| Here is another:
http://csound.ml.org/msg00302.html
Regards,
Hans Mikelson
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Date: Fri, 11 Dec 1998 11:43:48 +0100
From: Josep M Comajuncosas
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Subject: Re: Pulse width modulation!
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Paul Winkler wrote:
> This should please the analog fans...
>
> Some time ago there was a discussion of simulating pulse width
> modulation. I don't remember anyone posting a solution. Well, the other
> day, inspiration struck, and I came up with the idea to do it by
> indexing a square wave in a funny way...
Horror! a graphycal approach to PWM synthesis guarantees massive
aliasing
;-)Unless you plan to use it for techno hardcore I strongly reccomend to
get
PWM waves in the following way:
Generate 2 pulses with "buzz"
Delay de second pulse a fraction of the cicle (this sets the pw amount)
with
"delay" (or with deltapi if you want to change the pw factor on the fly)
Substract the second pulse from the first (or viceversa)
Integrate the previous result with "integ"
It will sound much better by sure, because all the process is
bandlimited.
Josep M Comajuncosas
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Subject: [ANNOUNCE] unofficial linux csound 3.49.3.3e available
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are of course the hard work of J.P.Fitch (jpff@maths.bath.ac.uk).
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initial support of the 'control' and 'cdisplay' opcodes under unix
(no sliders yet, by Nicola Bernardini), and long option support (by
Fred Floberg). Many others have contributed in useful comments and hints.
Thanks to all,
Enjoy.
------------------------------------------------------------------------
Nicola Bernardini
E-mail: nicb@axnet.it
Re graphics: A picture is worth 10K words -- but only those to describe
the picture. Hardly any sets of 10K words can be adequately described
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the AIMI server
ftp://musart.dist.unige.it/pub/CSOUND/csound-3.49.3.3e-*.tar.gz
in binary form (dynamically linked), binary form w/o X11 support (dynamically
linked) and source form.
*THIS IS NOT THE OFFICIAL DISTRIBUTION*
The official distribution can be found at
ftp://ftp.maths.bath.ac.uk/pub/dream/newest. The official 3.493 sources
are of course the hard work of J.P.Fitch (jpff@maths.bath.ac.uk).
This distribution features a merged port of the official 3.493 sources,
ALSA (i.e. free full-duplex and multiple cards) I/O drivers (by Fred
Floberg), linux scheduler priority control (by Fred Floberg),
improved MIDI out device control (by Dave Phillips and Paul Barton-Davis),
initial support of the 'control' and 'cdisplay' opcodes under unix
(no sliders yet, by Nicola Bernardini), and long option support (by
Fred Floberg). Many others have contributed in useful comments and hints.
Thanks to all,
Enjoy.
------------------------------------------------------------------------
Nicola Bernardini
E-mail: nicb@axnet.it
Re graphics: A picture is worth 10K words -- but only those to describe
the picture. Hardly any sets of 10K words can be adequately described
with pictures.
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From: Paul Winkler
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Josep M Comajuncosas wrote:
> Horror! a graphycal approach to PWM synthesis guarantees massive
> aliasing
> ;-)Unless you plan to use it for techno hardcore
Maybe. :)
> I strongly reccomend to
> get
> PWM waves in the following way:
(snip)
> It will sound much better by sure, because all the process is
> bandlimited.
I found your old message where you posted an example orc. Your approach
does sound a lot nicer on the higher notes. *BUT*...
--it requires sr=kr which I frequently don't like.
--First impression: it sounds subjectively weaker in the bass compared
to my approach. Maybe that's fixable.
--it glitches badly below 50 hz, and I don't understand your approach
well enough to fix that.
Today I spent some time playing with another approach:
use sine wave as the index to a table containing a straight line from -1
to 1. Amplify the index so that the output is clipped to a pseudo-square
wave, but add an offset to the index so that it's asymmetrical (at large
offset, it looks a lot like a narrow pulse). So the offset is our
"width" control. The trick is to limit the amplification and offset as
frequency goes up, so that at higher pitches, the output gets closer and
closer to a sine wave. This sounds a lot like my original version but
with a lot less aliasing (though there still is some).
I'll post it when I've got it cleaned up and tweaked a bit better.
--P |