| Most high-order filters are implemented as cascaed (ie in series) second-order
sections, so as a (very) rough hack, you could simply run several filters in
series. the only alternatice is for someone to write one!
Richard Dobson
David Schuyeteneer wrote:
>
> I know that order of the standard Butterworth filter in Csound is 2, but I
> want a
> higher (like 6th or 8th...) order Butterworth.....Does it exist or how can
> it be
> created ???
>
> I read something in the manual about a filter that can be filled in with
> custom values
> in its "coefficients", but that's a little way out of my knowledge on
> digital sound theory..
> So a little advice is wanted as I have not a clue how to use those filter
> values/poles/coefficients and all that..
>
> David.
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From: Richard Dobson
Organization: Composers Desktop project
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Could be any number of things!
Crude debugging methods:
1: ripple your 'out' opcode backwards, to audition intermediate results.
2: use the print opcodes to monitor levels.
3: look at your code ~really carefully~!
4: if all else fails, post your orc to the list. you never know - you may have
hit a bug!
Richard Dobson
David Schuyeteneer wrote:
>
> My latest piece in Csound has annoying subtle distortion sometimes however
> the signal is **never** out of range !!
> I checked the range in a GUI sample editor and also Csound never said
> during
> the performance that there was even a single out of range sample.
>
> anyone ?
>
> David.
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Date: Wed, 22 Jul 1998 09:24:12 -0400
From: jp
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David Schuyeteneer wrote:
>
> My latest piece in Csound has annoying subtle distortion sometimes however
> the signal is **never** out of range !!
> I checked the range in a GUI sample editor and also Csound never said
> during
> the performance that there was even a single out of range sample.
>
k-rate too low? Try ksmps at 10 or lower for best results.
--
________________________________________________________
Jean Piche
Universite de Montreal
http://mistral.ere.umontreal.ca/~pichej
http://www.musique.umontreal.ca/electro/CEC/
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Date: Wed, 22 Jul 1998 22:54:50 -0400
From: Job van Zuijlen
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Subject: Re: [?] Higer order Butterworth filter
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David's question about butterworth filters evoked some
old-time memories from the time (some 20 years ago) when I was
designing analog synthesizers and other electronic music
equipment.
One thing I remember from that time is that cascading lower
order filters does not result in a higher order filter *unless*
you include some form of feedback. The effect of cascading, for
example, three low-pass second-order Butterworth filters is
a low-pass filter with a slope of 36db/octave, but with a very
round cut-off region (i.e. the steep slope doesn't start right
away after the cut-off frequency). The feedback helps to make
this point "sharper" (This though to explain with pictures and I
don't want to bore you with 10k words ;-)
I used to be able to design filters and work with poles and zeros.
It is part of standard analog filter theory, so may be you can find
a book about it. If I can find my notes, I might want to try it
out myself, which I will let you know.
Job van Zuijlen
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Date: Wed, 22 Jul 1998 23:10:34 -0400 (EDT)
From: Kevin Gallagher
To: Csound Discussion List
Subject: MIDI input
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Dear Csounders,
I have been experimenting with Realtime MIDI input and Csound. I had
posted to the group a couple months ago to get advice on the limitations
of Csound and whatever gear I was planning to buy. Well, I have all my
gear. A Roland GR30 guitar synth (with GK2A pickup) running into my
computer (IBM Aptiva Pentium II 300Mhz) via a MIDI to serial adaptor.
My problem is that I get about a 0.2 second lag time between my attack and
the output of the signal. Just enough to be annoying. I've tried a few
things. I tried using Gabriel Maldonado's VMCI to see if my external
controller was the problem. It's not...the delay is still there with
VMCI. I've tried a few scripts. Here is the simplest one I could think of:
orchestra===========
sr = 22050
kr = 441
ksmps = 50
nchnls = 1
instr 1
ipch pchmidi
a1 pluck 5000, cpspch(ipch), cpspch(ipch), 0, 1
out a1
endin
score=============
f0 600
e
I also have a much more complex script (which I'll share if anybody's
interested), and both give roughly the same 0.2 second delay so I'm not
sure how much more I could streamline my scripting.
I'm also pretty sure that my computer has enough horsepower, although I
could be wrong.
I don't know how to change my buffer sizes in the interface I use (WCShell
and RTSound 1.8.)
Can anybody with experience in this area offer insight into why I can't
get rid of my lag time? Any help would be appreciated, Thanks!
Kevin Gallagher, kgallagh@astro.temple.edu
Web Address - http://astro.temple.edu/~kgallagh
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Date: Wed, 22 Jul 1998 21:28:38 -0700 (MST)
From: Mark T Vigorito
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To: Kevin Gallagher
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Subject: Re: MIDI input
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Try the latest Maldonado build - DirectCsound v.2. This version uses
DirectX to drastically reduce latency... quite playable on a 166Mhz
pentium!
Cheers,
Mark Vigorito
mtv@u.arizona.edu
On Wed, 22 Jul 1998, Kevin Gallagher wrote:
> [...]
> I don't know how to change my buffer sizes in the interface I use (WCShell
> and RTSound 1.8.)
^^^^^^^^^^^^
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"The imminent synchronic nexus necessitates acute cortical activity with
maximal olfactory awareness of the pyroclastic arabica infusion."
- Factor X
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Date: Thu, 23 Jul 1998 10:34:16 +0200
From: Gabriel Maldonado
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Kevin,
I have got a guitar controller too, a gk-2 with a gr-50, and there is a
noticiable dalay even with MIDI sinthesizers. The new version of
CsoundRT, called DirectCsound, uses directSound APIs to reduce the
delay. The only problem is that you must have an audio card compatible
with directSound (and obviously you must have Microsoft DirectX 3.0 or
higer installed on your computer) . There are some problems with audio
cards. With my SB16 and my (very old and slow) pentium 133, however I
can get a very, very low delay (about 1/50 of second in stereo, less in
mono).
You must find the optimum value to assign to the flag -+X (in
DirectCsound -+X has another function than in older versions).
Kevin Gallagher wrote:
> Dear Csounders,
> I have been experimenting with Realtime MIDI input and Csound. I had
> posted to the group a couple months ago to get advice on the
> limitations
> of Csound and whatever gear I was planning to buy. Well, I have all
> my
> gear. A Roland GR30 guitar synth (with GK2A pickup) running into my
> computer (IBM Aptiva Pentium II 300Mhz) via a MIDI to serial adaptor.
>
> My problem is that I get about a 0.2 second lag time between my attack
> and
> the output of the signal. Just enough to be annoying. I've tried a
> few
> things. I tried using Gabriel Maldonado's VMCI to see if my external
> controller was the problem. It's not...the delay is still there with
> VMCI. I've tried a few scripts. Here is the simplest one I could think
> of:
>
> orchestra===========
>
> sr = 22050
> kr = 441
> ksmps = 50
> nchnls = 1
>
> instr 1
> ipch pchmidi
> a1 pluck 5000, cpspch(ipch), cpspch(ipch), 0, 1
> out a1
> endin
>
> score=============
>
> f0 600
> e
>
> I also have a much more complex script (which I'll share if anybody's
> interested), and both give roughly the same 0.2 second delay so I'm
> not
> sure how much more I could streamline my scripting.
>
> I'm also pretty sure that my computer has enough horsepower, although
> I
> could be wrong.
>
> I don't know how to change my buffer sizes in the interface I use
> (WCShell
> and RTSound 1.8.)
>
> Can anybody with experience in this area offer insight into why I
> can't
> get rid of my lag time? Any help would be appreciated, Thanks!
>
> Kevin Gallagher, kgallagh@astro.temple.edu
> Web Address -
> http://astro.temple.edu/~kgallagh
--
Gabriel Maldonado
http://www.agora.stm.it/G.Maldonado/home2.htm
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From: David Schuyeteneer
To: Csound List
Subject: [www page] digital filter theory !
Date: Thu, 23 Jul 1998 10:56:05 +0200
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Short but good page here about digital filter theory ! (for those who
didn't knew it allready)
http://www.cldc.howard.edu/~rbaz/projects/s_proj/page5.html
seeya,
David
|