extract rms detector to separate file

dynamics/rms_detector.h

@@ -0,0 +1,23 @@
+#pragma once
+#include <cmath>
+
+namespace trnr {
+struct rms_detector {
+	float alpha;
+	float rms_squared;
+};
+
+inline void rms_init(rms_detector& d, float samplerate, float window_ms)
+{
+	float window_seconds = 0.001f * window_ms;
+	d.alpha = 1.0f - expf(-1.0f / (samplerate * window_seconds));
+	d.rms_squared = 0.0f;
+}
+
+template <typename sample>
+inline sample rms_process(rms_detector& d, sample input)
+{
+	d.rms_squared = (1.0f - d.alpha) * d.rms_squared + d.alpha * (input * input);
+	return sqrtf(d.rms_squared);
+}
+} // namespace trnr