US 5,331,346 A · Approximating sample rate conversion system

Abstract

A sample rate conversion system converts from an input sample rate stream having a predetermined input sample rate to an output sample stream having a predetermined output sample rate by interpolating output samples from the input samples using first and second approximate sample rate ratios. The system includes circuitry which selects a sequence of interpolation filters from among a set of filters, the sequences being defined by one of these approximate ratios, and circuitry which monitors the magnitude of the accumulated error introduced by the approximation. When this accumulated error becomes greater than a threshold, the system changes to use a further sequence of interpolation filters based on the other approximate ratio. The accumulated error changes in a positive sense with each successive sample while one of the two approximate ratios is used. The accumulated error changes in a negative sense with each successive sample while the other of the two approximate ratios is used. The system switches between these sample rate ratios to maintain the magnitude of the position error of the interpolated samples below a predetermined threshold value. A sample rate conversion system which converts a television signal in CCIR (601) format into a Phase Alternate Line (PAL) video signal is disclosed.

Claims15

Dependent claims

A sample rate conversion system which resamples a first sampled data signal having a first predetermined sample rate to generate a second sampled data signal having a second predetermined sample rate, the sample rate conversion system comprising:

resampling means, responsive to a control signal for alternately resampling the first sampled data signal according to respective first and second approximate sample ratios to produce samples of the second sampled data signal which have respective sample position errors, such that, between any two consecutive samples of the second sampled data signal, an accumulated sample position error changes in a positive sense while resampling according to one of the first and second approximate sample ratios and changes in a negative sense while resampling according to the other of the first and second approximate sample ratios;
monitoring means for accumulating the sample position errors of the samples produced by the resampling means to generate the control signal which causes the resampling means to switch between the first and second approximate sample ratios when the accumulated sample position error has a magnitude greater than a predetermined threshold value.

A video signal sample rate conversion system which resamples a first sampled data video signal having a first predetermined sample rate to generate a second sampled data video signal having a second predetermined sample rate, the sample rate conversion system comprising:

resampling means, responsive to a control signal for alternately subjecting the first sampled data signal to respective first and second interpolation operations, such that, between any two consecutive samples of the second sampled data signal, an accumulated sample position error changes in a positive sense while subjecting the first sampled data signal to one of the first and second interpolation operations and changes in a negative sense while subjecting the first sampled data signal to the other of the first and second interpolation operations;
monitoring means for accumulating the sample position errors of the samples produced by the resampling means to generate the control signal which causes the resampling means to switch between the first and second interpolation operations when the accumulated sample position error has a magnitude greater than a predetermined threshold value.

Dependencies are inferred from the claim text.

Approximating sample rate conversion system

Life of this patent

Approximating sample rate conversion system

Life of this patent

Abstract

Claims15