Add distortion effect

libs/audio/include/psemek/audio/effect/distortion.hpp

@@ -0,0 +1,17 @@
+#pragma once
+
+#include <psemek/audio/stream.hpp>
+
+namespace psemek::audio
+{
+
+	struct distortion_control
+		: stream
+	{
+		virtual float strength() const = 0;
+		virtual float strength(float value) = 0;
+	};
+
+	stream_ptr distortion(stream_ptr stream, float strength = 100.f);
+
+}

libs/audio/source/effect/distortion.cpp

@@ -0,0 +1,65 @@
+#include <psemek/audio/effect/distortion.hpp>
+
+#include <cmath>
+#include <atomic>
+
+namespace psemek::audio
+{
+
+	namespace
+	{
+
+		struct distortion_impl
+			: distortion_control
+		{
+			distortion_impl(stream_ptr stream, float strength)
+				: stream_(std::move(stream))
+				, strength_(strength)
+			{}
+
+			float strength() const override
+			{
+				return strength_.load();
+			}
+
+			float strength(float value) override
+			{
+				return strength_.exchange(value);
+			}
+
+			std::optional<std::size_t> length() const override
+			{
+				return stream_->length();
+			}
+
+			std::size_t read(float * data, std::size_t sample_count) override
+			{
+				auto result = stream_->read(data, sample_count);
+				float strength = strength_.load();
+
+				for (std::size_t i = 0; i < result; ++i)
+				{
+					data[i] = std::tanh(strength * data[i]);
+				}
+
+				return result;
+			}
+
+			std::size_t played() const override
+			{
+				return stream_->played();
+			}
+
+		private:
+			stream_ptr stream_;
+			std::atomic<float> strength_;
+		};
+
+	}
+
+	stream_ptr distortion(stream_ptr stream, float strength)
+	{
+		return std::make_shared<distortion_impl>(std::move(stream), strength);
+	}
+
+}