Alexandre Porres wrote:
"I feel Max produce a smoother audio than Pd. Didit"
Well, if you use [tabread4~] or any of the many other Pd objects that use the same broken interpolation algorithm (copy/paste programming), you get horrible noise. If you use [tabread4] to interpolate graphical parameters for animations, the discontinuities in the derivatives are really obvious.
See attached patch - it would be interesting to see if a Max/MSP port of this patch exhibits the same problem.
nusmuk audio tabread4c~ uses the correct interpolation algorithm, correct me if I'm wrong.
See also this long discussion: http://lists.puredata.info/pipermail/pd-list/2008-06/062878.html Claude -- http://claudiusmaximus.goto10.org
#N canvas 0 0 699 665 10; #X obj 163 97 cos~; #X obj 197 123 expr~ cos($v1*3.14159265359*2.0); #X obj 163 147 -~; #N canvas 0 0 450 300 (subpatch) 0; #X array \$0-brokenness 4096 float 2; #X coords 0 1 4096 -1 600 128 1; #X restore 44 333 graph; #X obj 77 195 tabwrite~ \$0-brokenness; #X obj 77 74 bng 15 250 50 0 empty empty empty 17 7 0 10 -262144 -1 -1; #X obj 46 145 metro 1000; #X obj 46 74 tgl 15 0 empty empty empty 17 7 0 10 -262144 -1 -1 1 1 ; #X obj 162 171 *~ 25000; #X text 405 122 <--- pure sine wave; #X text 209 97 <--- cos~ uses [tabread4~ costab] internally \, impure ; #X text 298 61 <--- same phase source for comparison; #X obj 196 60 phasor~ 100.01; #X text 259 187 [tabread4~] uses a broken 4-point interpolation algorithm \, different to the standard 2-point/2-slope cubic algorithm known to be correct for centuries \; it is nonsensical to have a piece-wise cubic that goes through all 4 points \, when that piece is only used between the innermost 2 points \; continuity of slope at the switching points between the pieces of cubics is broken in [tabread4~] \, leading to lack of smoothness \; if [tabread4~] was good enough \, the array would flatline; #X text 209 150 <--- spot the difference \, horrible distortion (-48dB) ; #X text 39 18 [tabread4~] interpolation is wrong; #N canvas 0 0 450 300 (subpatch) 0; #X array \$0-spectrum 2048 float 2; #X coords 0 1 2048 0 600 128 1; #X restore 44 486 graph; #N canvas 270 88 565 387 \$0-fft 0; #X obj 15 25 block~ 4096 4 1; #X obj 130 60 inlet~; #X obj 131 150 rfft~; #X obj 124 184 *~; #X obj 150 185 *~; #X obj 128 212 +~; #X obj 126 293 tabwrite~ \$0-spectrum; #X obj 43 62 inlet; #X obj 130 106 *~; #X obj 156 25 table \$0-window 4096; #X obj 146 83 tabreceive~ \$0-window; #X obj 317 28 loadbang; #X obj 317 55 f 4096; #X obj 317 81 until; #X obj 317 116 f 0; #X obj 352 106 + 1; #X obj 352 129 mod 4096; #X obj 295 28 bng 15 250 50 0 empty empty empty 17 7 0 10 -262144 -1 -1; #X obj 236 214 tabwrite \$0-window; #X obj 236 162 expr 0.5*(1.0-cos($f1*3.14159265359*2.0/4096.0)) \; $f1; #X obj 128 238 expr~ sqrt($v1); #X obj 127 267 /~ 256; #X connect 1 0 8 0; #X connect 2 0 3 0; #X connect 2 0 3 1; #X connect 2 1 4 0; #X connect 2 1 4 1; #X connect 3 0 5 0; #X connect 4 0 5 1; #X connect 5 0 20 0; #X connect 7 0 6 0; #X connect 8 0 2 0; #X connect 10 0 8 1; #X connect 11 0 12 0; #X connect 12 0 13 0; #X connect 13 0 14 0; #X connect 14 0 15 0; #X connect 14 0 19 0; #X connect 15 0 16 0; #X connect 16 0 14 1; #X connect 17 0 12 0; #X connect 19 0 18 0; #X connect 19 1 18 1; #X connect 20 0 21 0; #X connect 21 0 6 0; #X restore 46 229 pd \$0-fft; #X obj 149 232 dac~; #X msg 586 52 \; pd dsp 1; #X connect 0 0 2 0; #X connect 1 0 2 1; #X connect 2 0 8 0; #X connect 5 0 4 0; #X connect 5 0 17 0; #X connect 6 0 4 0; #X connect 6 0 17 0; #X connect 7 0 6 0; #X connect 8 0 4 0; #X connect 8 0 17 1; #X connect 8 0 18 0; #X connect 8 0 18 1; #X connect 12 0 1 0; #X connect 12 0 0 0;
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