DSP ELEMENTS IN MAX/MSP

Transcription

1 DSP ELEMENTS IN MAX/MSP Maarte va Walstij PBASS Sessio 8: DSP Elemets i Max/MSP Why Physical Modellig PM i Max/MSP? real-time iteractive dyamic parameter cotrol ituitive graphical oject programmig cotrol Max ojects cotrol rate calculatios physical model MSP ojects audio rate calculatios Suited to exploratio of soic/music potetial difficult i Matla PBASS Sessio 8: DSP Elemets i Max/MSP

2 Best Way to Programme Physical Models i Max/MSP: Exteral Ojects! C/C/java/javascript Complete physical models with o-liear iteractio caot e scaled aritrarily to avoid roudig errors; umer precisio doules, floats is critical, Max/MSP is much coarser tha C, java, Matla. Precise cotrol over umerical details is usually required; ofte ot possile withi Max/MSP. Computatioally more efficiet tha withi Max/MSP Allows for more fuctioality such as umer of modes Disadvatage: fairly elaorate to programme! Do-ale withi Max/MSP: Simple ojects, o o-liear iteractio. Advatage: easy to programme, helps uderstadig physical models PBASS Sessio 8: DSP Elemets i Max/MSP 3 Mai MSP Ojects for DWG/SDL Modellig Filters iquad~ Delay-Lies: tapi~ & tapout~ implemets a secodorder digital filter Useful for creatig oscillators or atteuatio filters implemets a iterpolated fractioal delay, allows feedack Useful for creatig delay-lies that simulate wave propagatio PBASS Sessio 8: DSP Elemets i Max/MSP 4

3 PBASS Sessio 8: DSP Elemets i Max/MSP 5 Secod-Order Filter: iquad~ x y 0 a a H 0 y a y a x x x y NOTE: the Max/MSP help file uses a otatio i which the a s ad the s are switched. PBASS Sessio 8: DSP Elemets i Max/MSP 6 Delay that allows Feedack: tapi~ & tapout~ feedack g delay i ms -N FD t x yt xt yt g D N H Feedig the sigal ack i is allowed with tapi~/tapout~, ut ot with delay~. D T N t t t x t y d d

4 Some Other Geerally Useful Ojects MSP: ~, -~, *~, /~ DSP-level arithmetic operators click~ sigle impulse geerator oise~ oise geerator lie~ evelope geerator Max: loadag metro expr output iput ags whe patch is loaded regular ags evaluates a C/Matla-like expressio iput i su-patch output i su-patch PBASS Sessio 8: DSP Elemets i Max/MSP 7 Idepedet Su-Patches iir4~ 4 th -order IIR filter usig iquads i cascade PBASS Sessio 8: DSP Elemets i Max/MSP 8

5 Implemetig Propagatio Use tapi~/tapout~ for delay with feedack Use Hatt~ as atteuatio filter Filter tued to correct decay rate at frequecies: α α 0 ω c propagatio over distace d tapi~ tapout~ td delay d t d c P d td f c alp0 alp Hatt~ atteuatio PBASS Sessio 8: DSP Elemets i Max/MSP 9 Implemetig a Feed-Forward System that Allows a Zero Delay Delay td must e ale to go to ero. Miimum delay etwee tapi & tapout is ~ ms! td tapi~ td tapi~.0.0td tapout~ tapout~ tapout~ ~ ~ Solutio: two tapouts~: differece of td PBASS Sessio 8: DSP Elemets i Max/MSP 0

6 Parameter Traslatio A Max exteral i Java script strigpar is supplied for the traslatio of physical strig parameters to SDL model parameters: physical parameters SDL model parameters Note that oe has to eter js at the start of the max ox, followed y the ame of the Java script. Output is created y chagig ANY of the ilets as opposed to stadard Max ojects that oly react to the left ilet. PBASS Sessio 8: DSP Elemets i Max/MSP Parameter Cotrol STRING PARAMETERS L strig legth rho mass desity Te tesio air dampig iteral dampig re relative excitatio poit rp relative pick-up poit SDL MODEL PARAMETERS f fudametal frequecy c wave speed R characteristic impedace alp0 decay rate at f 0 alp decay rate at ff te delay for excitatio sectio Tsdl delay for SDL sectio tp delay for pick-up sectio slider/other cotrollers: scalig/rage eeds to e addressed. Sed/receive might e hady to avoid messy patches s x wireless r x PBASS Sessio 8: DSP Elemets i Max/MSP

7 Impulsive Hammer/Mallet Excitatio ag hardess > 0 hit~ hard total output eergy is cosistet, idepedet of hardess soft PBASS Sessio 8: DSP Elemets i Max/MSP 3 Remider Rememer to use floats iside arithmetic operatio ojects: -~ 0.0 *~ /.0 otherwise you might ot get out what you expect Max/MSP expectig iput as itegers, ad roudig off to ero PBASS Sessio 8: DSP Elemets i Max/MSP 4

8 Supatches to Dowload \\ \mvawalstij\Sites\pass\patches.html strigpar.js traslates physical strig parameters ito SDL model parameters. atteuatioa.js traslates SDL model parameters ito iquad~ filter coefficiets withi Hatt~. Hatt~ atteuatio filter. hit~ simulates simplified hammer excitatio. Some other example files are availale. PBASS Sessio 8: DSP Elemets i Max/MSP 5