"A sample and hold uses a periodic wave as an input. The wave is sampled at regular
intervals. The resulting values are used as a control. It "samples" the wave and "holds" that
value until a new value is sampled. It can be thought of as an analog to digital converter with
a low frequency sampling rate (though technically the wave being sampled is also digital).
The effect is similar to a strobe light or motion picture film taking snapshots of a smooth
process. That smooth process is then quantized into discrete steps.

"How is this useful in synthesis? Why would you want to freeze-frame a wave form?

The idea is that even though the sample rate is too low to accurately represent the true shape
of the wave, patterns will still emerge because the wave is periodic, and the sample rate is

periodic."

[David Cottle, _Computer Music with Examples in Supercollider 3]

(This can be done in ChucK; the sndBuf containing the wave can be sampled via .valueAt without directly playing it.)

On Sun, Apr 19, 2020 at 9:50 PM Forrest Curo <treegestalt@gmail.com> wrote:

I've achieved  dreadfulness with this. Okay, will vary the rhythm etc and reduce the range, get a more interesting scale, but... hmm!

SawOsc s => JCRev r => dac;
.1 => s.gain;
.1 => r.mix;
1 => int incsamp;
0 => int ps;
1 => float height;
0 => float maxsofar;
0 => float freq;
SndBuf buf;

"/home/forrest/chuck/examples/basic/om.wav" => buf.read;

buf.samples()  => int numSamples;
 Std.rand2(1, numSamples-1) => incsamp;
while(true){
(incsamp + ps) % numSamples => ps;
buf.valueAt(ps) + 0.125 => height;
Std.mtof(Math.ceil(Std.fabs(500.0 * height)) ) => freq => s.freq;

if(freq > maxsofar) {
freq => maxsofar;
<<< maxsofar >>>;
}
0.75::second => now;
}

On Sun, Apr 19, 2020 at 1:42 PM Forrest Curo <treegestalt@gmail.com> wrote:

Um. that works.

So does this:

SndBuf s => blackhole;
"/home/forrest/chuck/examples/basic/om.wav" => s.read;
float samples;
0 => int i;
while (s.pos() < s.samples())  {
    <<< s.last() >>>;
    s.pos() => i;
    (s.valueAt(i)) => samples;
    <<< samples >>>;
    samp => now;

}

I was having trouble trying to read a sndBuf like an array, or put its contents into an array.

Maybe I was reading numbers off the end of the file. Declaring

'float samples[]; '

and doing

's.valueAt(i) => samples[i];'

got me a 'Null pointer' error.

Stumbling over syntax, I guess. Thanks for help!

On Sun, Apr 19, 2020 at 10:54 AM Perry Cook <prc@cs.princeton.edu> wrote:

This is truly odd.  I don’t have easy means to test it.   I don’t
know why it wouldbe broken dependent on the dac, however.

For fun you might try something like this, just to verify that the
valueAt() function is what’s busted.

SndBuf s => blackhole; 
“Fred.wav” => s.read;

while (s.pos() < s.samples())  {
    <<< s.last() >>>;
    samp => now;
}

PRC

> On Apr 19, 2020, at 9:00 AM, chuck-users-request@lists.cs.princeton.edu wrote:
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>   1. sndBuf.valueAt (Forrest Curo)
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> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sun, 19 Apr 2020 07:30:15 -0700
> From: Forrest Curo <treegestalt@gmail.com>
> To: ChucK Users Mailing List <chuck-users@lists.cs.princeton.edu>
> Subject: [chuck-users] sndBuf.valueAt
> Message-ID:
>       <CAAn-Ecy0LKVHCWmoUL2Y7w67rsibhRAHOOkN1neZyU=az3vm=g@mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Using chuck linux-jack this gives me reasonable numbers between -1 and 1.
> Using chuck linux-alsa I'm able to play the file I've read into sndBuf; but
> trying to copy it via .valueAt gives absurdly high ["out of range"] numbers
> at each point. [It can be a different high number different times I run
> chuck, but the number it is turns up at every point I sample.]
>
> Is there a fix for this? Aside from using jack on a computer where it
> befnurgles the midi?
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