[chuck-users] SinOsc UGen

Wed Oct 24 02:43:27 EDT 2018

Hi Joel, Perry,

thanks for getting back to me. I remember there was a discussion about
SinOsc, just I couldn't remember the outcome of that.
I'll give SndBuf/Wavetable/GenX a try and report some results back here in
case there are any worth sharing.

thanks,
Mario

On Tue, 23 Oct 2018 at 22:43, Joel Matthys <jwmatthys at gmail.com> wrote:

> Hi Mario.
>
> We had a discussion about this on the chuck-dev a couple of years ago,
> when I created the Wavetable Chugin. I've copied below a very interesting
> comment from Perry Cook. To my surprise, on modern architectures, RT trig
> isn't really any more expensive than table lookup. I tested the Wavetable
> chugin vs SinOsc and found no significant difference in performance.
>
> I still think a wavetable UGen would be a good addition to ChucK (maybe
> adapted from my Chugin) but it seems that, unless someone were able to
> create some additional optimizations, it wouldn't be any more efficient
> than the existing SinOsc.
>
> Joel
>
> -------------------
> Forwarded message from Perry Cook below:
>
> Hey all,
>
> Chiming in on the various Sine-related topics here. SinOsc was designed
> like most of ChucK, to do things from the definition, without particular
> regard for  efficiencies. In fact, a native Math.sin(BLAH) call isn’t that
> hideous. It used to be in the olden days, and we avoided it like the
> plague. The Motorola DSP 56000 had a built in quarter-wave of sine in ROM.
> (It also had an 8-bit muLaw decoding table built in as well). Many papers
> (Snell, Others) were written about the optimal length, bit-depth, etc of a
> sine table given different types of interpolation. Yamaha chips stored sine
> quads in both linear (for addition) and log (for multiplication) ROM, or
> hard-coded into gates for the absolute minimum expense.
>
> Wavetables:
>
> Indeed, SndBuf is ChucK’s built-in wavetable (in .loop mode). And, it
> could be a  little cheaper, and it has built-in linear interpolation. If
> you want less distortion, just make your table longer. The “table” here is
> a .wav file you create and load.  All you need add is an accessing function
> to set rate as a function of frequency.
>
> And you could also add FM, PM, and other .sync-like functions as well. By
> this time, it might be worth comparing to SinOsc efficiency for FM and
> other audio- rate modulation tho. I just did a quick check and find SndBuf
> to be about equal to SinOsc (the number I can run before audio starts
> breaking up, just over 400).
>
> See code below.
>
> Note also that there are some other wavetable-like UGens already in the
> GenX family in ChucK. I don’t know about the relative efficiency of those,
> and I do know that that you need to drive (some of) them with a Phasor. So
> again, it might not end up being significantly cheaper.
>
> On unit-circle sine generation: Spencer has already given us a great
> ChuGen called MagicSine, that does the rotation-based sine generation using
> only a couple of multiplies and adds. It’s most efficient if you’re not
> changing frequency rapidly.
>
> Julius and I also did a “waveguide resonator” oscillator (similar to
> Magic  Sine), but it also had built in exponential envelope (phasor that
> spins outward or inward), and allowed for modulation of the parameters for
> FM-like wave distortion. Not particularly efficient if you just want a sine
> wave. I have a ChuGen for that too, but never released it.
>
> So the topic "many ways to skin a sine" is still active today!!
>
> My comparison codes (in terminal, miniAudicle may vary, also Audio BUFSIZE
> might help):
>
> /* SinOscCompare.ck ***************************************/
>
> SinOsc s[1000];
> Gain outMix => dac;
> for (int i; i < 4000; i++) {
> if (i%100 == 0) <<< "Sines", i+1 >>>; // this could be costing us some
> s[i] => outMix;
> Math.random2f(100,3000) => s[i].freq; // as would this
> 1.0/(i+1.0) => outMix.gain; // and this
> 10*ms => now; // but if those dominated, we’d probably hear 100 Hz
> distortion
> }
>
> /* SndBufCompare.ck ***************************************/
>
> SndBuf s[1000];
> Gain outMix => dac;
> for (int i; i < 4000; i++) {
> if (i%100 == 0) <<< "SndBufs", i+1 >>>; // this could be costing us some
> "special:dope" => s[i].read; // maybe this too, but cacheing should help
> 1 => s[i].loop;
> s[i] => outMix;
> Math.random2f(0.2,5.0) => s[i].rate; // as would this
> 1.0/(i+1.0) => outMix.gain; // and this
> 10*ms => now; // but if those dominated, we’d probably hear 100 Hz
> distortion
> }
>
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> On Oct 23 2018, at 9:28 am, Mario Buoninfante <mario.buoninfante at gmail.com>
> wrote:
>
>
> Hi,
>
> As already pointed out by someone else here, I noticed we've got the
> SinOsc UGen that doesn't use a wavetable but instead uses the sin function.
> I don't know what the reason behind this decision, but I was wondering
> whether it would be possible to also have a variant that uses wavetable as
> well. I presume that would help a bit in terms of performances, and I think
> it would be useful in scenarios where ChucK runs on platforms like
> Raspberry Pi.
>
> cheers,
> Mario
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