Construct polynomial sample-rate converter (POLYSRC) filter designer


d = fdesign.polysrc(l,m)
d = fdesign.polysrc(l,m,'Fractional Delay','Np',Np)
d = fdesign.polysrc(...,Fs)


d = fdesign.polysrc(l,m) constructs a polynomial sample-rate converter filter designer D with an interpolation factor L and a decimation factor M. L defaults to 3. M defaults to 2. L and M can be arbitrary positive numbers.

d = fdesign.polysrc(l,m,'Fractional Delay','Np',Np) initializes the filter designer specification with Np and sets the polynomial order to the value Np. If omitted Np defaults to 3.

d = fdesign.polysrc(...,Fs) specifies the sampling frequency (in Hz).


This example shows how to design sample-rate converter that uses a 3rd order Lagrange interpolation filter to convert from 44.1kHz to 48kHz:

[L,M] = rat(48/44.1);
f = fdesign.polysrc(L,M,'Fractional Delay','Np',3);
Hm = design(f,'lagrange');
% Original sampling frequency
Fs = 44.1e3;
% 9408 samples, 0.213 seconds long
n = 0:9407;
% Original signal, sinusoid at 1kHz
x  = sin(2*pi*1e3/Fs*n);
% 10241 samples, still 0.213 seconds
y = filter(Hm,x);
% Plot original sampled at 44.1kHz
hold on
% Plot fractionally interpolated signal (48kHz) in red
xlabel('Time (sec)');ylabel('Signal value')
legend('44.1 kHz sample rate','48 kHz sample rate')
This code generates the following figure.

For more information about Farrow SRCs, see the "Efficient Sample Rate Conversion between Arbitrary Factors" example, efficientsrcdemo.

See Also

Introduced in R2011a

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