Installed in oscillators.lib
Let me know if there should be any further changes.
Thanks,
- Julius
On Sun, Jun 23, 2019 at 10:28 AM Dario Sanfilippo
<sanfilippo.da...@gmail.com> wrote:
>
> Nice one, Oleg. Yes, 1 and 0 should be the correct initial samples. Thanks
> for this. :)
>
> D
>
> On Sun, 23 Jun 2019 at 18:56, Oleg Nesterov <o...@redhat.com> wrote:
>>
>> On 06/15, Dario Sanfilippo wrote:
>> >
>> > quad_osc(f) = tick ~ (_ , _)
>> > with {
>> > init = 1-1';
>> > w = 2*ma.PI*f/ma.SR;
>> > k1 = tan(.5*w);
>> > k2 = 2*k1/(1+k1*k1);
>> > tick(u, v) = omega-k1*(v+k2*omega) , v+k2*omega
>> > with {
>> > omega = (u+init)-k1*v;
>> > };
>> > };
>>
>> another case when we need to initialize the delay line ;)
>>
>> Dario, it is not that I suggest to change this code, please ignore,
>> but just for record... note that in this case we can avoid this hack
>> and write
>>
>> quadosc(f) = tick ~ (_,_) : +(1),_ with {
>> k1 = tan(f * ma.PI/ma.SR);
>> k2 = 2*k1 / (1 + k1 * k1);
>>
>> tick(u_0,v_0) = u_1,v_1 with {
>> tmp = u_0 - k1 * v_0;
>> v_1 = v_0 + k2 * (tmp + 1);
>> u_1 = tmp - k1 * v_1;
>> };
>> };
>>
>> This generates a slightly better code. And, this allows to add (mem,mem)
>>
>> quadosc(f) = tick ~ (_,_) : mem+1,mem with {
>> k1 = tan(f * ma.PI/ma.SR);
>> k2 = 2*k1 / (1 + k1 * k1);
>>
>> tick(u_0,v_0) = u_1,v_1 with {
>> tmp = u_0 - k1 * v_0;
>> v_1 = v_0 + k2 * (tmp + 1);
>> u_1 = tmp - k1 * v_1;
>> };
>> };
>>
>> to ensure that it always ouputs (1,0) at the very first tick. Not that I
>> think this is very important, but this matches other oscillators and looks
>> more clean imo.
>>
>> Oleg.
>>
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--
Julius O. Smith III <j...@ccrma.stanford.edu>
Professor of Music and, by courtesy, Electrical Engineering
CCRMA, Stanford University
http://ccrma.stanford.edu/~jos/
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