A Sample and Hold for audio signals

lalo · 13 Nov 2005

i'm doing one using noise signal and mono to float then sample and hold the float signal...it will only work for mono... for poly we should get voice management to deal with the 4 sse channels

sambean · 13 Nov 2005

Here's a quick stream S & H..

streamin signal; streamin freq; streamout SH;

float counter;

SH = SH - (counter>=1.0)&(SH - signal);

counter = counter - (counter >= 1.0)&1.0;

counter = counter + freq;

tested it, seems to work..

pretty straightforward: freq should be between 0 and 1.

It works using a counter, every time it exceeds 1, the input signal is sampled..

With a freq of 1, the SH signal will be the same as the input..

It's pretty crude but does the job, hope it helps..

oddson · 25 Nov 2005

Hey Sam

Your Sample and Hold code works fine, but if you feed the non-random noise from standard overdriven sine generator you get the same sample and hold pattern on each note.

I tried to use the rand() function that I've seen used in Jorge's Karplus but in only works in arrays and a var[1] array doesn't work either.

Any ideas? (example OSM)

p.s. - does the rand() function only effect stage 0 in code?

sambean · 25 Nov 2005

Hey Oddson

I imagine you're getting the same patter as each time you press a note the code is getting generated exactly the same..

A quick fix solution (as we don't have a proper random number generator) that I can think of just now is to use the green components to generate some sort of clock (timer and counter perhaps) running all the time to generate a float that you add to the phase of the sine osc, each time the noise is generated then it should be different..

Rand() only works for stage 0 at the moment as far as I can tell, there's a thread somewhere about generating pseudo random numbers in the code, but again, if you do this in poly code, the random pattern will be the same each time..

The example I put on this thread should not really be called a sample and hold, more a sample rate reducer..

A proper sample and hold would be:

streamin signal; streamin trig; streamout SH;

// If we get a trigger sample the signal;

SH = SH - (trig>=1.0)&(SH - signal);

This can be preceded by a trig generator:

streamin in; streamout trig; float in1;

// If previous sample is less than 0 and // new sample is greater or equal to 0 // then send a trigger;

trig = (in1 < 0.0)&(in >= 0.0)&1; in1 = in;

With this you could use an osc as a trigger for the S&H..

Nice example btw, pure 70s SiFi..

Sam

oddson · 26 Nov 2005

Cool, thanks. 😀 What I did was take your pseudo-random (green) generator mod and hook it's trigger to the ticker then added it's output to the overdriven sine generator and got what I wanted [updated eg file above]. I was going to add a 'nevermind' message to my post last night but thought I'd leave it and find out what you (and others maybe) thought about the issue.

(My solution is a little heavy on CPU methinks)

Greatful for your help as always! 🙂 🙂 😀 😀

ROMplERbuDE · 29 Jun 2006

Hy to all. Late post but here is another quick simple S&H, if only sends a trigger when == 1.

// Code S&H streamin in; streamin H; streamout out; float y0; y0 = (H != 1) &(out * 1) + (H == 1) & in; out = y0;

& a

// Simple Quant. counter streamin quan; // Integer + min 2; streamout out; float cnt; cnt=cnt + 1; cnt = cnt- (cnt>=quan) &quan; out = cnt;

AngularMomentum · 1 Jul 2006

Thanks for that S&H, now I can finally go on with my emu of the ARP Odyssey! 😀