// "Greyhole" demo with decimation/down/upsampling // By Perry R. Cook, October 2012 // This demonstrates a couple of things // 1) using FIR Sinc filters for bandlimiting and reconstruction // 2) decimation, for doing signal processing at lower rates // or just for fun int decFactor; // can specify like: chuck TestDownUpSample.ck:8 if (me.args() > 0) Std.atoi(me.arg(0)) => decFactor; else 16 => decFactor; // or it will default to what is here Gain decimate; // anything chucked to here will run at lower rate adc => FIR lowpass => blackhole; // initial band limiting if needed Step holdout => FIR lp2 => WvOut w => dac; // hold and reconstruct "test.wav" => w.wavFilename; 0.1 => w.fileGain; // lowpass is here to bandlimit before downsampling 1.0 => lowpass.gain; 128 => lowpass.order; decFactor => lowpass.sinc; // lp2 is here to get rid of decimation critters after upsampling // but doesn't have to be as high order (driven by a step) 1.0 => lp2.gain; 64 => lp2.order; decFactor => lp2.sinc; spork ~ decimateBy(decFactor); 1 => int notDone; SinOsc s => decimate; // test to prove decimation works 10000.0 => s.freq; // sine freq won't be this, it will 0.1 => s.gain; // be thisFreq / decFactor because it // only runs at the lower rate!! 1.0 => lowpass.gain; // this sets/mutes the microphone input while(notDone) { 0.05 :: second => now; // hang out here and do nothing } fun void decimateBy(int factor) { while (notDone) { // only take every factor-th lowpass => decimate; // sample from our input(s) decimate => blackhole; // hook things up and let 1 :: samp => now; // one sample through decimate.last()=> holdout.next; // sample to output lowpass =< decimate; // now disconnect everybody decimate =< blackhole; // (probably too enthusiastically) (factor - 1) :: samp => now; // and hang around between } }