Hi Andrew

I finally got around to following up on my hunch that a slightly
modified version of the trapezoidal integrated svf (ie a modified
version of the one I previously posted) should have excellent
numerical properties.

Care to reveal what is the "modification"? Did you measure the precision of the "unmodified" version?

Regards,
Vadim

----- Original Message ----- From: "Andrew Simper" <a...@cytomic.com>
To: "A discussion list for music-related DSP" <music-dsp@music.columbia.edu>
Sent: Tuesday, September 27, 2011 10:09
Subject: [music-dsp] Noise performance of f32 iir filters


I finally got around to following up on my hunch that a slightly
modified version of the trapezoidal integrated svf (ie a modified
version of the one I previously posted) should have excellent
numerical properties. My initial tests confirm this in spectacular
fashion. I used all sorts of tests, but the one to show up most
problems was a bell filter with q=2, gain=12 dB, and look at the
cutoffs 20, 200, 2k, 20k. I compare the modified state variable
filter, normalised ladder, normalised direct wave form, direct form 1,
and direct form 2 transposed. The only filter to match the low
quantization error of the modified svf is the normalized ladder
filter, but none of the filters can match the coefficient rounding
error, as is shown in the time domain error of the 20 Hz example:

http://www.cytomic.com/files/dsp/SVF-vs-DF1.pdf

The modified SVF works fine down to very low frequencies with all
single precision computation, which makes it ideal for use even at 192
kHz sample rates. I'll get around to writing it up some time, but I've
got a few plugins and other work to get on with for the moment.
--
dupswapdrop -- the music-dsp mailing list and website:
subscription info, FAQ, source code archive, list archive, book reviews, dsp links
http://music.columbia.edu/cmc/music-dsp
http://music.columbia.edu/mailman/listinfo/music-dsp


--
Vadim Zavalishin
Senior Software Developer | R&D

Tel +49-30-611035-0
Fax +49-30-611035-2600

NATIVE INSTRUMENTS GmbH
Schlesische Str. 29-30
10997 Berlin, Germany
http://www.native-instruments.com

Registergericht: Amtsgericht Charlottenburg
Registernummer: HRB 72458
UST.-ID.-Nr. DE 20 374 7747

Geschaeftsfuehrung: Daniel Haver (CEO), Mate Galic

--
dupswapdrop -- the music-dsp mailing list and website:
subscription info, FAQ, source code archive, list archive, book reviews, dsp 
links
http://music.columbia.edu/cmc/music-dsp
http://music.columbia.edu/mailman/listinfo/music-dsp

Reply via email to