Make audio channel a separate class

examples/audio.cpp

@@ -5,6 +5,8 @@
 #include <psemek/audio/wave/square.hpp>
 #include <psemek/audio/wave/triangle.hpp>
 #include <psemek/audio/effect/volume.hpp>
+#include <psemek/audio/effect/fade_in.hpp>
+#include <psemek/audio/effect/fade_out.hpp>
 #include <psemek/audio/duplicate.hpp>
 #include <psemek/audio/stereo.hpp>
 #include <psemek/audio/mixer.hpp>
@@ -19,6 +21,16 @@ using namespace psemek;
 
 static std::map<SDL_Keycode, int> const key_to_midi
 {
+	{SDLK_z, 59},
+	{SDLK_x, 60},
+	{SDLK_c, 61},
+	{SDLK_v, 62},
+	{SDLK_b, 63},
+	{SDLK_n, 64},
+	{SDLK_m, 65},
+	{SDLK_COMMA, 66},
+	{SDLK_PERIOD, 67},
+	{SDLK_SLASH, 68},
 	{SDLK_a, 69},
 	{SDLK_s, 70},
 	{SDLK_d, 71},
@@ -30,6 +42,18 @@ static std::map<SDL_Keycode, int> const key_to_midi
 	{SDLK_l, 77},
 	{SDLK_SEMICOLON, 78},
 	{SDLK_QUOTE, 79},
+	{SDLK_q, 80},
+	{SDLK_w, 81},
+	{SDLK_e, 82},
+	{SDLK_r, 83},
+	{SDLK_t, 84},
+	{SDLK_y, 85},
+	{SDLK_u, 86},
+	{SDLK_i, 87},
+	{SDLK_o, 88},
+	{SDLK_p, 89},
+	{SDLK_LEFTBRACKET, 90},
+	{SDLK_RIGHTBRACKET, 91},
 };
 
 struct audio_app
@@ -41,8 +65,8 @@ struct audio_app
 		mixer_ = audio::make_mixer();
 
 		auto [ dup1, dup2 ] = audio::duplicate(mixer_);
-		left_volume_ = audio::volume(dup1, 0.f, 0.1f);
+		left_volume_ = audio::volume(dup1, 0.5f, 0.1f);
-		right_volume_ = audio::volume(dup2, 0.f, 0.1f);
+		right_volume_ = audio::volume(dup2, 0.5f, 0.1f);
 		auto result = audio::stereo(left_volume_, right_volume_);
 		engine_.output(result);
 	}
@@ -55,7 +79,7 @@ struct audio_app
 		{
 			int midi = key_to_midi.at(key);
 			auto tone = audio::sine_wave(440.f * std::pow(2.f, (midi - 69) / 12.f));
-			channels_[key] = mixer_->add(tone);
+			channels_[key] = mixer_->add(audio::fade_in(tone, 0.01f));
 		}
 	}
 
@@ -65,7 +89,8 @@ struct audio_app
 
 		if (channels_.contains(key))
 		{
-			channels_[key]->stop();
+			auto & ch = channels_[key];
+			ch->stream(audio::fade_out(ch->stream(), 0.01f));
 			channels_.erase(key);
 		}
 	}
@@ -83,7 +108,7 @@ private:
 	audio::engine engine_;
 	audio::mixer_ptr mixer_;
 	std::shared_ptr<audio::volume_control> left_volume_, right_volume_;
-	std::map<SDL_Keycode, audio::mixer::channel_ptr> channels_;
+	std::map<SDL_Keycode, audio::channel_ptr> channels_;
 
 	util::clock<> clock_;
 };

libs/audio/include/psemek/audio/channel.hpp

@@ -0,0 +1,43 @@
+#pragma once
+
+#include <psemek/audio/stream.hpp>
+
+#include <atomic>
+#include <memory>
+
+namespace psemek::audio
+{
+
+	struct channel
+	{
+		channel(stream_ptr stream)
+			: stream_(std::move(stream))
+		{}
+
+		stream_ptr stream() const
+		{
+			return std::atomic_load(&stream_);
+		}
+
+		stream_ptr stream(stream_ptr new_stream)
+		{
+			return std::atomic_exchange(&stream_, std::move(new_stream));
+		}
+
+		stream_ptr stop()
+		{
+			return stream(nullptr);
+		}
+
+		bool is_stopped() const
+		{
+			return stream() != nullptr;
+		}
+
+	private:
+		stream_ptr stream_;
+	};
+
+	using channel_ptr = std::shared_ptr<channel>;
+
+}

libs/audio/include/psemek/audio/mixer.hpp

@@ -1,7 +1,7 @@
 #pragma once
 
 #include <psemek/audio/stream.hpp>
-#include <psemek/util/function.hpp>
+#include <psemek/audio/channel.hpp>
 
 #include <memory>
 
@@ -11,19 +11,6 @@ namespace psemek::audio
 	struct mixer
 		: stream
 	{
-		struct channel
-		{
-			virtual void stop() = 0;
-
-			virtual bool is_stopped() const = 0;
-
-			virtual void replace(util::function<stream_ptr(stream_ptr)> modifier) = 0;
-
-			virtual ~channel() {}
-		};
-
-		using channel_ptr = std::shared_ptr<channel>;
-
 		virtual channel_ptr add(stream_ptr stream) = 0;
 	};
 

libs/audio/source/mixer.cpp

@@ -10,35 +10,6 @@ namespace psemek::audio
 	namespace
 	{
 
-		struct channel_impl final
-			: mixer::channel
-		{
-			stream_ptr stream;
-
-			void stop() override;
-
-			bool is_stopped() const override;
-
-			void replace(util::function<stream_ptr(stream_ptr)> modifier) override;
-		};
-
-		void channel_impl::stop()
-		{
-			std::atomic_store(&stream, stream_ptr());
-		}
-
-		bool channel_impl::is_stopped() const
-		{
-			return std::atomic_load(&stream) != nullptr;
-		}
-
-		void channel_impl::replace(util::function<stream_ptr(stream_ptr)> modifier)
-		{
-			stream_ptr stream = std::atomic_load(&(this->stream));
-			stream = modifier(std::move(stream));
-			std::atomic_store(&(this->stream), std::move(stream));
-		}
-
 		struct mixer_impl final
 			: mixer
 			, std::enable_shared_from_this<mixer_impl>
@@ -48,19 +19,18 @@ namespace psemek::audio
 			std::size_t read(float * data, std::size_t sample_count) override;
 
 		private:
-			std::vector<std::shared_ptr<channel_impl>> channels_;
+			std::vector<channel_ptr> channels_;
-			std::vector<std::shared_ptr<channel_impl>> alive_channels_;
+			std::vector<channel_ptr> alive_channels_;
 
 			std::vector<float> buffer_;
 
 			std::mutex new_channels_mutex_;
-			std::vector<std::shared_ptr<channel_impl>> new_channels_;
+			std::vector<channel_ptr> new_channels_;
 		};
 
-		mixer::channel_ptr mixer_impl::add(stream_ptr stream)
+		channel_ptr mixer_impl::add(stream_ptr stream)
 		{
-			auto result = std::make_shared<channel_impl>();
+			auto result = std::make_shared<channel>(std::move(stream));
-			result->stream = std::move(stream);
 
 			{
 				std::lock_guard lock{new_channels_mutex_};
@@ -73,7 +43,7 @@ namespace psemek::audio
 		std::size_t mixer_impl::read(float * data, std::size_t sample_count)
 		{
 			{
-				std::vector<std::shared_ptr<channel_impl>> new_channels;
+				std::vector<channel_ptr> new_channels;
 				{
 					std::lock_guard lock{new_channels_mutex_};
 					new_channels = std::move(new_channels_);
@@ -88,7 +58,7 @@ namespace psemek::audio
 
 			for (auto & ch : channels_)
 			{
-				auto stream = std::atomic_load(&(ch->stream));
+				auto stream = ch->stream();
 				if (!stream)
 					continue;