Re: Question about nyquist frequency

Date	1999-01-29 13:14
From	Jens Groh
Subject	Re: Question about nyquist frequency
	Jonathan Drexler wrote: >I have been finding that when I generate a sawtooth wave in the >treble register (somewhere around an octave or more over >middle c) that I am getting some strong undertones as well. >I am using a sample rate of 44100. I have tried it using >Gen7 and also Gen10. > >Is this happening because some of the upper >partials are running into the Nyquist boundary? Does >anyone know a practical way of handling this? Would be >very grateful for help. > Hello list, hello Jonathan! Yes - you get aliasing of upper harmonics. You can use a wave table with fewer harmonics to circumvent the problem, but then it will sound dull in the bass register. A better, yet more 'expensive' solution is to 'filter at the source'. Here is a _very_ primitive filter with three taps which are spaced at half the sample period. The coefficients are {0.5,1.0,0.5}. It is realized by three weighted sawteeth with appropriate phase shifts. (Note that the phasor itself is used as a sawtooth generator here.) ifreq = .... iampl = .... asaw0 phasor ifreq, 0.0 asaw1u phasor ifreq, 0.5 * ifreq / sr asaw1d phasor ifreq, 1.0 - 0.5 * ifreq / sr asaw = iampl * (asaw0 + 0.5 * (asaw1d + asaw1u)) A candidate for a new opcode? Have fun! Jens Received: from wallace.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa14876; 29 Jan 99 13:43 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by wallace.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106ECX-00054u-00; Fri, 29 Jan 1999 13:43:13 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (NAA12843); Fri, 29 Jan 1999 13:25:25 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Fri, 29 Jan 1999 13:25:11 GMT Received: from sparticus.bright.net [205.212.123.14] by hermes via ESMTP (NAA04140); Fri, 29 Jan 1999 13:25:01 GMT Received: from brutus (find1-cs-5.dial.bright.net [209.143.26.6]) by sparticus.bright.net (8.9.1/8.9.1 ComNet Build) with SMTP id IAA20070; Fri, 29 Jan 1999 08:23:57 -0500 (EST) Message-ID: <36B1B5A4.11D984D1@bright.net> Date: Fri, 29 Jan 1999 08:20:36 -0500 From: Dave Phillips X-Mailer: Mozilla 3.0 (X11; I; Linux 2.0.36 i586) MIME-Version: 1.0 To: Gabriel Maldonado CC: Csound Mail-list Subject: Re: moscil not responding to krate values References: <19990128164731.10F7E382B@toad.ilogic.com.au> <36B0954F.6A9A89EC@bright.net> <36B18AD4.D51576F9@agora.stm.it> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk Greetings: > It is normal, because you have set kdur = p3, so moscil wait p3 seconds before > next > note-on, but after p3 second the score note is deactivated. Try to set > kdur = p3/10 That fixed the problem, thank you. So, the basic rule is: when using krate envelopes for knum do not use kdur=p3, is that correct ? Btw, some wild possibilities exist for realtime audio/MIDI output. Thanks for the opcodes ! == Dave Phillips http://www.bright.net/~dlphilp/index.html http://www.bright.net/~dlphilp/linux_soundapps.html Received: from wallace.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa15011; 29 Jan 99 14:37 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by wallace.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106F30-0005AS-00; Fri, 29 Jan 1999 14:37:26 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (OAA15290); Fri, 29 Jan 1999 14:25:13 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Fri, 29 Jan 1999 14:24:56 GMT Received: from camel7.mindspring.com [207.69.200.57] by hermes via ESMTP (OAA08993); Fri, 29 Jan 1999 14:24:34 GMT Received: from guest1.ngt.sungard.com (user-38ld2rk.dialup.mindspring.com [209.86.139.116]) by camel7.mindspring.com (8.8.5/8.8.5) with SMTP id JAA29706; Fri, 29 Jan 1999 09:24:01 -0500 (EST) Message-ID: <001c01be4b93$b056b220$748b56d1@guest1.ngt.sungard.com> From: Michael Gogins To: Roger Klaveness , csound list Subject: Re: TB-303 like Lowpass-Filter Date: Fri, 29 Jan 1999 09:28:38 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 4.72.3110.5 X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3110.3 Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk I think this is a fantastic idea. It might also be interesting to create a general-purpose filter design program in Java, so all platforms can use it, that would format the filter coefficients into a line of Csound orc code for filter2. -----Original Message----- From: Roger Klaveness To: csound list Date: Friday, January 29, 1999 4:30 AM Subject: Re: TB-303 like Lowpass-Filter >Josep M Comajuncosas wrote: >> >> Talking about general filter design routines... I think it would be a nice idea to >> implement a public domain filter design package (Are Meteor or the Pakrs McLean >> free?) in the Csound sources, to be able to design filters from Csounbd itself as >> needed in the filter2 opcode. > >I think that's a great idea. >In that case one could also have an opcode which >takes filter-spesifications as an argument, avoiding >the need to first design filter in an utility-program >an then using the coefficients with filter2. > >maybe something like this > >ar filtgen asig, iftype, ibandtype, iripple, iorder, icorner2, icorner2 > >where >iftype : filtertype 1=Butterworth,2=Chebychev,3=Bessel >ibandtype : Bandtype 1=Lowpass , 2=Highpass, 3=Bandpass, 4=Bandstop >iripple : ripple in dB for Chebychev filter >iorder : order of filter >icorner1 : cornerfrequency 1 >icorner2 = cornerfrequency 2, for Bandpass/Bandstop filters > >the opcode would then at inittime design the filter and maybe show >a graphic output of freq ,phase and impulse response. > >at http://www.cs.york.ac.uk/~fisher/mkfilter/ there is an online >interactive filter design page. >The source code is available to download too, but I haven't found anything >about license. >If this is interesting one could off course ask the author if it's okay >to use his sources in csound. > >Roger K Received: from wallace.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa15172; 29 Jan 99 15:58 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by wallace.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106GJv-0005Hp-00; Fri, 29 Jan 1999 15:58:59 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (PAA08315); Fri, 29 Jan 1999 15:53:31 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Fri, 29 Jan 1999 15:53:22 GMT Received: from Thuban.AC.HMC.Edu [134.173.53.8] (may be forged) by hermes via ESMTP (PAA15655); Fri, 29 Jan 1999 15:53:17 GMT Received: from [134.173.38.61] (Spjut.Eng.HMC.Edu) by THUBAN.AC.HMC.EDU (PMDF V5.1-11 #D3207) with ESMTP id <01J73T5KAAJ69TDZS7@THUBAN.AC.HMC.EDU> for csound@maths.ex.ac.uk; Fri, 29 Jan 1999 07:51:46 PST Date: Fri, 29 Jan 1999 07:45:21 -0800 From: Erik Spjut Subject: Re: Question about nyquist frequency In-reply-to: <199901291314.OAA06617@dav.irt.de> X-Sender: spjut@thuban.ac.hmc.edu To: csound@maths.ex.ac.uk Message-id: MIME-version: 1.0 Content-type: text/plain; charset="us-ascii" Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk You can't actually filter out an aliased frequency unless you know the frequency it's been aliased to. You have to generate the signal at a higher sample rate, lowpass filter, and then resample at the final rate. A better approach for Csound is to generate a series of function tables of band-limited sawtooths (sawteeth?) with different limits and have the instrument select the correct waveform according to the pitch of the note. It's very fast at the cost of a little memory. BTW to check for aliasing start with the frequency of the note, multipy it by the number of the highest partial. If the result is greater than sr/2 you have aliasing. For example if you have: F1 0 4096 10 1 0 1 4 1 -1 0 1 1 your highest harmonic is #9. If sr=44100, then sr/2=22050 so 9pitch must be less than 22050 or pitch (in cps) must be less than 2450 to prevent aliasing. At 2:14 PM +0100 1/29/99, Jens Groh wrote: >Jonathan Drexler wrote: >>I have been finding that when I generate a sawtooth wave in the >>treble register (somewhere around an octave or more over >>middle c) that I am getting some strong undertones as well. >>I am using a sample rate of 44100. I have tried it using >>Gen7 and also Gen10. >> >>Is this happening because some of the upper >>partials are running into the Nyquist boundary? Does >>anyone know a practical way of handling this? Would be >>very grateful for help. >> > >Hello list, hello Jonathan! >Yes - you get aliasing of upper harmonics. >You can use a wave table with fewer harmonics to circumvent the problem, but >then it will sound dull in the bass register. >A better, yet more 'expensive' solution is to 'filter at the source'. Here >is a _very_ primitive filter with three taps which are spaced at half the >sample period. The coefficients are {0.5,1.0,0.5}. It is realized by three >weighted sawteeth with appropriate phase shifts. (Note that the phasor >itself is used as a sawtooth generator here.) > >ifreq = .... >iampl = .... >asaw0 phasor ifreq, 0.0 >asaw1u phasor ifreq, 0.5 ifreq / sr >asaw1d phasor ifreq, 1.0 - 0.5 * ifreq / sr >asaw = iampl * (asaw0 + 0.5 * (asaw1d + asaw1u)) > >A candidate for a new opcode? > >Have fun! >Jens ------------------------------------------------------------------------------- Erik Spjut (spyoot, rhymes with cute) - Associate Professor of Engineering and Associate Director for Engineering Computing, Center for Design Education Harvey Mudd College, Claremont, CA 91711-5990 USA Erik_Spjut@hmc.edu Ph & Voice mail (909) 607-3890 Fax (909) 621-8967 Received: from wallace.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa15182; 29 Jan 99 16:02 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by wallace.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106GMx-0005I2-00; Fri, 29 Jan 1999 16:02:07 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (PAA10684); Fri, 29 Jan 1999 15:55:19 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Fri, 29 Jan 1999 15:55:10 GMT Received: from Thuban.AC.HMC.Edu [134.173.53.8] (may be forged) by hermes via ESMTP (PAA08676); Fri, 29 Jan 1999 15:55:04 GMT Received: from [134.173.38.61] (Spjut.Eng.HMC.Edu) by THUBAN.AC.HMC.EDU (PMDF V5.1-11 #D3207) with ESMTP id <01J73T9I7IMO9TDZS7@THUBAN.AC.HMC.EDU> for csound@maths.ex.ac.uk; Fri, 29 Jan 1999 07:54:56 PST Date: Fri, 29 Jan 1999 07:53:23 -0800 From: Erik Spjut Subject: Re: Filter Design (was Re: TB-303) In-reply-to: <001c01be4b93$b056b220$748b56d1@guest1.ngt.sungard.com> X-Sender: spjut@thuban.ac.hmc.edu To: csound list Message-id: MIME-version: 1.0 Content-type: text/plain; charset="us-ascii" Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk As usual, the devil is in the details. I used the filter design page to generate some of the coefficients I used to test filter2 for IIR filters. The filters work fine in infinite-precision math but fail miserably in Csound's single-precision math. I agree that the proposed opcode would be most wonderful. However, whoever does it is in for some tedious work in finite precision arithmetic. At 9:28 AM -0500 1/29/99, Michael Gogins wrote: >I think this is a fantastic idea. It might also be interesting to create a >general-purpose filter design program in Java, so all platforms can use it, >that would format the filter coefficients into a line of Csound orc code for >filter2. > >[stuff deleted] >> >>maybe something like this >> >>ar filtgen asig, iftype, ibandtype, iripple, iorder, icorner2, icorner2 >> >>where >>iftype : filtertype 1=Butterworth,2=Chebychev,3=Bessel >>ibandtype : Bandtype 1=Lowpass , 2=Highpass, 3=Bandpass, 4=Bandstop >>iripple : ripple in dB for Chebychev filter >>iorder : order of filter >>icorner1 : cornerfrequency 1 >>icorner2 = cornerfrequency 2, for Bandpass/Bandstop filters >> >>the opcode would then at inittime design the filter and maybe show >>a graphic output of freq ,phase and impulse response. >> >>at http://www.cs.york.ac.uk/~fisher/mkfilter/ there is an online >>interactive filter design page. >>The source code is available to download too, but I haven't found anything >>about license. >>If this is interesting one could off course ask the author if it's okay >>to use his sources in csound. >> >>Roger K ------------------------------------------------------------------------------- Erik Spjut (spyoot, rhymes with cute) - Associate Professor of Engineering and Associate Director for Engineering Computing, Center for Design Education Harvey Mudd College, Claremont, CA 91711-5990 USA Erik_Spjut@hmc.edu Ph & Voice mail (909) 607-3890 Fax (909) 621-8967 Received: from wallace.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa15348; 29 Jan 99 16:49 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by wallace.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106H6O-0005MA-00; Fri, 29 Jan 1999 16:49:04 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (QAA08016); Fri, 29 Jan 1999 16:43:53 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Fri, 29 Jan 1999 16:43:37 GMT Received: from [203.36.219.100] by hermes via SMTP (QAA15744); Fri, 29 Jan 1999 16:43:12 GMT Received: from RossBencina (unverified [203.56.205.5]) by www.webpage.com.au (EMWAC SMTPRS 0.83) with SMTP id ; Sat, 30 Jan 1999 03:37:58 +1100 Message-ID: <005101be4ba5$87d01280$05cd38cb@RossBencina> From: Ross Bencina To: csound@maths.ex.ac.uk MMDF-Warning: Parse error in original version of preceding line at UK.AC.Bath.maths.omphalos Subject: Re: Filter Design (was Re: TB-303) Date: Sat, 30 Jan 1999 03:06:18 +1030 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 4.72.3110.5 X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3110.3 Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk Sorry excuse me for coming in half way through this conversation... Another thing you could consider is the elliptical (IIR I think) filter available in cmix - although the original code used a fortran coeff algorithm there are C versions floating around (I can dig up a cleaned f2c version is someone is interested in dealing with it). This filter allows lp, bp or hp configurations with good time/accuracy trade-offs. Ross. >>>where >>>iftype : filtertype 1=Butterworth,2=Chebychev,3=Bessel >>>ibandtype : Bandtype 1=Lowpass , 2=Highpass, 3=Bandpass, 4=Bandstop >>>iripple : ripple in dB for Chebychev filter >>>iorder : order of filter >>>icorner1 : cornerfrequency 1 >>>icorner2 = cornerfrequency 2, for Bandpass/Bandstop filters >>> >>>the opcode would then at inittime design the filter and maybe show >>>a graphic output of freq ,phase and impulse response. >>> >>>at http://www.cs.york.ac.uk/~fisher/mkfilter/ there is an online >>>interactive filter design page. >>>The source code is available to download too, but I haven't found anything >>>about license. >>>If this is interesting one could off course ask the author if it's okay >>>to use his sources in csound. >>> >>>Roger K > > >--------------------------------------------------------------------------- ---- >Erik Spjut (spyoot, rhymes with cute) - Associate Professor of Engineering >and Associate Director for Engineering Computing, Center for Design Education >Harvey Mudd College, Claremont, CA 91711-5990 USA >Erik_Spjut@hmc.edu Ph & Voice mail (909) 607-3890 Fax (909) 621-8967 > > Received: from wallace.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa15461; 29 Jan 99 17:29 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by wallace.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106Hj5-0005QN-00; Fri, 29 Jan 1999 17:29:03 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (RAA02383); Fri, 29 Jan 1999 17:24:31 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Fri, 29 Jan 1999 17:24:18 GMT Received: from dns2.seanet.com [199.181.164.2] by hermes via ESMTP (RAA08079); Fri, 29 Jan 1999 17:24:16 GMT Received: from seanet.com (cy47.dialup.seanet.com [207.12.136.47]) by mx.seanet.com (8.8.8/Seanet-8.7.3) with ESMTP id JAA14922; Fri, 29 Jan 1999 09:24:11 -0800 (PST) Message-ID: <36B1EE81.7164CBBD@seanet.com> Date: Fri, 29 Jan 1999 09:23:13 -0800 From: Sean Costello X-Mailer: Mozilla 4.05 [en] (Win95; I) MIME-Version: 1.0 To: Hans Mikelson CC: csound@maths.ex.ac.uk Subject: Re: Fwd: ;97x97 References: <001501be4b1c$0b746ee0$c499170c@default> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk Hans Mikelson wrote: > > Hi, > > Well the site basically crashed/locked my SGI. I had to telnet in from > another system and kill Netscape to get out of it. I recommend not going to > that URL unless you want to see your system hang. I had to do a Ctrl-Alt-Delete in Windows 98 and shut down Netscape in order to get out of the page. Why was this site recommended? Does it have anything to do with Csound, if you have the proper hardware/software setup to avoid crashing while viewing the page? Or is it just some annoying "cyberpunk" who can't get attention by creating something useful, and tries to get noticed by being as annoying as possible? Sean Costello P.S. On a completely unrelated topic, has anyone here constructed their own allpass filters in Csound? I am trying to construct a reverb that uses allpass filters with tapped delay lines, so I can't use the standard alpass opcode. Any advice? Received: from shaun.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa15501; 29 Jan 99 17:40 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by shaun.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106HuC-00055A-00; Fri, 29 Jan 1999 17:40:32 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (RAA18422); Fri, 29 Jan 1999 17:37:31 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Fri, 29 Jan 1999 17:37:19 GMT Received: from zit-108.irt.de [194.172.230.108] by hermes via ESMTP (RAA03060); Fri, 29 Jan 1999 17:37:18 GMT Received: from pctb151 (pctb151.irt.de [192.168.3.151]) by dav.irt.de (8.9.1/8.9.1) with SMTP id SAA17941 for ; Fri, 29 Jan 1999 18:37:16 +0100 (MET) Date: Fri, 29 Jan 1999 18:37:16 +0100 (MET) Message-Id: <199901291737.SAA17941@dav.irt.de> X-Sender: groh@mail X-Mailer: Windows Eudora Version 1.4.4 Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" To: csound@maths.ex.ac.uk From: Jens Groh Subject: Re: Question about nyquist frequency Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk Erik Spjut wrote: >You can't actually filter out an aliased unless you know the >frequency it's been aliased to. You have to generate the signal at a higher >sample rate, lowpass filter, and then resample at the final rate. Look again at my code: That's what it does (with a sample rate of sr*2 and the filter being far from perfect). >A better approach for Csound is to generate a series of function tables of >band-limited sawtooths (sawteeth?) with different limits and have the >instrument select the correct waveform according to the pitch of the note. >It's very fast at the cost of a little memory. The better idea, I admit. Jens Received: from wallace.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa15567; 29 Jan 99 18:12 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by wallace.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106IOm-0005TM-00; Fri, 29 Jan 1999 18:12:08 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (SAA12526); Fri, 29 Jan 1999 18:03:59 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Fri, 29 Jan 1999 18:03:45 GMT Received: from kmt.hku.nl [192.87.219.66] by hermes via ESMTP (SAA10166); Fri, 29 Jan 1999 18:03:44 GMT Received: from student-kmt.hku.nl (student-kmt.hku.nl [192.87.219.67]) by kmt.hku.nl (980427.SGI.8.8.8/8.8.8) with ESMTP id TAA32600 for ; Fri, 29 Jan 1999 19:03:14 +0100 (MET) Received: from 2e-fase (M1K5I3.hku.nl [192.87.216.200]) by student-kmt.hku.nl (980427.SGI.8.8.8/8.8.8) with SMTP id TAA06896; Fri, 29 Jan 1999 19:03:14 +0100 (MET) Message-Id: <199901291803.TAA06896@student-kmt.hku.nl> From: Dave Perry To: visorc@student-kmt.hku.nl, csound@maths.ex.ac.uk Date: Fri, 29 Jan 1999 19:02:44 +0100 MIME-Version: 1.0 Content-type: text/plain; charset=US-ASCII Content-transfer-encoding: 7BIT Subject: Visual Orchestra 1.95 documentation and projects available for download Priority: normal X-mailer: Pegasus Mail for Win32 (v3.01b) Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk Greetings, Documentation for Visual Orchestra 1.95.4 is available for download from , at present this is in Word95 for Windows format - text version to follow. Also on the same page, a zipfile containing some example projects I created or transcribed using VisOrc over the last few months. And probably of more interest to those on the VisOrc list, the 1.95.5 prerelease is also available from the rebuild's page. Any feedback on this would be greatly appreciated. Thanks, Dave Received: from shaun.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa15801; 29 Jan 99 21:18 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by shaun.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106LJ5-0005GT-00; Fri, 29 Jan 1999 21:18:27 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (VAA00398); Fri, 29 Jan 1999 21:16:50 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Fri, 29 Jan 1999 21:16:38 GMT Received: from echo.flash.net [209.30.0.40] by hermes via ESMTP (VAA18406); Fri, 29 Jan 1999 21:16:37 GMT Received: from flash.net (p125.amax28.dialup.ftw1.flash.net [209.30.57.125]) by echo.flash.net (8.9.1/8.8.5) with ESMTP id PAA28997 for ; Fri, 29 Jan 1999 15:15:52 -0600 (CST) Message-ID: <36B22566.B05629A5@flash.net> Date: Fri, 29 Jan 1999 15:17:26 -0600 From: pete moss Organization: pete moss GmbH X-Mailer: Mozilla 4.5 [en] (Win98; U) X-Accept-Language: en MIME-Version: 1.0 To: csound Subject: command line or CsOptions Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk which has preference? the command line parameters or the parameters set up in CsOptions in a .csd file? which one overrides the other? pete Received: from shaun.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa15872; 29 Jan 99 21:55 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by shaun.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106Lsh-0005IK-00; Fri, 29 Jan 1999 21:55:15 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (VAA04220); Fri, 29 Jan 1999 21:53:19 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Fri, 29 Jan 1999 21:53:07 GMT Received: from jaguars-int.cableinet.net [193.38.113.9] by hermes via SMTP (VAA13508); Fri, 29 Jan 1999 21:53:06 GMT Received: (qmail 5209 invoked from network); 29 Jan 1999 21:49:58 -0000 Received: from unknown (HELO cableinet.co.uk) (194.117.146.97) by jaguars with SMTP; 29 Jan 1999 21:49:58 -0000 Message-ID: <36B22E6C.C0C9DF98@cableinet.co.uk> Date: Fri, 29 Jan 1999 21:55:56 +0000 From: Richard Dobson Organization: Composers Desktop Project X-Mailer: Mozilla 4.5 [en] (WinNT; I) X-Accept-Language: en MIME-Version: 1.0 To: csound@maths.ex.ac.uk Subject: Re: Fwd: ;97x97 References: <001501be4b1c$0b746ee0$c499170c@default> <36B1EE81.7164CBBD@seanet.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk It was a java bug (his main system is the Mac, and java conformance etc is still widely inconsistent across platforms - especially for sound!). The page is now down for revisions. I realized after the event I hadn't tried ALT-F etc to see if the menus came up! Those who have heard antiorp's music say it is pretty remarkable - I don't know, but it it highly possible he uses Csound. It would be difficult to disagree with the suggestion that he is experimental and non-conmformist. I am not particularly interested in other sorts of speculations. Re allpass filters in Csound: Hans Mikelson himself posted several a while back (relating to nested allpasses for Gardner reverbs). Perhaps it's time for a revival? Richard Dobson Sean Costello wrote: > > Hans Mikelson wrote: > > > > Hi, > > > > Well the site basically crashed/locked my SGI. I had to telnet in from > > another system and kill Netscape to get out of it. I recommend not going to > > that URL unless you want to see your system hang. > > I had to do a Ctrl-Alt-Delete in Windows 98 and shut down Netscape in > order to get out of the page. Why was this site recommended? Does it > have anything to do with Csound, if you have the proper > hardware/software setup to avoid crashing while viewing the page? Or is > it just some annoying "cyberpunk" who can't get attention by creating > something useful, and tries to get noticed by being as annoying as > possible? > > Sean Costello > > P.S. On a completely unrelated topic, has anyone here constructed their > own allpass filters in Csound? I am trying to construct a reverb that > uses allpass filters with tapped delay lines, so I can't use the > standard alpass opcode. Any advice? -- Test your DAW with my Soundcard Attrition Page! http://wkweb5.cableinet.co.uk/rwd CDP homepage: http://www.bath.ac.uk/~masjpf/CDP/CDP.htm Received: from shaun.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa15913; 29 Jan 99 22:24 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by shaun.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106MKy-0005KA-00; Fri, 29 Jan 1999 22:24:28 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (WAA06622); Fri, 29 Jan 1999 22:23:16 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Fri, 29 Jan 1999 22:23:04 GMT Received: from dns2.seanet.com [199.181.164.2] by hermes via ESMTP (WAA01164); Fri, 29 Jan 1999 22:23:03 GMT Received: from seanet.com (cy25.dialup.seanet.com [207.12.136.25]) by mx.seanet.com (8.8.8/Seanet-8.7.3) with ESMTP id OAA15004; Fri, 29 Jan 1999 14:22:59 -0800 (PST) Message-ID: <36B235BB.EA02013E@seanet.com> Date: Fri, 29 Jan 1999 14:27:07 -0800 From: Sean Costello X-Mailer: Mozilla 4.05 [en] (Win95; I) MIME-Version: 1.0 To: Richard Dobson CC: csound@maths.ex.ac.uk Subject: Allpasses (was Re: Fwd: ;97x97) References: <001501be4b1c$0b746ee0$c499170c@default> <36B1EE81.7164CBBD@seanet.com> <36B22E6C.C0C9DF98@cableinet.co.uk> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk Richard Dobson wrote: > Re allpass filters in Csound: Hans Mikelson himself posted several a > while back (relating to nested allpasses for Gardner reverbs). Perhaps > it's time for a revival? Thanks for the tip. Mikelson's orchestra for the Gardner reverbs is available at http://www.werewolf.net/~hljmm/csound/gardverb.orc. I was actually trying to implement a reverb described in a Gardner article, although the original source was in a JAES article by Joe Dattorro. The cool aspect of the Dattorro reverb is that it uses interpolating taps in the allpass delay lines, modulated by a low frequency (~1 Hz) sine wave. The modulation of the delay lines results in dynamic alterations of the resonant frequencies, to decreate tonal coloration. So far, my reverb has a tendancy to clip internally and/or blow up, so the Mikelson orchestra should help in properly implementing the allpass stages. BTW, has anyone on the list tried implementing any of the feedback delay network (FDN) reverbs as described by Stautner and Puckette, Jot, Julius Smith, etc.? They seem promising. I'll probably try to design such a reverb this weekend, and will post it if and when I get it working. Sean Costello Received: from shaun.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa16056; 29 Jan 99 23:29 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by shaun.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106NMB-0005NE-00; Fri, 29 Jan 1999 23:29:47 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (XAA17631); Fri, 29 Jan 1999 23:28:44 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Fri, 29 Jan 1999 23:28:31 GMT Received: from [12.23.152.10] by hermes via ESMTP (XAA18357); Fri, 29 Jan 1999 23:28:29 GMT Received: from default (dial168.werewolf.net [12.23.153.168]) by howl.werewolf.net (8.9.0/8.9.0) with SMTP id RAA24013 for ; Fri, 29 Jan 1999 17:24:05 -0600 (CST) Message-ID: <000a01be4bdf$c89746a0$a899170c@default> From: Hans Mikelson To: csound@maths.ex.ac.uk MMDF-Warning: Parse error in original version of preceding line at UK.AC.Bath.maths.omphalos Subject: Re: Question about nyquist frequency Date: Fri, 29 Jan 1999 17:33:31 -0600 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 4.72.3110.5 X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3110.3 Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk >Is this happening because some of the upper >partials are running into the Nyquist boundary? Does >anyone know a practical way of handling this? Would be >very grateful for help. Try the vco opcode (>3.50) for bandlimited sawtooth waveforms. Hans Mikelson Received: from shaun.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa16080; 29 Jan 99 23:41 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by shaun.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106NXA-0005Nl-00; Fri, 29 Jan 1999 23:41:08 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (XAA00910); Fri, 29 Jan 1999 23:39:51 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Fri, 29 Jan 1999 23:39:39 GMT Received: from howl.werewolf.net [12.23.152.10] by hermes via ESMTP (XAA18282); Fri, 29 Jan 1999 23:39:37 GMT Received: from default (dial168.werewolf.net [12.23.153.168]) by howl.werewolf.net (8.9.0/8.9.0) with SMTP id RAA02219; Fri, 29 Jan 1999 17:35:10 -0600 (CST) Message-ID: <002301be4be1$5571d1c0$a899170c@default> From: Hans Mikelson To: Sean Costello Cc: csound@maths.ex.ac.uk MMDF-Warning: Parse error in original version of preceding line at UK.AC.Bath.maths.omphalos Subject: All-Pass filters Re: Fwd: ;97x97 Date: Fri, 29 Jan 1999 17:44:36 -0600 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 4.72.3110.5 X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3110.3 Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk Hi, These are implemented in Gardner Reverbs on my web page: http://www.werewolf.net/~hljmm/csound/ The nested all-pass filter opcode is in progress, it's taking me a while to get around to it. The form is something like: aout nestedap ain, imaxtime, imode, itim1, igain1[, itim2, igain2, itim3, igain3] Hans Mikelson Received: from wallace.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa16147; 30 Jan 99 0:21 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by wallace.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106O9l-0005mH-00; Sat, 30 Jan 1999 00:21:01 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (AAA04576); Sat, 30 Jan 1999 00:20:12 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Sat, 30 Jan 1999 00:19:59 GMT Received: from jaguars-int.cableinet.net [193.38.113.9] by hermes via SMTP (AAA08452); Sat, 30 Jan 1999 00:19:59 GMT Received: (qmail 12262 invoked from network); 30 Jan 1999 00:16:50 -0000 Received: from unknown (HELO cableinet.co.uk) (194.117.146.233) by jaguars with SMTP; 30 Jan 1999 00:16:50 -0000 Message-ID: <36B250D9.40C66591@cableinet.co.uk> Date: Sat, 30 Jan 1999 00:22:49 +0000 From: Richard Dobson Organization: Composers Desktop Project X-Mailer: Mozilla 4.5 [en] (WinNT; I) X-Accept-Language: en MIME-Version: 1.0 To: csound@maths.ex.ac.uk Subject: Re: All-Pass filters Re: Fwd: ;97x97 References: <002301be4be1$5571d1c0$a899170c@default> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk >From the Gardner descriptions, adding an (optional) pre-delay to the allpass-filter input might also be worthwhile? Richard Dobson Hans Mikelson wrote: > > Hi, > > These are implemented in Gardner Reverbs on my web page: > > http://www.werewolf.net/~hljmm/csound/ > > The nested all-pass filter opcode is in progress, it's taking me a while to > get around to it. The form is something like: > > aout nestedap ain, imaxtime, imode, itim1, igain1[, itim2, igain2, itim3, > igain3] > > Hans Mikelson -- Test your DAW with my Soundcard Attrition Page! http://wkweb5.cableinet.co.uk/rwd CDP homepage: http://www.bath.ac.uk/~masjpf/CDP/CDP.htm Received: from shaun.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa16185; 30 Jan 99 1:03 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by shaun.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106Oor-0005Rb-00; Sat, 30 Jan 1999 01:03:29 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (BAA05656); Sat, 30 Jan 1999 01:02:37 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Sat, 30 Jan 1999 01:02:25 GMT Received: from astor.interport.net [199.184.165.18] by hermes via ESMTP (BAA05070); Sat, 30 Jan 1999 01:02:24 GMT Received: from [209.122.227.27] (209-122-227-27.s27.tnt2.nyw.erols.com [209.122.227.27]) by astor.interport.net (8.8.5/8.8.5) with ESMTP id UAA08513 for ; Fri, 29 Jan 1999 20:03:36 -0500 (EST) X-Sender: jose@pop.interport.net Message-Id: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Date: Fri, 29 Jan 1999 20:07:17 -0400 To: csound@maths.ex.ac.uk From: jose halac Subject: SSDIR..jpff Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk Thanks John... jose halac wrote: > > I'm trying to use gen1 on Maldonado's CSound (WinSound). I installed it > according instructions, set up a SSDir folder on the exe and still when I > calculate a simple fog orchestra that involves a sound file to be > processed, it give me the message "file not found" or that it can't find > the sample directory at all... > > any help appreciatted > > JH I am using Winsound. I did set up an environment in DOS and it created a folder called Samples. Then I put a sample inside, open winsound and still doesn't recognize the folder. Job van Zuijlen suggeted me to check if there is a space after the = sign. I'll do that right now. I will keep you posted. Thanks! JH Received: from shaun.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa16334; 30 Jan 99 2:34 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by shaun.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106QFG-0005VV-00; Sat, 30 Jan 1999 02:34:50 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (CAA03860); Sat, 30 Jan 1999 02:33:31 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Sat, 30 Jan 1999 02:33:19 GMT Received: from howl.werewolf.net [12.23.152.10] by hermes via ESMTP (CAA03524); Sat, 30 Jan 1999 02:33:18 GMT Received: from default (dial107.werewolf.net [12.23.153.107] (may be forged)) by howl.werewolf.net (8.9.0/8.9.0) with SMTP id UAA23181 for ; Fri, 29 Jan 1999 20:28:53 -0600 (CST) Message-ID: <001201be4bf9$9ab75a80$6b99170c@default> From: Hans Mikelson To: csound@maths.ex.ac.uk MMDF-Warning: Parse error in original version of preceding line at UK.AC.Bath.maths.omphalos Subject: Re: All-Pass filters Date: Fri, 29 Jan 1999 20:38:20 -0600 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 4.72.3110.5 X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3110.3 Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk >From the Gardner descriptions, adding an (optional) pre-delay to the >allpass-filter input might also be worthwhile? Why not just use delay? Hans Mikelson Received: from shaun.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa16549; 30 Jan 99 4:10 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by shaun.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106RkF-0005Zz-00; Sat, 30 Jan 1999 04:10:55 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (EAA02550); Sat, 30 Jan 1999 04:10:02 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Sat, 30 Jan 1999 04:09:49 GMT Received: from lorica.ucc.usyd.edu.au [129.78.64.15] by hermes via ESMTP (EAA14125); Sat, 30 Jan 1999 04:09:46 GMT Received: from mail.usyd.edu.au (mp-8-49.mp.usyd.edu.au [129.78.57.111]) by lorica.ucc.usyd.edu.au (8.9.1a/8.9.1) with ESMTP id PAA21672 for ; Sat, 30 Jan 1999 15:09:01 +1100 (EST) Message-ID: <36B28592.2D64FD4E@mail.usyd.edu.au> Date: Sat, 30 Jan 1999 15:07:48 +1100 From: Bob Douglas Reply-To: rdouglas@mail.usyd.edu.au Organization: Sydney Conservatorium X-Mailer: Mozilla 4.03 (Macintosh; I; PPC) MIME-Version: 1.0 To: CSound list Subject: Re: TB-303 like Lowpass-Filter References: <36B16C06.70324B95@intercom.es> <36B17E91.8D2B6A6F@apas.no> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk > Roger Klaveness wrote: (snip) > ar filtgen asig, iftype, ibandtype, iripple, iorder, icorner2, icorner2 > > where > iftype : filtertype 1=Butterworth,2=Chebychev,3=Bessel > ibandtype : Bandtype 1=Lowpass , 2=Highpass, 3=Bandpass, 4=Bandstop > iripple : ripple in dB for Chebychev filter > iorder : order of filter > icorner1 : cornerfrequency 1 > icorner2 = cornerfrequency 2, for Bandpass/Bandstop filters (snip) Would it make sense to allow the args to vary at k-rate ? Clearly some args must be integers only, but it might open up the possibility of time-varying filter design, with all the goodies that implies - conditional filters tested at k-rate, intermediate designs on a continuum between 2 conventional designs, etc. Bob Douglas Received: from wallace.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa16606; 30 Jan 99 5:06 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by wallace.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106Sbk-0005zA-00; Sat, 30 Jan 1999 05:06:12 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (FAA13528); Sat, 30 Jan 1999 05:04:22 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Sat, 30 Jan 1999 05:04:07 GMT Received: from caracal.noc.ucla.edu [169.232.10.11] by hermes via ESMTP (FAA07270); Sat, 30 Jan 1999 05:04:05 GMT Received: from smtp ([164.67.88.7]) by caracal.noc.ucla.edu (8.9.1a/8.9.1) with SMTP id VAA10088 for ; Fri, 29 Jan 1999 21:04:05 -0800 (PST) Received: from UCLA-Message_Server by smtp with Novell_GroupWise; Fri, 29 Jan 1999 20:57:34 -0800 Message-Id: X-Mailer: Novell GroupWise 4.1 Date: Fri, 29 Jan 1999 21:08:26 -0800 From: Jonathan Drexler To: csound@maths.ex.ac.uk Subject: Problem getting to csound ftp Mime-Version: 1.0 Content-Type: text/plain Content-Disposition: inline Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk I tried to download the new version csound winhelp but kept getting an error saying that the directory does not exist. The url I am connecting to is this: ftp://ftp.maths.bath.ac.uk/pub/dream/newest/ It is a subdirectory under this URL, containing the 1/99 version of winhelp, where the problem is When I tried to go into the subdirectory I got the error. I wondered if there might be a problem with the site? Thanks. Received: from shaun.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa16720; 30 Jan 99 6:58 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by shaun.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106UMN-0005lZ-00; Sat, 30 Jan 1999 06:58:27 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (GAA10181); Sat, 30 Jan 1999 06:56:45 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Sat, 30 Jan 1999 06:56:33 GMT Received: from vcn.bc.ca [207.102.64.2] by hermes via ESMTP (GAA02427); Sat, 30 Jan 1999 06:56:31 GMT Received: from localhost (wfreno@localhost) by vcn.bc.ca (8.9.2/8.9.2) with ESMTP id WAA24294; Fri, 29 Jan 1999 22:52:33 -0800 (PST) Date: Fri, 29 Jan 1999 22:52:33 -0800 (PST) From: Wayne Freno To: Jonathan Drexler cc: csound@maths.ex.ac.uk Subject: Re: Problem getting to csound ftp In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk I also could not download csound_win.zip tonight from the bath site , good thing the Montreal server is there: ftp://ftp.musique.umontreal.ca/pub/mirrors/dream On Fri, 29 Jan 1999, Jonathan Drexler wrote: > I tried to download the new version csound winhelp but > kept getting an error saying that the directory does not > exist. > > The url I am connecting to is this: > ftp://ftp.maths.bath.ac.uk/pub/dream/newest/ > > It is a subdirectory under this URL, containing the > 1/99 version of winhelp, where the > problem is When I tried to go into the subdirectory > I got the error. I wondered if there might be a > problem with the site? > > Thanks. > > > end soundbite Received: from wallace.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa16861; 30 Jan 99 8:44 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by wallace.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106W1J-0006Bo-00; Sat, 30 Jan 1999 08:44:49 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (IAA05618); Sat, 30 Jan 1999 08:43:39 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Sat, 30 Jan 1999 08:43:31 GMT Received: from root@lix.intercom.es [194.179.21.2] by hermes via ESMTP (IAA13226); Sat, 30 Jan 1999 08:43:29 GMT Received: from intercom.es (iv2-28.intercom.es [195.76.206.28]) by lix.intercom.es (8.7.3/8.6.12) with ESMTP id JAA24839; Sat, 30 Jan 1999 09:40:30 +0100 Message-ID: <36B2C5AB.5F07B351@intercom.es> Date: Sat, 30 Jan 1999 09:41:15 +0100 From: Josep M Comajuncosas X-Mailer: Mozilla 4.05 [en] (Win95; I) MIME-Version: 1.0 To: Hans Mikelson CC: csound@maths.ex.ac.uk Subject: Re: All-Pass filters References: <001201be4bf9$9ab75a80$6b99170c@default> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk Another idea to try could be making the delay time variable... I really need an allpass unit with variable delay time to easily implement phaser effects without deltapi units. Hans Mikelson wrote: > >From the Gardner descriptions, adding an (optional) pre-delay to the > >allpass-filter input might also be worthwhile? > > Why not just use delay? > > Hans Mikelson Received: from shaun.maths.bath.ac.uk by omphalos.maths.Bath.AC.UK id aa17080; 30 Jan 99 11:06 GMT Received: from [144.173.6.14] (helo=exeter.ac.uk) by shaun.maths.bath.ac.uk with esmtp (Exim 1.92 #2) for jpff@maths.bath.ac.uk id 106YEO-0005va-00; Sat, 30 Jan 1999 11:06:28 +0000 Received: from noether [144.173.8.10] by hermes via SMTP (LAA10039); Sat, 30 Jan 1999 11:05:34 GMT Received: from exeter.ac.uk by maths.ex.ac.uk; Sat, 30 Jan 1999 11:05:21 GMT Received: from jaguars-int.cableinet.net [193.38.113.9] by hermes via SMTP (LAA17686); Sat, 30 Jan 1999 11:05:20 GMT Received: (qmail 30150 invoked from network); 30 Jan 1999 11:02:12 -0000 Received: from unknown (HELO cableinet.co.uk) (194.117.146.13) by jaguars with SMTP; 30 Jan 1999 11:02:12 -0000 Message-ID: <36B2E81E.4D3748F9@cableinet.co.uk> Date: Sat, 30 Jan 1999 11:08:14 +0000 From: Richard Dobson Organization: Composers Desktop Project X-Mailer: Mozilla 4.5 [en] (WinNT; I) X-Accept-Language: en MIME-Version: 1.0 To: csound@maths.ex.ac.uk Subject: Re: All-Pass filters References: <001201be4bf9$9ab75a80$6b99170c@default> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-csound-outgoing@maths.ex.ac.uk Precedence: bulk I was thinking about efficiency, and more flexilbility in ordering the opcodes. And, as John might say, 'it helps the abstraction'. Richard Dobson Hans Mikelson wrote: > > >From the Gardner descriptions, adding an (optional) pre-delay to the > >allpass-filter input might also be worthwhile? > > Why not just use delay? > > Hans Mikelson -- Test your DAW with my Soundcard Attrition Page! http://wkweb5.cableinet.co.uk/rwd CDP homepage: http://www.bath.ac.uk/~masjpf/CDP/CDP.htm

Date	1999-01-29 15:45
From	Erik Spjut
Subject	Re: Question about nyquist frequency
	You can't actually filter out an aliased frequency unless you know the frequency it's been aliased to. You have to generate the signal at a higher sample rate, lowpass filter, and then resample at the final rate. A better approach for Csound is to generate a series of function tables of band-limited sawtooths (sawteeth?) with different limits and have the instrument select the correct waveform according to the pitch of the note. It's very fast at the cost of a little memory. BTW to check for aliasing start with the frequency of the note, multipy it by the number of the highest partial. If the result is greater than sr/2 you have aliasing. For example if you have: F1 0 4096 10 1 0 1 4 1 -1 0 1 1 your highest harmonic is #9. If sr=44100, then sr/2=22050 so 9pitch must be less than 22050 or pitch (in cps) must be less than 2450 to prevent aliasing. At 2:14 PM +0100 1/29/99, Jens Groh wrote: >Jonathan Drexler wrote: >>I have been finding that when I generate a sawtooth wave in the >>treble register (somewhere around an octave or more over >>middle c) that I am getting some strong undertones as well. >>I am using a sample rate of 44100. I have tried it using >>Gen7 and also Gen10. >> >>Is this happening because some of the upper >>partials are running into the Nyquist boundary? Does >>anyone know a practical way of handling this? Would be >>very grateful for help. >> > >Hello list, hello Jonathan! >Yes - you get aliasing of upper harmonics. >You can use a wave table with fewer harmonics to circumvent the problem, but >then it will sound dull in the bass register. >A better, yet more 'expensive' solution is to 'filter at the source'. Here >is a _very_ primitive filter with three taps which are spaced at half the >sample period. The coefficients are {0.5,1.0,0.5}. It is realized by three >weighted sawteeth with appropriate phase shifts. (Note that the phasor >itself is used as a sawtooth generator here.) > >ifreq = .... >iampl = .... >asaw0 phasor ifreq, 0.0 >asaw1u phasor ifreq, 0.5 ifreq / sr >asaw1d phasor ifreq, 1.0 - 0.5 * ifreq / sr >asaw = iampl * (asaw0 + 0.5 * (asaw1d + asaw1u)) > >A candidate for a new opcode? > >Have fun! >Jens ------------------------------------------------------------------------------- Erik Spjut (spyoot, rhymes with cute) - Associate Professor of Engineering and Associate Director for Engineering Computing, Center for Design Education Harvey Mudd College, Claremont, CA 91711-5990 USA Erik_Spjut@hmc.edu Ph & Voice mail (909) 607-3890 Fax (909) 621-8967