From alsa-devel-owner@alsa.jcu.cz  Thu Jul 23 11:20:04 1998
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Date: Thu, 23 Jul 1998 11:19:55 +0200
From: Thomas Sailer <sailer@ife.ee.ethz.ch>
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To: Marcus Brinkmann <Marcus.Brinkmann@ruhr-uni-bochum.de>
CC: alsa-devel@jcu.cz
Subject: Re: ALSA driver 0.2.0-pre2
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> Isn't converting to different sample rates the same as drawing a straight line
> on bit planes?
> 
> The Bresenham algorithm has a nice integer solution for this. I can work out
> the details, if you want. It wouldn't be too time consuming, I think.
> (Maybe you want to do this in libraries user space, though).
> 
> Marcus

Ugh. What you're suggesting is linear interpolation.
This is indeed used in commercial sample rate converter chips,
_BUT_ only as a last stage, preceded by a polyphase low pass filter,
and this is what you have to do if you want decent quality.
Just using linear interpolation gives you significant new (and thus
unwanted) spectral components.

Tom

