Rewrite of audio data processing/beat detection.

Consolidated audio processing code into the PCM class, removing the BeatDetect class in the process. Beat detection now uses the same algorithm as Milkdrop, passing the proper relative bass/mid/treb values to presets. Makes many presets look less jumpy/flickering, as the values are now (smoothly) alternating around 1.0.

Updating frame audio is now done in a function that must specifically be called. Any subsequent calls to GetFrameAudioData() will then return the exact same copy of the audio data. As of now with the exception that new waveform data may be passed in via a separate thread, which will then be returned and might not match the spectrum data. Will fix that in a later commit.

Author: kblaschke

src/libprojectM/Audio/BeatDetect.cpp

@@ -1,14 +1,14 @@
 
 add_library(Audio OBJECT
         AudioConstants.hpp
-        BeatDetect.cpp
-        BeatDetect.hpp
         MilkdropFFT.cpp
         MilkdropFFT.hpp
         FrameAudioData.cpp
         FrameAudioData.hpp
         PCM.cpp
         PCM.hpp
+        Loudness.cpp
+        Loudness.hpp
         )
 
 target_include_directories(Audio

src/libprojectM/Audio/BeatDetect.hpp

@@ -0,0 +1,62 @@
+#include "Loudness.hpp"
+
+#include <cmath>
+
+namespace libprojectM {
+namespace Audio {
+
+Loudness::Loudness(Loudness::Band band)
+    : m_band(band)
+{
+}
+
+void Loudness::Update(const std::array<float, SpectrumSamples>& spectrumSamples, double secondsSinceLastFrame, uint32_t frame)
+{
+    SumBand(spectrumSamples);
+    UpdateBandAverage(secondsSinceLastFrame, frame);
+}
+
+auto Loudness::CurrentRelative() const -> float
+{
+    return m_currentRelative;
+}
+
+auto Loudness::AverageRelative() const -> float
+{
+    return m_averageRelative;
+}
+
+void Loudness::SumBand(const std::array<float, SpectrumSamples>& spectrumSamples)
+{
+    int start = SpectrumSamples * static_cast<int>(m_band) / 6;
+    int end = SpectrumSamples * static_cast<int>(m_band) / 6;
+
+    m_current = 0.0f;
+    for (int sample = start; sample < end; sample++)
+    {
+        m_current += spectrumSamples[sample];
+    }
+}
+
+void Loudness::UpdateBandAverage(double secondsSinceLastFrame, uint32_t frame)
+{
+    float rate = AdjustRateToFps(m_current > m_average ? 0.2f : 0.5f, secondsSinceLastFrame);
+    m_average = m_average * rate + m_current * (1.0f - rate);
+
+    rate = AdjustRateToFps(frame < 50 ? 0.9f : 0.992f, secondsSinceLastFrame);
+    m_longAverage = m_longAverage * rate + m_current * (1.0f - rate);
+
+    m_currentRelative = std::fabs(m_longAverage) < 0.001f ? 1.0f : m_current / m_longAverage;
+    m_averageRelative = std::fabs(m_longAverage) < 0.001f ? 1.0f : m_average / m_longAverage;
+}
+
+auto Loudness::AdjustRateToFps(float rate, double secondsSinceLastFrame) -> float
+{
+    float const perSecondDecayRateAtFps1 = std::pow(rate, 30.0f);
+    float const perFrameDecayRateAtFps2 = std::pow(perSecondDecayRateAtFps1, static_cast<float>(secondsSinceLastFrame));
+
+    return perFrameDecayRateAtFps2;
+}
+
+} // namespace Audio
+} // namespace libprojectM