RE: [linux-audio-dev] Software filter engines for high end audio

New Message Reply About this list Date view Thread view Subject view Author view Other groups

Subject: RE: [linux-audio-dev] Software filter engines for high end audio
From: Richard W.E. Furse (richard_AT_muse.demon.co.uk)
Date: ke helmi  16 2000 - 07:54:55 EST


What is Warped FIR? Does any of this get near the speed of fast
convolution?

I'm interested in an implementation of a very fast FIR implementation for
my MN audio library, even if only for its low latency, however I really
would want float in->float out. Us Linux folk really do need to agree a
decent plugin API ;)

Incidentally, I recently read a very interesting and straightforward paper
by Angelo Farina on compensating room (and car) acoustics using Ambisonics.
I think it was in the past couple of years' AES conference pre-prints.

-- Richard

-----Original Message-----
From: Anders Torger [SMTP:torger_AT_ludd.luth.se]
Sent: Wednesday, February 16, 2000 11:18 AM
To: linux-audio-dev_AT_ginette.musique.umontreal.ca
Subject: [linux-audio-dev] Software filter engines for high end audio

Are there any FIR (or IIR or Warped IIR or Warped FIR) filter engines out
there, suitable for audio applications? I'm asking, because I am working
on an own, and would like to know if there are any more out there. My
software currently only implements a Warped FIR filter, which can take 16
- 24 bit audio as input and produces 24 bit output. Later I will add a FIR
filter, capable of about 3000 taps on a 266 MHz Pentium II (16 bit 44.1
kHz input, 24 bit output, and no risk for overflow), which however is
limited to only 16 bit samples as input. The high performance is achieved
from analysing the filter coefficients and generating assembler code
especially fit for the given set, which is then compiled and attached to
the filter engine. The release of the FIR filter is at least a few weeks
away though, since I need to finish an ALSA driver for the RME Digi96
digital I/O first.

I plan to use the filter in software driven room correction systems, and
in fact I have already a working prototype based on the WFIR filter, found
at http://www.ludd.luth.se/~torger/filter.html. Complete with an MLS
measuring system. All GPL'd of course. I'd love to get comments and
questions about the system :-)

The plan is to make a room correction system based on the FIR filter
later, which will be able to correct phase problems, as well as magnitude.
The current system does not correct phase.

I find this area very interesting, since it is possible to make your Linux
machine (which must be rather fast, I use a dual P2 266, one processor per
channel) into a room correction system that is on par or surpasses
commercial systems that cost around 4000 US dollars. The problem so far
has been the lack of quality digital I/O cards for Linux, but soon we will
have a driver for RME Digi96, the best alternative (price/performance) I
have found for two channel systems.

/Anders Torger


New Message Reply About this list Date view Thread view Subject view Author view Other groups

This archive was generated by hypermail 2b28 : pe maalis 10 2000 - 07:23:27 EST