Add AudioLoudness class

Author: adazem009

src/audio/CMakeLists.txt

@@ -19,6 +19,7 @@ target_sources(scratchcpp-audio
     iaudiooutput.h
     audiooutput.cpp
     audiooutput.h
+    iaudioloudness.h
 )
 
 if (LIBSCRATCHCPP_AUDIO_SUPPORT)
@@ -28,11 +29,15 @@ if (LIBSCRATCHCPP_AUDIO_SUPPORT)
         internal/audioengine.h
         internal/audioplayer.cpp
         internal/audioplayer.h
+        internal/audioloudness.cpp
+        internal/audioloudness.h
     )
 else()
     target_sources(scratchcpp-audio
       PUBLIC
         internal/audioplayerstub.cpp
         internal/audioplayerstub.h
+        internal/audioloudnessstub.cpp
+        internal/audioloudnessstub.h
     )
 endif()

src/audio/iaudioloudness.h

@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: Apache-2.0
+
+#pragma once
+
+namespace libscratchcpp
+{
+
+class IAudioLoudness
+{
+    public:
+        virtual ~IAudioLoudness() { }
+
+        virtual int getLoudness() const = 0;
+};
+
+} // namespace libscratchcpp

src/audio/internal/audioloudness.cpp

@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: Apache-2.0
+
+#include <miniaudio.h>
+#include <cmath>
+#include <iostream>
+
+#include "audioloudness.h"
+
+using namespace libscratchcpp;
+
+static int loudness = -1;
+static float lastValue = 0.0f;
+
+static void data_callback(ma_device *pDevice, void *pOutput, const void *pInput, ma_uint32 frameCount)
+{
+    const float *pMicDataArray = static_cast<const float *>(pInput);
+
+    // https://github.com/scratchfoundation/scratch-audio/blob/068aca613604e39b2adbe785b17931cc43eec35f/src/Loudness.js#L36-L80
+    // Compute the RMS of the sound
+    float sum = 0.0f;
+
+    for (ma_uint32 i = 0; i < frameCount; i++) {
+        float value = pMicDataArray[i];
+        sum += value * value;
+    }
+
+    float rms = std::sqrt(sum / static_cast<float>(frameCount));
+
+    // Smooth the value, if it is descending
+    if (lastValue != 0.0f) {
+        rms = std::max(rms, lastValue * 0.6f);
+    }
+
+    lastValue = rms;
+
+    // Scale the measurement
+    rms *= 1.63f;
+    rms = std::sqrt(rms);
+    // Scale it up to 0-100 and round
+    rms = std::round(rms * 100.0f);
+    // Prevent it from going above 100
+    rms = std::min(rms, 100.0f);
+
+    loudness = rms;
+}
+
+AudioLoudness::AudioLoudness()
+{
+    ma_device_config deviceConfig = ma_device_config_init(ma_device_type_capture);
+    deviceConfig.capture.format = ma_format_f32;
+    deviceConfig.capture.channels = 1; // mono
+    deviceConfig.sampleRate = 44100;
+    deviceConfig.periodSizeInFrames = 2048;
+    deviceConfig.dataCallback = data_callback;
+    deviceConfig.pUserData = NULL;
+
+    m_device = new ma_device;
+
+    if (ma_device_init(NULL, &deviceConfig, m_device) != MA_SUCCESS) {
+        std::cerr << "Failed to initialize audio capture device." << std::endl;
+        delete m_device;
+        m_device = nullptr;
+        return;
+    }
+
+    if (ma_device_start(m_device) != MA_SUCCESS) {
+        std::cerr << "Failed to start audio capture device." << std::endl;
+        ma_device_uninit(m_device);
+        delete m_device;
+        m_device = nullptr;
+        return;
+    }
+}
+
+AudioLoudness::~AudioLoudness()
+{
+    if (m_device) {
+        ma_device_uninit(m_device);
+        delete m_device;
+    }
+}
+
+int AudioLoudness::getLoudness() const
+{
+    return loudness;
+}

src/audio/internal/audioloudness.h

@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: Apache-2.0
+
+#pragma once
+
+#include "../iaudioloudness.h"
+
+struct ma_device;
+
+namespace libscratchcpp
+{
+
+class AudioLoudness : public IAudioLoudness
+{
+    public:
+        AudioLoudness();
+        ~AudioLoudness();
+
+        int getLoudness() const override;
+
+    private:
+        ma_device *m_device = nullptr;
+};
+
+} // namespace libscratchcpp

src/audio/internal/audioloudnessstub.cpp

@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: Apache-2.0
+
+#include "audioloudness.h"
+
+using namespace libscratchcpp;
+
+AudioLoudness::AudioLoudness()
+{
+}
+
+int AudioLoudness::getLoudness() const
+{
+    return -1;
+}

src/audio/internal/audioloudnessstub.h

@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: Apache-2.0
+
+#pragma once
+
+#include "../iaudioloudness.h"
+
+namespace libscratchcpp
+{
+
+class AudioLoudness : public IAudioLoudness
+{
+    public:
+        AudioLoudness();
+
+        int getLoudness() const override;
+};
+
+} // namespace libscratchcpp