Subject: Re: [linux-audio-dev] Sample rate conversion (was .....)
From: Erik de Castro Lopo (erikd-lad_AT_mega-nerd.com)
Date: Fri Dec 21 2001 - 23:39:32 EET
On Fri, 21 Dec 2001 21:35:41 +0200
Juhana Sadeharju <kouhia_AT_nic.funet.fi> wrote:
> >From: Erik de Castro Lopo <erikd_AT_mega-nerd.com>
> >
> >My version uses sinc interpolation by small integer factors (2,3,4,..)
> >followed by linear or cubic interpolation. This should even allow time
> >varying SRC.
>
> Two step FIR interpolation followed by spline/lagrange interpolation
> seems to be used quite often. But anyway, I'm willing to test your
> program.
I already have a very rigourous test suite set up I just don't have the
filters yet.
I'll be happy to add you to the test suite :-).
> Why we would not use one FIR filter designed with remez algorithm
Two problems.
I need a multi-rate style filter. For the interpolate by 2 filter it
has odd length, every second coefficient equal to zero except for the
middle one which is 1.0. Filters like this are far more efficient to
implement and Remez can't design them.
I am aiming for a filter with a very narrow transition band and stop
band attentuation of at least 96dB. This requires large numbers of
coefficients (>256) and for problems like this, the Remez algorithm
fails miserably.
Erik
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