[music-dsp] resampling question (about libsamplerate, aka secret rabbit)

Steve Harris S.W.Harris at ecs.soton.ac.uk
Thu Oct 28 03:47:25 EDT 2004


On Thu, Oct 28, 2004 at 08:22:41AM +0100, Ed Wildgoose wrote:
> Hi folks,
> 
> I just wanted to confirm a quick point.  When libsamplerate says that it 
> is using it's best mode, ie "high quality sinc interpolation", this does 
> imply that it's using a sinc approximation to fill in the extra data 
> points on upsampling yes?
> 
> I only ask because, this is my understanding, but the author of the lavc 
> resampler boldly claimed that there are no non-linear interpolators used 
> for audio resampling?  Never having had to try to write a high speed 
> resampler, I was worried for a moment that I might be confused and have 
> misunderstood how libsamplerate and the like are actually doing their 
> interpolation?

Yes, it uses sinc() to interpolate. Non-linear may mean two things; either
things that are non linear, or things that are nonlinear. The first being
things like cubic interpolators and the second being things like nonlinear
filters. A very different beast:
http://www2.mdanderson.org/app/ilya/NONLINEAR.htm

- Steve



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