be combined only they have been processed by key signals totaling one or less. For example, if a first keyed video signal has been processed by a key signal of 0.5 and a second keyed video signal has been processed by a key of 0.4, the two keyed video signals could be combined, because the total of the key signals is 0.9, which is less than one. However, a video signal processed by a key of O.5 cannot be combined with a video signal processed by a key of 0.6, because the total of the key signals would be 1.1, which is greater than one. In practice, a decision is not usually made on whether to combine video signals based on their associated keys, but rather key signals are adjusted so as to allow the combining of video signals.

1 3 2 8 9 2 0 - 4 ~ AV-3358 Cl An unfortunate pro~lem ns~clated w~th the s~le of ~pecial effects mach~ne~ 15 th~t the ~ore often a partlcular effect is u6ed, it~ novelty disappears and thu6 ~t6 ~bility t~ ~ttr~ct attention d~m~nishe6. Thu~ there is ~ con~tnnt need for new ef~ects. Additionally, the larger the library of potential effects available to the operator, the les~
often the operator Will need to C811 upon a particular effect. There 1~ a need, therefore, for a var~ety of 6pecial effect~.
Framestores have been used in the video industry f or many years. A framestore is a mem~ry device that can store one complete frame of vide~ data. ~ramestores are commonly digital. Digital framestores allow manipulati~n of stored video data. Digital framestores are commonly used in digital special effects systems.
Framestores are typically configured to input a frame of video from one part of a ~ystem and output the frame to another part of the system. When a new frame of video is inputted the framestore, the previous frame is completely overwritten.
A frame of video is actually composed of two interlaced fields of video. A frame of video contains a certain number of horizontal lines of video information ~for example, 525 lines in the NTSC system used in the United States). Each field is composed of every other line which are interlaced to form a fr~me of video data. A frame of video is recorded by first recording one the fields an successively recording the other field. A typical time period between the recording of successive fields is o-ne-sixtieth of a second (in NTSC system). If there is significant movement in the images of the video signal, there will be an annoying flicker when two fields are viewed as a video still frame. This can be a problem when such fields are combined in a framestore. One method to solve this problem is to use only a process called alternate field interpolation. Alternate field interpolation uses only one field of video from each frame and interpolates the second field from the first field. Because the second field is ~ 9~ ~ -5- C AV-3358 Cl b~8ed entlrely on the f~r~t fleld, there 1B no ~ovement between ~ield6 ~n ~ frame. The d$6adv~ntage of t~ ethod i6 that one h~lf o~ the video in~ormat~on ~0 being thrown away. ~hen there i6 l~ttle or no movement between field6, the ent~re frame s~ould be used. Therefore, there ~8 a need ~or a method ~nd ~pparatus to prevent flicker when there ls movement between two field~ of frame of video that makes use of the entire original ~rame.
It would be adv~ntageous $f the output of a frame~tore could be xecircul~ted back through the framestore with the addition of new input frames. This would allow the combining of many frames of video to from an output ~ignal.
A number of special effects can be created by this recirculation, including blurs, smears, and trails, all ~ighly desirable special effects. Such recirculation requires the ability to combine video signals. This ability to combine video signals requires the ability to manipulate video signals and associated key signals. Such a framestore would require key signal processing, storage and recirculating capability.
Another desirable special effect would be the ability to decay or selectively remove recirculated frames.
Recirculated frames can be decayed in a variety of ways, including decaying in a preset order or in a random pattern.
If decayed in some preset order, a method needs to be provided to determine the order of decay. If removed randomly, a method of generating the random decay needs to be provi~ed.
While such a framestore could desirably be operated as part of many video systems, such as a switcher or digital special effects system, it could also be operated as a stand alone unit. A particularly desirable use is in conjunction with a video combiner or concentrator. A video concentrator is a device which selectively combines various video signals and their associated key signals to form one or more output video signals. An example of such a video concentrator, is the ADO Concentrator of Ampex Corporation.
Because of the variety of input signals available, the video ~ 32 8 q ~0 ~V-3358 Cl concentrator 1~ an ldeal locnt~on for a ~pec~al effects ~r~me 8tore.

SUMMARY OF THE INVENTION

The present ~nvention fulfill~ a need for prov~ding a variety of 6pec~1 effect6 by use of a recirculating ~ame 6tore u6ing a variety of de~aying method~. Additionally, the present invention provides for a selective method of preventing flicker between su~cessive fields of video. The present invention, further, provides for the operation of a recir~ulatin~ framestore as part of a video concentrator.
In accoxdance with the present invention, a video framestore is provided with a recirculation path that allows the output of the framestore to be combined with new input video the combined video being returned to the framestore for storage. The corresponding key signals for both the recirculated video and input video are processed along with the video and stored in a key framestore. This co-processing of key signals along with the video signals allows recirculation and combininq of video signals. A
number of control systems within the recirculating framestore system enable the creation of a variety of effects.
One control system used in connection with the present invention is a key signal gain processor. Such gain processors allow a uniform reduction in the gain of either the recirculated key signal or the input key signal. These key signals are used to further process the video signals that are being added to or recirculated in the framestore.
The manipulation of these gain processors can define how recirculated video is combined with the new input video.
Further, by setting the input gain to zero, no new video signal will be combined into the framestore, 80 that the video signals present in the framestore may be retained or decayed, but not be written over by new input video ~ignals.
Setting the recirculation gain to zero causes no video ~ ~ 32aq ~ o ~ ~l av-335~ Cl slgnal to be reclrculate~, ~nd the fr~me6tore ~11 thus be written over by lnput vldeo r Using ~U8t the g~$n processor6, a still lmage or freeze frame can be created or input vldeo signal6 can be passed through un~ltered. Other effect6 can be cre~ted ~y adjustment of the gain processors.
An ~mp~rt~nt aspect of a rec$rculating framestore is the manner in whi~h recirculated video i6 dec~yed.
Different ~ethods of decaying video create different special effects. One method ~s not to decay the recirculating video signal at all. This creates the effect of the video images always writing over old images, when viewed on a video monitor. If there is movement in the video signal, a non-decaying trail is created.
Video frames can also be decayed by the above discussed gain processors. By setting the gain on the recirculated key to a value less than one, but greater than zero, recirculated images will fade on each recirculation until they disappear. The closer the gain is to zero, the faster the recirculated video will fade. Each image added to the framestore will decay at the same rate, but will be at different stages of decay, dependinq on when the image was added to the framestore. At any one time, the recirculated video might contain an image recently added as well as images added much earlier, and if the recirculated video was decayed by the gain processor, the images added to the framestore earlier will be more transparent than those added more recently, if viewed on a monitor.
Another control system to decay recirculating video uses the key signal as a time. The recirculating key signal is decayed by the gain processor in the selected manner. However, the key signal is not allowed to process the video signal, and the output key signal is maintained at a value of one and does not reflect the diminishing value of the key signal. When the key signal associated with a particular image reaches a predetermined bottom threshold value, the key signal is set to zero. The zero key value is then used to process the video signal and is outputted as 2 ~ ;' 2 iJ -8- ~~ AV-335B Cl the ~ey ~ign~ he eff~ct of thl~ tlmed dec~y 1~ th~t an im~ge 1~ moved and lt leave6 ~ trall of old ~mages~ eac~
old ~mage lnstant~neously dis~ppe~r w~thout ~ gr~u~l decay, in the order ln which lt w~6 ~dded to the frame store. If the images be~ng added are sm~ller than the bound~r~e6 of the frame of video, the effect created appe~r6 ~omething like the movement of a cent~pede, when viewed on a ~onitor.
As new images are addedto the front of the trail of ima~e~, the oldest images are one by one disappearing off the bac~, creating a desirable æpecial effect.
To create another effect, either of two preset gain values are applied to the gain processor instead of a uniform value being applied. ~his requires a recirculating gain control generator which upon receiving a random signal, selects either of the two possible gain values. The effect thus created causes different parts of recirculated images to randomly decay at two different rates. The effect resembles the twinkling of stars at night.
The random signal generator used to create the random control signal uses a random sequencer rather than a random number generator. A good random number generator is difficult to produce. The random sequencer, which produces a random two state signal, is easier to implement and produces a more truly random output. This two state output is used in conjunction with a presetable counter. The preset on the counter is used to determine a threshold level. By adjusting the threshold level, the frequency of the gain control signal can be controlled.
The present invention provides for a method of solving the inter-field flicker problem by modification of alternate field interpolation. In traditional alternate field interpolation, only one of each pair of fields is actually used. The present invention actually splits the ~ramestore and its video and key recirculation paths into two channels, one for each field of video. These two channels are completely recirculated during the period each field is received, instead of being recirculated onceduring the period a full ~rame is received.

~ ~2~92~
Thu6 when the fir~t flel~ 1~ be~ng prcces~ed, an ~nterpolated second field ~6 belng proce6~ed at the same time. N~rmally one field 16 proces~ed at a time. Thi6 proce8~ing ~t the field rate m~int~ins t~e resolutlon of a non-interpolated ~ignal, while el~minating inter-field frame ~licker.
An ideal l~cati~n for 8uch ~ recirc~lating frame6tore i~ as part of ~ vldeo concentrator. By ~ts nature, the recirculating fr~mestore must have ~cce~ to key as well as video signals. In a video concentrator, all the needed signals are available . Further, the effectiveness of the special effects is enhance by a number of possible input images, including multiple-image images that ~an be created by the concentrator. The concentrator also allows the output of the recirculating frame store to be combined with other signals being outputted.
Various of the above-mentioned and further features and advantaqes will be apparent from the specific examples described hereinbelow of an exemplary apparatus and method.

BRIEF DESCRIPTION OF TBE DRAWINGS
Figure 1 is a schematic representation of components of a concentrator utilizing a recirculating special effects framestore in accordance with this invention.
Figure 2 is a schematic representation of a recirculating special effects framestore in accordance with the present invention.
Figure 3 is a schematic representation of a key processor in accordance with the present invention.
Figure 4 is a representation of an output frame of video of a recirculating special effects framestore view on a video monitor.
Fiqure 5 is a schematic representation of a random signal generator in accordance with this invention.

~, -9a- ~

Figure 6 is a schematic representation of the control circuit for the luminance alternate field interpolator.
Figures 7, 8 and 9 are waveforms of signals appearing in the circuit of Figure 6.

.':: ' ". ' "~; ' -lo- 1 32892Q
DETAILED DESCRIPTION
Flgure 1 i~ an ~ll~strAtlon o~ ~ typlcal vlde~
concentr~tor 10. An lnput bu6 12 recelve6 t~e v~rlou~ Lnput s~gn~l6 ana route~ them to other part~ of the ~oncentr~tor ~ccording to control rignal 28, Input ~hannel~ 14, 16, 18, ~nd 20 ~nput both a video signal and ~ key Rignal. The vide~ s~gnal ~ an ~nkeyed video signal, which i~ a video s~gnal that ~s not been processed by it~ corresponding key 6ignal. The key signal accompanies the ~deo sign~l as an indicator of the within the concentrator. The ource of these input channels may be a number of video devices, such as switchers or digital special effects system. While four input signal pairs are shown, it is understood that any number of input channels would be allowable.
There are preferably two background channels 22 and 24. These channels are vide~ signal only inputs that usually provide a color background, although any video signal can be used. Background channels 22 and 24 are used to fill in the areas of the output frame that do not contain keyed video signals. In areas where the linear key is greater than 2ero but less than one, the background is added to make the value total key signal equal to one. As with the input channels, any number of background channels are allowable.
The other input signal on input bus 12, is a framestore channel input 26. Framestore channel input 26 contains both a keyed video signal and an associated key 6ignal, indicative of the key processing already performed on the ~ideo signal. ~ramestore channel input 26 is the output of recirculating special effects framestore 30.
Input bus 12 routes the various signals to three concentrator channels 32, 34 and 36. Control signal 28 determines which ~ignals are passed to which channel.
Control signal 28 is derived from operator inputs at a c~ntrol panel.
The three concentrator channels 32, 34, 36 receive input signals from input bus 12 according to control signals 28. Concentrator channel A, 32 and concentrator channel B, 34 preferably are identical channels. Both channels A, 32 11 1 32~q20 AV-335~ Cl ~nd B, 34, c~n accept any comb~natlon of lnput ch~nnel~
16, 10 ~n~ 20, or fr~mestore ch~nnel 2C, an~ comblne them ~cc~rd~ng t~ ~oncentr~tor control ~iqn~ls ~. Bac~ground channel~ 22 and 24 can only be routed to concentr~tor ch~nnel6 ~2 and 34. Becau6e the output o~ the fr~me~tore 30 ~ust be outputted through one o~ the ot~er concentr~tor ~hannel~, there ~6 ~n opportunity to add n b~ckground ~ignal at that Bt~ge. ~
The output of concentrator channel~ A and B, 32 and 34, are output ~i~nals 38 and 40. Output fiignals 38 and 40 both have a video signal and a key signal. Once again, the key ~ignal i~ indicative of the previ~us key processing.
The output of concentrator framestore channel 36, i~ a concentrator framestore channel output channel 46, which contains both a vide~ and key signal inputted to recirculatin~ special effects framestore 30.
In operation, signals are selected of input bus 12 and are fed to each of the concentrator channels, 32, 34 and 36. As an example, concentrator channel A, 32, receives tw~
input channels, 14 and 16, and a background channel 22. The c~ncentrator control signals 44 dictate that input channel 14 should have priority over input channel 16. The video signals of input channel 14 and 16 are processed and combined accordingly, and then keyed into background channel signal 22 to form a channel A output signal 38.
Continuinq the above example, input channels 18 and 20 are ed into concentrator framestore channel 36.
Input channels 18 and 20 are combined and outputted to the recirculating framestore 30. In framestore 30, new images are combined with old recirculated images according to framestore control signal 47 and outputted to frame store channel input 26 as a video and key ~ignals. Framestore channel input 26 is fed to the input bus 12, and in turn fed by the input bus 12 to concentrator channel B, 3~.
Background channel 22 i~ also fed to concentrator channel B, 34, where it is added as background to the framestore channel input 26. The result is outputted as channel B
output signal8 40. These 8ignals can then be fed to any 1 328920 12- ~ AV-3358 Cl vl~eo ut~ atlon ~evlce, ~uch aB a ~onltor, ~l~eo t~pe recor~er, or bro~cast ~y~tem.
In the a~ove ex~mple, the routing of ~lgnals W~8 arb~trar~ly cho~en to 111~6trat~ ~ typ~cal oper~tlon of the concentrator. The operator ~a6 complete control over a large number of potenti~l routin~6 of ~ignals.
Next, the operat~on of the rec~rculating framestore 30 w~ll be d~scu6sed. Whi~e the frame~tore 30 i~
preferably located within a ~ideo concentrator, ~t ~8 clear that it could operate with numerou6 video systems and as a self contained system.
Referring now to Figure 2, recirculating framestore 30 is shown. In ~igure 2 there are three types of signals which are routed about the recirculating framestore 30. They are video signals, which are shown as double bus lines, key signals, and contr~l signals. If this system is digital, which is the preferred embodiment, the video and key signals of binary signals.
Both video and key signals are recirculated. The video follows a relatively simply recirculation path and will be discussed first. Input video signal 60 can originate from a variety of video devices. If framestore 30 is part of the concentrator 10 of Figure 1, then input video signal 60 will originate in concentrator framestore channel 36 as output signal 46.
Input video signal 60 is fed to video gain processor 66 where it is processed with input gain signal 62. Input gain signals are numbers between zero and one, and input gain signal 62 specifies the amount of gain reduction to impose on input video signal 60. Input gain signal 62 preferably is generated by a control system from operator i~put. Video gain amplifier 66 can be implemen~ed as a simple digital multiplier available in integrated circuit packages.
The output of video gain proressor 66 is fed into alternate field interpolator 64. Interpolator 64 operates in two modes. The first mode is used where there is little or no movement between fields of video. In this mode no -13- AV-335~ Cl interpolatlon take3 place. The second mode 18 used when there is movement between the field~ of video. The operat~ng mode ~s determined by lnterpolator ~ontrol signal 6B. This signal preferably is generated by the control system from operator input. When the operator notices a flicker in the output signal displayed on a video monitor, the operator sets this signal ~o the second mode.
If automatic generation of the interpolator control signal 68 is desired, input video signal 60 can be monitored by a motion detector in a well known manner. Sueh a motion detector will set the interpolation control signal 68 to the second mode whenever motion greater than a selected threshold amount is detected.
In~erpolator 64 has two channels, A and B.
Channel A receives video field one, and channel B receives video field two. Channel A outputs an input channel A video signal 70 to a channel A video combiner 72, where it is combined with a recirculating channel A video signal 74.
Ch2nnel B outputs an input channel B vide~ signal 76 to a channel B video combiner 78, where it is combined with a recirculating channel B video signal 80.
If interpolator 64 is operating in the first mode, corresponding to a condition of no movement on flicker, then interpolator 64 acts as a routing device. According to a field control signal 82, the input video signal from video gain processor 66, is fed to either channel A or B for output as either input channel A video signal 70 or input channel B video signal 76. Field control signal 82 is generated by the control system and indicates whether the current field being received is the first or second field of ~he video frame.
- If interpolator 64 is operating in the second mode, alternate field interpolation is occurring. When field oontrol signal 82 indicates that the first field is being inputted, the input video signal is outputted directly on channel A as input channel A video signal 70. From the first field video ~ignal, a second field v~deo signal is mterpolated and outputted by channel B as input channel 1 328q20 AV-335~ C

vld~o lgn~l 76. ~he proce~s of altern~te f~el~
lnterpolat~on 16 ~ell knvwn to t~se !k~ d in the art.
When Yiel~ control sign~l 82 lndicate~ th~t the ~c~nd fiel~
1B being inputted, the lnput video ~ign~l $~ outputted .
~irectly on ch~nnel B a~ input ch~nnel ~ vldeo signal 76.
Fr~m the ~econd field v~deo ~ign21, ~ second field video signal i6 interpolsted ~nd outputted by channel A a~ lnput channel A video siqnal 70.
Input channel A video signal 70 18 combined w~th recirculating channel A video fiiqnAl by channel A video combiner 72. In the preferred embodLment, video combiner 72 i~ implemented as a digital adder, which is available as an integrated circuit. Channel A video ~ombiner 72 outputs an output channel A video signal 82. Output channel A vide~
~ignal 82 is fed to both output video ~witch 84 and cha~nel A fieldstore 86.
Output video switch 84 is operated in tandem with output key switch 88. Both switches are operated by output field celect signal 90. Output field select signal 90 is generated by interpolator 64 based upon field control signal 82. The switch positions are alternated corresponding every field of video to form a standard video signal. The output of video switch 84 is the output of framestore 30. If the framestore 30 is located in the concentrator 10 of ~igure 19 the output video signal is part of the framestore input channel 26.
Input channel B video signal 76 is combined with recirculating channel B video signal by channel ~ video combiner 78. Video co~biner 78 is the ~ame as channel A
video combiner 72. Channel B video combiner 78 outputs an output channel B video signal 82. Output channel B video ~ignal 82 is fed to both output video switch 84 and channel B fieldstore 84.
Output channel A video ~ignal 82 is also fed into the channel A fieldstore~ ~ideo ~ignals are ~onstantly being read in and out of fieldstore 86. Each pixel of video data remains in the fieldstore for the time duration of one field of video. ~ieldstore 86 outputs recirculating channel ^ ~ 1 328920 '~5' ~ AV-335B Cl A vlde~ ~gnal 96, ~h~c~ 1~ fad to vl~oo ~ln pr~e-~or 98.
Vlfleo ga1n processor 98 i~ the ame a~ to lnput v1deo galn pr~ces~or 66. Reclrculnt$ng channel A ~ldeo 1gnal 96 1~
proce~sed wlth a channel A key ~gnal 97. The deri~at~on of thi8 key ~1gnal ~11 be dl~cus~ea bel~w. The output of channel h ga$n proce660r ~ fed lnto ch~nnel A vldeo comb~ner 72 and comb~ned ~ith video ~lgn~l 70 to produce v~deo s~gnal 82 ~hieh i8 recircul~ted bac~ through the field~tore 86.
~ he channel B video recirculation path i8 identical to channel A. Output channel B video signal 92 i6 also fed into the ~hannel B field store. ~ieldstore 94 outputs recirculating channel B video signal 100, which is fed to ~ideo gain processor 102. Video gain processor 102 is the same as video gain processors 66 and 98.
Recirculating channel B video signal 100 is processed with a channel B key signal 104. The derivation of this key signal will be discussed below. The output of channel B gain processor is fed into channel B ~ideo combiner 78 and combined with video signal 76 to produce-video signal 92 which is recirculated back through the fieldstore 94. This completes the input and recirculation paths for the video signals in recirculating framest~re 30.
The path of the key ~iqnals will be discussed next. Input ~ey signal 106 indicates the previous processing of input video signal 60. ~ecause input video signal 60 is directly processed with input gain signal 62, input key signal 106 is also processed with that signal so that it will remain reflective of the processing of input video signal 60. Input key signal 106 is processed by input key processor 108. Input key processor can be implemented as a digital multiplier. The output of input key processor 108 i~ fed into interpolator 64.
Interpolator 64 dses process the input key ~ignal 106 in the same manner that the input video signal 60 is processed. Key signal6 that correspond to the irst field are routed to channel A and outputted as input channel A key ~ignal 110. Rey signals that correspond to the ~econd field ` 1 328920 -16- AV-3358 Cl are routed to ~hannel B and outputted a~ input channel B key ~ignal 112. Input channel A and B key video ~gn~ls, 110 and 112, are fed to channel A and B key processors, 114 and 116, respectively.
Each of the channel A and ~ key processors, 114 snd 116, actually is a combination key processor, key loop, and key store. Another input to key processor 114 and 116 is recirculation gain lla. The derivation of recirculation gain 118 will be discussed below. To the key processor 114 and 116, recirculation gain 118 is used to process an internal recirculating key signal.
~ eferring to Figure 3, the channel A key processor 114 is shown. It is understood that the channel B key processor 116 is identical. Inside the key processor 114, the input key signal 110 is subtracted from o~e by the l-XIN processor 250 to form a remainder key signal 252. The.
remainder key signal 252 represents the amount of key signal not used by the input video signal 70 of Figure 2. The ~ N processor 250 can be implemented, for example, as an inverter and digital adder. The output of the 1-KIN -processor 250 is fed to a minimum processor 254.
A recirculation key signal 25S represents the key signal used by the video currently in the channel A field store 86 of figure 2. The recirculation key signal 256 is processed wi~h the recirculation gain signal 118 by key signal processor 258. Key signal processor 258 is identical to key signal processor 108. The resulting signal is the processed recirculation key signal RRECIRc~ 260, which is fed to minimum processor 254 with remainder key signal 252.
Minimum processor 254 determines ~he minimum of the key signals input thereto and outputs the signal as minimum key signal ~MIN~ ~62. Minimum processor 254 can be implemented as a diqital comparator. The output of minimum processor is fed to both key signal adder 266 and ratio processor 264.
Ratio processor 264 determines the ratio of the minimum key signal X~IN, 262, to the processed recirculation key signal XREc~Rc, 260, to form the 1 3289~
-17- AY-3358 Cl recirculat~ng ch~nnel A key ~ignal 128. Ratio proce~sor 264 can be ~mplemented a~ an ar~thmetic processor integrated circuit, but is preferably implemented as a look-up table in a ROM memory.
The output key signal 127 is ~lso fed to an internal key store 268, from which ~t is outputted as the re~irculation key signal 256. Key store is simply a memory array of the same number of pixel locations as the channel field stor~ 86.
The key processor 114 also outputs the sum of the minimum key signal 262 and the input key signal XIN, 110, as the recirculatins channel A output key signal 127.
Referring again to Figure 2, key processor 114 is designed to allow input video 70 to use as much of the available signal gain is it needs. It is said to have priority over the recirculating video 96. All of the remaining gain is available to the recirculating video 95.
If necessary, the recirculating video 96 is processed down to the level of the remaining key space. If the recirculating video 96 can use all the remaining gain, then the output key signal 127 is one. However, if the recir-culating video 96 has already been reduced, or will be reduced by the recirculation gain signal 118 to a level less than the remaining gain, then recirculating channel A key signal 128 will be at that level and the output key signal 127 will represent the total of the input key signal 110 and the minimum key signal 262 (Figure 3), which will be less than one. Video signals that have been reduced in gain have lost information because these signals exist in only limite-d resolution. Thus when they are reduced, they lose resolution and if increased in gain, they will not reproduce their original values. Ihus video signal preferably are only reduced in gain, and not generally increased.
The recirculating channel A and B key signals, 128 and 130 fed to channel A and B decay processors, 132 and 134, whose function will be explained below. If not activated, decay proces~or 132 and 134 pass their input ~ignals unaffected. Thus recirculating channel A and ~ key A~-3358 Cl ~gnals are outputted as channel A and a ~ey signals 97 ~nd 104.
~ he channel A ~nd B output key slgnals are al~o fea to channel A and B decay processor~ 132 and 134, ~nd are also pass unaffected if decay processors 132 and 134 are not activated as channel A and B key output s~gnals, 131 and 13~. The channel A and B key output ~ignals, 131 and 133, are fed to ~ey switch 88. Xey switch 88 is operated in tandem with video switch 84. The output of key switch 88 is the output of framestore 30. If the framestore 30 is located in the concentrator 10 of Figure one, the output key signal is part of the framestore input channel 26.
The recirculation gain signal 118, used by both key processors, is generated by recirculating gain processor 120. Recirculating gain processor 120 operates in two modes. These mode are selected by gain control signal 1~6, which is generated by the control system, preferably from operator input. In the first mode, recirculating gain processor 120 outputs recirculating gain 1, 1~2, and outputs it as recirculation gain signal 118. This is considered the normal operating mode.
In the second mode, recirculating gain processor 120 receives a random control signal 136. This two state signal is generated by a random signal generator 150 of Figure 5, to be discussed below. The random control signal 136 selects either recirculation gain 1, 122, or recir~ulation gain 2, 124, as recirculation gain signal 118.
Decay processors 132 and 134, when activated, output key signals having a value of one regardless of their input signals, unless their input key signals are under a low threshold level, when they output signals of zero. The purpose of this processin~ will be discussed below.
This completes the discussion of the interconnection of the elements of Figure 2. Next, the operation of Figure 2 will be explained.
The operation of re~irculating framestore 30 i9 best understood w~thin a typical example. ~he goal of thi~
example i~ to create a special effect called a trail. A

2 8q 2 0 -19- ~ ~V-335~ C1 trall 1~ lllu-trat~ ln F~gure 4. ~lgure ~ 1- a repre~entatlon of a vldeo ~lgnal vlewed on a vlaeo non~tor.
A ~e reduc~ frame 200 1~ ~ove~ fro~ a tartlng locat~on 210 to a flnal l~cation 200. AB lt ~oves along the path, ~t leave~ old reduce~ frame6 such a~ 210, 212, 21~, 201 and 202.
In thi~ example the ~nput vldeo 60 IFlgure 2) comprise~ a size reduced frame of v~deo ~n an ~therw~e empty full fr~me 190. Such a v~deo signal can be created by a digital 6pec~al effects 6ystem which ~s capable of reducin~ a video 6ignal and positioning it within a full frame of video. If reduced frame 210 were not partial obscured by reduced frame 212, and reduced frame 210 were t~e only reduced frame in full frame 190, then Figure 4 would be a representation of input video signal 60. It should be assumed that frame 210 contains a video picture, such as a field of flowers or a news anchorman reading the news. Over a period of time, the frame of active video is moved in relation to the full frame of video. Frame 210 follows the path shown by the other boxes in the full frame on the video monitor. Unlike Figure 4, which actually represents the desired trail effect to be created by the recirculating framestore 30, input video 60 does not leave a trail, but rather only one frame is visible at any one time.
The moving frame starts at the location of frame 210, and follows the path shown and stops at the location of frame 200.
Input key signal 106 (Figure 2)is created with input video fiignal 60 and has a value of one where it corresponds to the reduce frame 200 and a value of zero elsewhere. In this example, both the input gain signal 62 and recirculating gain ~ignal 118 are set at one. ~owever, the effectc of changing these ~ignals will be discussed below. For this example it i~ also assumed that fieldstores 86 and 94 ~tart empty.
Framestores are commonly 6aid to recirculate at frame rate. Thi~ means that the contents of the framestore, one $rame (two fields) of video, recirculates once in the tLme it takes a new frame to be inputted. Because 1 32892~ -20_ AV-335~ Cl frame~tose 30 18 ~ct~nlly compo~ed of two f~eld ~toros ~nd recirculation p~ths, ~ramestore 30 can bc reclrcul~t~d at field rate. This mean~ th~t the content~ of the fr~mestore 10 are completely recirculated in the time it ta~es to input a new field. It is this doubled rate that allows every-field interpolation ~y the interpolator 64. Operation Of interpolator 64 on the luminance and chrominance components of the input video signal 60 is described in two sections of Ampex manual by David Trytko, one of the present inventors, entitled "ADO Infinity - Target Framestore System - System Theory and OperationK. A COpy of these sections are attached hereto as The Appendix.
The input video signal 60 and input key signal 106 pass unaffected by processors 66 and 108, because the input gain si~nal 62 in this example, is set to one. If interpolator 64 is off, the first field of video and key are sent to ch2nnel A. Nothing is sent to channel 8. Anything recirculat n~ in channel B is allowed to recirculate without additional material. The second field of video and key are sent to channel B and nothing is sent to channel A.
If interpolator 64 is on, then as field one of video and key is routed to channel A, an interpolated second field of video and key is sent out on channel ~. When the real second field is encountered, it is sent out on channel B and an interpolated first field of video and key is sent out on channel A. This alternating interpolation allows the fieldstores to be updated with new material every field, instead of every frame, producing improved picture quality in the resulting video ima~e.
The common method of alternate field interpolation in prior art devices would be to receive the first field and video and pass them on channel A and send nothing on channel B. Upon receiving the second field, the second field is discarded and a new second field of video and key is interpolated from the first field and sent out on channel ~.
Nothing ~s sent out on channel A. When the interpolator i8 off, the field stores are only updated with new material every frame. Thi$ pre~erves the full resolution of the origi~al fr~me of video. Under 1 ~28920 21- ~ AV-335B ~1 the co~mon Detho~ of ~nt~rpol~tlon, one of the flel~ ln a frame 1B ai-c~raed ~n f~vor of an lnterpolate~ flel~ ~o a6 to el~n~te lnter-f~eld fl~cker. Interpol~tor 6~ u~es both fields ln the fr~me to lnterpolate, an~ reduce or ellmlnate flicker. By using both field~ ~nd updated on f~eld bAsls, there i~ no los~ of re~olut~on ~s comp~red to the more common ~et~od of altern~ted fi~ld interpolation.
The channel A input video signal 70, ~fter leaving interp~l~tor 64, 16 combined with the channel A
recircul~ting vide~ ~4. Before beiny combined with the channel A input video, recirculating video 74 must be processed with the output cf the key processor 11~. For this first frame of video, the fieldstore 86 was defined as being empty. Thus the output of the framestore 30 is the input vide~ signal. The input video signal 70 is stored in fieldstore 86 and the input key signal 110 is stored in key store 268 (Figure 3). The second field of video and key is processed in the same manner.
For the sake of this example, it will be assumed that the second frame of input video contains the size reduced frame of video now moved from position 210 in Figure 4 to position 212. The input video signal 70 is passed normally to video combiner 72,. The input key signal 110 is also passed to key processor 114.
Referring to Figure 3, the input key ~ignal 110 defines the area of reduced frame 212 in Figure 4. The key signal 110 is subtracted from one to form the remainder key signal 252, which indicates what key signal 6pace is available to the recirculating video. Xey store 268 contains the key signal from the first frame, which defines the area of reduced frame 210 in Figure 4. Because the recirculation gain 118 is defined as one for this example, the minimum processor 254 determines the minimum between the recirculating key signal and one minus the input key ~ignal.
There are three areas of interest in this determination.
First is the area outside both reduced frames 210 and 212 of Figure 4. In that area of the key ~ignal the minimum value i~ zero from the recirculating key signal 260.

~ 3~ 8q ~ -22- AV-33S~ Cl . ~he next area of the ~y l~nal ~ the ar~a of the ~econ~
r~Auce~ frame 212 (F~gure ~). Note ~hat thl~ rume part~aily ob~ure~ tbe flr~t frame 210. ~h~ fr~me 1~ psrt of the lnput key lgnal, by de~ign, ~t ~a~ pr~orlty ov~r any ~mage be~ng reclrculated. It ~hould be noted th~t ~ey proce~80r 11~ could easlly be design ~uch th~t rec~rculated key ~ignal would have priority over ~nput ~ey ~ignal~. In the area defined by input key ~ign~l for the ~econd fr~me, min~mum process~r 254 output~ ~ero from the one ~inu~ input key 6ignal 110. The third ~rea 16 the ~rea of the first reduced frame that i~ not obscured by the reduced frame 212 (Figure 4) ~n the ~econd input frame. Thi6 can be ~een as the backward ~L~ shaped area labelled 210 in Figure 4. Both input ~ignals to minimum processor 254 have this area of the key signal at one. Thus the minimum key signal 262 only defines this backward ~L~ ~haped arear The minimum key signal 262 is added to the input key signal to form the output key signal 131 and the recirculation key signal to be stored in the key store 268.
This key signal indicates area of interest in the output key signal is the combined srea of the first and second input keys 6ignals defining the two overlapping reduced frames of video, 210 and 212.
The ratio of the minimum key 262 and the recirculating key 260 is the minimum key 262, which becomes the channel A key fiignal 97. The ratio i5 used to determine how to process the recirculating video signal to a desired level while taking into account the previous processing of that video 6ignal. The channel A key signal 97 is used to process the recirculating video 96. Recirculating video 96 contains the reduced frame 210 (Figure 4) from the first output frame. After being processed by the channel A key fiignal 97, the recirculating video signal is no longer the full reduced frame 210 (Figure 4) but rather an ~L~ shaped area of video. When added to the input video signal 70, an output video ~ignal 82 is formed which is a video ~ignal in the 6hape of two overlapping reduced frames, 210 and 212.
Thi~ video 6ignal i6 al~o 6ent to the f~eldstore 86, to be 1 3 2 8 9 2 0 -2~ AV-~351l ~1 u~e~ e reolrcul~t~ ~deo ~lgn~l ~or the n~xt lnput ~rame., The above discu~ion h~ been ~e~tricted to channel A for t~e ~ake of cl~rity ~ ~t i6 cle~r th~t lt ~pplles equ~lly to chnnnel B and the 6econa f ield6 .
Referring to Figure ~, fr~me 210 ~6 referr~d to as tr~l. A~ frames are ~dded, the ~ame process occur6 until the end of the .~pot~ on with ~rame 20û afi the ~nal fr~me .
Each new fr~me would obscure a port$on o~ the previou6 frame, yielding a full fr~me 190 as 6hown in Figure ~. The trail i~ a basic speci~l effect of the recirculating framestore 30. Other special effects may be described as variations on the trail effect. The following will dis~uss the effects of changing the control 6ignals.
Changing the input gain signal 62 to a value less than one causes the new frames to have a transparent look.
If the frame is not m~ved, then a number of input frames must be to added on top of each other to form a frame of full intensity. Because even an apparently still picture contains a slight amount of mo~ement of the originating camera, the image becomes a blurred wherever movement occurs producing a desirable special effect. If the frame is moving, then the Lmage smears, which is also considered a desirable effect. If the input gain signal 94 were set to zero, no new video would ~e added to the recirculation path.
If the recirculation gain 118 was set to one at the same time a freeze effect would be created.
Changing the recirculation gain one, 122, causes a decaying of old Lmages. Each old image would become more transparent until it finally disappeared. The more times a particular image is recirculated the more its key signal is reduced. ~f the added images are ~oved while being added, a very pleasing trail that resembles the tail of a comet, is created.
~ here are two other systems within the recirculating framestore 30 to create special effects. The first is the decay processors and the second is the recirculating gain pro~essor.

- ~ 3~89~ ~V-335B Cl - ~he ~pec~al offect c~oat~ by t~e ~ac~y proce~r~ 132 and 134 u-es the r~clrculatinq ~y ~gn~l, 250 ~F~ure 4), ;~
~n ~ey proces~or~ and ~16, ~6 ~ collectlon of ~own counter~. The re~rculatlng key ~ignal ~ ~ec~yed normally by the rec~r~ulat~ng gain oignal 118, ~ut the recirculat~ng ~ey s~gnal~ ~re not ~llowed to decay the recirculating video 6ignal6, 96 and 100, or oUtpUt ~ey 6ignal~, 127 and 129.
$~e recirculat~ng~ vi~eo e~gnsl6 96 ~nd 100 are proce6~ed with ~ gai~ of one ~nd t~e output ~ey signal is outpu~ted at one. Th~s effect, re~erring to F~gure ~, allows t~e old frame images to remain at full ~nten~ity each old frame image instantaneously disappear~ in the order they were added as their key values go below a lower threshold value.
The effect looks something like the movement of a centipede.
To accomplish this effect, decay processors 132 and 134, when activated, output a key signal of one, regardless of their input, unless their input is below the low threshold, when they output zero. The low threshold value is necessary because the key signal will never actually reach zero as it is always multiplied by an amount which only reduces its value.
The other effect system is the recirculating gain processor 120. Recirculating gain processor 120 is activated by gain control signal 126. Unless activated, recirculating gain processor 120 passes recirculating gain one, 122, unchanged-. ~hen activated, it passes either recirculating gain one, 122, or 2, 124, depending on the state of random control signal 136. Both recirculating gain one and 2 are generated by the control system from operator input. For a maximum effect, these two values should be relatively different in value, although they could be 6et to any values. The effect created by this two-rate deoay is a sort of twinkling of the trail, ~imilar to the twinkling of star6 at night.
~ hile a random control signal can be created in a variety of ways, the preferred method is shown in Figure 5.
The control random signal 136 is the carry ~ignal of up counter 140. The frequency of the control random 6ignal 136 1 3 2 8 9 2 ~ -25~ 335B Cl ls ~etor~ined by the preret lnput 1~2 of counter ~0. The larger the pro~et, ~e ~re trequently the r~n~om control algnal 136 will be l-sue~. -The pul~es used to lncr~ment the counter ~re supplied to the clock input 1~ of th~ counter.
The frequency of the clock pulses hould be at the rate of ~igltal aampling of the system, that iB the rate the pixels move through the system. The r~ndom factor i8 created by random ~equencer, 146, whi~h randomly output either zero or one into the enable the counter 1~0. ~he effect of thi6 Arrangement is that the counter 140 counts down fr~m the preset 142 only when enabled by the random sequencer 146.
Counter 140 can be implemented as a simple digital up counter. Random sequencer can be implemented as a white noise generator with a threshold output.
In summary, the recirculating framestore can be adjusted by a variety of control signals and system to create a variety of special effects. When there is movement between consecutive fields of video, the framestore can operate in an interpolation mode the interpolator interpolates every field as opposed to every frame, to reduce or eliminate flicker. The recirculating framestore can operate in many video devices and even as a stand alone device, but is preferably 5ituated in a video concentrator, which acts as a ideal input and output system for the framestore.
While the embodiments disclosed herein are preferred, it will be appreciated that they are merely examples, and that various alternatives, m~difications, variations or improvements thereon may be made by those skilled in the art from this teaching, which are intended to be encompassed by the following claims.

~5 CONT~OL - LUM~NANC~ ALTERNAT~ ~ELD ~NSERPOLA~oR

~ he Lu~1n-ne ~t~rn-t~ ~leld Int-rpola~r p-r~orm- the ~ollovlnQ funct~on-~

lS) Aver-g-~ the Curr~nt Line luminanc- ~nd Prev~ou~ Line ~min~nc- to cr--te n lnt~rpol-ted L~n- o~ lumin-nce p~eially betveen the tYo.

~ ~I ) Formats thc Current Line ~d Interpolat~d tin~ ~ampl~ into a 13.S ~hz Field I Lu~inance Output ~nd ~ 13.S Mhz ~ield 11 Lu~inance OYtPUt tO t~e TF S SIGNAL Board .

Refer to ~lgure 7 and the schematic of Figure 6 during the folloving xplanation. She Current L~ne luminance (Y) rample~ are buffered in 9~ and are t~en lat~h~d in 2C ~nd 2D. The l~tch ~ignals detailed on Flgur~ 7 r~pre-ent t~e ~mplcs latchæd intern~lly ~t t~e output of the~e cl~ip- ~nd re not vieYable on an 06cilloscope. She m~tu~lly xclusive ~ ~nd ~ ignall~ ~rom ~he ~emory Contrsl Circuitry indicat~ Yhi~h ~iel~ i~ pre-ently being receiv-d. w~en Field I 1- being rocei~ed, the Current Line ~ample~ beco~e ~he ~ield I Lumirun~ tput (lt~I) ~y ~n~bl~ng the output of 2C Yith Fl .
Sl~l~rly, ~h-n F~el~ b-ing ~e~elv~d, the ~u~rent Line Ja~ples be~ome the Fl-ld ~ Luminanee oueput (YFSI) by en~b~$ng ~e output of 2D vit~ ~I$.

1 328q20 ~ n ord r to upd t- both ri-ad ~to~ - v-ry ~l-ld th Lumln~nc-A~ ~n-t- r~ nt-rpo~-tor ~ynther~zes ~k~ n~ r~-ld by ~v-r~gln~ ~b- Curr ne Lln- ~n~ Pr-vlou~ L~n- Lumlnan~n 0~ eh. P~-~-nt F~-ld In t~ y, n Sn~-rpol-~-d Lln- o~ ~m~nane ~p-cl~lly k-tY--n eh- t~c ~r --nt lln - 1- er-~t-d ~n~ uJ-d to r-pr---nt th~
lnt-rl-c d l$n o~ t~ Ml--in~ F$-1d Th- cusr nt Lln (Y) and Pr-~.r$ou- t ln (~Y) S 12nin~nc~ r- ~ r-g-d by 11~ ~OF, nd 9E
eo b-~ome on- lnput to n B-b~t t~ lnput l-etor llE nd lOE vho~e other lnput ~- zero ~ n tb F~eld Mode l~'~me~Foar~ ~ 1), tbe lnt~rpolat~d amples ~re ~ t-d nd laee~ed $n lC nd lD Dur~n~ Field S, th -e ~mpl~s become t~e F$eld II Lu~in~nc~ Output (YFlI) by n~bling the output of lD Yith F~ During Field II, th-~e ~mple~ become the Fleld Luminance Outpue (YFI) by nabling the output o~ lC Yith ~II In this v~y, the ~ in~ F$-1d $~ lnterpolated from the Pr~-ent F$eld P:oviding Lun~n-nc for both ~i-ld- durin~ every f$~1d eli~inates the ~nt-r-f$-1d motlon fllcker of V$d-o Fr-~e, but redu~e~ the re-olut$on o~ th~ tor-d $~ge~

In t~ Fr~m- ~od- tFrame Mode ~ O), the ~el~ctor outputs ~ value of z ro to r g~-t~r- lC ~nd lD Thl- llOv- the F$~1d Stor~ of the M~- d ng Fl-ld to r c~rcul-t- d thout be$ng updat~d ~y Snpue Video Sh- ~o ~ lu becomer th Fi-ld ~S ~u~$n n~e Output (YFSS) during ~$~ nd lt b co~e~ the F$~1~ S Lu~ln~nc- Output ~YF~) during ~l-ld S~. ~S# Fr~m~ Mod- pr~ tb ~r~ olution of the ~tored $~g~r but 1- un~ble to r-m4v lnt~r-fl-ld mot~on ~l~ek~r and YFSS OutpuC- thu- r-Pr~ t th ~npl t Lu~ nc~
o~ tb~lr x<~ d ~ro~--or-.

~S CONS~OL--ChRO~A~XEY ALTERNA~E ~S~LD ~UTERPOLA~o~

~ h~ Chsom~X~y ~l~-rn-t- rl-~d Snt-rpol~Dr F-r~orm~ th~
~olloY$ng ~unc~cn--(I) Av r-g-- th~ rr~nt i.~ne Chroma/RQy an~ Pr-v~ou- Llne C~rom-/Xey to cr--te n Interpolae-d Lln~ o~ roma~Kcy p-cially ~e~Yeen the tvo.

(II) For~t- t~e Current Lin~ nd Int-rpolat-d L~n- 6.~5 Mhz Chrom~ pl~- into ~ult~pl-xed 13.5 M~z Chroma Output by alternating Field ~ Chroma amples (CI) uith ~ield I~ Chroma ~amples (C~I).

~ II) Form~t- t~e Current Line ~nd Interpolated Line 6.75Mh2 Xey ~amples lnto ~ultipl~xed 13.SH~z Key Output by ltern-ting ~ield I
~ey amples (~ t~ Fi~ld S~ ~ey ~amples ~XIl).

Re~er eO F~gNr~ 8 and the schematic of Figure 6 during the folloYing xpl-n3tlon- T~- Current Line C~roma/K-y (XC) ~mpl~ ~re ~uf~red ln ~E ~nd ~ come the lnput- to 2E nd 2~. The Curr-nt Line C~rom~ ~a~pl~ ~re late~ed ~n 2E Yith ~g~ nd t~ Curr-nt Line Xey ~mpl~ tc~Jd ln 2~ Y~th .5X. ~ tc~ ign~ t~iled on ~gure 7~pr~r~nt e~ npl~ tc~ d lnt~rna~y at t~ output o~

tb~-~ ch~p~ ~nd ~r- no~ Y ~l- on n 08cil~o~0p-.

1 328~20 ~n o~ to llpae- ~oth ~ to~o- ~ry tl-l~, th C~ro~ y J~lt-~at~ nt~ tor ~nt~ th ~ no rl-ld ~y v r~ g t~ nt Lln ~nd P~r~ ~n Ch~_~ Y 0~ th nt rl-ld Sn tbl- ~y, n 2nt-rpol~t~ ~n- o~ Cl~aOl~Qy ~cl-lly ~t~n th t~o p~ nt ~ t~ uJ-d eO
r~pr-~-nt tb~ ~nt-rl-~ lln- o~ lng ?l-ld. ~ nt Llne (XC1 and p~ ou~ Lln t~XC) C~rom~-y ~ r- svs~og~d by ~, ~F, 9E, ~nd 6G .

~h- tro~ nt ~ormat or tb c~rom~ r-q~ir~ ign xt-n~ion o~ t~ st $~ni~eant blt o~ -ch Ampl~ k ~or~
addit~on ean ~e p~r~or~ d- ~he X~y ~pl--, hov v-r, ~r- ln un-igned ~n~ry ~ormat an~ efinnot b~ ~gn ~xt-n~-~. Th- t~o -ct~on~ o~ 6G
ratis~y the~e r~qu~r~ment~ ~y ign ~xtending the MS9 o~ t~e C~roma a~ple~ ~.SX - 1) and introducing ~n M5~ o~ zero ~or th~ X-y ~mples .5x - O).

Th~ ~nt-~po~-t-d Chroma/K-y ~mple~ r~ on- input to ~n ~-bit tno input ~ ctor 7C and 7~ ~o-e ot~ar ln~ut ~ Z~ro. Dur~n~ F~eld Hode tFram ~b~- - 13, lE ~ill late~ an Int-rpolat~d Chro~a ~a~ple ~$th .5X and lF Y~ tch a~ ~nt-rpolat~d Key ~mple ~ith .SX.
Durlng r~.~ No~- (F~ Msde - O), lE ~nd 1~ ~ill both latc~ ~ro V~lu~

Tb ~orm~t o~ tb- 13.S~h2 Chro~ Output to th- ~S SI~NA~ ~oard oontaln- t~ld ~ C~rom~ ~pl~- Yhi~ 5X 1- lsv, ~nd F$-1~ SS Chroma s~mpl-~ vh~ X 1- b~g~. Du~n~ r~ S, 3A-6 ~ .SX and 3A-~ 8 ~SX~

~ 328920 r, 2~ abl--d an~ out~t~ rr-nt C~roaa S~. ~Ihl3.~ 19)~, Slt 1~ onab~ ~d o~tput~ 2nt-~po~t~d CSI ln Fl-la ~ or ~ ~o v~ or CII ~n F~
~d-. ~ln~ rl-~d ~s"a-6 ~ nd 3A-8 .5X, r~r~ln~ t~
ord-r. ~,- .5X ~- lov, lE l~ bl-d end out~ut- ~n ~nt-rpol~t~d ~hro~ s~ or C2 lrl rl~ Dd- or n ~-ro v~lu- for C~S ln ~r~m~
~d~. l~I- .SX 1- )~gh, 2E ~ n~bI-d and oue~ut- Curr~nt CSIroma r~mpl~ ~or C~.

Th ~on~t o~ th~ 13.5M~ 1~-y Output to th~ T~S SICNAI, Board ~ t-ln~ F~ S ~Qy ~mpl~ .5X ~ hl~, and Fl~ld S~ X-y U:lp~ fhll- .5X 18 lo~- Durlr~g Fl~ld I, 3A-6 ~ .Sx ~r~d 3A-~ ~ .SX.
X l- hlg)lo 2F lr nabl~ n~ outputs ~ curr~ne R y ~mplQ ~or XI. ~hll- . 5x ~ , lF 1~ n-bl-~ ~nd output3 ~n Snt~rpolated xey a~npl~ ~or XII ln Fl~ld t~de or zero v~lue for RII ln Fram~ Mode.
During Fi~ld IS, 3A-6 ~ .~ and 3A-8 ~ .SX, r-ver-~n~ the order.
~il~ .SX ~ h~gh, lF ~- ~bl-~ and output~ ~n Sntr~polated Xey r~mple ~or XI ln Fl-l~ ~d- or ~-ro v~lu~ for ~ ~n Frame ~ode.
~ilc .5X ~ loY, 2F 1- n~blff~ ~nd output- a eurr~nt Key ~ple ~or Rli.

P~r~d~ nput Cbro~`X y o~ or ~oth f$~1d~ ~ur$ng evory fltl~l ln ~l--ld ~ ~n t~- t~ lnt-r~ ld ~ot~on n~cker o~
Vl~!l o Fr~e, but r ~u~s thQ n~olutlor~ of the ~tor d :~ga-.

~n t~# F~ , th ~l~ceor out~ut8 z-ro ~lu - ~or th~
M~--lng r~ Chr~/K y ~mpl~ A~ F~ Storn of t31e 1 328q20 -dn5~ Pl-~ to r c~rc~ t- ~t~out ~lnlJ u~t~ ~3y Snput Vld-o.
~ Fra~ ~ t~ rr-~ r -olutlon o~ th- tor~ l~g -INt 1- un~ to r ~ lnt-r~ otlon ~llck r-

Claims (27)

1 . Apparatus for processing video signals comprising first and second interlaced fields of lines, with lines of each field having a different raster position upon display, said apparatus comprising:
interpolation means receiving a second field of input video signal for producing an interpolated first field of input video signal from said second field of input video signal;
combining means for successively receiving said first field of input video signal and said interpolated first field of input video for producing a first field of output video signal;
recirculating means receiving said first field of output video signal for recirculating said first field of output video signal to produce a first field of recirculated video signal, said combining means combining said first field of recirculated video signal with said interpolated first field of input video signal when said combining means receives said interpolated first field of input video signal, and combining said first field of recirculated video signal with said first field of input video signal when said combining means receives said first field of input video signal.

2 . Apparatus for processing video signals of claim 1 further comprising output means receiving said first field of output video signal when said combining means receives said first field of video signal.

3. Apparatus for processing video signals of claim further comprising:
interpolation means receiving a first field of input video signal for producing an interpolated second field of input video signal from said first field of input video signal;
combining means for successively receiving said second field of input video signal and said interpolated second field of input video for producing a second field of output video signal;
recirculating means receiving said second field of output video signal for recirculating said second field of output video signal to produce a second field of recirculated video signal, said combining means combining said second field of recirculated video signal with said interpolated second field of input video signal when said combining means receives said interpolated second field of input video signal, and combining said second field of recirculated video signal with said second field of input video signal when said combining means receives said second field of input video signal.

4. Apparatus for processing video signals of claim 3 further comprising output means receiving said second field of output video signal when said combining means receives said second field of video signal.

5. Apparatus for processing video signals of claim 3 further comprising output means receiving said first field of output video signal when said combining means receives said first field of video signal and receiving said second field of output video signal when said combining means receives said second field of video signal.

6. Apparatus for processing video signlas of claim 3 wherein each of said video signals has a level identified by the balue of respective key signals that signify differences between the level of the video signal and a selected reference level, portions of said keys signals corresponding to said first fields of said video signals and other portions of said key signals corresponding to said second fields of said video signals, said apparatus further comprising:
interpolation means receiving a first field of input key signal for producing an interpolated second field of input key signal from said first field of input key signal, and receiving a second field of input key signal for producing an interpolated first field of input key signal from said second field of input key signal.

7. Apparatus for processing video signals of claim 1 wherein said combining means comprises a video adder.

8. Apparatus for processing video signals of claim 1 wherein said combining means comprises a digital adder.

9. Apparatus for processing video signals of claim 1 wherein said recirculating means comprises a video fieldstore.

10. Apparatus for processing video signals of claim 1 wherein said recirculating means comprises a memory store.

11. Apparatus for producing a video special effect by combining an input video signal with a recirculated video signal to produce an output video signal, each of said video signals having a gain identified by the value of respective key signals that signify differences between the gain of the video signal an a selected reference gain, said apparatus comprising:
a source of input video signal and an input key signal such that at least a portion of said input key signal has a value less than one but greater than zero;
combining means receiving said input video signals and said recirculated video signal for producing said output video signal corresponding to an output key signal equal to the combined values of said input key signal and a recirculated key signal;
recirculated means receiving said output video signal for producing said recirculated video signal by recirculating said video signal; and means for reducing the gain of said recirculated video signal such that the output key signal has a value not greater than one.

12. Apparatus for producing a video special effect of claim 11 wherein said means for reducing the gain of said recirculated video signal further reduces the gain of said recirculating video signal in accordance with a gain reduction signal.

13. Apparatus for producing a video special effect of claim 11 wherein said means for reducing the gain of said recirculated video signal further reduces the gain of said recirculating video signal in accordance with one of a plurality of a gain reduction signal, randomly selected.

14. Apparatus for producing a video special effect of claim 11 wherein said means for reducing the gain of a recirculated video signal further reduces the gain of said recirculating video signal in accordance with a recirculation gain reduction signal.

15. Apparas for producing a video special effect of claim 11 further comprising a gain reduction means for reducing the gain of said input video signal and correspondingly reducing the value of said input key signal.

16. Apparatus for producing a video special effect of claim 11 further comprising a gain reduction means for reducing the gain of said recirculating video signal and correspondingly reducing the value of said recirculating key signal.

17. Apparatus for producing a video special effect of claim 11 further comprising a gain reduction means for randomly reducing the gain of said recirculating video signal and correspondingly reducing the value of said recirculating key signal.

18. Apparatus for producing a video special effect of claim 11 wherein said combining means comprises a video combiner.

19. Apparatus for producing a video special effect of claim 11 wherein said combining means comprises a digital adder.

20. Apparatus for producing a video special effect of claim 11 wherein said recirculating means comprises a video framestore.

21. Apparatus for producing a video special effect of claim 11 wherein said recirculating means comprises a plurality of video fieldstores.

22. Apparatus for producing a video special effect of claim 11 wherein said means for reducing the gain of said recirculated video signal comprises:
video gain processor receiving a processing key signal indicative of the necessary gain reduction of said recirculated video signal for reducing the gain of said recirculated video signal according to said processing key;
and key processing means for producing said processing key signal.

23. Apparatus for producing a video special effect of claim 11 further comprising a gain reduction means for randomly reducing the gain of said recirculating video signal and correspondingly reducing the value of said recirculating key signal according to a random control signal produced by a random control signal generating means.

24. Apparatus for producing a video special effect of claim 23 wherein said random control signal generating means comprises:
a random sequencer for producing a two state signal;
a counter receiving said two state signal, said counter counting up from a preset threshold value on a clock signal only when enabled by said two state signal, said counter producing said random control signal when said counter reaches a maximum count.

25. Apparatus for processing a plurality of sequential frames of input video signals comprising:
video concentrator means having a plurality of video inputs and a plurality of corresponding key signal inputs, for receiving a plurality of video input signals defining a plurality of current frames of video, and for receiving a plurality of corresponding input key signals indicating the level adjustments to be made by said video concentrator means of the corresponding video input signal, and having a combined video signal input for receiving a combined video signal defining a current frame of a plurality of sequential frames of said combined video signal, and having a combined video key signal input for receiving a combined video key signal corresponding to said combined video signal indicating the level of said combined video signal, and having at first video output and a corresponding key signal output and having a second video output and a corresponding second key signal output, for combining a selected combination of said input video signals after adjusting the levels thereof in accordance with the corresponding input key signals with said combined video signal to generate an output video signal at said first video output and for outputting at said key signal output a concentrator output key signal indicative of the level of said output video signal, and for combining a selected combination of said input video signals after level adjustment thereof in accordance with the corresponding input key signals with said combined video claim 25, continued signal to generate a second output video signal at said second video output and for combining the keys signals corresponding to the video signals combined to generate said second output signal to generate a second output key signal so as to have a level indicative of the level of said second output video signal and for outputting said second output key signal at said second key signal output;
a recirculating framestore means, including a keystore means, having a video input coupled to said second video output and having a key input coupled to said second key signal output of said video concentrator means and having a video output coupled to said combined video signal input, and having a key signal output coupled to said combined video key signal input, for receiving said second video output signal and said second output key signal and for combining said second video output signal with a level adjusted recirculated video signal comprised of stored video signals from previous frames of said second video output signal from said video concentrator means, and for outputting the resultant combined video signals to said video concentrator means combined video signal input as said combined video signal, and for storing said combined video signals for a predetermined interval and then outputting said stored combined video signals as said recirculated video signals for combination with a new frame of said second video output signals from said video concentrator means, claim 25, continued said framestore means further comprising means for receiving said second output key signal corresponding to said current frame of said second video output signal and for calculating a new recirculated key signal from said second output key signal and a recirculated key signal from the previous frame, and for receiving said recirculated video signal and for adjusting the level of said recirculated video signal in accordance with the value of said new recirculated key signal to generate said level adjusted recirculated video signal, and for storing said new recirculated key signal for a predetermined interval and then outputting the stored new recirculated key signal as said recirculated key signal.

26. The apparatus of claim 25 further comprising means for selectively, randomly altering said new recirculated key signal used to adjust the level of said recirculated video.

27. The apparatus of claim 26 further comprising means for decreasing the values of said new recirculated key signal but not altering the level of said recirculated video signal until the level of said new recirculated key signal falls below a predetermined threshold, and then for decreasing the level of said recirculated video signal to zero.