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Claims  |
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We claim:
1. A digital video color corrector comprising means for receiving digital
video input signals representing pixels of a video picture, digital
detecting means for detecting the color of each of said video signals and
for producing corresponding digital color signals, and generating means
for receiving said color signals and for generating digital output
signals, said generating means including digital computer means,
responsive to operator control signals, with look-up table means for
storing values which are a function of the phase angle of the color
detected, and for producing corresponding modification signals, and
digital combining means for combining said color and modification signals
to produce digital output signals whose hue and/or saturation is different
from those characteristics of the corresponding input signals.
2. A digital video device as in claim 1, in which said look-up table means
stores values proportional to the sine and cosine of said phase angle.
3. A device as in claim 1 in which said digital combining means comprises
digital multiplier means for multiplying said color signals and said
modification signals together to produce digital output signal whose hue
and/or saturation and/or luminance is different from that of the
corresponding input signals.
4. A device as in claim 1, including a digital record player source of said
video input signals, control means for producing said control signals,
said control means including a plurality of digital controls, selected
from the group consisting of; color balance controls; hue controls;
saturation controls; and luminance controls.
5. A digital color corrector for correcting the hue and/or the saturation
of digital input video signals whose hues falls within one of a plurality
of separate discrete regions of the color spectrum, said corrector
comprising digital color detector means for detecting which of said
regions a given digital input signal falls into, adjustment means for
separately adjusting the parameters of the hue and/or the saturation
and/or the luminance of signals whose hues fall within different ones of
said regions, said color detector means comprising three primary detectors
for detecting primary colors and three secondary detectors for detecting
secondary colors and means for combining the output of one of said primary
detectors with the output of one of said secondary detectors to produce
two output signals which together define the hue of the detected video
signals.
6. A device as in claim 5, including means for combining said output of
said one secondary detector with said output of said primary detector to
produce a new luminance signal.
7. A device as in claim 5, including storage means for storing values which
are a function of the phase angle of the color detected, selecting among
said values, and using said values in a digital multiplier to multiply the
detected color signal by said function.
8. A device as in claim 5, in which said output signals are equal to R-Yc
and B-Yc, respectively.
9. A digital color corrector for correcting the hue and/or the saturation
of digital input video signals whose hue falls within one of a plurality
of separate discrete regions of the color spectrum, said corrector
comprising color detector means for detecting which of said regions a
given digital input signal falls into, adjustment means for separately
adjusting the hue and/or the saturation and/or the luminance parameters of
signals whose hues fall within different ones of said regions, said
adjustment means including register file means for storing signals
representing a plurality of different digital signal levels, and means for
selecting one of said signal levels, wherein said color corrector includes
window forming means for forming a window of variable size and position on
a video screen, means for permitting color corrections only either inside
of or outside of said window, and means for selecting one of a plurality
of different hues to which said window is to apply exclusively, the
remaining ones of said hues being unaffected by said window.
10. A color corrector for correcting the hue and/or the saturation of input
video signals whose hue falls within one of a plurality of separate
discrete regions of the color spectrum, said corrector comprising color
detector means for detecting which of said regions a given input signal
falls into, adjustment means for separately adjusting the hue/ and/or the
saturation and/or the luminance parameters of signals whose hues fall
within different ones of said regions, wherein said color corrector
includes window forming means for forming a window of variable size and
position on a video screen, means for permitting color corrections only
either inside of or outside of said window, means for selecting one of a
plurality of different hues to which said window is to apply exclusively,
the remaining ones of said hues being unaffected by said window, and means
for forming a visible outline around said window, and giving said outline
said one hue.
11. A device as in claim 10, in which said plurality of separate discrete
regions define the three primary and three secondary colors of the color
spectrum.
12. A digital color corrector, said digital color corrector comprising, in
combination, means for detecting the hue of an input digital video signal
when it falls within a relatively narrow band of the color spectrum, means
for varying the position of said band in the color spectrum with
essentially infinite variability, adjustment means for adjusting color
parameters, digital computer means, said adjustment means including
look-up table means for storing values which are a function of the phase
angle of the hue detected, for converting adjustments of said color
parameters into digital adjustment signals for adjusting the phase and/or
amplitude of said video signal to adjust the hue and/or saturation
thereof, and means for combining said adjustment signals with said input
signals.
13. A device as in claim 12, including means for storing and retrieving
signals corresponding to adjustment signals for each scene, means for
retrieving stored adjustment signals and applying them to a later scene,
and for using to retrieved signals, with modifications, to correct said
later scene.
14. A device as in claim 12, said color corrector including window forming
means for forming a window of variable size and position on a video
screen, means for permitting color corrections only either inside of or
outside of said window, and means for selecting one of a plurality of
different hues to which said window is to apply exclusively, the remaining
ones of said hues being unaffected by said window, said window forming
means including register file means for storing signals representing a
plurality of different signal levels, and mean for selecting one of said
signal levels, and means for varying progressively the ones of said levels
selected while forming a boundary for said window, so as to give said
window a "soft" edge.
15. A device as in claim 12, in which said digital computer means includes
said look-up table means for converting adjustments made by said
adjustment means into signals which are a function on the sine and cosine
of the phase angle of the detected color.
16. A device as in claim 12 including window forming means for forming a
window of variable size and position on a video screen, means for
selectively permitting color corrections inside and outside of said
window, and means for selecting one of a plurality of different hues to
which said window is to apply exclusively, the remaining ones of said hues
being unaffected by said window.
17. A digital color detector circuit including a plurality of digital
subtracting circuit means for subtracting various combinations of color
component signals from one another, means for providing an output color
detection indication when the magnitude of one of said signals exceeds the
others, and means for delivering a digital output signal from one of said
subtracting circuit means to indicate the magnitude of the color component
signal detected.
18. A device as in claim 17 in which there are three of said subtracting
circuit means, and an AND gate connected to receive the outputs from two
of said subtracting circuit means to provide said color indication.
19. A device as in claim 18 including a multiplexer connected to select
between the outputs of two of said subtracting circuit means, the
remaining one of said subtracting circuit means providing a selecting
output signal to said multiplexer, the output of said multiplexer
comprising said digital output signal.
20. A device as in claim 17 including input terminals, each for receiving a
different color component signal, each of said subtracting circuit means
comprising a digital subtractor circuit connected to at least two of said
input terminals to subtract one of said color component signals from the
other.
21. A plurality of digital color detector circuits as in claim 20 forming a
multi-vector fixed-sector color detector, there being one of said devices
for detecting each of the three primary colors and the three secondary
colors in the color spectrum.
22. A method of digitally color correcting digital video signals, said
method comprising the steps of:
using a digital color detector for digitally detecting the color of a
specific area of a video picture to be color corrected,
producing a digital color signal corresponding to the detected color,
providing storage means with stored signals corresponding to functions of
the phase angle of the detected color,
selecting at least one of said stored signals to provide a selected hue
correction signal, and
digitally combining said digital color signal with said selected hue
correction signal to produce a hue-corrected video output signal.
23. A method as in claim 22 in which said stored signals are functions of
the sine and cosine of said phase angle.
24. A method as in claim 22 in which said combining step comprises
digitally multiplying said digital color signal with said selected hue
correction signal, said stored signals including signals representing
saturation and/or luminance coefficients, and including the step of
selecting said saturation and/or luminance coefficients from said stored
signals, and digitally multiplying said digital color signal by the
selected coefficient to provide adjustments to the saturation and/or
luminance values of the video signals forming said area of said video
picture.
25. A method as in claim 22 including the further steps of storing said
corrected signals for application to frames in a video sequence, recalling
said corrected signals for later use, and recording said signals on a
video record medium.
26. A method as in claim 22 including the steps of sequentially displaying
frames in a video moving picture sequence, stopping said video sequence,
performing corrections, re-starting the motion of said sequence, and
recording the corrected picture sequence on a digital video recorder
capable of starting and stopping during recording of a sequence, and
starting and stopping said recorder in synchronism with the stopping and
starting of said sequential display. |
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Claims |
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Description |
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This invention relates to the color correction of video signals, and
particularly to the digital color correction of digital and analog video
signals.
Modern video color correctors are highly versatile and accurate in
separating and correcting various colors in video signal programs. The
"Sunburst" color corrector sold by Corporate Communications Consultants,
Inc., and shown in U.S. Pat. No. 4,862,251, and others, is an example of
such prior art color correction systems and methods.
The color correction processes performed in such equipment are basically
analog in nature. Essentially, all analog systems are subject to the
problems of electrical noise in the signals, drift, and, under certain
circumstances, lack of reliability. Also, there are problems caused by the
vectorial combination of analog signals in some prior analog devices. It
long has been desired to produce a digital color corrector and method to
take advantage of the fact that digital systems are essentially
noise-free, free of drift, and highly reliable in operation, and it long
has been desired to provide color correction free from the other problems
mentioned above.
Although equipment has been offered claiming to perform some color
correction procedures digitally, it is not known that anyone has yet
provided an operating, full-feature digital color corrector or method.
Accordingly, it is an object of the present invention to provide a digital
color corrector which overcomes or alleviates the foregoing problems.
More particularly, it is an object to provide such a color corrector which
performs all or substantially all of the sophisticated functions of prior
analog equipment, but does so in the digital domain.
Furthermore, it is an object to provide such equipment which is relatively
noise-free, highly reliable, and is relatively free of drift.
Still further, it is an object to provide such a color corrector and method
which avoid the problems associated with the vectorial combination of
analog video signals in the usual analog color correction system and
method.
It is another object to the invention to provide such a device and method
which is a relatively simple and inexpensive to use.
Another problem with prior color correctors using windows to restrict the
areas in which color changes are effective is that such devices prevent
the correction of other areas without first disabling the window or moving
it. Furthermore, prior windows are restricted in their usefulness.
Therefore, it is yet another object of the invention to provide a video
color corrector and method in which windows are provided which do not have
the foregoing deficiencies, and which permit greater flexibility and
utility in their use.
In accordance with the present invention, the foregoing objects are met by
the provision of a color corrector and method in which corrections are
made entirely digitally, without the vectorial combination of analog
signals. A digital computer is provided to convert color parameter
adjustments into digital correction signals which will change the apparent
phase and amplitude of the signals in a manner so as to create the desired
corrections.
Preferably, separate fixed-range color detectors are provided, each with
controls to adjust the hue and/or saturation and/or luminance of signals
which fall within that fixed sector of the color spectrum. Advantageously,
the fixed sectors correspond to the sectors for the three primary and
three secondary colors; that is red, blue, green, yellow, magenta, and
cyan. A separate adjustment knob is provided for each of the hue,
saturation and luminance parameters for each of the six sectors.
Advantageously, a second color correction circuit is provided in which
correction of the hue, saturation and luminance of colors falling within a
single relatively narrow band can be accomplished. The position of the
band in the color spectrum is essentially infinitely variable. Preferably,
the width of the band is variable to a very narrow width.
It also is preferred that digital means is provided for forming one or more
windows on a video screen displaying the pictures being corrected. The
windows are given "soft" edges or boundaries by storing different signal
levels in register files and progressively shifting the signal levels to
change colors gradually when forming the boundaries of the windows.
In addition, a color corrector is provided in which it is possible for the
operator to select one color out of many for exclusive operation with a
window. The group of hues among which a selection can be made
advantageously includes the three primary and secondary colors. Moreover,
a separate window can be provided for each of those six colors. Together
with a separate window for the narrow-band circuit a total of at least
seven windows can be formed and used in a given picture.
Advantageously, correction of the selected color can be made inside the
window, and a different one outside of the window. All other hues remain
unaffected by a window dedicated to one hue, and can be color-corrected
simultaneously with the selected color, in all parts of the picture.
The foregoing objects, features and advantages of the invention will be set
forth in or apparent from the following description and drawings.
IN THE DRAWINGS
FIG. 1 is a schematic circuit diagram showing a color correction system
constructed in accordance with the present invention;
FIGS. 2, 3, 4 and 5 are schematic circuit diagrams of the digital video
processor of the system shown in FIG. 1; and
FIGS. 6 and 7 are schematic circuit diagrams of a portion of the circuit of
the system of FIGS. 1-5.
GENERAL DESCRIPTION
FIG. 1 shows a color correction system 10 which includes control panels 12
and 14, a main data processor 28, and a digital video processor 30.
Digital video signals are developed by a digital video tape or disc player
32. The player 32, such as the Sony DVR10 professional recorder-player,
converts analog video signals into digital form. Analog-to-digital
convertors for the same purpose also are commercially available.
The digital video signals are sent to the digital video processor 30 which
performs color correction and produces color-corrected digital output
signals corresponding to the input signals. The output signals are
recorded on a digital recorder 36. The color corrected pictures are
displayed on a "digital" color monitor 34. This monitor is an analog
monitor with digital-to-analog converter means.
In use, digital video signals are developed by the player 32. Color
corrections are made by use of the control panels 12 and 14, and
digitally-corrected color signals are stored in the main data processor 28
for each separate scene or frame in a video program.
Preferably, the player 32 is stopped at or near the beginning of each new
scene in the video program so that a frame from that scene is displayed on
the digital color monitor 34. The color corrections are made by operation
of the controls on the control panels, the connected signals are stored in
the main data processor, and the player is started and moved to the next
scene where the procedure is repeated.
If desired, any prior correction which has been stored in the main data
processor can be recalled and applied to a later scene or frame in
essentially the same manner as shown and described in the "Sunburst" U.S.
Pat. No. 4,862,251; the "Rainbow" U.S. Pat. No. 4,096,523; the
"Call-a-Picture" U.S. Pat. No. 4,763,186 and other prior patents
identified in those patents.
After the entire program has been color corrected in this manner, the tape
player 32 can be re-wound to its start position, and the entire color
corrected program can be recorded by use of the digital recorder 36, with
color corrections being recalled from memory in the main data processor 28
upon the detection of the first frame of a new scene, etc., as is
well-known in the prior art.
Advantageously, unlike most or all analog recorders, the digital recorder
36 is capable of recording with intermittent motion. Therefore, each scene
of the program can be recorded immediately after corrections are complete,
without returning the player 32 to its starting position and replaying the
input record.
The color-corrected digital output signals can be used at intermediate
points in editing systems, and in other systems or equipment in which such
signals are used.
CONTROL PANELS
The control panels 12 and 14 have essentially the same controls as shown in
FIG. 2 of the drawings of the Sunburst U.S. Pat. No. 4,862,251.
The controls include a group 16 of color balance controls including rotary
adjustment knobs for gain, gamma and pedestal for red, green, blue and
luminance. Preferably, each of the controls is a rotary shaft-position
encoder device which provides a digital output indication of its movement.
The section 18 includes 18 rotary controls; six each for hue saturation and
luminance for yellow, green, cyan, blue, magenta and red, the primary and
secondary or complementary colors.
The controls 20 include a variable-vector selector control 21 for selecting
a narrow band of the color spectrum in which to detect colors, and other
controls for setting the width of the band, and setting the saturation
level of signals detected in the band, as well as knobs for adjusting the
hue, saturation and luminance of the colors detected.
The controls 22 include a variety of further controls, as further explained
in the Sunburst patent.
The controls in the lower portion 26 of panel 14 include all of the
functions as shown in FIG. 3 in the Sunburst patent, as well as controls
for the "Interweave" function of U.S. patent application Ser. No. 257,647
filed Oct. 14, 1988, Now U.S. Pat. No. 4,954,883, and the "Call-A-Picture"
function shown in U.S. Pat. No. 4,763,186 which enable the operator to
select color corrections from a prior corrected scene by choosing the
scene from a display of miniature images of prior scenes on a supplemental
monitor (not shown).
The panel sections 24 and 26 also include the usual controls for starting
and stopping the video signal source, storing data, etc., as set forth in
the Sunburst patent.
DIGITAL VIDEO PROCESSOR
FIGS. 2 through 7 show the digital video processor 30 in some detail. The
figures are drawn so that the output signals on the lines at the right of
each of FIGS. 2, 3 and 4 are continued as input lines to the circuitry on
the following sheet, with exceptions as noted on the sheets themselves.
Therefore, to obtain a complete diagram, the four sheets, FIGS. 2, 3, 4
and 5 should be laid side by side, in numerical sequence. FIGS. 6 and 7
show a portion of the circuitry in greater detail.
Now referring to FIG. 2, the input lines 38 at the left are adapted to
accept digital video signals, and lines 40 will accept analog video
signals. Digital video inputs can be applied to each of the two lines A
and B, and the machine selects the input to be processed.
Digital video signals on either line A or B pass through an input processor
and digital matrix circuit 42, of known construction, which converts the
signals into digital R,G,B, and Y signals; that is, red, green, blue and
luminance signals. Those signals are delivered to an input selector
circuit 48, which is a multiplexer which selects among the digital video
inputs, analog video inputs, or test signals from a test signal generator
46, depending upon the form of the input signals to be corrected.
Analog input signals are converted to digital form by an analog-to-digital
convertor 44. Once the signals are converted to digital form, the
processing continues in the same way as for digital video input signals.
The multiplexer is controlled by signals received through a line 62 from a
computer data bus 60 labelled "C DAT" from a microprocessor computer 54.
The computer 54 receives serial data on an input line 56 from the control
panel by way of the main data processor 28, or from the main data
processor itself. The microprocessor is a 16-bit processor such as the NEC
V40.
The microprocessor 54 operates with a set of tables 58 which take the form
of EPROM's which store data and algorithms for use in converting shaft
position changes of the control knobs, etc. into corrections for the
various color parameters corrected by the system, as it will be explained
in greater detail below.
The R,G,B, and Y signals output from the input select circuit 48 go to a
color balance circuit 50. The color balance circuit 50 includes a red
processor 51, a green processor 53, a blue processor 55, and a luminance
processor 57. Each of these processors is known and will not be described
herein. It is used to modify the gain, gamma and pedestal of each of the
red, green, blue and luminance signals in accordance with the operation of
the controls on the panel 16 (FIG. 1). The signals from those controls are
sent through the microprocessor 54, the data bus 60 and the line 64 to the
processors 51, 53, 55 and 57.
After being modified digitally in the color balance processors, the R,G,B,
and Y signals are sent to a color level processor 52 which performs
essentially the same functions as those set forth in U.S. Pat. No.
4,866,511.
Responsive to signals received over the line 66, the color level processor
digitally modifies the overall color level of the signals.
Modification of colors in accordance with pre-determined curves is
performed substantially as described in U.S. Pat. No. 4,866,511 for
signals whose luminance is in the high range; or in the mid-range, or in
the low range. The data establishing the curves is stored in look-up
tables. In addition, the color level processor subtracts the luminance
signal from each of the R,G and B signals and supplies the R-Y, G-Y and
B-Y signals on the output lines 68 which go to FIG. 3. The luminance
signal by-passes the circuitry of FIGS. 3 and 4 and goes directly to the
circuit of FIG. 5.
COLOR DERIVATIVE CIRCUIT
FIG. 3 shows digital color derivative circuit 69. In that circuit, the R-Y,
G-Y and B-Y inputs at 68 are delivered to a 6-Sector discrete sector hue
detector 70. The detector 70 contains individual circuits 72, 73, 74, 75,
76 and 77, each of which is adapted to detect signals in a particular
sector or band of the color spectrum; specifically in the red, green,
blue, yellow, magenta or cyan sector, respectively.
Each of the circuits 72-74 produces an output signal on its output line 80,
81 or 82 when the data representing a pixel of the picture represents red,
green or blue. It should be noted that the pixel can have only one of the
three primary colors. Therefore, the output lines 80, 81 and 82 are
connected together ("ORed") at a point, 84 to reduce the circuitry
required.
Each pixel may have one of the three secondary colors yellow, magenta or
cyan, but it cannot have more than one of the secondary colors. Therefore,
the output lines 86, 87 and 88 of the three detector circuits 75, 76, and
77 are similarly connected together at a point 90.
Each circuit 72-77 has an output line 78 upon which a signal appears
whenever it detects color. Each of these lines 78 is connected to a
register files circuit 92 which has seven levels of output latching
circuits. Each of the seven levels represents a different level of output
magnitude.
Register files circuit 92 delivers signals over three output lines 100 to
each of three multipliers 104, and each of three other output lines 102
delivers signals to one of three multipliers 105. The signals delivered on
lines 100 and 102 are pre-determined functions of the sine and cosine of
.THETA., the phase angle of the detected color.
As it is disclosed in the Sunburst U.S. Pat. No. 4,862,251, by varying the
sine and cosine of .THETA., one can change the hue of the output digital
signals to make hue corrections.
Similarly, saturation corrections are made by increasing the co-efficient
of the sine and cosine functions.
The outputs of the ones of the circuits 72-77 which detect color then are
directed, together with a signal on one of the lines 100, 102 to one of
the multipliers 104, where the signals are digitally multiplied together
to produce, respectively, R-Y', B-Y' and .DELTA.Y', R-Y.sup.c, B-Y.sup.c,
and .DELTA. Y.sup.c (the prime stands for "primary" and the "c" stands for
complementary or secondary color).
The outputs of the multipliers 104 and 105 are connected as shown to three
adding circuits 106. One of the adding circuits produces an output signal
equal to R-Y.sub.c. The second produ | | |
