Texas Instruments Corporation

John Michael Hayden

Bing Ouyang

Troy Lane Ethridge

Anuradha Sundararajan

Larry D Dickinson

Hong Jin Cho

Jeff Kordel

A system and method for detecting a sampling clock offset of an analog-to-digital converter used to digitize an analog image signal. A method comprises buffering samples of an analog image signal, computing a value of an autocorrelation function using the buffered samples and a delayed version of the buffered samples, and repeating the computing a value for delays in a range of delays. The method also comprises computing a sampling frequency offset from the values of the autocorrelation function and changing a sampling frequency using the sampling frequency offset.

System and method for clock offset detection

A method and apparatus for an analog-to-digital video signal converter. The converter is controlled by a clock with controllable frequency and phase for sampling an analog signal. A circuit corrects the clock frequency using a period of a columnar frame differences as a function of columnar location. The sampling clock frequency is changed by an amount dependent on the period of the columnar differences. A second measure of the difference between successive frames is computed for a sequence of clock phases. The frequency of the clock is verified using a characteristic of the second measure. The characteristic can be the ratio of the maximum to the minimum of the second measure over selected clock phases. Other characteristics can be used such as a difference of a maximum and a minimum measure.

Method and apparatus for analog graphics sample clock frequency offset detection and verification

A method and apparatus for an analog-to-digital video signal converter. The converter is controlled by a clock with controllable frequency and phase for sampling an analog signal. A measure of the difference between successive frames of the image is computed for a sequence of clock phases. The measure can be a count taken over pixels of the magnitude of the difference between a pixel in one frame and the corresponding pixel in a following frame exceeding a threshold value. The frequency of the clock is verified using a characteristic of the frame difference. The characteristic can be the ratio of the maximum measure to the minimum measure over the selected clock phases. Other characteristics can be used such as a difference of a maximum and a minimum measure.

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John Michael Hayden