Abstract: A digital video synchronizer for providing parallel and coordinated synchronization paths for decoded and undecoded video. Processing is added for a parallel path in a synchronization memory that bypasses the comb filter and video decoder circuitry to allow a digitized composite video to pass through unchanged. This parallel path is coordinated with the decoder path to provide features of both a composite video synchronizer and a digital component decoder/synchronizer with time base corrector. A digital encoder transforms component video back into modulated composite video. The digital encoder generates a synchronizing and color burst signal to replace the sync and burst signals of the composite video signal. The synchronized composite and synchronized encoded signals are adjusted in timing, gain and DC offset to match one another so that the signals can be faded, mixed, or multiplexed without detectable differences.

Abstract: A time base corrector apparatus for removing time base errors from video signals. A voltage-controlled oscillator (VCXO) is locked to the chroma burst of the input signal. The VCXO is used to digitize the input video, to comb filter and to demodulate chroma signals. Time base correction is accomplished by lengthening or shortening each video line in sub-pixel increments by using an interpolator circuit to interpolate consecutive pixels. A sync error detector circuit determines the sync threshold position to sub-pixel accuracy. Sync error process logic circuit determines the integrated line length and line to line error. A coefficient generator determines the coefficients necessary to correct this error for every pixel. The interpolator then uses a polynomial interpolation technique. The interpolator compensates for too few pixels per line by compressing the stretched pixels to the proper size and by creating new pixels from a portion of the pixels immediately before and after the created pixel.

Abstract: A digital comb filter for decoding composite video signals into a luminance and a chrominance component. A Fast Fourier Transform (FFT) circuit or a band split filter circuit is used to determine important characteristics of an input video signal without demodulating the video signal. The circuits produce a signature signal by which each of the video lines can be correlated. Signature signals on various surrounding video lines that are of opposite subcarrier phase with the current line are compared to determine similarity and appropriate weighting coefficients for the surrounding lines. If none of the surrounding lines are similar, the comb reverts to a band split filter to form chrominance. A noise measure circuit determines an error signal input used to adjust the weighting coefficients as the noise level increases or decreases. Multiplexer combines high pass and low pass taps of a band split filter into a single data stream.

Abstract: A composite video decoder that separates digitized composite video signals into luminance and chrominance, demodulates the chrominance signal to its R-Y and B-Y components, removes time base errors, synchronizes the output to the station reference signal and converts three parallel digital signals to a serial digital output signal. A three dimensional digital comb filter, an interpolation circuit for time base correction, a sync error detector circuit, a noise measurement circuit and a means of using the noise measurement level to adapt the other circuits for best operation at various noise levels of the video input signal provide high quality translation from a composite video input to a serial digital interface output (SDI). A digital line recursive filter is used to extract the horizontal synchronizing signal whether the signal is clean or masked by a very high noise level riding on the video signal.

Abstract: A digital comb filter for decoding composite video signals into a luminance and a chrominance component. A Fast Fourier Transform (FFT) circuit or a band split filter circuit is used to determine important characteristics of an input video signal without demodulating the video signal. The circuits produce a signature signal by which each of the video lines can be correlated. Signature signals on various surrounding video lines that are of opposite subcarrier phase with the current line are compared to determine similarity and appropriate weighting coefficients for the surrounding lines. If none of the surrounding lines are similar, the comb reverts to a band split filter to form chrominance. A noise measure circuit determines an error signal input used to adjust the weighting coefficients as the noise level increases or decreases. Multiplexer combines high pass and low pass taps of a band split filter into a single data stream. Line delays delay the current video signal to form two additional lines of video.