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This commit makes ops_sin stateful by tracking last_ticks_ms and its
theta angle.
Unfortunately that necessitates serializing ops_sin on the output
path, currently done using a mutex.
See larger comment in ops_sin.c for why this is all necessary.
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sig_t collides with some signals-related system header on macos.
Just prefix it under the sig namespace.. leaving sig_ops alone
for now, but maybe they'll become sig_sig_ops in the future too.
Note nothing in master actually uses libs/sig currently, but I
have an experimental branch with a dusty module using it.
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Added a triangle wave
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This builds minimally upon the existing sine wave code,
just use the sign to drive the signal high or low.
Wikipedia shows a third state for 0 values, but that's for a -1..+1
signal. I'm producing all 0-1 signals as it's more convenient for
this application, but it seems like it would be awkward to return
.5f for the 0 case. So 0 is being treated as just another positive
value; high.
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Seems broken, fix it correctly later.
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off by one order of magnitude
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The whole idea was to produce values 0-1, except of course
sig_ops_{mult,const} where one could deliberately get out of
these bounds.
Everything else should stay within 0-1 as it makes everything
much more composable.
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Now hz can vary with time as well...
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This adds a small framework of sorts for creating and composing signal
generators.
Two generators are implemented at this time; sig_ops_sin and sig_ops_mult
sig_ops_sin accepts a hz variable and will produce a sine wave of that
frequency.
sig_ops_mult accepts two sig_t generators and multiplies their outputs
Callers may construct their own sig_ops_t ops structs and supply them to
sig_new(), but it's expected that libs/sig will grow a collection of
commonly used generators which can then be used by simply passing their
sig_ops_$foo to sig_new().
See the test code at the bottom of libs/sig/sig.c for some contrived
sample usage. Note by composing multiple sig_ops_sin generators with
a sig_ops_mult generator, one can already easily construct a synth-like
LFO generator.
Some obvious todos are to add triangle/sawtooth/square wave generators.
More compositional generators may be interesting as well, like additive
and subtractive for example. Those will need to implement clipping, as
it's expected that the generators *always* stay within unity (0-1).
No modules use this yet, but I expect to wire this up to rtv for driving
knobs.
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