| Are you referring to the MMX instructions? They do SIMD-like
operations, mainly for graphics but could be used for other purposes.
==John
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To: csound@maths.ex.ac.uk
Subject: Re: Optimizations
In-reply-to: Your message of "Wed, 12 May 1999 13:35:52 -0000."
Date: Wed, 12 May 1999 09:27:14 -0400
From: Paul Barton-Davis
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>Are you referring to the MMX instructions? They do SIMD-like
>operations, mainly for graphics but could be used for other purposes.
the new P-III MMX instructions could potentially be very useful to
a highly-Pentium-optimized sound generator. They are even better than
the old MMX set. However, it seems pointless to do asm-coding of
Csound, given that one of its strongest benefits is its portability
due to its use of C. Better to wait for compiler technology to use the
right instructions the right way (pgcc already does some of this for
the initial MMX set, I believe).
--p
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From: luis jure
To: steve@babcom.u-net.com
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Cc: CSound list
Subject: ampdb (RE: oscil3 glitch problem)
Date: Wed, 12 May 1999 13:10:55 -0230
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>> according to the manual, ampdb returns a raw value of 32000 for 90dB,
thus
>> if you take 0dB as your maximum output, a value of 90 would give almost
0dB
>> for 16 bits (-0.3 in fact) and not -6 dB as you seem to want.
>>
>> by the way, looking at the output, ampdb doesn't seem to be extremely
>> precise. or is it?
>
>Hmm! I was under the impression that (perfect) 16 bit audio had a 96 dB
>dynamic range, hence the above. Perhaps ampdb is calibrated wrong, or am I
>missing something?
it seems you're talking about different things.
one thing is the signal to noise ratio of a given device. a simple way to
calculate the approximate _theoretical_ S/N of a digital to analog converter
is multiplying 6*number of bits. thus, for a 16 bit DAC you get
approximately 96dB in theory. with good and expensive (and i mean expensive)
cards you can get close to that figure, i guess. cheaper cards used in
personal computers can have a significantly lower performance.
but you know dB is not a magnitude in itself, just the log of a ratio. if
you take 0dB as your maximum amplitude, you have a raw value 32767 as 0dB
for a definition of 16 bits. now, in Csound ampdb returns 32000 (that
is -0.3 dB) for an input of 90, so if you use ilevl = ampdb(96 + p4), for p4
= 0 you'll get ampdb(96), i. e. a raw amplitude of 64000. in fact you'll get
cliping for all values of p4 greater than -6. not that ampdb is calibrated
wrong, it's just a convention.
i'm sorry all this is so simple, but i don't even have my pohlman handy, so
don't expect too much from me.
completely apart from this, it's true that ampdb is _not_ very well
calibrated; for 90 it returns 31622.8 and not 32000 as the manual says.
below is a table comparing what i and real values given by amdb:
90 32000 31622.8
89 28508.76 28183.8
88 25398.43 25118.9
87 22627.42 22387.2
86 20158.75 19952.6
85 17959.39 17782.8
84 16000 15848.9
83 14254.36 14125.4
82 12699.2 12589.2
81 11313.69 11220.2
80 10079.36 10000.0
79 8979.71 8912.5
78 8000 7943.3
and so on. as you see, deviations can be considered negligible.
all that if i calculated well, that might not be the case.
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Date: Wed, 12 May 1999 21:48:50 +0100
Subject: (OT) Re: [ANNOUNCE] Concerts a/in Montreal
From: Javier Ruiz
To: csound@maths.ex.ac.uk
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Looking at part of the message Mr. Piche forwarded, it seems that the French
speaking people in Canada are really different from the English speaking
ones.
As Spanish, I prefer the French ad.
Happy May to everyone.
________________________________________________________________
> And the long awaited world premiere of live
> video performance band:
> Luce Tucrue
________________________________________________________________
> Et en premiere mondiale, les elucubrations irreverencieuses de:
> Luce Tucrue
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Date: Thu, 13 May 1999 10:38:24 +1000
From: Bob Douglas
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To: CSound list
Subject: Re : Mac running Linux
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I have a PowerPC 7200 90MHz 48M RAM 1G HDD MacOS8.0, and I'm considering
installing Linux. I have checked up the Linux site - the 7200 is listed as
capable of supporting it.
Can anyone advise me if there would be any substantial gain in the performance
of Csound under Linux compared to MacOS8.0? Also are there any known pitfalls
of which I should be aware?
Any help would be much appreciated.
Bob Douglas
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Date: Wed, 12 May 1999 23:32:34 -0400
From: "Job M. van Zuijlen"
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To: csound@maths.ex.ac.uk
Subject: Re: (OT) Re: [ANNOUNCE] Concerts a/in Montreal
References: <19990512213518.AAD11896@[62.81.84.123]>
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In defense of the English-speaking Canadians I would like to suggest the
possibility that the English originated from a non-English speaking
Canadian ;-)
Job van Zuijlen
Javier Ruiz wrote:
>
> Looking at part of the message Mr. Piche forwarded, it seems that the French
> speaking people in Canada are really different from the English speaking
> ones.
> As Spanish, I prefer the French ad.
>
> Happy May to everyone.
>
> ________________________________________________________________
> > And the long awaited world premiere of live
> > video performance band:
> > Luce Tucrue
>
> ________________________________________________________________
> > Et en premiere mondiale, les elucubrations irreverencieuses de:
> > Luce Tucrue
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Message-ID: <3739B727.9959ACFC@fabaris.it>
Date: Wed, 12 May 1999 19:15:19 +0200
From: Riccardo Bianchini
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To: csound@maths.ex.ac.uk
Subject: Bug in linseg (recent versions)
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While trying to resynthesize a piece, I found a bug in linseg in recent
versions of Csound (from 3.50).
I use linseg as an audio generator for exfitation signal in a waveguide
simulation of plucked string. Try this orc/sco:
;orc:
sr=44100
kr=44100 ;<-----!
ksmps=1
nchnls=1
instr 1
aecc linseg 0,1/kr,1,2/k3,-1,1/k3,0,p3-4/kr,0
out a1
endin
;sco:
i1 0 1
Apparently, linseg is no more able to work properly if the durations are
very small.
Happy Csounding!
--
*************************************
Riccardo Bianchini, composer
Professor, Scuola di Musica Elettronica
Conservatorio "S.Cecilia", Roma
http://www.fabaris.it/bianchini
http://www.geocities.com/Heartland/Acres/4768
Conservatorio: http://space.tin.it/musica/ilipc
*************************************
|