visualizer: scale automatically if multiplier is 1

src/status.cpp

@@ -526,6 +526,9 @@ void Status::Changes::songID(int song_id)
 	playing_song_scroll_begin = 0;
 	first_line_scroll_begin = 0;
 	second_line_scroll_begin = 0;
+#	ifdef ENABLE_VISUALIZER
+	myVisualizer->ResetAutoScaleMultiplier();
+#	endif // ENABLE_VISUALIZER
 	if (m_player_state != MPD::psStop)
 	{
 		auto &pl = myPlaylist->main();

src/visualizer.cpp

@@ -148,8 +148,23 @@ void Visualizer::update()
 	}
 
 	const ssize_t samples_read = data/sizeof(int16_t);
-	std::for_each(buf, buf+samples_read, [](int16_t &sample) {
-		int32_t tmp = sample * Config.visualizer_sample_multiplier;
+	if (Config.visualizer_sample_multiplier == 1.0)
+	{
+		m_auto_scale_multiplier += 1.0/fps;
+		std::for_each(buf, buf+samples_read, [this](int16_t &sample) {
+			double scale = std::numeric_limits<int16_t>::min();
+			scale /= sample;
+			scale = fabs(scale);
+			if (scale < m_auto_scale_multiplier)
+				m_auto_scale_multiplier = scale;
+		});
+	}
+	std::for_each(buf, buf+samples_read, [this](int16_t &sample) {
+		int32_t tmp = sample;
+		if (Config.visualizer_sample_multiplier != 1.0)
+			tmp *= Config.visualizer_sample_multiplier;
+		else if (m_auto_scale_multiplier <= 50.0) // limit the auto scale
+			tmp *= m_auto_scale_multiplier;
 		if (tmp < std::numeric_limits<int16_t>::min())
 			sample = std::numeric_limits<int16_t>::min();
 		else if (tmp > std::numeric_limits<int16_t>::max())
@@ -474,6 +489,11 @@ void Visualizer::FindOutputID()
 	}
 }
 
+void Visualizer::ResetAutoScaleMultiplier()
+{
+	m_auto_scale_multiplier = std::numeric_limits<double>::infinity();
+}
+
 #endif // ENABLE_VISUALIZER
 
 /* vim: set tabstop=4 softtabstop=4 shiftwidth=4 noexpandtab : */

src/visualizer.h

@@ -60,6 +60,7 @@ struct Visualizer: Screen<NC::Window>, Tabbable
 	void SetFD();
 	void ResetFD();
 	void FindOutputID();
+	void ResetAutoScaleMultiplier();
 
 private:
 	void DrawSoundWave(int16_t *, ssize_t, size_t, size_t);
@@ -78,6 +79,7 @@ private:
 
 	int m_fifo;
 	size_t m_samples;
+	double m_auto_scale_multiplier;
 #	ifdef HAVE_FFTW3_H
 	size_t m_fftw_results;
 	double *m_fftw_input;