From ba74a824658f7f59add288d28006ff48bf46b963 Mon Sep 17 00:00:00 2001 From: Vito Caputo Date: Mon, 3 Feb 2020 00:29:09 -0800 Subject: libs/sig: introduce a signal generator abstraction 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. --- src/libs/sig/sig.h | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) create mode 100644 src/libs/sig/sig.h (limited to 'src/libs/sig/sig.h') diff --git a/src/libs/sig/sig.h b/src/libs/sig/sig.h new file mode 100644 index 0000000..cd22d4d --- /dev/null +++ b/src/libs/sig/sig.h @@ -0,0 +1,30 @@ +#ifndef _SIG_H +#define _SIG_H + +#include +#include + +typedef struct sig_t sig_t; + +typedef struct sig_ops_t { + size_t (*size)(va_list ap); /* return size of space needed for context for given ap */ + void (*init)(void *context, va_list ap); /* initialize context w/given ap */ + void (*destroy)(void *context); /* destroy initialized context */ + float (*output)(void *context, unsigned ticks_ms); /* output a value 0-1 from context appropriate @ time ticks_ms */ +} sig_ops_t; + +sig_t * sig_new(const sig_ops_t *ops, ...); +sig_t * sig_free(sig_t *sig); +float sig_output(sig_t *sig, unsigned ticks_ms); + +extern sig_ops_t sig_ops_sin; + +/* TODO: +extern sig_ops_t sig_ops_tri; +extern sig_ops_t sig_ops_saw; +extern sig_ops_t sig_ops_sqr; +*/ + +extern sig_ops_t sig_ops_mult; + +#endif -- cgit v1.2.3