Note: Descriptions are shown in the official language in which they were submitted.
PATENT
333-2053
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_ACKGROUND OF THE INVENTION
The invention relates to systems and methods for
color correcting video picture signals. More particularly,
the present invention pertains to improved systems and
methods for increasing the quality and speed of color
correction operations. This patent application describes
improvements upon the color correction systems and methods
disclosed in ~.S. Patents No. 4,096,523 (the "Rainbow"
patcnt); No. 4,223,343 (the ~Anamorphic" patent); No.
4,410,908 (the "Luminance~ patent); commonly owned U.S.
Patent No~ 4,679,067, entitled "Color Correction System and
Method With Localized Color Sampling~; Patent No. 4,694,329,
entitled "Color Correction System and Method Wlth Scene-
Change Detection"; and Patent No. 4,750,050, entitled
"Editing System and Yethod".
There is a continuing need to improve the efficiency,
speed, and quality of the color correction of video picture
signal~, especially in film-to-tape and tape-to-tape
transfers, and particularly in scene-by-scene color
correction. For instance, there is a need to better isolate
particul~r ob~ects for color correction. Furthermore, there
i~ a need to better select a specific color or a ~pecific
range of color~ for color correction. ~
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Accordingly, an ob~ective is to
sati~fy the above needs and provide a system and method for
color correcting video picture signals with lncrea~ed
efficien~y, speed, ~nd quality.
Another ob~ective i8 to provide an
apparatus and a method for improving the accuracy with which
a specific color or a specific range of colors may be color
corrected.
An additional ob~ective i8 to
provide an apparatus and a method for more easily
identifying and recalling the color corrections associated
with particular scene~ in an image recording medium that is
to be color corrected.
A further ob~ective la to provide an ,o provide an
apparatus and a method for better ~egregating a particular
area of the picture produced by the video picture signals
and color correcting this partlcular area. It is a further
object to blend the edges of the area into the remainder of
the picture and make the edges less noticeable.
Yet another ob~ective is to provide s to provide
an apparatus and a method for improving the ability to color
correct color signals having certain level~.
SUMMARY OF THE INVENTION
According to a fir~t aspect of the invention there
i8 provided a color correction ~ystem for color correcting
video picture ~ignals repre~entative of image~ stored in an
image recording madium and di3played as video pictures on a
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first display means. The system includes color correction
means for selectively generating color correction signals for
at least one selected frame of each of a plurality of scenes
recorded on the image recording medium. Storage means is
provided for stoxing the color correction signals. The system
also includes second display means for displaying a plurality
of pictures, each picture corre~ponding to the video picture
signals fcr one of the selected frames, and recall means for
recalling from storage the color correction signals for a
selected one of the frames displayed on the second display
means.
Another aspect of the invention provides a method of
a color correcting video picture signals representative of
images stored in an image recording medium. The method
include~ the steps ofs producing video picture signals
representative of each of the images stored in the image
recording medium; displaying pictures correspond1ng to each of
the images stored in the image recording medium on a fir~t
display means; selectively generating color correction signals
for at least one selected frame of each of a plurality of
scenes recorded on said image recording medium; storing said
color correction signals; displaying on a second display means
a plurality of pictures, each picture corresponding to the
video picture signals for one of said ~elected frames; and
recalling from storage the color correction signals for a
selected one of said selected frames di~played on said second
display means.
A still further aspect of the invention provides
video ~ignal ~olor correction apparatus comprising, in
combination, a color correction computer including mean~ for
developing color correction signals ~or video ~ignals from a
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video source, memory means for storing signals correspondingto said color correction signals and location signals
indicating the location of corrected pictures relative to
other pictures in a video program sequence, and for storing
signals representative of each of a plurality of said
eorrected pictures, and display mean~ for displaying each of
said correeted pictures and means for recalling from said
memory means and applying to other pietures the signals
eorresponding to eolor correction signals for a selected one
of said corrected pictures.
Also disclosed herein is an apparatus in whieh a
predetermined range of colors around an infinitely variable
prineipal eolor are seleeted. Color eorreetions
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for the video picture s~gnals corresponding to the
predetermined range of colors are selectively developed, and
then the color corrections are applied to the video picture
~ignals, thereby producing color corrected video picture
signals. Accordingly, any object in the video picture may
be selected based upon its color. Preferably, the size of
the predetermined range of colors is adjustable. Therefore,
all of the colors in the object may be selected for color
correction, even if the object consists of a wide range of
colors. However, the range may be adjusted to be very
narrow, if the operator so desires, and this can be done
substantially independently of the saturation of the colors.
Thus, particular ob~ects may be selected for color correction
based upon their colors. ~he principal color may be selected
from any hue, regardless of the saturation levels. This
advantage result~ in an improvement in the quality of the
color corrected videotape. Moreover, this advantage decreases
the time, and therefore the cost, of color correcting motion
picture film and videotape.
A color corrector may include circuit~ for
discriminating the video picture signals in a specific area
from the video picture signals forming the remainder of the
picture. Color correction signals are applied to the video
picture ~ignals either inside of or outside of the ~pecific
area.
Preferably, the edges of the area are formed so
that the area blends well with the remainder of the picture.
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This can be done, for example, by using a linear dissolve to
form the edge6 of the area.
The size and/or the pos$tion of the specific area
may be changed at the beginning of each new scene or frame.
Consequently, the area may "follow~ a particular object as
it moves from place to place in successive frames or scenes.
Hence, greater object selectivity for color corrections is
obtained, and better color corrections are developed.
The color corrections for a particular scene may be
identified or labeled with a video picture from that
particular scene. The video picture is displayed for the
operator, preferably on an auxiliary monitor scr¢en, or on
the main monitor screen. The operator may use the display
to recall the color corrections for that particular scene
and apply them to the video picture signals for the present
scene. Several video pictures may be shown on the same
display, and the operator may utilize an array of
pushbuttons arranged like the video pictures on the screen
or a light pen in order to choose the color corrections to
be recalled.
Altcrnatively, the display may include a "touch
screen,~ and the operator may touch the video picture
associated with the desired color corrections in order to
recall them. Numerical data givinq locations of the
corrections for prior scenes preferably are displayed next
to the pictures on the auxiliary display. Thus, the
operator also can use the numerical correction location
information displayed next to each picture to rctrieve the
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associated correct;on values. The operator does not have to
remember the scene number for the particular scene, which
may change as the motion picture film or the videotape is
edited. The operator can then readily identify, locate, and
recall the color corrections he or she desires to work with.
This greatly increases the speed with which a motion picture
film or a videotape may be color corrected.
The color corrector may include circuits for
discriminating video picture ~ignals based upon their color
levels. Specifically, such discrimination circuits may
discriminate signals above a predetermined level or signals
below a predetermined level or signals between two
predetermined levels. Color corrections are selectively
developed for the discriminated signal~, and the color
corrcctions are applied to the associated video signals to
produce color corrected video picture signals. This aspect
of the invention further increases object selectivity and
speeds the color correction process.
The features outlined above each increase the
efficiency of the color correction process. In addition,
when two or more features are used together, even greater
efficiency results, such efficiency previously being
unattainable.
~RIEF DESCRIPTION OF THE DRAWINGS
Thc above and other objects, featurcs, and advan-
tages of thc presen~ invention will becomc apparent upon
considcration of the following dctailed description of
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PATENT
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illustrative embodiments thereof, especially when taken in
conjunction with the accompanying drawings, wherein:
Figure 1 is a diaqrammatic illustration of a color
correction system according to the invention;
Figure 2 is a top plan view of the front panel for
the color corrector shown in Figure l;
Figure 3 is an enlarged view of a portion of the
front panel shown in Figure 2;
Figure 4 is an enlarged view of another portion of
the front panel shown in Figure 2;
Figures 5A-5D are diagrammatic illustrations of
waveforms on a vectorscope and depict the functions of the
variable vector controls;
Figures 6A-6C are enlarged views of the auxiliary
monitor and the main monitor for the color correction system
shown in Figure 1;
Figures 7A-7B are a block diagram of the color
correction circuits in a color correction system according
to the invention;
Figure 8 is a block diagram of the variable vector
control circuits for a color correction system according to
the invention;
Figure 9 is a block diagram of a coefficient
processor for the variable vector control circuits illus-
trated in Figure 8;
Figure 10 is a schematic diagram for the level
discrimination circuit illustrated in Figure B;
Figures llA-11C are waveform diagrams for the
level discrimination circuit illustrated in Figure 10.
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333-2053
Figure 12 is a vector diagram representing some of
the variables in the operation of the device shown in Figure
8;
Figure 13 is a schematic circui~ diagram of a
component of the device shown in Figure 8;
Figure 14 is a diagram illustrating the
operational characteristics of a typical prior art device;
Figures 15A-15D are waveform diagrams illustrating the
principles of operation of the circuit of Fiqure 8; and
Figures 16 and 17 are flowcharts of steps in
computer programs that may be employed to implement the
"Call-A-Picture~ feature of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EM~ODIMENTS
_
General DescriPtion
Figure 1 shows a color correction system 10
constxucted according to the invention. The color
correction system 10 includes a color corrector 11 having a
front panel 12. Portions of the front panel 12 are
illustrated in greater detail in Figures 2-4. The front
panel 12 has a set of variable vector controls 14 and a set
of six vector controls 16. The six vector controls 16
function as outlined in the Rainbow and Luminance patents.
Referring now to the lower left-hand portion of
Figure 2, the front panel 12 includes a set of color balance
controls 18 and ~window" controls 20. The "window" controls
20 are described and depicted in greater detail in
Patent No. 4,679,067 as well as Patent No. 4,694,329. -
The front panel 12 additionally includes video signal
sourcs controls 22. The video signal source controls
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22 adjust parameters such as the PEC gain and negative gain
for each of the red, green, and blue channels. Moreover,
the video signal source controls adjust other parameters,
for instance, the horizontal pan, the vertical pan, the
zoom, and the contours. Each of the controls ln the sets of
controls 14, 16, 18, and 22 includes a control knob which is
coupled to a shaft-position encoder, as described in
Pstent No. 4,679,067 snd Patent No. 4,694,329.
The right side of the front panel 12 includes
pushbuttons and displays. Specifically, this portion of the
front panel includes two rows of pushbuttons 24, which are
shown in greater detail in Figure 4, and three rows of
pushbuttons 26, which are shown in greater detail in Figure
3. The functions of many of these pushbuttons are described
in the Rainbow and Luminance patents. A display 28 (Figure
4) shows the scene number for the color corrections stored
in the A ~uffer and the ~ buffer. Moreover, the display 28
shows the scene number for the current scene.
Still referring to Figure 4, a keypad 30 and a
display 32 are used to recall the color corrections for a
particular scene and apply them to the present scene. For
example, if the operator wanted to use the color corrections
for scene number 1,234 for the current scene, the operator
would press the NcallN pushbutton in the upper one of the
rows 24 and then the buttons 1, 2, 3, and 4 of the keypad 30
in this seguence in ordcr to recall the desired color
corrections.
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333-2053
Also shown in Figure 4 is an array 34 of
pushbuttons and a row of pushbuttons 36 for use in the
"Call-A-Picture" feature of the invention, which feature is
used for recalling color correction signals for previous
scenes in another manner. The operation of the
"Call-A-Pict~re" feature will be described in detail below.
The portion of the front panel 12 shown in Figure 3 has
waveform pushbuttons and indicators 38 for selecting various
waveforms for viewing on an oscilloscope (not shown) as well
as monitor selector pushbuttons and indicators 40 for
selecting various signals for monitoring.
Referring again to Figure 1, the system 10 has a
computer 42, which is connected to each of the color
corrector 11, a video signal source 44, a videotape recorder
46, and a video memory 48. The video signal source 44 may
be a film chain or telecine, a videotape player, or the
like. The video signal source 44 produces video signals
from the associated image recording medium. These video
signals are delivered to the color corrector 11 so that they
can be corrected. The color corrector 11 provides color
corrections for the video signals from the video signal
source 44 under the direction of the operator and the
computer 42, and it produces color corrected video signals.
The color corrected video signals are sent to a main monitor
50, and, at the appropriate time, to the videotape recorder
46. The operator may observe the effect of the color
corrections on the video signals by looking at the video
picture on the main monitor 50. The videotape recorder 46
records the color corrected video signals on a videotape 54,
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333-2053
usually during a second run after color corrections have
been made during a first run, thereby producing a color
corrected videotape.
The main monitor is shown with windows Wl and W2.
The use of the windows W1 and W2, which are movable in size
and/or position, is described further below.
An auxiliary monitor 52 is connected to the
computer 42. The auxiliary monitor 52 displays a plurality
of video pictures, such as the video pictures 56a-56d. The
function of the auxiliary monitor 52 and the video memory 48
is described below during the discussion of the
"Call-A-Picture" feature.
Referring now to Figure 2, above each of the
control knobs in the sets of controls 14, 16, 18, and 22 is
a horizontal linear group 35 of four light-emitting diodes
~"LEDs"), which are referred to as "rangefinder" LEDs. The
two inner LEDs of each group 35 are green, while the two
outer LEDs are red. When the associated control knob is in
its center position, the two inner LEDs are energized. If
the control knob is turned to the right, the two inner LEDs
are deenergized and the rightmost LED is energized.
Correspondingly, if the control knob is turned to the left,
the two inner LEDs are deenergized, and the leftmost LED is
energized. Accordingly, the operator may quickly determine
the position of any of the control knobs.
Reset buttons 64, 66, and 68, are provided to
permit the operator to readily center the control knobs in
the sets of controls 16, 18, and 22, respectively.
Specifically, the operator presses a reset button, and all
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PATENT
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of the control knobs in the associated set of controls are
electronically centered by zeroing the counter connected to
the control knob. The controls 16, 18, and 22 include
active memory pushbutton-indicators 70, 72, and 74,
respectively.
Referring now to the lower part of Figure 4, the
"notch" pushbutton sets the scene boundary between scenes;
that is, pressing the "notch" button stores the frame number
of the first frame of a new scene. The "color correct
enable" pushbutton in the same row makes the "notch"
pushbutton effective for color correction events. The "pan
enable" pushbutton makes the "notch" pushbutton effective
for position related events, such as horizontal pans,
vertical pans, and zooms.
The "carry forward mode" is entered by pressing
the "carry forward mode" pushbutton in the upper row 24. In
this mode, the color corrections from the last scene are
carried forward for the next scene. That is, once the
operator establishes color corrections for a particular
scene and then sets the scene boundary between that scene
and the next scene, these color corrections are both stored
for the particular scene and applied to the next scene.
Thus, the operator may use these color corrections as a
basis for color correcting the next scene.
The "picture file" pushbutton is used with the
video scene recall feature, i.e., the "Call-A-Picture"
feature of the invention, which is described below. The
"picture file" pushbutton enables the array of pushbuttons
34 and the row of pushbuttons 36~
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The "diss." pushbutton is used to produce a linear
transition between the color corrections for a given scene
and the color corrections for the subsequent scene. For
example, the operator may make color corrections for a given
scene and then make color corrections for the subsequent
scene. If the operator wants a smooth transition between
scenes, the operator presses the "dissolve" pushbutton at a
frame near the end of the given scene and again presses the
"dissolve" pushbutton at a frame near the beginning of the
subsequent scene. The computer is programmed to
automatically provide a linear transition, for instance, on
a frame-by-frame basis, between the color corrections for
the given scene and the color corrections for the subsequent
scene for all frames between the two dissolve points.
The "source 1," "source 2, n n source 3," and
"source 4" pushbuttons, which are shown in row 26a of Figure
3, enable the operator to select one of a variety of video
signal sources. For example, the operator may select a
telecine as the video signal source by pressing the "source
1" pushbutton, or select a videotape player as the video
signal source by pressing the "source 2" pushbutton.
The ~load count" pushbutton (next to the "source
4" button) allows the frame counter to be initialized to any
number at the beginning of a new job. The "count mode"
pushbut~on allows the operator to select among various
counting modes for the frame counter, such as, counts by
hours, minutes, seconds and film frames; or PAL video
framcs; or NTCS video frames.
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333-2053
The "matte ext," nvariable vector matte on," "six
vector matte on," and "matte store" pushbuttons are de-
scribed below during the description of the "Traveling
Matte" feature of the invention.
The "disc load," "disc save," "disc format," "auto
save," and "disc test" pushbuttons are utilized to control
an external storage device (not shown) for the computer,
such as a floppy disc drive or a hard disc drive.
Variable Vector Controls
The upper left-hand portion of Figure 2
illustrates the set of variable vector controls 14. The
controls 14 include a variable vector position control 80, a
delta control 82, a factor control 84, a saturation control
86, a hue control 88, and a luminance control 90.
Furthermore, the variable vector controls 14 include a "set
up" pushbutton 92, the function of which is described below.
A ring of LEDs 94 is located around the circumference of the
variable vector position control 80. The LEDs 94 indicate
the angular orientation of the variable vector position
control 80. The angular orientation of the variable vector
position control 80 corresponds to one of the colors on a
vectorscope.
The variable vector position control 80 is used to
select a particular range of colors for color correction.
The principal color within the range of colors is determined
by the angular orientation of the variable vector position
control 80. The variable vector position control 80 may be
used to select any principal color within the precision of
the associated counter. For example, if the associated
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counter is a 12-bit counter, any one of 4,096 different
principal colors may be selected with the variable vector
position control 80. Thus, the principal color is
essentially infinitely variable.
The functions of the various controls 80-90 are
better explained in conjunction with Figures 5A-5D. The
circle 96 in Figures 5A-5D diagrammatically illustrates a
vectorscope screen. The waveform 98 illustrates the
response of the variable vector control circuits when the
input signal to the color corrector is from a device which
generates a spectrum of color signals, that is, a signal
whose color varies throughout the visible spectrum. The
angular orientation of the waveform 98 corresponds to a
given angular orientation of the variable vector position
control 80. Figure 5A shows the effect of turning the
variable vector position control 80. For example, if the
control 80 is turned clockwise from the position of waveform
98 to select a different principal color, the response of
the vectorscope becomes the waveform 98a. Then, if the
control 80 is turned further cloc~wise to select another
principal color, the response of the vectorscope becomes the
waveform 98b. Similarly, if the control 80 is turned
counterclockwise to select yet another principal color, the
response of the vectorscope becomes the waveform 98c.
Accordingly, the control 80 may be turned to select
virtually any hue as the principal color.
The variable vector controls are nominally effec-
tive for a predetermined range of colors around the
principal color. For example, colors within plus or minus 5
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degrees of the principal color will be color corrected along
with the principal color; however, the effectiveness of the
color corrections will decrease as the angular distance from
the principal color increases.
The delta or bandwidth control 82 is provided in
order to adjust the width of the predetermined range of
colors effected by the variable vector control position
control 80. Fiqure 5B shows the effect of rotating the
delta control 82. The delta control 82 may be rotated
clockwise in order to increase the width of the range of
colors or rotated counterclockwise in order to decrease the
width of the range of colors. Hence, the width of the range
of colors may be made as large or as small as the operator
desires, within the limits ~f the equipment. For instance,
the width of the range of colors may be changed anywhere
from plus or minus about 2 degrees around the principal
color to plus or minus 90 degrees around the principal
color. Figure 5B shows a waveform 100 with the same
principal color as the waveform 98 but with an increased
bandwidth " ~ 2." The waveform 100 was obtained by turning
the delta control 82 clockwise. Figure 5B also shows a
waveform 102 with the same principal color as the waveform
98 but with a decreased bandwidth " ~3." The waveform 102
was obtained by turning the delta control 82
counterclockwise.
Once the desired principal color and the desired
range of colors around it have been selected with the
variable vector position control 80 and the delta or
bandwidth control 82, the saturation control 86, the hue
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333-2053
control 88, and the luminance control 90 may be employed to
generate color correction signals for the video picture
signals corresponding to the selected range of colors. More
particularly, the hue control 88 is used to alter the colors
in the selected range of colors and shift them in the color
spectrum, while the saturation control 86 is used to change
the levels or intensity of the colors in the selected range
of colors. Additionally, the luminance control 90 is
utilized to vary the luminance or brightness of the colors
in the selected range of colors.
Figure 5C shows the effect of rotating the hue
control 88. To shift the colors in the selected range of
colors, the hue control 88 is turned clockwise or
counterclockwise. Figure 5C shows a waveform 104 and a
waveform 106. The waveform 104 was produced by turning the
hue control 88 clockwise after the waveform 98 was selected.
Similarly, the waveform 106 was produced by turning the hue
control 88 counterclockwise after the waveform 98 was
selected. The hue control may shift the color within the
selected range of colors by any desirable amount, within the
limits of the equipment. For example, the hue control may
be designed to shift the principal color by up to 60 degrees
in one direction or the other.
Figure 5D shows the effect of turning the satu-
ration control 86. The saturation control 86 may be rotatedclockwise or counterclockwise to increase or decrease,
respectively, the saturation levels of the colors in the
selected range of colors. As an example, the waveform 108
illustrates what happens when the saturation control 86 is
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333-2053
rotated clockwise once the waveform 98 has been selected.
The waveform 108 has a saturation level above that of the
waveform 98. The waveform 110 illustrates what happens when
the saturation control is rotated counterclockwise once the
waveform 98 has been selected. The waveform 110 has a
saturation level below that of the waveform 98.
The luminance control 90 may be used to increase
or decrease the brightness of the colors within the selected
range of colors. Of course, the luminance control 90, the
hue control 88, and the saturation control 86 may be
employed together to alter the associated parameters of the
colors within the selected range of colors. The variable
vector control knob 80 and the del a control knob 82 are
utilized to set the selected range of colors, as noted
above. The factor control 84 is used to select those colors
within the selected range of colors that have saturation
levels either above or below a specified level. The
function of the factor control 84 is described in greater
detail below during the description of Figures 10 and 11.
As an example of the use of the variable vector
controls 14, the color correction of a particular scene will
be described. Assume the operator desires to color correct
a specific object, such as an apple appearing in a picture
on the main monitor 50. The operator initially presses the
"set up" pushbutton ~2, which is part of the variable vector
controls 14. This causes all portions of the picture which
have colors within the nominal range of colors set by the
variable vector position control 80 to become a neutral
gray. If the apple does not become gray, the operator
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rotates the variable vector position control 80 until the
apple becomes gray. If only a portion of the apple becomes
gray because the apple contains colors outside of the
selPcted range, the operator rotates the delta control to
increase the delta or bandwidth of the selected range until
the entire apple becomes gray. This signifies that the
colors the operator desires to correct, i.e., the colors
forming the apple, are encompassed within the selected
range. The operator again presses the "set up" pushbutton
92, and the colors are displayed in an unaltered fashion.
Alternatively, the "set up" button may be
connected so that objects with the selected color appear
normally on the monitor while objects having other colors
appear to be gray. The modifications to Figure 7A that are
necessary to implement this feature are readily apparent to
a person having ordinary skill in the art and, therefore,
will not be described in detail here.
Now, the operator may turn any or all of the
saturation control 86, ~he hue control 88, or the luminance
control 90 in order to adjust the corresponding parameter of
the colors within the selected range of colors. For
instance, the operator may rotate the hue control 88 to
change the color of the apple from a greenish red to red.
Once the operator has developed the color corrections with
the controls 86, 88, and 90, the operator causes the color
corrections to be stored in the computer 42. The storage
and retrieval of the color corrections may be accomplished
as described in the Rainbow patent. The color corrections
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are read from the memory in the computer and used to produce
the color corrected videotape 54 during the "run" mode.
In this manner, the video picture signals forming
the apple may be color corrected to produce a desirable
image. With the variable vector controls, the apple may be
segregated from any of the other objects in the picture and
then color corrected. Accordingly, the variable vector
controls permit greater object selectivity during color
correction and speed the color correction procedure. That
is, an object can be segregated from others having hues very
close to that of the selected object, or even from objects
having the same hue but a different saturation level. It is
believed that the hue of the selected object can be closer
to that of other similarly colored objects and still be
effectively segregated for color correction purposes than
with prior color correction devices. This not only improves
the speed of color correction, but makes some color
corrections possible for the first time, thus significantly
improving the color correction quality.
Video Scene_Recall (~Call-A-Picture") Feature
Referring now to Figure 4, pushbuttons 34 and 36,
together with the auxiliary monitor 52 shown in Figure 1,
may be used to implement the video scene recall or
J'Call-A-Picture" feature of the invention. This feature
gives a miniature reproduction on the monitor 52 of a frame
from each of several prior scenes which have been
color-corrected~ This allows the operator to visually
select thc prior scene whose corrections are to be recallcd
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without running the telecine or tape player backwards or
using slow prior methods.
In the specific preferred embodiment shown in the
drawings, the auxiliary monitor 52 displays up to twelve
different video pictures, such as the video pictures 56a-56d
shown in Figures 1 and 6 The twelve video pictures are
displayed in an array with four columns and three rows.
Each of the twelve video pictures corresponds to one of the
twelve pushbuttons 34 shown in Figures 2 and 4. Each video
picture is associated with the color corrections for the
scene which ~ncludes that video picture, and each pushbutton
34 is associated with one of the video pictures.
Specifically, the pushbuttons 34a-34d correspond to the
video pictures 56a-56d, respectively. The pushbuttons
correspond to the video pictures based upon their placement
in the associated array.
When the operator desires to recall the color
corrections for the scene with the video picture 56b, for
example, the operator presses the pushbutton 34b, and those
color corrections are recalled and applied to the output of
the video s~ignal source 44. The information for producing
the video pictures on the a~xiliary monitor is stored in the
video memory 48. This information is recalled and directed
to the auxiliary monitor under the control of the computer
42. The video memory 48 can be any commercially available
video picture storage device. One such device which has
bcen used successfully is the Model ICB Image Capture Board
sold by AT&T, which is a digital device for storing and
retrieving video picture signals.
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- 1 32607 1 PATENT
333-2053
The video scene recall feature of the invention
enables the operator to quickly and easily determine and
recall particularly useful color corrections. The operator
does not have to reme~ber what scene corresponds to the
contents of buffer A or what scene corresponds to the
contents of buffer B. Moreover, the operator does not have
to think of a name for the color corrections for a given
scene and type it onto a display or write it down somewhere.
This feature of the invention presents the operator with an
easily recognizable label for specific color corrections.
Thus, the operator is better able to recall and utilize
previous color corrections. As a result, the time necessary
for color correcting a videotape is shortened. The video
scene recall feature is an alternative to the use of the
"call" pushbutton and the keyboard 30 for recalling previous
color corrections.
Figures 6A-6C show the main monitor 50 and the
auxiliary monitor 52 on a lar~er scale than in Figure 1.
Figure 6A illustrates the auxiliary monitor 52 after the
operator has identified the color corrections for two
previous scenes. The operator has used video pictures 56a
and 56b for the identification of the color corrections. In
particular, the operator has identified the color
corrections for scene 0081 with a video picture
corresponding to a person's face, and the operator has
identified the color corrections for scene 0097 with a video
picture corresponding to a house. A different video
picture, i.e., a video picture from the current scene, is
displayed on the main monitor 50 in the lower left hand
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1 32607 1 333-2053
corner of Figure 6. The operator determines the color
corrections for the current scene, as set forth above and in
the Rainbow patent, and now wishes to identify those color
corrections for later use. The operator simply presses the
"store" pushbutton, which is located in the row of
pushbuttons 36 (Figure 4), and then the operator presses the
pushbutton 34c.
Figure 6B illustrates what happens after the
operator presses these pushbuttons. The picture on the main
monitor 50 is displayed on the auxiliary monitor as the
video picture 56c, which corresponds to the pushbutton 34c,
and the scene number for the present scene, i.e., 0110, is
displayed in the auxiliary display below the video picture
56c. At any later time the operator may press the
pushbutton 34c, and the color corrections for scene 01~0
will be recalled and applied to the then current scene.
~ he operator is not required to use the video
pictures on the auxiliary monitor 52 and the pushbuttons 34
to identify the color corrections in any specific order.
For example, the operator could have pressed the button 34d
in order to identify the color corrections for the current
scene. If the operator had done so, the video picture of
the dancer would have been displayed in location 56d instead
of location 56c.
Figure 6C depicts a variation of the video scene
recall feature of the invention. If the oper~tor wishes to
compare the color corrections for two given scenes, the
operator may press the "next to" pushbutton, which is
located in the row of pushbuttons 36 in Figure 4. As an
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1 3 2 6 0 7 1 333-2053
example, assume that ~he operator has identified the color
corrections for three scenes as shown by the auxiliary
monitor 52 in Figure 6B and that the operator has pressed
the pushbutton 34b to apply the corresponding color
corrections stored for scene 0097 to the current cene shown
in the lower right hand portion of Figure 6. Now, the
operator desires to compare the effect of the color
corrections for the current scene, i.e., scene 0115, with
the effect of the color corrections for scene 0097. The
operator simply presses the "next to" pushbutton. As it is
shown in Figure 6C, the picture of the dog on the main
monitor 50 is then displayed next to the picture for scene
0097 on the auxiliary monitor, and the picture that was in
location 56c is automatically moved to location 56d.
Consequently, the operator may readily compare the color
corrections for scene 0097 with the color corrections for
scene 0115 on the auxiliary monitor 52. If the operator
wishes to examine the color correct~ons for these two scenes
on a larger scale, the operator may use the "next to master"
pushbutton, which is shown in Figure 3, thereby causing the
two video pictures to be displayed simultaneously
side-by~side on the master monitor 50.
Of course, either video picture can be shown alone
on the master monitor 50. The ability to thus display a
prior scene or frame on the master monitor 50 without
running the telecine or tape player back saves wear and tear
on the film or tape and minimizes damage due to scratching.
As a further variation, it should be understood
that the identification frames of prior scenes can be
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'`` 1 32607 1
PATENT
333-2053
selectively called up from the video memory and displayed on
the master monitor 50 instead of the auxiliary monitor. The
array of identification frames can be displayed in part of
the screen while the current scene is displayed on the rest
of the screen, or the full array of identification frames
can be displayed by itself, as desired.
The video memory 48 contains sufficient storage
for the twelve video pictures 56 on the auxiliary monitor
52. If the identification of color corrections for more
than twelve scenes is desired, the video memory 48 may
contain additional storage for the additional video
pictures. That is, the video memory 48 may contain
additional pages of memory. In order to move from one page
of the video memory, with an associated display of up to
twelve video pictures on the auxiliary monitor, to another
page of video memory, with a different display of up to
twelve video pictures on the auxiliary monitor, the "page
up" and "page down" pushbuttons are employed. ~he "page up"
and "page down" pushbuttons are located in the row of
pushbuttons 36 in Figure 4.
Figure 16 of the drawings is a flowchart
illustrating a computer program used to operate the
"Call-A-Picture" feature of the invention. The routine is
generally dcsignated by the reference numeral 500.
Initially, the routine checks to ascertain
whether the "store" button in the row 36 (Figures 2 and 4)
has been pressed, as indicated at 502. If so, the routine
then checks to determine whether a bu~ton in the array 34 of
buttons has been pressed, as denoted at 504. However, if
1 32607 l PATENT
333-2053
the "store" button in the row 36 has not been pressed, the
routine simply inquires whether a button in the array 34
(Figures 2 and 4) has been actuated, as indicated at 506.
The left branch of the flowchart in Figure 16, starting with
the decision block 504, may be considered as a ~write" mode
since video picture information is stored during this mode.
Correspondingly, the right branch of the flowchart in Figure
16, starting with the decision block 506, may be considered
as a "read" mode since video picture information is recalled
during this mode.
Once the "store" button (Figure 4) and a button in
the array 34 (Figure 4) have been pressed, the routine
determines specifically which button in the array 34 was
actuated, as shown at 508. Then, the routine stores the
video signals for the video picture appearing on the main
monitor 50 (Figure 1) in the video memory 48 (Figure 1), as
illustrated at 510. Subsequently, the routine displays a
video picture from the video memory 48 (Figure 1) on the
auxiliary monitor 52 (Figure 1) in the location 56 (Figures
1 and 6) corresponding to the button in the array 34 that
was just actuated, as indicated at 512. In addition, the
routine stores the scene number for the current scene on the
auxiliary ~onitor 52 in the numerical display directly
beneath the appropriate location 56, as depicted at 514.
Moreover, the routine identifies the color cor-
rections for the current scene with a flag corresponding to
the button in the array 34 that was just pressed, as shown
at 516. This flag will bc used during the "read" mode in
ord2r to access these color corrections and recall them from
the computer 42 ~Figure 1). For example, a button in the
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1 3 2 6 0 7 1 PATEN~
- 3~3-2053
array 34 of buttons may ~e identified with a flag through
the use of a suitable subroutine. A person having ordinary
skill in the art would understand that various techniques
may be employed to accomplish this task. Consequently, such
steps will not be discussed here in detail.
Referring now to the right branch of the routine
illustrated in Figure 16, i.e., the steps used in the "read"
mode, this mode is entered by simply pressing a button in
the array 34 of buttons (Figures 2 and 4), as shown by the
decision block 506. Once this mode has been entered, the
routine determines specifically which button in the array 34
was actuated, as indicated at 518. The routine then reads
the flag corresponding to the button that was just pressed,
as illustrated at 520.
Next, the routine uses the flag to retrieve the
associated color corrections from the computer 42
(Figure 1), as depicted at 522. For instance, a suitable
subroutine may be called and utilized to retrieve the color
corrections for the previous scene from the computer 42. A
person having ordinary skill in the art would understand
that various techniques may be employed to accomplish this
task. Accordingly, such steps will not be discussed here in
detail.
After the color corrections for the previous scene
have been retrieved from the computer 42 (Figure 1), they
are applied to the uncorrected video signals from the video
signal source 44 (Figure 1), as denoted at 524, to produce
color corrected video signals. These color corrected video
signals are delivered to the main monitor 50 ~Figure 1),
which then displays a co~or corrected picture.
1 3 2 6 07 1
PATENT
333-2053
Referring again to the right branch of the xoutine
shown in Figure 16, the blocks below block 524 depict addi-
tional aspects of the "Call-A-Picture" feature of the in-
vention.
Namely, the routine inquires whether the n next to"
button in the row 36 of buttons (Figure 4) has been pushed.
If not, no further action is taken by the routine. However,
if the "next to" button has been actuated, the routine
stores the video signals for the video picture appearing on
the main monitor 50 (Figure 1) in the video memory 48
(Figure 1), as designated at 528. The video picture on the
main monitor 50 shows the effects of the recalled color
corrections for the previous scene after they have been
applied with or without modifications to the present scene.
Specifically, the color corrections obtained through the
steps shown by blocks 518, 520, 522, and 524 are applied to
the video picture for the current scene, and then this color
corrected video picture is stored in the video memory 48, as
indicated at 528.
Subsequently, the routine displays the video
picture that was just stored in the video memory 48 on the
auxiliary monitor 52 (Figure 1), as illustrated at 530.
This video picture is displayed in a location 56 (Figures 1
and 6) that is adjacent to the location 56 corresponding to
the button in the array 34 that was pressed to enter the
"read" mode. The routine also rearranges the other video
pictures on the auxiliary monitor 52, as shown st 532, if
necessary, in order to properly position the miniaturized
video picture for the present scene.
r 1 3 2 6 0 7 l PATENT
333-2053
Blocks 534, 535, and 538 in Figure 16 illustrate
an additional aspect of the "Call-A-Picture" feature of the
invention. Starting with the decision block 534 in the
lower right-hand portion of Figure 16, the routine
ascertains whether the "next to master" button in the middle
row 26 of buttons (Figure 3) has been pushed. If not, the
routine takes no further action. However, if the "next to
master" button has been actuated, the routine reads the
video picture information for two video pictures from the
video memory 48 (Figure 1), as indicated at 536. Namely,
the video picture information for the picture that was
stored during the steps designated by block 530 is read from
the video memory 48, as is the video picture information for
the location 56 corresponding to the button in the array 34
that was pressed to enter the "read" mode. The retrieved
video picture information is displayed on the main monitor
S0 (Figure 1), as shown at 538. Accordingly, the operator
may observe the effects of certain color corrections on both
the present scene and a prior scene, and, as noted
previously, these color corrections may be modified when
théy are applied to the present scene. This observation may
be made on the main monitor S0 through the use of the "next
to master" button in order to enable the operator to clearly
view the two video pictures on an enlarged scale.
Figure 17 of the drawings is a flowchart
illustrating another computer program that may be used to
operate the "Call-A-Picture" feature of the invention. The
routine is qenerally designated by the reference numeral
600.
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1 3 2 6 0 7 ~ PATEN~
333-2053
Initially, the routine checks to determine whether
the "store" button in row 36 lFigures 2 and 4) has been
pressed, as indicated at 602. If so, the routine then
checks to determine whether a button in the array 34 of
buttons (Figures 2 and 4) has been actuated, as denoted at
604. However, if the "store" button has not been pressed,
the routine just inquires whether a button in the array 34
has been actuated, as indicated at 606. As in the flowchart
of Figure 16, the left branch of the flowchart of Figure 17
may be considered as a "write" mode, while the right branch
of the flowchart may be considered as a "read" mode.
After the "write" mode has been entered by
pressing the "store" button and then by pressing one of the
buttons in the array 34, the routine determines exactly
which button in the array 34 was pressed, as denoted at 608.
The xoutine next displays the video picture from the main
monitor 50 (Figure 1) in a reduced form on the auxiliary
monitor 52 (Figure 1), as shown at 610. The reduced video
picture is displayed in the location corresponding to the
button in the array 34 that was just actuated. The routine
then stores the present color corrections in a suitable
location in the memory of the computcr 42 (Figure 1), as
illustrated at 612. Specifically, a number of memory
locations in the computer 42 have been allocated for the
miniaturized video pictures that may be displayed on the
auxiliary monitor 52. The storage step shown at 612 causes
the present color corrections to be stored in the memory
location corresponding to the button in the array 34 that
was ju~t pressed. This storage step is the last task
performed in the "write" mode.
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1 ~607 1 P~TENT
333-2053
Referring now to the right branch of the routine
illustrated in Figure 17, i.e., to the steps used in the
"read" mode, this mode is entered merely by pressing a
button in the array 34 of buttons (Figures 2 and 4), as
shown by the decision block 606. Once this mode has been
entered, the routine determines exactly which button in the
array 34 was pressed as denoted at 614.
The routine then inquires whether the "next to"
button in the row 36 (Figure 4) has been pushed, as denoted
at 616. If so, the routine forms a split screen on the
auxiliary monitor 52, as indicated at 618. Subsequently,
the routine checks which of several split screen options has
been selected by the operator and then uses the appropriate
split screen option to divide the display on the auxiliary
monitor 52, as indicated at 620. For example, the screen of
the auxiliary monitor may be divided into left and right
halves, or into top and bottom halves~ Additionally, the
screen may be divided into three sections, with one video
picture appearing in the center section and anothcr video
picture appearing in the two sections bordering the center
section. Furthermore, the dividing line between the two
portions of the screen may be positioned as desired by the
operator.
The routine then ascertains whether the "next to"
button has again been pressed, as indicated at decision
block 622. If not, the routine repeats the steps in blocks
618 and 620. If thc "next to" button has again been
pressed, the routine restorcs the normal twelve-picture
display on the auxiliary monitor 52, as shown at 624.
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1 3 2 6 0 7 1 PATENT
- 333-2053
Referring to the right branch of the flowchart of
Figure 17, if the routine is in the "read" mode and the
"next to" button has not been actuated, the routine inquires
whether the "A" button or the "B" button or the "picture
file" button in the upper row of buttons 24 (Figure 4) has
been pressed, as indicated by the decision blocks 626, 634,
and 642.
When the "A" button is actuated during the "read"
mode, the routine changes the pointer associated with the
"A" buffer, as designated at 628. That is, the routine
causes the pointer for the "A" buffer to assume a value
corresponding to the memory location in the computer 42
associated with the button in the array 34 that was pressed
to enter the "read" mode. Then, the routine uses the
pointer to read the appropriate color corrections from the
computer 42, as illustrated at 630. The routine next
applies these recalled color corrections to the uncorrected
video signals from the video signal source 44, as indicated
at 632, to produce color corrected video signals, which are
displayed on the main monitor 50.
If the "A" button has not been pressed during the
"read" mode, the routine inquires whether the "B" button has
been pressed, as denoted at 634. If 80, the routine carries
out substantially the same steps as shown in the blocks 628,
630, and 632, in the blocks 636, 638, and 640.
If the "A" button and the NB" button have not been
pressed during the "readN mode, the routine determines
whether the ~pi~ture fileN button in the upper row of
buttons 24 (Figure 4) has been actuated. This step is
illustrated by the decision block 642. The purposc of the
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1 3 2 6 0 7 1 333-2053
"picture file" button is to cause the selected miniature
video picture in the twelve-picture display to be displayed
over the entire area of the auxiliary monitor. Accordingly,
when the "picture file" button has been pressed during the
"read" mode, the routine changes the pointer for the
"picture file" buffer, as designated at 644. The steps used
to carry out the function denoted at block 644 are
essentially the same as the steps used to carry out the
functions denoted at the blocks 628 and 636. After the
pointer has been changed, the routine uses the pointer to
read the appropriate color corrections from the computer 42,
as shown at 646. These retrieved color corrections are then
applied to the uncorrected video signals from the video
signal source 44, as indicated at 648, to produce color
corrected video signals, which are displayed on the main
monitor S0. Additionally, the routine displays the video
picture associated with the button in the array 34 that was
pressed to enter the "read" mode over the entire area of the
auxiliary monitor 52, as illustrated at 650. In other
words, the auxiliary monitor 52 shows the selected video
picture on an enlarged scale, i.e., on a scale like that of
the main monitor S0.
If neither the "A" button nor the "B" button nor
the "picture file" button has been pressed during the "read"
mode, the routine inquires whether the equipment is in the
"next to" mode, as indicated at 652. The "next to~ mode is
entered by once pressing the "next to~ button. If so, the
routine again checks which of several split screen options
has bcen selected by the operator and then uses the
appropriate split screen option ~o divide or redivide the
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1 3 2 6 0 7 1 PATENT
333-2053
display on the auxiliary monitor 52. This step is
designated at 620.
The "next to" button as described above in
connection with the flowchart of Figure 17 permits the
operator to compare two full-size video pictures
simultaneously on the auxiliary monitor. This i8
accomplished with a split screen. One video picture was
previously stored and is now being recalled, while the other
video picture is identical to the video picture on the main
monitor. However, the video signals used to produce the
latter video picture are subjected to essentially the same
type of signal processing as the video signals used to
produce the former video picture. In other words, the video
signals producing the picture on the main monitor are
initially converted into digital signals and subsequently
converted back to analog signals. This signal processing
techni~ue results in pictures on the auxiliary monitor that
are affected in the same way by the digitizing process.
Thus, the operator is better able to observe the effects of
certain color corrections on the present scene as compared
to the prior scene. Furthermore, the use of two full-size
video pictures permits the operator to better match the
telecine position and/or size adjustments for the present
scene with the prior scene.
The switching between the two video pictures on
- the auxiliary monitor may be accomplished while the signals
are in their digital form. Consequently, differential
distortions arising from conventional analog switching
circuits, e.g., wiping circuits, are eliminat~d.
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1 3 2 6 0 7 1 PATENT
333-2053
The video picture storage technique described
above in connection with Figure 17, i.e., the technîque in
which specific memory locations in the computer 42 are
allocated for color corrections associated with the
miniature video pictures on the auxiliary display, may be
thought of as "video scratch-pad memory.~ That is, the
color corrections stored in the allocated memory locations
are not necessarily related to color correction events.
These color corrections may be accessed at random, with the
miniature video pictures on the auxiliary display being
useful to remind the operator of what these color
corrections relate to. This feature permits the operator,
on a random basis, to store and recall color corrections
that were originally created on a temporary basis.
Color Correction Circuit Block Diaqram
Figures 7A and 7B together comprise a block
diagram for the color correction circuit of the color
corrector 11.
The components 130 through 176 and their
interconnections, all shown in Fiqure 7A, are described in
detail in Patent No. 4,750,050 and that description will not
be repeated in detail hera.
Referring now to Figure 7B, the serial receiver
180 and the digital logic circuits 182 serve the same
functions as described in Patent No. 4,750,050
but are modified to receive control signals for the variable
vector control circuits 184 as well as control signals for
the variablc vector mattc generator 186 and the 5iX vector
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. .
1 32607 1
~ PATENT
333-2053
matte generator 188. The variable vector control circuits
184 are described in greater detail below in connection with
Figures 8 and 9. The circuits for the variable vector matte
generator 186 and the six vector matte generator 188 are
shown and described in Patents Nos. 4,679,067 and 4,694,329.
Specifically, four programmable counters may be employed for
each of the matte generators 186 and 188. The counting
information for each of the programmable counters is
supplied by the computer 42 over the coaxial cable 178 to
the serial receiver 180. The serial receiver then delivers
correspondinq signals to the matte generator circuits 186
and 188.
In Figure 7~, the saturation multibank assembly
164 is the circuitry operated by the six control knobs in
the top row of knobs on the panel 16 in Figure 2.
Similarly, the hue multibank assembly 166 is controlled by
the six knobs in the middle row, and the luminance multi~ank
assembly 168 i8 controlled by the six knobs in the bottom
row of the panel 16. As it is well ~nown, each of the
eighteen knobs in the panel controls a parameter for colors
within a fixed sector of the color circle represented on a
vectorscope screen.
The correction summation circuit 170 sums the
signals it receives and produces correction signals for the
red ~"Rn), blue (~Bn), and green ~nG~) signals, while the
luminance summation circuit 172 similarly generates a
correction signal for the luminance ~Y~) signal~ as
described in Patent No. 4,750,050. The magnitude~ of thedcs
correction signal~ depend upon the level~ of the D.C.
X
1 3 2 6 0 7 1 333-2053
signals received from the serial receiver 180. Similarly,
the variable vector control circuits 184 provide correction
signals for the R, ~, G, and Y signals. The variable vector
control circuits receive D.C. signals from the serial
receiver 180. The magnitudes of the correction signals for
the R, B, G, and Y signals depend upon the levels of the
associated D.C> signals. The correction signals are
identified as the +R, +B, +G, and +Y signals in Figures 7A
and 7B.
The correction signals from the variable vector
control circuits 184 are added to the correction signals
from the correction summation circuit 170 and the luminance
summation circuit 172 at points 194, 196, 198, and 200. The
added correction signals are delivered to the combiner 160
(Figure 7A), where they are combined with the ~, B, G, and Y
signals from the processors 142-148 to produce color
corrected R, B, and G signals. The color corrected R, B,
and G signals are sent from the combiner 160 to an encoder
176, which produces a color corrected composite video
signal. The color corrected composite video signal is sent
to the main monitor 50 and the video tape recorder 46, as
shown in Figure 1.
The variable vector control circuits 184 output a
variable vector ~ignal when the vector determined by the R,
B, and ~ signals at the input is within the range set by the
variable vector controls. The variable vector ~ignal is
sent ovcr a line 190 to an AND gate 192 (Figure 7A). The
othor input to the AND gate 192 is a variable vector Hset
up" signal from the Nset up" pushbutton 92 on the front
panel 12. When the "set up~ pushbutton is pressed and the
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`
1 326071
~ PATENT
333-2053
variable vector signal is present, the output of the AND
gate 192 becomes HIGH and actuates a switching circuit 202.
The switching circuit 202 shorts together the R, B, and G
output signals from the combiner 160. Accordingly, a
neutral gray is produced as the composite video output of
the encoder 176. As a result, the opexator may observe on
the main monitor 50 which colors are within the range ~et by
the variable vector controls. If the colors the operator
wants to correct are not within this range, the operator may
adjust the variable vector position control 80, the delta
control 82, and/or the factor control 84, as discussed
previously.
The control knobs are each connected to a circuit
that provides a numerical value indicative of the amount of
rotation of the knob. It should be understood that this
circuit which determines the amount of rotation of one of
the control knobs 86, 88, and 90 i8 automatically reset to
zero after each storage of its settings. ~his operation
"zeros" the knobs in preparation for further corrections.
Travelinq Matte Feature
The correction signals from the variable vector
control circuits 184, the correction summation circuit 170,
and the luminance summation circuit 172 may be and normally
are applied to the video picture signals for the entire
picture. Moreover, by the use of the ~traveling ~matte"
feature of the invention, the correction signals from the
variable vector control circuits 184 may be applied to the
video signals in a predetermined area of the video picture
which is smaller than the area of the entire picture.
Similarly, the correction signals from the correction
1 32607 1 333-2053
summation circuit 170 and the luminance summation circuit
172 may be applied to another predetermined area of the
video picture which is ~maller than the area of the entire
picture.
When the operator desires to apply the correction
signals from the variable vector control circuits 184 to the
video picture signals in only a limited area of the picture,
the operator presses the "variable vector matte on"
pushbutton IFigure 3) on the front panel 12, which produces
a variable vector matte enable signal on a line 204 (Figure
7B). The variable vector matte enable signal on the line
204 is delivered to one input of an AND gate 206. The other
input of the AND gate 206 is supplied by the variable vector
matte generator 186 through a switching circuit 208.
Consequently, the output of the variable vector matte
generator 186 determines whether the output of the AND gate
206 is HIGH or LOW. I output of the AND gate 206 is HIGH,
the switches in a switching circuit 210 all are closed, but
if the output of the AND gate 206 is LOW, the switches are
open. The switching circuit 210 permits the correction
signals from the variable vector control circuits 184 to
travel to the combiner 160 (Figure 7A) only when the output
of the AND gate 206 is HIGH. The variable vector matte
generator 186 may be programmed to supply a HIGH signal to
the input of the AND gate 206 either inside of the
associated predetermined area or outside of the associated
predctermined area. Therefore, the correction signals from
the variable vector control circuits 184 may be applied to
the video picture signals either inside of or outside of the
specified area.
- 3B -
PATENT
1 3 2 6 0 7 1 333-2053
When the operator desires to apply the correction
signals from the correction summation circuit 170 and the
luminance summation circuit 172 to the video picture signals
in only a limited area of the picture, the operator presses
the "six vector matte on" pushbutton (Figure 3) on the front
panel 12, which produces a six vector matte enable signal on
a line 212 (Figure 7B). The six vector matte enable signal
on the line 212 is delivered to one input of an AND gate
214. The other input of the AND gate 214 is provided by the
six vector matte generator 188 through a switching circuit
216. Consequently, the output of the six vector matte
generator 188 determines whether the output of the AND gate
214 is HIGH or LOW. If the output of the AND gate 214 is
HIGH, the switches in a switching circuit 218 are closed,
but if the output of the AND gate 214 is LOW, the switches
in circuit 218 are open. The switching circuit 218 permits
the correction signals from the correction summation circuit
170 and the luminance summation circuit 172 to travel to the
combiner 160 only when the output of the AND gate 214 is
HIGH. The six vector matte generator 188 may be programmed
to supply a HIGH signal to the input of the AND gate 214
either inside o or outside of the associated predetermined
area. Thus, the correction signals from the correction
summation circuit 170 and the luminance summation circuit
172 may be applied to the video picture signals either
inside of or outside of the specified area.
An external matte generator, such as a special
effects generator, may be used to determine the window for
the correction signals from the variable vector control
circuits 184 and/or the window for the correction signals
- 39 -
1 32607 ~ 333-2053
from the correction summation circuit 170 and the luminance
summation circuit 172. The external matte generator
produces an external matte signal, which is delivered to
each of the switching circuits 208 and 216. The external
matte signal is enabled by the "matte external" pushbutton
(Figure 3) on the front panel 12. The operator controls the
state of the switching circuits 208 and 216 so that the
external matte generator supplies a signal to the AND gate
206 and/or the AND gate 214. Thus, the external matte
generator may determine a limited area of the picture to be
color corrected.
As an example of the foregoing, Figure 1 shows the
outlines of two windows, window W1 and window W2. The
correction signals from the variable vector control circuits
184 may be applied to the video picture signals either
inside of or outside of the window Wl. Correspondingly,
the correction 6ignals from the correction summaticn circuit
170 and the luminance summation circuit 172 may be applied
to the video picture signals either inside of or outside of
the window W2.
The size and/or the position of each of the
windows W1 and W2 may be changed by the operator by using
the window controls 20 (Figure 2) on the front panel 12.
The window controls 20 are described in detail in
application Serial No. 598,468 and application Serial No.
722,801. The windows Wl and W2 may overlap, as depicted in
Figure l.
Signals that determine the size and the position
of the windows W1 and W2 may be stored in the computer 42
for each scene or frame; just as signals for determining the
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color corrections are stored in the computer 42 for each
scene or frame. For instance, if each matte generator
includes four programmable counters, the count information
for each counter may be stored for each scene or frame.
The operator employs the window controls 20 to
determine the size and the position of a window. Once the
desired window is obtained, the operator presses the "matte
store" pushbutton (Figure 3) and signals indicative of the
size and the position of the window are stored in the
computer. The window may be altered for each new scene or
frame, if necessary. Accordingly, a window may be placed
around an object in a particular scene or frame and color
corrections applied within the window using, for example,
the variable vector controls. In subsequent scenes or
frames, the size and/or the position of the window may be
changed to follow the object. Thus, a window may "travel
with" the object from scene to scene or from frame to frame.
This feature of the invention allows greater object
selectivity and improves the quality of the final color
corrected videotape. Furthermore, this feature of the
invention in combination with the variable vector controls
permits even greater object selectivity and further improves
the quality of the final color corrected videotape.
Normally, a single window location can be used for
many different successive frames despite movement by the
object to be segregated from the remainder of each picture
frame. ~his can be accomplished by simply making the window
size and shape such that it will enclose the object at all
times during each successive frame. Then, when the movement
of the object takes it outside of the window boundaries, a
1 3 2 6 0 7 1 PATENT
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new window can be formed and stored for the frame where this
occurs, and for subsequent frames.
Of course, if the location of the boundaries of
the window must be very close to the object, a new window
can be constructed and stored for each frame or every other
frame, etc. during a particular frame sequence.
In accordance with another feature of the
invention, the boundaries of the window are made "soft" so
as to cause the color corrections made in the segregated
area to blend in with the adjacent areas as smoothly as
possible. This makes it possible to apply a color
correction in a specific portion of a relatively large
colored area and blend the corrected and uncorrected areas
togethex smoothly. For example, it is possible to form a
window in the middle of a cheek of a person's face and add
some red in the window to make the person's cheek look
rosier. The edges of the rosy area are blended smoothly
with the other portions of the cheek to give the cheek a
natural rosy appearance.
The "soft" edges of the window are formed by
forming two windows, one inside the other and spaced apart
by a predetermined distance, and by performing a linear
dissolve between the signals at the two window boundaries.
The computer may be programmed to provide a smooth
transition between the window in one scene and the window in
another scene. This may be accomplished in much the same
manner as the ~dissolve" pushbutton is employed to produce a
smooth transition between the color corrections in one scene
and the color corrections in the following scene. More
p~rticularly, each window boundary may be changed on a
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1 3 2 6 0 7 ~ 333-2053
frame-by-frame basis starting at a frame near the end of one
scene and ending at a frame near the beginning of the
subsequent scene.
With this travelling matte feature, the precise
outlines of an object to be color corrected do not have to
be defined in order for color corrections to occur over the
selected hue or hues. All that is necessary is that the
matte is positioned to include the object to be corrected
and exclude objects whose colors are to remain unchanged.
Block Diagrams for the Variable Vector Control Circuits
Figures 8 and 9 are block diagrams for the vari-
able vector control circuits 184 of Figure 7. In Figure 8,
red ("R"), green (nG"), and blue (nB") signals from the
decoder enter a luminance matrix 230 and produce a luminance
signal ("Y") at the output of the luminance matrix.
An R-Y signal is one input of a four-quadrant
multiplier 232. A B-Y signal is one input of a
four-quadrant multiplier 234. The R-Y and B-Y signals are
in quadrature. Accordingly, any vector may be selected by
taking appropriate portions of the R-Y and B-Y signals. The
sin~ and cos~ signals from the coefficient processor (shown
in detail in Figure 9) are used to select the appropriate
portions of the R-Y and B-Y signals. Other signals which
are in quadrature, such as the I and Q signals, may be
employed, however. The sin~ signal is delivered to the
other input of the four-quadrant multiplier 232, while the
cos6 signal is supplied to the other input of the
four-quadrant multiplier 234. The output signals from the
four-quadrant multipliers 232 and 234 determine the
1 32607 1 333-2053
principal color in the range of colors set by the variable
vector position control.
The range around this principal color is, however,
relatively large. Consequently, the four-~uadrant
multipliers 238, 240, and 242 are employed to narrow the
range. The R-Y signal is one input of the four-quadrant
multiplier 238, and the B-Y signal is one input of the
four-quadrant multiplier 240. A Dcos~ signal is the other
input of the four-quadrant multiplier 238, and a Dsin~
signal is the other input of the four-quadrant multiplier
240. The Dcos~ signal is like the cos6 signal except that
the amplitude is changed by the value D. Similarly, the
DsinQ signal is like the sin~ signal except that the
amplitude is changed by the value D. The output signals
from the four-quadrant multipliers 238 and 240 determine a
vector which is in quadrature with the vector determined by
the output signals from the four-quadrant multipliers 232
and 234.
The vector determined by the output signals from
the four-quadrant multipliers 238 and 240 is squared by a
four-quadrant multiplier 242 in order to eliminate any
negative portions of it. The difference between the output
signal from the four-quadrant multiplier 242 and a reference
signal is one input of a four-quadrant multiplier 236. The
other input of the four-quadrant multiplier 236 is the
difference between the output signals from the four-quadrant
multipliers 232 and 234. Consequently, the output signal
from the four-quadrant multiplier 242 modifies the vector
determined by the output signals from the four-quadrant
multipliers 232 and 234. In particular, the output signal
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from the four-quadrant multiplier 242 narrows the range
around the principal color. The value D determines the
width of the range around the principal color. By changing
the value D, the magnitude of the output signal from the
four-quadrant multiplier 242 is changed, and a larger or
smaller amount is subtracted from the reference signal at
the input of the four-quadrant multiplier 236. An
explanation of how the value D is obtained is included below
during the description of the coefficient processor.
The output signal from the four-quadrant
multiplier 236 is sent to a level discrimination circuit
244. The level discrimination circuit 244 is shown in
Figure 10 and described in greater detail below. In short,
the level discrimination circuit 244 discriminates signals
above a first preset level from signals below the first
preset level, and it discriminates signals above a second
preset level from signals below the second preset level.
Signals above the first preset level are supplied over a
line 248 to each of the four-quadrant multipliers 252, 254,
256, and 258. Furthermore, signals above the second preset
level are delivered over a line 250 to each of the four-
quadrant multipliers 252, 254, 256, and 258.
The difference between the signal on the line 248
and the signal on the line 250 is used as one input of each
of the four-quadrant multipliers 252, 254, 256, and 258.
The other input of each of the four-quadrant multipliers
252, 254, and 256 is provided by the coefficient processor,
while the other input of the four-~uadrant multiplier 2S8 is
supplied by the serial receiver 180 (~igure 7~). The
coefflcient processor d~livers signals identificd as 0,
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- 1 32607 ~
- PATENT
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120~, and 240. These signals resolve the variable vector
signal into components corresponding to the R, G, and B
signals. The signal from the serial receiver is a luminance
correction signal, which corresponds to the position of the
variable vector luminance control 90 (Figure 2) on the front
panel 12. This correction signal produces a luminance
correction ("+Y") at the output of the four-quadrant
multiplier 258. The luminance correction is delivered to
the combiner 160 (Figure 7A).
Figure 8 depicts an alternative location for the
circuit which controls the variable vector window. Namely,
a switching circuit 246 is located between the level
discrimination circuit 244 and the four-quadrant multipliers
252-258. The switching circuit 246 receives a variable
vector matte control signal, such as the output signal from
the AND gate 206 (Figure 7B), which controls whether the +R,
+G, +B, and +Y correction signals will be supplied to the
combiner 160 (Figure 7A). When the switches in the
switching circuit 246 are in the position shown in Figure 8,
the correction signals will be sent to the combiner 160;
when the switches are in the other position, the output
signals from ~he discrimination circuit 244 on the lines 248
and 250 are grounded. Consequently, no +R, +G, ~B, and +Y
signals are developed at the outputs of the four-quadrant
multipliers 252-258 and no such correction signals are
provided to the combiner 160 when thc switching circuit 246
is in its other position. Thus, the variable vector matte
control signal enables and disables the variable vector
control circuit at the boundaries of the window.
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The right-hand portion of Figure 8 illustrates a
wideband differential amplifier 259, which is connected to
the output lines of the level discrimination circuit 244 and
the switching circuit 246. The amplifier 259 provides the
variable vector signal in its output line 190. The variable
vector signal is mentioned above during the description of
Figures 7A and 7B.
As it can be seen from the foregoing description,
the circuitry shown in the left-hand portion of Figure 8 is
a versatile, accurate video color detector. Although the
foregoing description is adequate, the following
supplemental discussion should help in understanding it in
even greater depth.
Figure 12 of the accompanying drawings is a
schematic vector representation of the hue and saturation of
a given color video signal, as it is shown on the familiar
"vectorscope" used in video production equipment. The angle
"6" of the vector represents the hue or color of the
signals, and the length "S" of the vector represents the
saturation or intensity of the signals.
The color detector circuit of Figure 8 makes it
possible to rotate the vector "S" through an angle of 360
or more so as to select almost any hue as the principal
color to be detected. The hue selection control is
essentially infinitely variable.
The details of the manner in which the foregoing
is accomplished can be explained with the further assistance
of Figure 13.
Figure 13 is an enlarqed and more detailed view of
the multiplier circuit 232 shown in Figure 8. The circuit
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232 is an integrated circuit including a pair of
differential amplifiers 441 and 443 which deliver their
outputs to an analog multiplier circuit 445, which delivers
to an amplifier 447 a signal proportional to the product of
its two input signals X and Z. Amplifier 447 delivers an
amplified signal proportional to the product (X)~Z) on one
output line 451, and an inverted signal proportional to the
product ~X)IZ) on another output line 449.
One satisfactory integrated circuit chip for this
use is the MC1595L multiplier sold by Motorola, Inc.
Thus, the input signal (R-Y) is formed by the
differential amplifier 441, which has (R) applied to its (+)
input terminal and (Y) to its (-) terminal.
Each multiplier circuit shown in Figure 8, that
is, each of the multipliers 232, 234, 236, 238, 240, 242,
252, 254, 256, and 258, has the same structure as the
multiplier 232 shown in Figure 13.
Referring again to Figure 8, in a similar manner,
the (B-Y) signal is formed as one input to the four-quadrant
multiplier circuit 234. As is shown in Figure 12, the (R-Y)
and (B-Y) signals are defined to be in quadrature. The
vector "S" of Figure 12 is the resultant of the (R-Y) and
(B-Y) vector signals. The angle ~ formed by the vector "S"
is the measure of the hue of the video signals.
~ s it has been noted above, the angle ~
corresponding to the hue to be detccted by the color
detector of Figure 8 can be selected at any angle from 0 to
360. This is accomplished, in effect, by the use of a
variable, selectable passband filter circuit which filters
out all signals other than those within a certain passband
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` 1 326071
PATENT
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around the selected hue corresponding to the angle ~. Thus,
the signal (sin ~) is supplied as a second input to the
multiplier 232, and the signal ~cos ~) is supplied as a
second input to the multiplier 234. The output of
multiplier 232 is proportional to (R-Y)sin ~, and that from
multiplier 234 is proportional to (B-Y)cos 6.
The outputs from multipliers 232 and 234 are
delivered to the (+) and (-) input terminals, respectively,
of the multiplier circuit 236 so as to form the input signal
[(R-Y)sin ~ - (B-Y)cos ~].
Although the resultant color vector detected can
be rotated through an angle of 360 or more by varying 6,
the operation of the circuit described so far as a color
detector is unsatisfactory because the range of hues it
recognizes is so broad that it tends to recognize colors
substantially different from the principal color.
The latter problem is illustrated in Figure 14 in
which the curve 412 expresses the relationship between hue
and the output of the multiplier circuit 236 due solely to
the input signals described so far; that is, without
consideration of the signals applied to the lower pair of
terminals of the multiplier circuit 236. The curve 412 is
relatively broad and crosses the zero-axis at two points,
one of which leads ~ by 90, and one of which lags ~ by 90;
that is, the curve 412 covers an area spanning 180 of the
color spectrum. A second curve is shown at 416. This curve
results from a shift of the angle ~ to a new value ~'.
In prior art color dctectors, a level detector
ClrCUit i6 used to discriminate against all signals lower in
ma~nitude than a preset level 414. By this means, the range
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of hues detected by the circuit is narrowed to the area
between points A and B, where the preset level 414 crosses
the curve 412, without affecting the passband of the
detector circuit itself. Because the shape of the curve 412
remains very broad, usually the range of hues between points
A and B also is relatively broad. Furthermore, the shape of
the curve 412 makes the detector circuit largely dependent
on saturation levels rather than hue.
In accordance with a valuable feature of the
invention, the passband of the hue ~elector circuit itself
is narrowed by the use of the detector circuit shown in
Figure 8.
With this feature, the passband can be made as
narrow as 2 and as broad as 90D on either side of the
center, or principal color, subctantially independently of
the saturation of the input signals.
Multiplier 238 develops a signal of (R-Y) on its
upper terminals. A signal (Dcos ~) is developed on its
lower terminals by the circuit shown in Figure 9 which
multiplies the co~ ~ signal by a "delta" factor "D."
Similarly, (B-Y) and (Dsin ~) signals are
developed at the input terminals of the multiplier 240.
The outputs from multipliers 238 and 240 are
subtracted from one another by the input differential
amplifiers in the multiplier circuit 242 which, as noted
above, is used as a squarer. Thus, the quantity
¦(R-Y)(Dcos ~) - (B-Y)(Dsin ~)] is formed at the output of
each input differential amplifier (441 and 443 in Figure 13)
of the circuit 242~ Those signals are multiplied by one
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1 32607 1
PATENT
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another (multiplier 445 in Figure 13) to square that
quantity and produce a signal N:
N = [(R-Y)(Dcos ~) - (B-Y)~Dsin ~)]2
at the output of the squarer 242.
This signal N is sent to the lower negative input
terminal of multiplier 236 where it is subtracted from the
reference signal "REFERENCE." The resulting signal (l-N) is
multiplied with M = [(R-Y)sin ~ - (B-Y)cos 6~ and that
product is sent to the level discrimination circuit 244.
The effects of this signal processing are shown in
Figures 15A-15D, which are diagrams illustrating the
operation of the circuitry. The angle 6 or hue is plotted
horizontally against the D.C. output voltage in response to
the successive receipt of numerous signals of equal
magnitude ~ut whose hues vary throughout the visible
spectrum when a specific center hue ~ has been selected for
the passband of the circuit.
Figure lSA shows the variation of the signal M =
I(R-Y)sin ~ - (B-Y)cos ~] which is developed at one input of
the multiplier 236. It is a sine wave whose period
represents 360 of the color vector circle, with the
selected hue located at 6, the positive peak of the sine
wave.
Figure lSB shows the output of the squarer 242.
It is 90 out of phase with the wave shown in Figure 15A.
The purpose of squaring the wave at the input of the squarer
242 is to make all peaks of the wave positive. Figure 15B
basically is made up of positive loops, which have a sine2
form.
1 3 2 6 0 7 1 PATENT
333-2053
Figure 15C shows the result of subtracting the
signal N shown in Figure 15B from the reference signal. The
reference signal is a D.C. level which preferably is
selected to produce a multiplication of one when N = 0. The
waveform in Figure 15C has positive-going spikes 408 formed
by the cusps between the inverted sine loops formed by the
subtraction process.
The effects on the waveforms of a large delta
factor "D" and medium and small delta factors are indicated,
respectively, by dashed-line curve 410, solid curve 409, and
dashed-line curve 4~7 in Figure 15C.
The waveform resulting from multiplying signal M
(Figure 15A) by the signal shown in Figure 15C is shown in
solid lines in Figure 15D. The negative-going portion of
the waveform between the first and third half-cycles is
eliminated by a negative signal clipper in the level
discriminator circuit 244, so that only positive peaks
remain.
The waveforms in Figure lSD also express the
transmission characteristics for input signals of variable
hue. That is, signals having a phase angle equal to 6, the
selected phase angle defining the desired hue, are
transmitted with maximum values; other signals are
attenuated to a degree depending upon the shape of the
transmission curve, which depends on the delta "D" factor
and the number of degrees that the signal is distant from ~.
It can be seen in Figure 15D that, a~ the delta
factor "D" is increased, the passband ~1 of the circuit
decreases. With a large ~D~ factor, the passband ~1 is
relatively small. 6 is the center frequency or hue of all
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1 326071
PATENT
333-2053
of the passbands. The passband A~ formed by the use of a
medium "D" factor is wider, thus providing for the detection
of a wider range of hues around the center hue at ~.
Finally, the passband ~3 formed by a small "D~ factor is
very wide, almost 180.
Figures lSA, 15B, and 15D show the waveforms
resulting from a change of the selected hue from ~ to ~'.
The waveform for ~ has been omitted from Figure 15C to avoid
cluttering the drawing, and the waveform for ~' in Figure
15D has been separated from the waveform for 6 more than it
actually would be for the sake of clarity in the drawings.
It can be seen that the change of the selected hue
from ~ to ~' merely shifts the waveforms to the right in
Figures 15A - lSD. This changes the selected hue from near
red to a hue around magenta. If the knob 80 (Figure 2) is
turned in the opposite direction by the same amount as it
was turned to created the change from ~ to ~', shifting the
vector "S" counterclockwise from the reference burst axis
(see Figure 12), then the waveforms shift to the left by a
corresponding amount to select a color between green and
cyan. The angle ~ can be changed in very small steps or
increments, thus making the hue selection essentially
infinitely variable.
The amplitude of the signal transmitted to the
level discrimination circuit 244 is proportional to the
saturation of the color being detected. The level
discriminator circuit 244 is capable o rejecting all
signals whose saturation falls either above or below a
preset level ~uch as levels 411 and 413 shown in the
right-hand portion of Figure 15D.
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1 3 2 6 ~ 7 1 PATENT
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By setting the discrimination circuit 244 to pass only
those signals whose saturation is below a certain level, the
device 244 detects and differentiates low-saturation signals
from high-saturation signals of the same hue.
Quite significantly, low-saturation colors can be
detected without any siqnificant degradation of selectivity
in color detection. If preferred for a particular job,
high-saturation colors also can be detected for color
correction, and the ~aturation selection process avoids the
possibility of developing a detection signal in response to
the detection of a signal of the same hue but lower
saturation.
By permitting the passband to thus be variable in
both phase angle and width, the detector circuit can be
adjusted to ~elect virtually any hue, any one of a number of
different saturation levels, and a passband width so as to
adjust the detector to compen~ate for varying conditions,
and to eliminate or alleviate many of the problems mentioned
above with prior color detection devices.
Figure 9 is a block diagram of the coefficient
processor. The delta control signal, the variable vector
saturation control signal, the variable vector hue control
signal, and the variable vector position control signal are
supplied to the coefficient processor by the serial receiver
180. Each signal corresponds to the position of the
associated control on the front panel 12, or an associated
signal from the memory in the computer. Specifically,
variable vector position control signal corresponds to the
position of the variable vector position control 80; the
delta control signal corresponds to the position of the
- 54 -
1 32607 1 PATENT
333-2053
delta control 82: the variable vector saturation control
signal corresponds to the position of the saturation control
86; and the variable vector hue control signal corresponds
to the position of the hue control 88. These signals are
employed with the circuits shown in Figure 9 to produce the
sin~, cos~, Dcos~, Dsin~, 0, 120, and 240 D.C. output
signals from the coefficient processor.
The coefficient processor includes a square wave
generator 260, which produces a 2-MHz square wave signal.
The 2-MHz signal from the square wave generator 260 is sent
to a divide-by-four circuit 262. The output of the
divide-by-four circuit 262 is sent to another divide-by-
four circuit 264 and to a fundamental frequency filter 266.
The output signal from the divide-by-four circuit 264 is de-
livered to a one-shot circuit 268, which triggers a ramp
generator 270. The output signal from the fundamental
frequency filter 266 is a 500-KHz sine wave, while the
output signal from the ramp generator is a ramp. The ramp
extends for four cycles of the 500-~Hz sine wave.
In order to develop the sin6 and cos~ signals, the
variable vector position control signal is compared to two
different reference signals at the comparators 272 and 274.
The variable vector position control signal is delivered to
the minus input of each of the comparators 272 and 274. The
plus inputs of the comparators 272 and 274 are supplied by
the summation circuits 276 and 278, respectively. The
summation circuit 276 adds the ramp signal to a reference
signal, while the su~mation circuit 278 adds the ramp signal
to a different reference signal. The two different
reference signals are selected to correspond to a difference
1 ~2607 1 PATENT
- 333-~053
of 90 degrees along the 500-XHz sine wave. Accordingly, ~he
output signals from the comparators 272 and 274 change from
positive to negative at points 90 degrees apart along the
sine wave produced by the fundamental frequency filter 26~.
The output signals from the comparators 272 and
274 trigger the one-shot circuits 2B0 and 282, respectively.
The one-shot circuits 280 and 282, in turn, trigger the
sample-and-hold circuits 284 and 286, respectively. The
sample-and-hold circuits 284 and 286 sample the 500-KHz sine
wa~e from the fundamental frequency filter 266. Because the
reference signals at the summation circuits 276 and 278 were
set to correspond to a 90-degree difference, the sample-
and-hold circuits 284 and 286 sample the 500-XHz sine wave
at points which are 90 degrees apart. As a result, the
sample-and-hold circuits 284 and 286 output signals which
have a phase difference of 90 degrees, and these D.C.
signals are referred to as sin~ and cos~.
The variable vector position control signal
determines when the outputs of the comparators 272 and 274
change rom positive to negative. Consequently, the
variable position control signal determines the sin~ and
cos~ signals, and thereby sets the principal color in the
range of colors selected by the variable vector controls.
The sample and-hold circuits 288 and 290 operate
similarly to the sample-and-hold circuits 284 and 286 in
order to determine the Dcos6 and Dsin~ signals. However,
the sample-and-hold circuits 288 and 290 do not sample the
500-XHz sine wave from the output of the fundamental
fre~uency filter 266. Rather, the sample-and-hold circuits
288 and 290 sample the output signal from a multiplier 292.
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One input of the multiplier 292 is the 500-KHz sine wave
from the fundamental frequency filter 266, while the other
input of the multiplier 292 is the delta control signal.
Accordingly, the output signal from the multiplier 292 is a
500-KHz sine wave which has its amplitude modified by the
delta control signal.
When the one-shot circuits 280 and 282 trigger the
~ample-and-hold circuits 284 and 286, the one-shot circuits
280 and 282 simultaneously trigger the sample-and-hold
circuits 288 and 290. Thus, the 6ample-and-hold circuits
288 and 290 sample a 500-KHz sine wave whose amplitude has
been modified by the delta control signal to produce the
Dcos~ and Dsin6 signals, respectively. The delta control
signal, therefore, determines the value D, which sets the
width of the range of colors around the principal color.
The comparators 294-298, the summation circuits
300-304, the one-shot circuits 306-310, and the
sample-and-hold circuits 312-316 operate like the circuits
described above to produce the 0, 120, and 240 output
signals. However, the sample-and-hold circuits 312-316 do
not sample the 500-KHz sine wave from the output of the
fundamental frequency filter 266. Instead, the
sample-and-hold circuits 312-316 sample the output of the
multiplier 318, which is also a 500-KHz sine wave. The 500-
XHz sine wave output of the multiplier 318 is derived from
the 500-KHz sine wave output of the fundamental frequency
filter 266. One input of the multiplier 318 is the 500-KHz
sine wave from the fundamental frequency filter 266. The
other input of the multiplier 318 is a compensated
saturation control signal. The compensated saturation
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~ 1 326071
PATENT
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control signal modifies the amplitude of the 500-KHz sine
wave from the fundamental frequency filter 266 to produce
the output signal for the multiplier 318.
The compensated saturation control signal is
developed at the output of the summation circuit 320. One
input of the summation circuit 320 is provided by the
potentiometer 322, which delivers a portion of the variable
vector saturation control signal to the summation circuit
320. In order to generate the other input for the summation
circuit 320, a portion of the variable vector hue control
signal is supplied by a potentiometer 324 to a squaring
circuit 326. The squaring circuit 326 squares the input
signal and delivers an output signal to the summation
circuit 320. The output of the summation circuit 320 is a
saturation control signal which has been corrected for
changes in the hue control signal. Therefore, the hue of
the variable vector may be changed without altering the
saturation of the variable vector.
The sample-and-hold circuits 312-316 sample a 500-
XHz sine wave whose amplitude has been modified by the
compensated saturation control signal, as noted above. The
one-shot circuits 306-310 trigger the sample-and-hold
circuits 312-316, respectively, and the one-shot circuits
306-310 are triggered when the output signals from the
comparators 294-298, respectively, chanse from negative to
positive. The plus inputs of the comparators 294-298 are
supplied by the summation circuits 300-304, respectively.
One input of each of the ~ummation circuits 300-304 is
supplied by the ramp generator 270, while the other input is
a reference signal. The reference signals for the summation
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t 3 2 6 0 7 1 PATENT
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circuits 300-304 are set so that the sample-and-hold
circuits 312-316 sample the output of the multiplier 318 at
points which are 120 degrees apart along the associated sine
wave. The minus inputs of the comparators 294-298 are
provided with a compensated hue control signal.
The compensated hue control signal is developed at
the output of a summation circuit 328. One input of the
summation circuit 328 is the variable vector position
control siqnal, and the other input the summation circuit
328 is from a multiplier 330. A portion of the variable
vector saturation control signal is sent by a potentiometer
332 to the minus input of a comparator 334. The plus input
of the comparator 334 is a reference signal. The difference
between the reference signal and the portion of the variable
vector saturation control signal is delivered to one input
of the multiplier 330. The variable vector hue control
signal i8 furnished for the other input of the multiplier
330. Accordingly, the multiplier 330 produces as an output
a hue control signal which has been corrected for changes in
the saturation control signal. Thus, the saturation of the
variable vector may be changed without altering the hue of
the variable vector.
The output signal from the multiplier 330 is sent to
one input of the summation circuit 328. The summation
circuit 328 adds this signal to the variable vector position
control signal and delivers its output signal to the minus
inputs of the comparators 294-298. Consequently, the
ramp-plus-reference signals at the outputs of the summation
circuits 300-304 are compared to the compensated hue control
signal. The compensated hue control signal corresponds to
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the position of the hue corrected variable vector. The
ramp-plus-reference signals are used to resolve the hue
corrected variable vector signal into its R, G, and B
components.
The ramp-plus-reference signals together with the
summation circuits 300-304, the comparators 294-298, the
one-shot circuits 306-310, and the sample-and-hold circuits
312-316 cause the 0, 120, and 240 signals to be 120
degrees from one another since reference signals are set
appropriately. Hence, the hue corrected variable vector
signal may be resolved into its R, G and B components. The
compensated saturation control signal varies the amplitude
of the sine wave sampled by the circuits 312-314. Thus, the
compensated saturation control signal changes the magnitudes
of the 0, 120, and 240 signals to provide a correction
for the saturation level of the variable vector signal.
Level Discrimination Circuit
Figure 10 is a schematic diagram for the level
discrimination circuit 244 shown in Figure 8. The signal
from the output of the four-quadrant multiplier 236 enters
the level discrimination circuit 244 on a line 340. This
signal travels through a resistor R26 to the emitter of a
transistor Ql and through a resistor R25 to the emitter of a
transistor Q2. The base of the transistor Q1 is biased by
the potentiometer R16 and the resistors R17, Rl9, R21, and
R23 to prevent the conduction of all signals from the
emitter to the collector when the discrimination control
signal is zero or positive. The base of the transistor Q2
is biased by the potentiometer X15 and the resistors R18,
R20, R22 and R24 to permit the conduction of all signals
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from the emitter to the collector if the discrimination
control signal is zero. A diode CR1 prevents the bias of
the transistor Q2 from being changed by the discrimination
control signal when the discrimination control ~ignal is
negative.
The bias for the transistor Ql establishes
one discrimination level, and the bias for the transistor Q2
establishe~ another discrimination level. The level set by
the bias circuit for the transistor Ql is higher than the
level set by the bias circuit for the transistor Q2.
Signals below the associated discrimination level are
prevented from passing to the output, while signals above
the associated discrimination level are passed to the
output.
If the discrimination control signal is zero, the
transistor Ql passes no signals because the associated
discrimination level is relatively high, and the transistor
Q2 passes all positive signals because the associated
discrimination level is zero. Accordingly, the signal on
line 248 minus the signal on line 250 has a waveform like
that shown in Figure llA when the input signal to the color
correction circuit is provided by a device which generates a
spectrum of color signals.
As the discrimination control ~ignal becomes
increasingly positive from zsro, the discrimination levels
associated with the transistors Q1 and Q2 increase. The
transisto~ Q1 passes no signals because the associated
discrimination level is even higher than it was for a ~ero
discrimination control signal. The transistor ~2 passes
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only signals above the associated discrimination level.
Consequently, the signal on line 248 minus the signal on
line 250 has a waveform like that shown in Figure llB. The
discrimination level for the transistor Q2 is determined by
the discrimination control signal, which affects the bias of
the transistor Q2 through the resistor R20.
As the discrimination control signal becomes
increasingly negative from zero, the discrimination level
associated with the transistor Ql decreases, but the
discrimination level associated with the transistor Q2
remains at zero due to the diode CR1. The transistor Ql
passes only signals above the associated discrimination
level. The transistor Q2 passes all positive signals. As a
result, the signal on line 248 minus the signal on line 250
has a waveform like that shown in Figure llC. The
discrimination level for the transistor Ql is determined by
the discrimination control signal, which affects the bias of
the transistor Q1 through the resistor R19.
The sign and the magnitude of the discrimination
control signal may be adjusted by the operator with the
factor control 84 ~Figure 2) on the front panel 12 of the
color corrector 11. For instance, a clockwise rotation of
the factor control 84 may correspond to a positive
discrimination control ~ignal, and a counterclockwise
rotation of the factor control 84 may correspond to a
negative discrimination control signal. The amount of
rotation, clockwise or counterclockwise, set~ the magnitude
of the discrimination control signal.
The factor control 84 and the level discrimination
control circuit 244 provide the operator with greater
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selectivity for the color correction of particular objects.
For instance, if two objects in the video picture are
approximately the same color, but one has a relatively high
saturation level and the other has a relatively low
saturation level, the operator may select one of the objects
to receive color corrections by suitably adjusting the
factor control 84. The video picture signals for the other
object will not receive the color corrections. More
specifically, the operator may distinguish a light blue sky
from a dark blue shirt with the factor control B4 even
though these two objects have the same hue. Then, color
corrections may be developed for the selected object.
Because of this ability, the overall quality of the color
corrected videotape is improved since the operator may
develop color corrections not previously possible.
Other Variations
Even though the color corrector 11 i5 shown with
one set of variable vector controls, the color corrector may
be equipped with two or more sets of variable vector
controls. Accordingly, two or more principal colors may be
selected, one principal color by each set of variable vector
controls. In fact, a color corrector may have a sufficient
number of variable vector controls to allow the elimination
of the six-vector controls 16 (Figure 2). However, the
combination of the six-vector controls with the variable
vector controls in a single color corrector is particularly
advantageous. ~he six-vector controls usually provide
separation of the color corrections from one another which
is adequate for most color correction jobs. Since the use
of the dedicated knobs of the six-vcctor controls can be
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quite fast, the speed of operation of the equipment using
both types of controls can be fast as well as high quality.
While the level discrimination circuit is shown
and described in connection with the variable vector control
circuit, one or more of the color correction circuits for
red, green, blue, magenta, yellow, and cyan may be furnished
with such a level discrimination circuit.
The coefficient processor is illustrated and
explained with analog signal processing circuits, but a
suitably programmed qeneral purpose computer or
microprocessor may be employed in lieu of the analog signal
processing circuits. In addition, digital circuits may be
used for other components in the variable vector control
circuits.
Although particular illustrative embodiments
of the present invention have been described herein with
reference to the accompanying drawings, the present
invention is not limited to these particular embodiments.
Various changes and modifications may be made thereto by
those skilled in the art without departing from the spirit
or scope of the invention, which is defined by the appended
claims.
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