| 摘要 |
<p>A time base corrector apparatus for removing time base errors from video signals. A voltage-controlled oscillator (VCXO) (154) is locked to the chroma burst of the input signal. The VCXO (154) 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 (203) to interpolate consecutive pixels. A sync error detector circuit (207) determines the sync threshold position to sub-pixel accuracy. Sync error process logic circuit (208) determines the integrated line length and line to line error. A coefficient generator (209) determines the coefficients necessary to correct this error for every pixel. The interpolator (203) then uses a polynomial interpolation technique. The interpolator (203) 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. Interpolator (203) compensates for too many pixels per line by incorporating the values of the input pixels into the proper number of pixels by an interpolation technique. The pixel values are decimated and written to a write buffer (211).</p> |
