Mixer: use Peak dB instead of RMS dB

Author: RomanPudashkin

src/framework/audio/common/audiotypes.h

@@ -360,13 +360,11 @@ struct AudioParams {
 };
 
 struct AudioSignalVal {
-    float amplitude = 0.f;
     volume_dbfs_t pressure = 0.f;
 
     inline bool operator ==(const AudioSignalVal& other) const
     {
-        return muse::is_equal(amplitude, other.amplitude)
-               && pressure == other.pressure;
+        return pressure == other.pressure;
     }
 };
 
@@ -375,9 +373,9 @@ using AudioSignalChanges = async::Channel<AudioSignalValuesMap>;
 
 static constexpr volume_dbfs_t MINIMUM_OPERABLE_DBFS_LEVEL = volume_dbfs_t::make(-100.f);
 struct AudioSignalsNotifier {
-    void updateSignalValues(const audioch_t audioChNumber, const float newAmplitude)
+    void updateSignalValues(const audioch_t audioChNumber, const float newPeak)
     {
-        volume_dbfs_t newPressure = (newAmplitude > 0.f) ? volume_dbfs_t(muse::linear_to_db(newAmplitude)) : MINIMUM_OPERABLE_DBFS_LEVEL;
+        volume_dbfs_t newPressure = (newPeak > 0.f) ? volume_dbfs_t(muse::linear_to_db(newPeak)) : MINIMUM_OPERABLE_DBFS_LEVEL;
         newPressure = std::max(newPressure, MINIMUM_OPERABLE_DBFS_LEVEL);
 
         AudioSignalVal& signalVal = m_signalValuesMap[audioChNumber];
@@ -390,9 +388,7 @@ struct AudioSignalsNotifier {
             return;
         }
 
-        signalVal.amplitude = newAmplitude;
         signalVal.pressure = newPressure;
-
         m_needNotifyAboutChanges = true;
     }
 

src/framework/audio/common/rpc/rpcpacker.h

@@ -271,12 +271,12 @@ inline void unpack_custom(muse::msgpack::UnPacker& p, muse::audio::SoundTrackFor
 
 inline void pack_custom(muse::msgpack::Packer& p, const muse::audio::AudioSignalVal& value)
 {
-    p.process(value.amplitude, value.pressure);
+    p.process(value.pressure);
 }
 
 inline void unpack_custom(muse::msgpack::UnPacker& p, muse::audio::AudioSignalVal& value)
 {
-    p.process(value.amplitude, value.pressure);
+    p.process(value.pressure);
 }
 
 inline void pack_custom(muse::msgpack::Packer& p, const muse::audio::InputProcessingProgress::ChunkInfo& value)

src/framework/audio/engine/internal/mixer.cpp

@@ -182,8 +182,6 @@ void Mixer::setOutputSpec(const OutputSpec& spec)
 
     m_outputSpec = spec;
 
-    m_limiter = std::make_unique<dsp::Limiter>(spec.sampleRate);
-
     AbstractAudioSource::setOutputSpec(spec);
 
     for (auto& channel : m_trackChannels) {
@@ -557,37 +555,34 @@ void Mixer::completeOutput(float* buffer, samples_t samplesPerChannel)
         return;
     }
 
-    float totalSquaredSum = 0.f;
-    float volume = muse::db_to_linear(m_masterParams.volume);
+    const float volume = muse::db_to_linear(m_masterParams.volume);
+    float globalPeak = 0.f;
 
     for (audioch_t audioChNum = 0; audioChNum < m_outputSpec.audioChannelCount; ++audioChNum) {
-        float singleChannelSquaredSum = 0.f;
-        gain_t totalGain = dsp::balanceGain(m_masterParams.balance, audioChNum) * volume;
+        const gain_t totalGain = dsp::balanceGain(m_masterParams.balance, audioChNum) * volume;
+        float peak = 0.f;
 
         for (samples_t s = 0; s < samplesPerChannel; ++s) {
-            int idx = s * m_outputSpec.audioChannelCount + audioChNum;
+            const size_t idx = s * m_outputSpec.audioChannelCount + audioChNum;
+            const float resultSample = buffer[idx] * totalGain;
+            const float absSample = std::fabs(resultSample);
 
-            float resultSample = buffer[idx] * totalGain;
             buffer[idx] = resultSample;
 
-            float squaredSample = resultSample * resultSample;
-            totalSquaredSum += squaredSample;
-            singleChannelSquaredSum += squaredSample;
+            if (absSample > peak) {
+                peak = absSample;
+            }
         }
 
-        float rms = dsp::samplesRootMeanSquare(singleChannelSquaredSum, samplesPerChannel);
-        m_audioSignalNotifier.updateSignalValues(audioChNum, rms);
-    }
-
-    m_isSilence = RealIsNull(totalSquaredSum);
-    m_audioSignalNotifier.notifyAboutChanges();
+        m_audioSignalNotifier.updateSignalValues(audioChNum, peak);
 
-    if (!m_limiter->isActive()) {
-        return;
+        if (peak > globalPeak) {
+            globalPeak = peak;
+        }
     }
 
-    float totalRms = dsp::samplesRootMeanSquare(totalSquaredSum, samplesPerChannel * m_outputSpec.audioChannelCount);
-    m_limiter->process(totalRms, buffer, m_outputSpec.audioChannelCount, samplesPerChannel);
+    m_isSilence = RealIsNull(globalPeak);
+    m_audioSignalNotifier.notifyAboutChanges();
 }
 
 void Mixer::notifyNoAudioSignal()

src/framework/audio/engine/internal/mixer.h

@@ -34,7 +34,6 @@
 #include "../iclock.h"
 #include "../ifxresolver.h"
 
-#include "dsp/limiter.h"
 #include "mixerchannel.h"
 
 namespace muse {
@@ -113,8 +112,6 @@ class Mixer : public AbstractAudioSource, public Injectable, public async::Async
 
     std::vector<AuxChannelInfo> m_auxChannelInfoList;
 
-    dsp::LimiterPtr m_limiter = nullptr;
-
     std::set<IClockPtr> m_clocks;
 
     mutable AudioSignalsNotifier m_audioSignalNotifier;

src/framework/audio/engine/internal/mixerchannel.cpp

@@ -38,8 +38,7 @@ MixerChannel::MixerChannel(const TrackId trackId, IAudioSourcePtr source, const
                            const modularity::ContextPtr& iocCtx)
     : Injectable(iocCtx), m_trackId(trackId),
     m_outputSpec(outputSpec),
-    m_audioSource(std::move(source)),
-    m_compressor(std::make_unique<dsp::Compressor>(outputSpec.sampleRate))
+    m_audioSource(std::move(source))
 {
     ONLY_AUDIO_ENGINE_THREAD;
 }
@@ -219,39 +218,35 @@ samples_t MixerChannel::process(float* buffer, samples_t samplesPerChannel)
 
 void MixerChannel::completeOutput(float* buffer, unsigned int samplesCount)
 {
-    unsigned int channelsCount = audioChannelsCount();
-    float volume = muse::db_to_linear(m_params.volume);
-    float totalSquaredSum = 0.f;
+    const unsigned int channelsCount = audioChannelsCount();
+    const float volume = muse::db_to_linear(m_params.volume);
+    float globalPeak = 0.f;
 
     for (audioch_t audioChNum = 0; audioChNum < channelsCount; ++audioChNum) {
-        float singleChannelSquaredSum = 0.f;
-
-        gain_t totalGain = dsp::balanceGain(m_params.balance, audioChNum) * volume;
+        const gain_t totalGain = dsp::balanceGain(m_params.balance, audioChNum) * volume;
+        float peak = 0.f;
 
         for (unsigned int s = 0; s < samplesCount; ++s) {
-            int idx = s * channelsCount + audioChNum;
+            const unsigned int idx = s * channelsCount + audioChNum;
+            const float resultSample = buffer[idx] * totalGain;
+            const float absSample = std::fabs(resultSample);
 
-            float resultSample = buffer[idx] * totalGain;
             buffer[idx] = resultSample;
 
-            float squaredSample = resultSample * resultSample;
-            singleChannelSquaredSum += squaredSample;
-            totalSquaredSum += squaredSample;
+            if (absSample > peak) {
+                peak = absSample;
+            }
         }
 
-        float rms = dsp::samplesRootMeanSquare(singleChannelSquaredSum, samplesCount);
-        m_audioSignalNotifier.updateSignalValues(audioChNum, rms);
-    }
+        m_audioSignalNotifier.updateSignalValues(audioChNum, peak);
 
-    m_isSilent = RealIsNull(totalSquaredSum);
-    m_audioSignalNotifier.notifyAboutChanges();
-
-    if (!m_compressor->isActive()) {
-        return;
+        if (peak > globalPeak) {
+            globalPeak = peak;
+        }
     }
 
-    float totalRms = dsp::samplesRootMeanSquare(totalSquaredSum, samplesCount * channelsCount);
-    m_compressor->process(totalRms, buffer, channelsCount, samplesCount);
+    m_isSilent = RealIsNull(globalPeak);
+    m_audioSignalNotifier.notifyAboutChanges();
 }
 
 bool MixerChannel::isSilent() const

src/framework/audio/engine/internal/mixerchannel.h

@@ -28,7 +28,6 @@
 
 #include "../ifxresolver.h"
 #include "../ifxprocessor.h"
-#include "dsp/compressor.h"
 #include "track.h"
 
 namespace muse::audio::engine {
@@ -76,8 +75,6 @@ class MixerChannel : public ITrackAudioOutput, public Injectable, public async::
     IAudioSourcePtr m_audioSource = nullptr;
     std::vector<IFxProcessorPtr> m_fxProcessors = {};
 
-    dsp::CompressorPtr m_compressor = nullptr;
-
     bool m_isSilent = true;
 
     async::Notification m_mutedChanged;

src/framework/audio/tests/rpcpacker_tests.cpp

@@ -295,11 +295,9 @@ TEST_F(Audio_RpcPackerTests, AudioSourceParams)
 TEST_F(Audio_RpcPackerTests, AudioSignalVal)
 {
     AudioSignalVal origin;
-    origin.amplitude = 0.6f;
     origin.pressure = 0.5;
 
     KNOWN_FIELDS(origin,
-                 origin.amplitude,
                  origin.pressure);
 
     ByteArray data = rpc::RpcPacker::pack(origin);