The Grass Valley Group, Inc.

Tektronix, Inc.

Daniel J Chaplin

Christopher R Hansen

Paul Martell Trethewey

Brion L Dunbar

Paul M Trethewey

R Barry Angell

Paul S Miller

A motion detector and improved key signal interpolator using the same inputs a video signal to both a frame and a field based interpolator to produce both frame and field interpolated signals. The frame and field interpolated signals are input to a mixer. The frame interpolated signal also is input to a frame delay circuit, the output of which is subtracted from input to produce a motion signal. The motion signal is converted by an absolute value/lookup table into a mix signal that is also input to the mixer. The mix signal determines which interpolated signal at the input is passed to the output, the field interpolated signal being passed when motion is detected and the frame interpolation signal being passed when motion is not detected. A temporally filtered frame interpolation signal may be produced from the output and input of the frame delay circuit, and the mix signal in response to a temporal filter coefficient input to the absolute value/lookup table mixes the temporally filtered frame and frame interpolated signals to produce a final frame interpolated signal that in turn is mixed with the field interpolated signal to produce the output signal.

Motion detector and key signal interpolator using same

A graphic display for chroma keyer controls presents background hue as a radial spoke of an outer chroma vector circle, with selectivity being displayed as a wedge about the radial spoke. Foreground suppression may be added to the graphic display by providing a concentric inner chroma vector circle with the foreground suppression hue being a radial spoke of the inner circle and foreground selectivity being a wedge within the inner circle about such radial spoke. That portion of the outer circle that is overlapped by the inner circle is suppressed, or rendered invisible, so that the background chroma information appears as a torus about the inner chroma vector circle.

Graphical display of chroma keyer controls

A chroma keyer with correction for background defects generates a control signal that does not include variations associated with the background defects. The chroma magnitude of a reference signal that represents a chroma key set with a color background scene without a foreground object is used as a divisor for a hue select signal generated by a hue selector from a chrominance component of an input signal that represents the chroma key set with the foreground object to produce a chroma key control signal. The chroma key control signal is combined with the reference signal to produce a control signal for background suppression. The chroma key control signal also is input to a key circuit to produce a key signal for shaping a new background scene. The reference signal also may be combined with a uniform color signal from a reference matte generator to produce an error signal that is combined with the chroma key control signal to produce the control signal for correction of the background defects in the input signal.

Chroma keyer with correction for background defects

A self keyer with background gap fill adds background video to the gap between the background video and a fill video resulting from self key error. The self keyer performs the general function:

Self keyer with background gap fill

A chroma keyer with fringe control offset adds a fringe control offset value to a correlation output produced by a hue selector. The hue selector compares the hues of a foreground image, representing a foreground object in front of a reference matte background, with a reference hue corresponding to the reference matte background to produce the correlation output. The adjusted correlation signal is then negatively clipped and provided at the output of the hue selector as a hue select signal that is used for deriving a chroma key signal and for providing background suppression to the foreground image.

Chroma keyer with fringe control offset

A chroma key generation method and apparatus are provided (for both composite and component video) in which an operator selects a reference portion of a color television image to identify it as the background of the image, and a strobe signal is then generated whenever the video data that is presently passing through the keyer is within the reference portion of the color video image. This strobe causes the video data corresponding to that portion of the image to be stored. A microprocessor then determines attributes of the video in the reference portion of the color image from the stored video data, these attributes including a reference hue, .alpha.. The image hue .THETA. at each pixel in the color image is correlated with the reference hue .alpha. to produce a correlation signal that has a first range of values for points of the color image at which the image hue matches the reference hue and a second range of values for points of the color image at which the image hue does not match the reference hue. After further processing, this correlation signal becomes a chroma key signal. The attributes of the video in the reference portion of the image are employed via the microprocessor to process the video signal and associated chroma key signal in several ways, including background suppression matte generation, shadow clip level input to the shadow comparison circuitry and the gain of the key signal variable gain comparator.

Chroma key method and apparatus

Apparatus for combining video signals comprises first and second static effect channels for generating first and second full-field video signals respectively. A transition control signal generator generates first and second transition control signals each having a full-field domain and a predetermined range, the sum of the first and second control signals nowhere exceeding the predetermined range. Arithmetic circuitry multiplies the first video signal by the first transition control signal to generate a first addend signal, multiplies the second full-field video signal by the second transition control signal to generate a second addend signal, and sums the first and second addend signals to provide an output video signal.

Apparatus and method for combining video signals to provide an output

An improved self keyer generates a pre-emphasized fill video signal that compensates for the multiplication of the fill video signal with a self key signal derived from the fill video signal, i.e., reduces the black content at the transition. The fill video signal is multiplied by twice the complement of the self key signal and then added to the fill video signal to produce the pre-emphasized fill video signal. The pre-emphasized fill video signal is then combined with a background video signal under control of the self key signal.

Self keyer with pre-emphasized fill video

A keyer with variable shaping combines the benefits of a luminance keyer with those of a linear keyer using a single set of gain and clip controls. A key signal is input to a first amplifier having a high gain that is variable over an upper portion of a gain control signal's range. The output of the first amplifier is compared with a clip control signal and input to a second amplifier having a low gain that is variable over a lower portion of the gain control signal's range. The second amplifier includes a feedback circuit that provides minimum gain and shaping when the feedback signal is maximum, and provides maximum gain and shaping when the feedback signal is minimum.

Keyer with variable shaping

A non-linear keyer breaks a key processor transfer function into two pieces, one above and one below a clip level. Each piece may be modified independently and then recombined to produce the desired non-linear transfer function.

Non-linear keyer

An improved self keyer preconditions a fill video prior to mixing with a background video under control of a self key signal derived from the fill video. A variable gray luminance signal is substituted for low luminance portions of the fill video under control of a precondition key signal derived from the self key signal to produce the preconditioned fill video. The resulting output video has a smooth luminance transition between the fill and background videos in lieu of an unpleasant black artifact at the edges of the fill video.

Self keyer

A method for accumulating component video signals non-additively adds the luminance components to produce an accumulated luminance component, and additively adds the chrominance components to produce an accumulated chrominance component. The accumulated chrominance component may be clipped to limit chrominance values in an overlap area to legal color values. The intentional overlap of the component video signals produces an accumulation special effect in the overlap area.

Component video accumulation effect

Video effects apparatus comprises a pattern generator for generating a mix control signal which, when used to control the combination of first and second input video signals to provide an output video signal, defines the geometrical shape in a composite output scene of a transition between a first component scene represented by the first input video signal and a second component scene represented by the second video signal. The pattern generator responds to a size control signal by causing the mix control signal to vary in a manner such that the area of the composite output video scene that is occupied by the first component scene changes relative to the area of the second component scene while the geometrical shape of the transition between the component scenes remains the same. A shadow generator generates a signal which adjusts the visual characteristics of the second component scene synchronously with the variation of the control signal.

Shadow visual effects wipe generator

Video special effects apparatus comprises both an analog pattern generator and a digital pattern generator. The analog control signal generated by the analog pattern generator and the digital control signal generated by the digital pattern generator are combined to provide a hybrid control signal, and the hybrid control signal is used to control the wipe between two video signals.

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Nevada City, CA, United States of America

Daniel J Chaplin