<![CDATA[Avoid dsp loops with vd and delwrite?]]>Hello,
I think I managed to solve this a long time ago but forgot the solution. In Pd apparently it is impossible to have a feedback with "zero" delay, i.e. if a delwrite~ and delread~ objects are in feedback the minimum delay is one block, thus the only option is to use [block] and reduce the blocksize.

How can "zero" logical delay be achieved in feedback without resorting to reducing the block size?

L

Edit: just to be quick and clear: this is a trouble you stumble into when designing Karplus-Strong patches

]]>http://forum.pdpatchrepo.info/topic/7404/avoid-dsp-loops-with-vd-and-delwriteRSS for NodeSat, 08 Aug 2026 13:54:39 GMTWed, 15 May 2013 15:48:02 GMT60<![CDATA[Reply to Avoid dsp loops with vd and delwrite? on Wed, 15 May 2013 15:48:02 GMT]]>Hello,
I think I managed to solve this a long time ago but forgot the solution. In Pd apparently it is impossible to have a feedback with "zero" delay, i.e. if a delwrite~ and delread~ objects are in feedback the minimum delay is one block, thus the only option is to use [block] and reduce the blocksize.

How can "zero" logical delay be achieved in feedback without resorting to reducing the block size?

L

Edit: just to be quick and clear: this is a trouble you stumble into when designing Karplus-Strong patches

]]>http://forum.pdpatchrepo.info/topic/7404/avoid-dsp-loops-with-vd-and-delwritehttp://forum.pdpatchrepo.info/topic/7404/avoid-dsp-loops-with-vd-and-delwriteWed, 15 May 2013 15:48:02 GMT<![CDATA[Reply to Avoid dsp loops with vd and delwrite? on Wed, 15 May 2013 19:27:37 GMT]]>You have to use [block~ 1] for feedback loops. There is a workaround for feedforward delay lines, but for feedback you don't really have a choice. Unless you just want to write your Karplus-Strong as an external instead.

]]>http://forum.pdpatchrepo.info/topic/7404/avoid-dsp-loops-with-vd-and-delwrite/2http://forum.pdpatchrepo.info/topic/7404/avoid-dsp-loops-with-vd-and-delwrite/2Wed, 15 May 2013 19:27:37 GMT<![CDATA[Reply to Avoid dsp loops with vd and delwrite? on Wed, 15 May 2013 20:28:46 GMT]]>Or use fexpr~ ?

[ fexpr~ $x + ( $y[-50] + $y[-51] ) / 2 ]

Here the feedback delay (51 samples in my example) is bounded by the blocksize, so you might need to increase that for low pitches.

]]>http://forum.pdpatchrepo.info/topic/7404/avoid-dsp-loops-with-vd-and-delwrite/3http://forum.pdpatchrepo.info/topic/7404/avoid-dsp-loops-with-vd-and-delwrite/3Wed, 15 May 2013 20:28:46 GMT<![CDATA[Reply to Avoid dsp loops with vd and delwrite? on Thu, 16 May 2013 08:21:53 GMT]]>I will give a try to the fexpr~ to write a biquad (that's what I'm using at the moment) in fexpr~ language and the feedback...

]]>http://forum.pdpatchrepo.info/topic/7404/avoid-dsp-loops-with-vd-and-delwrite/4http://forum.pdpatchrepo.info/topic/7404/avoid-dsp-loops-with-vd-and-delwrite/4Thu, 16 May 2013 08:21:53 GMT<![CDATA[Reply to Avoid dsp loops with vd and delwrite? on Fri, 17 May 2013 08:52:50 GMT]]>Despite being fairly easy to use, [fexpr~] is a bit notorious for being a cpu hog. So, I would recommend trying both approaches and see how they affect your cpu usage.

This is actually a nice reminder for me. I've been meaning to see how a biquad in [fexpr~] compares to my vanilla abstraction (which uses [czero~] and [cpole~]). I would think it would be better, but everything that I've used with [fexpr~] has resulted in a noticeable cpu spike.

]]>http://forum.pdpatchrepo.info/topic/7404/avoid-dsp-loops-with-vd-and-delwrite/5http://forum.pdpatchrepo.info/topic/7404/avoid-dsp-loops-with-vd-and-delwrite/5Fri, 17 May 2013 08:52:50 GMT