Relative channel delay measurement
View Patent ↗A method of measuring relative channel delay between components of a video signal includes removing a local mean from each of the pair of input component signals and cross-correlating the resulting pair of input component signals. A mean is removed from the cross-correlation and a centroid for the cross-correlation is found within a region bound by nearest zero-crossing to a peak in the cross-correlation. The centroid is then converted to a delay time as a function of sample rate after removing a sample offset. Also a normalized peak value of the cross-correlation provides a figure of merit for the probable accuracy of the delay measurement.
1. A method of measuring relative channel delay between a pair of component signals of a video signal comprising the steps of:
removing a local mean from the pair of component signals to produce a pair of filtered component signals;
obtaining a cross-correlation between the pair of filtered component signals;
finding a centroid for the cross-correlation; and
converting the centroid to a delay time as a measure of the relative channel delay.
2. The method as recited in claim 1 further comprising the step of converting the pair of filtered component signals to absolute values prior to the obtaining step.
3. The method as recited in claims 1 or 2 wherein the finding step comprises the steps of:
locating nearest zero-crossing on each side of a peak in the cross-correlation; and
finding the centroid between the nearest zero-crossings.
4. The method as recited in claim 3 further comprising the step of removing a sample offset from the centroid to provide a sample delay for input to the converting step.
5. The method as recited in claim 4 wherein the converting step comprises the step of dividing the sample delay by a sample rate to obtain the delay time.
6. The method as recited in claims 1 or 2 further comprising the step of removing a sample offset from the centroid to provide a sample delay for input to the converting step.
7. The method as recited in claim 6 wherein the converting step comprises the step of dividing the sample delay by a sample rate to obtain the delay time.