Method and apparatus implemented in a computer system for determining the frequency used by a graphics source for generating an analog display signal

摘要

A display unit which can determine the frequency (original frequency) used by a graphics source for generating an analog signal. A sequence of test patterns are generated according to a predetermined convention. The sequence of test patterns are encoded in an analog display signal in a graphics source and transmitted to a digital display unit. The digital display unit samples the analog display signal to generate a sequence of sampled values. The digital display unit determines whether the sampled values equal one of the sequence of test patterns based on the predetermined convention. The digital display unit varies (changes) the sampling frequency until the sampled values equal one of the sequence of test patterns. The sampling frequency equals the original frequency when the sampled values equal the sequence of test patterns. In one embodiment, zeros and ones are used in alternate positions of each horizontal line. The absence of runs in the sampled values indicates that the sampling frequency equals the original frequency.