[PD] polynomial pairs in lpc filter

[Ed Kelly]

Hi Simon,

I remember trying to extract such information from pd-list members about 13 years ago...the silence was deafening!

I remember trying to get some help with why my ported lpc object wasn't initalizing properly earlier this week- also silence.

However, I soldier on regardless. If you have any ideas about why my mbc_lpc~ object doesn't load then please hack it and return(github details at the bottom) but also take a look at the original code for mbc.allpass~ - it contains various methods that are commented out for calculating filter coefficients, and there may be some clues in there for you to pick at.

I've never quite got to the bottom of calculating Line Spectrum Frequencies and manipulating these as formants, but it sounds like the project I was trying to pursue so many years ago (before my idiot managers pulled the funding and tried tobotch their own project together).

Anyway - here's how far I've got with the port - do you think you could share ideas and code with me? it may speed things up at my end...

Ed

edkellytista9/LPCToolkitPd



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edkellytista9/LPCToolkitPd

LPCToolkitPd - Mark Cartwright's LPC Toolkit for Pure Data
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    On Wednesday, 18 April 2018, 14:31:43 GMT+1, Simon Iten <itensimon at gmail.com> wrote:  
 
 calculate the zeroes (roots) of the polynomial i guess.

still hints are very welcome :)

> On 18 Apr 2018, at 11:51, Simon Iten <itensimon at gmail.com> wrote:
> 
> hi list,
> 
> this is more of a general DSP question...
> 
> i am working on an LPC playback and mangling system for axoloti. i have most of it working and i am now trying to shift formants in the filter to change voice character. i found functions to convert reflection coefficients into polynomial pairs and presumably i should be able to shift filter frequencies in this representation of the data. unfortunately i have no clue how to do that. any hints, papers, code snippets etc. are very welcome.
> 
> or if someone wants to take the time to explain, you are of course more then welcome
> 
> thanks for any suggestions
> 
> 


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