Cirrus Logic Inc.

Crystal Semiconductor Corporation

Juergen M Lutz

Ronald D Malcolm

Ligang Ke

A system and method for conversion of graphics from computer graphics formats to television formats is disclosed. More particularly, an improved scaling and flicker reduction system and method is disclosed for scaling personal computer (PC) graphics formats into different resolution television (TV) formats and for reducing flicker due to the conversion process of interlacing non-interlaced PC graphics to match interlaced TV formats. The scaling implementation reduces line buffer requirements by using a conditional scaling technique for converting graphics from a PC resolution format to a TV resolution format. The flicker reduction implementation provides a two-dimensional adaptive filter that selects between multiple filters so that different parts of an image may have different flicker reduction and different levels of trade off between flicker reduction and resolution. The system and method disclosed are more generally applicable to converting images from one resolution to another and to reducing flicker in images converted from a non-interlaced format to an interlaced format.

System and method for utilizing a two-dimensional adaptive filter for

A periodic multi-bit digital signal is synthesized having a frequency that is specified by the frequency of a periodic reference signal that is asynchronous with respect to a sampling clock of the periodic digital signal. In a digital video system, for example, a digital color subcarrier is synthesized and synchronized to a reference frequency of a crystal oscillator that is asynchronous with respect to a digital system clock for the digital video system. The periodic digital signal is generated by an adjustable digital oscillator clocked by the sampling clock. The frequency or phase of the periodic digital signal is compared to the frequency or phase of the periodic reference signal to produce an adjustment value for adjusting the periodic digital signal to synchronize the periodic digital signal with the periodic reference signal. The digital oscillator, for example, generates the periodic digital signal at the sampling rate by periodically incrementing an accumulator with the adjustment value. The frequency or phase of the periodic digital signal is compared to the frequency or phase of the periodic reference signal, for example, by an up/down counter that is incremented or decremented each cycle of the reference signal and is decremented or incremented each cycle of the digital carrier signal to compute the adjustment value.

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Austin, TX, United States of America

Juergen M Lutz