Documentation

Resampling

Signal Processing Toolbox™ provides a number of functions that resample a signal at a higher or lower rate.

Operation

Function

Apply FIR filter with resampling

upfirdn

Cubic spline interpolation

spline

Decimation

decimate

Interpolation

interp

Other 1-D interpolation

interp1

Resample at new rate

resample

For examples, see

resample Function

The resample function changes the sample rate for a sequence to any rate that is proportional to the original by a ratio of two integers. The basic syntax for resample is

y = resample(x,p,q)

where the function resamples the sequence x at p/q times the original sample rate. The length of the result y is p/q times the length of x.

One resampling application is the conversion of digitized audio signals from one sample rate to another, such as from 48 kHz (the digital audio tape standard) to 44.1 kHz (the compact disc standard). See Convert from DAT Rate to CD Sample Rate for an example.

resample applies a lowpass filter to the input sequence to prevent aliasing during resampling. The function designs this filter using the firls function with a Kaiser window. You can control the filter length and the beta parameter of the Kaiser window. Alternatively, you can use the function intfilt to design an interpolation filter.

decimate and interp Functions

The decimate and interp functions are equivalent to resample with p = 1 and q = 1, respectively. These functions provide different antialiasing filtering options, and they incur a slight signal delay due to filtering.

upfirdn Function

The toolbox also contains a function, upfirdn, that applies an FIR filter to an input sequence and outputs the filtered sequence at a sample rate different than its original. See Multirate Filter Bank Implementation.

spline Function

The standard MATLAB® environment contains a function, spline, that works with irregularly spaced data. The MATLAB function interp1 performs interpolation, or table lookup, using various methods including linear and cubic interpolation.