Re: [Csnd] unexpected integ offset

Date	2011-09-25 04:35
From	"Partev Barr Sarkissian"
Subject	Re: [Csnd] unexpected integ offset
	Victor, I think that makes sense. Correct me if I'm wrong, but when you mathemtically break down a signal into it's components, with a number of Low-Pass filter types, isn't there a DC component in there? That Split Side-Band paper you did (in JAES, September 2008 was it?), wasn't there a DC component in the Taylor Series Expansion you did? Regards, cheers, -Partev ================================================================ --- Victor.Lazzarini@nuim.ie wrote: From: Victor.Lazzarini@nuim.ie To: csound@lists.bath.ac.uk Subject: Re: [Csnd] unexpected integ offset Date: Wed, 21 Sep 2011 20:12:18 +0100 The integrtator is an IIR LP filter, so it will produce a signal with a certain amount of DC as it has a pole at 0Hz. The code assumes this to be about 0.5 and tries to remove it. I'd say a more robust approach is to use a DC blocker. Victor ----- Original Message ----- From: ebmtranceboy Date: Wednesday, September 21, 2011 6:37 pm Subject: [Csnd] unexpected integ offset To: csound@lists.bath.ac.uk > Hi all, > Sorry in advance if this is not the right place to ask this kind of > question. > I'm trying to understand the following instrument and I'm > puzzled by the > "asaw = asawdc - .5" line > > ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; > instr 1; band limited sawtooth wave > ; coded by Josep M Comajuncosas / jan98 > ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; > > iamp > = 10000; intended max. amplitude > kenv linen 1, .2,p3,.2; volume envelope > kfreq > = cpspch(p4) > ibound = sr/4; > set it to sr/2 for true BL square wave > apulse buzz 1, kfreq, ibound/kfreq, 1 > asawdc integ apulse > asaw > = asawdc - .5 > out asawdciampkenv > endin > > Indeed, if the fundamental period is 2pi and N the number of required > harmonics (ibound/kfreq in instr 1), buzz opcode provides a > signal (assumely > continuous) > > b(t) = (sum { cos(kt), k = 1.. N}) / N > > so, by integration, > > saw(t) = integ [b(u)du, u = 0..t] > saw(t) = (sum { sin(kt) / k, k = 1.. N}) / N > > which is precisely the reconstruction of the signal whose Fourier > coefficients are (N times smaller than) (1,1/2,1/3,...,1/N) that > is just the > asaw signal we're trying to build and I don't understand where > the 1/2 > offset comes from. > > Is it a numerical (discrete signal) consequence ? If so, why > this 1/2 > coefficient doesn't depend of N (setting ibound to sr/2 for > example still > requires the offset set to 1/2 to get the asaw expected). > > Help me with my maths please! > > > > -- > View this message in context: > http://csound.1045644.n5.nabble.com/unexpected-integ-offset- > tp4827197p4827197.htmlSent from the Csound - General mailing > list archive at Nabble.com. > > > Send bugs reports to the Sourceforge bug tracker > https://sourceforge.net/tracker/?group_id=81968&atid=564599 > Discussions of bugs and features can be posted here > To unsubscribe, send email sympa@lists.bath.ac.uk with body > "unsubscribe csound" > Dr Victor Lazzarini, Senior Lecturer, Dept. of Music, National University of Ireland, Maynooth _____________________________________________________________ Netscape. Just the Net You Need. Send bugs reports to the Sourceforge bug tracker https://sourceforge.net/tracker/?group_id=81968&atid=564599 Discussions of bugs and features can be posted here To unsubscribe, send email sympa@lists.bath.ac.uk with body "unsubscribe csound"

Date	2011-09-25 10:24
From	Victor Lazzarini
Subject	Re: [Csnd] unexpected integ offset
	yes, there is a DC and that is what the code tries to remove. But I would use a DC blocker instead. Victor On 25 Sep 2011, at 04:35, Partev Barr Sarkissian wrote: > Victor, > > I think that makes sense. Correct me if I'm wrong, but when you > mathemtically break down a signal into it's components, with a > number of Low-Pass filter types, isn't there a DC component in > there? That Split Side-Band paper you did (in JAES, September > 2008 was it?), wasn't there a DC component in the Taylor Series > Expansion you did? > > > Regards, cheers, > -Partev > > > ================================================================ > > > --- Victor.Lazzarini@nuim.ie wrote: > > From: Victor.Lazzarini@nuim.ie > To: csound@lists.bath.ac.uk > Subject: Re: [Csnd] unexpected integ offset > Date: Wed, 21 Sep 2011 20:12:18 +0100 > > The integrtator is an IIR LP filter, so it will produce a signal with > a certain amount of DC as it has a pole at 0Hz. The code assumes this > to be about 0.5 and tries to remove it. I'd say a more robust > approach is to use a DC blocker. > Victor > ----- Original Message ----- > From: ebmtranceboy > Date: Wednesday, September 21, 2011 6:37 pm > Subject: [Csnd] unexpected integ offset > To: csound@lists.bath.ac.uk >> Hi all, >> Sorry in advance if this is not the right place to ask this kind of >> question. >> I'm trying to understand the following instrument and I'm >> puzzled by the >> "asaw = asawdc - .5" line >> >> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; >> instr 1; band limited sawtooth wave >> ; coded by Josep M Comajuncosas / jan98 >> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; >> >> iamp >> = 10000; intended max. amplitude >> kenv linen 1, .2,p3,.2; volume envelope >> kfreq >> = cpspch(p4) >> ibound = sr/4; >> set it to sr/2 for true BL square wave >> apulse buzz 1, kfreq, ibound/kfreq, 1 >> asawdc integ apulse >> asaw >> = asawdc - .5 >> out asawdciampkenv >> endin >> >> Indeed, if the fundamental period is 2pi and N the number of > required >> harmonics (ibound/kfreq in instr 1), buzz opcode provides a >> signal (assumely >> continuous) >> >> b(t) = (sum { cos(kt), k = 1.. > N}) / N >> >> so, by integration, >> >> saw(t) = integ [b(u)du, u = 0..t] >> saw(t) = (sum { sin(kt) / k, k = 1.. > N}) / N >> >> which is precisely the reconstruction of the signal whose Fourier >> coefficients are (N times smaller than) (1,1/2,1/3,...,1/N) that >> is just the >> asaw signal we're trying to build and I don't understand where >> the 1/2 >> offset comes from. >> >> Is it a numerical (discrete signal) consequence ? If so, why >> this 1/2 >> coefficient doesn't depend of N (setting ibound to sr/2 for >> example still >> requires the offset set to 1/2 to get the asaw expected). >> >> Help me with my maths please! >> >> >> >> -- >> View this message in context: >> http://csound.1045644.n5.nabble.com/unexpected-integ-offset- >> tp4827197p4827197.htmlSent from the Csound - General mailing >> list archive at Nabble.com. >> >> >> Send bugs reports to the Sourceforge bug tracker >> > https://sourceforge.net/tracker/?group_id=81968&atid=564599 >> Discussions of bugs and features can be posted here >> To unsubscribe, send email sympa@lists.bath.ac.uk with body >> "unsubscribe csound" >> > Dr Victor Lazzarini, Senior Lecturer, Dept. of Music, > National University of Ireland, Maynooth > > > > > _____________________________________________________________ > Netscape. Just the Net You Need. > > > Send bugs reports to the Sourceforge bug tracker > https://sourceforge.net/tracker/?group_id=81968&atid=564599 > Discussions of bugs and features can be posted here > To unsubscribe, send email sympa@lists.bath.ac.uk with body > "unsubscribe csound" > Dr Victor Lazzarini Senior Lecturer Dept. of Music NUI Maynooth Ireland tel.: +353 1 708 3545 Victor dot Lazzarini AT nuim dot ie Send bugs reports to the Sourceforge bug tracker https://sourceforge.net/tracker/?group_id=81968&atid=564599 Discussions of bugs and features can be posted here To unsubscribe, send email sympa@lists.bath.ac.uk with body "unsubscribe csound"