Method and apparatus for reducing the effect of alias components produced through non-linear digital signal processing, such as gamma correction, by selective attenuation

摘要

In non-linear digital video processing, high frequency components resulting from the non-linearity may appear as spurious low frequencies due to mirror image spectral reflection in the sampling frequency fs. The non-linear circuit may be a gamma corrector (35). The effect of the alias components is reduced by the use of a modifier circuit (50) before the gamma corrector, and a corresponding equalizer circuit (52) after it. The modifier attenuates the high frequency signal components, especially in the region fs/4 to fs/2. The equalizer substantially reinstates the overall frequency response. Both modifier and equalizer may be transversal filters (FIGS. 5 to 8) which, more generally, may be one dimensional or two dimensional (FIGS. 9 and 10). The system is also particularly relevant to progressively scanned sources; including telecine.