[PD] 4-point interpolation changes timbre depending on sample rate

[Dan Wilcox]

Maybe I'm opening a can of worms, but I could imagine tabread etc taking an argument to specify which algorithm to use among a (small) list of those available. The current algorithm would be the default so as not to break existing patches. :)

I'm no expert, but if there are a known set of tried-and-true approaches, maybe they could added through a simple API. This is sort of how I refactored the soundfile type handling in the (as yet unmerged) soundfile object update branch: https://github.com/pure-data/pure-data/blob/0061a083e85ba2548668825b693a72fdf98ceef3/src/d_soundfile.h#L47 <https://github.com/pure-data/pure-data/blob/0061a083e85ba2548668825b693a72fdf98ceef3/src/d_soundfile.h#L47>

> On May 3, 2021, at 3:37 PM, pd-list-request at lists.iem.at wrote:
> 
> Message: 2
> Date: Mon, 3 May 2021 15:24:10 +0200
> From: Clemens Wegener <clemens at chair.audio <mailto:clemens at chair.audio>>
> To: Charles Z Henry <czhenry at gmail.com <mailto:czhenry at gmail.com>>
> Cc: Pd-List <pd-list at lists.iem.at <mailto:pd-list at lists.iem.at>>
> Subject: Re: [PD] 4-point interpolation changes timbre depending on
> 	sample rate
> Message-ID: <B6FDFF69-EE54-4F59-8234-5A53D086229C at chair.audio <mailto:B6FDFF69-EE54-4F59-8234-5A53D086229C at chair.audio>>
> Content-Type: text/plain; charset="utf-8"
> 
> I think now would be a good place to pause the implementation and discuss 
> if there is a need for this kind of algorithm in the PD community. 
> 
> We saw some use cases for the Whittaker-Shannon interpolation where
> we gain in quality and/or speed. Namely waveguides and pitch shifters. 
> 
> Is there anything else, where we would like to use this interpolation kernel?
> Like in general resampling?
> In the tabread~ for sample playback?
> Are there really quality or speed issues that we could solve there?
> 
> For our use case the code I submitted is good enough. But I would be happy 
> to spend more time optimizing if there is a need / a broad use of that algorithm.
> In that case we need another restructuring and some help from somebody
> who is very proficient in writing pd source code. :)

--------
Dan Wilcox
@danomatika <http://twitter.com/danomatika>
danomatika.com <http://danomatika.com/>
robotcowboy.com <http://robotcowboy.com/>



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