Re: [SoX-users] fir option to use SoX als offline convolver

[Schumacher Marlon <marlon.schumacher@music.mcgill.ca>]

Hi there,

Picking up on this email from 2013 as I have a related question:
Just wanted to verify what is the limit of the number of coefficients for the “fir” effect? In my tests I empirically determined 65536 (2^16). Can anyone confirm this? Are there specific reasons for this limit or could it be changed for the next binary release? 

PS I'm using "fir" for convolution with impulse responses - hence, these applications are limited to the use of IRs which are shorter than this number of samples (about 1.5secs @44kHz ... which is rather short :-S)

Regards,
Marlon

On Mar 23, 2013, at 20:31 , nihil.sine.causa@t-online.de wrote:

> Ulrich,
> 
> thank you for your fast answer. I tried a much shorter version of the FIR filter with 6000 Samples and it worked fine. So I can confirm your suggestion, that I run into the limit on the number of coefficients.
> 
> To change the source code and to compile and bind the project would need some effort for me, but I will think about that. Do you have any idea where to finde this limit in the code? 
> 
> Best Regards,
> Harald
> 
> Von: Ulrich Klauer <ulrich@chirlu.de>
> An: sox-users@lists.sourceforge.net
> Cc: nihil.sine.causa@t-online.de
> Betreff: Re: [SoX-users] fir option to use SoX als offline convolver
> Datum: Sat, 23 Mar 2013 17:30:35 +0100
> 
> nihil.sine.causa@t-online.de:
> 
>> filter with a number of samples 2^18 = 262144.
> 
>> Assertion failed!
>> File: effects_i_dsp.c, Line 95
>> Expression: num_taps * 2 < result
> 
> There is a limit on the number of coefficients, and it is less than 2^18. :) I'm not sure that limit is necessary, it can probably be raised. Only by changing the source and recompiling, though.
> 
> Ulrich
> 
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