From 1e7cd06d0e5ed13497977cc30e89519a08393e51 Mon Sep 17 00:00:00 2001
From: Brad Hefta-Gaub <brad@highfidelity.io>
Date: Sat, 28 May 2016 20:34:27 -0700
Subject: [PATCH] add audio peak limiter to audio mixer

---
 assignment-client/src/audio/AudioMixer.cpp      | 17 +++++++----------
 .../src/audio/AudioMixerClientData.cpp          |  9 ++++++++-
 .../src/audio/AudioMixerClientData.h            |  6 ++++++
 libraries/audio/src/AudioConstants.h            |  3 +++
 4 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/assignment-client/src/audio/AudioMixer.cpp b/assignment-client/src/audio/AudioMixer.cpp
index 0f51bd00b1..1832c29d1e 100644
--- a/assignment-client/src/audio/AudioMixer.cpp
+++ b/assignment-client/src/audio/AudioMixer.cpp
@@ -339,21 +339,18 @@ bool AudioMixer::prepareMixForListeningNode(Node* node) {
         }
     });
 
-    int nonZeroSamples = 0;
+    // use the per listner AudioLimiter to render the mixed data...
+    listenerNodeData->clampAudioSamples(_mixedSamples, _clampedSamples, AudioConstants::NETWORK_FRAME_SAMPLES_PER_CHANNEL);
 
-    // enumerate the mixed samples and clamp any samples outside the min/max
-    // also check if we ended up with a silent frame
+    // check for silent audio after the peak limitor has converted the samples
+    bool hasAudio = false;
     for (int i = 0; i < AudioConstants::NETWORK_FRAME_SAMPLES_STEREO; ++i) {
-
-        _clampedSamples[i] = int16_t(glm::clamp(int(_mixedSamples[i] * AudioConstants::MAX_SAMPLE_VALUE),
-                                                AudioConstants::MIN_SAMPLE_VALUE,
-                                                AudioConstants::MAX_SAMPLE_VALUE));
         if (_clampedSamples[i] != 0.0f) {
-            ++nonZeroSamples;
+            hasAudio = true;
+            break;
         }
     }
-
-    return (nonZeroSamples > 0);
+    return hasAudio;
 }
 
 void AudioMixer::sendAudioEnvironmentPacket(SharedNodePointer node) {
diff --git a/assignment-client/src/audio/AudioMixerClientData.cpp b/assignment-client/src/audio/AudioMixerClientData.cpp
index 93a51b1df2..6a25027310 100644
--- a/assignment-client/src/audio/AudioMixerClientData.cpp
+++ b/assignment-client/src/audio/AudioMixerClientData.cpp
@@ -17,6 +17,8 @@
 #include <udt/PacketHeaders.h>
 #include <UUID.h>
 
+#include <AudioLimiter.h>;
+
 #include "InjectedAudioStream.h"
 
 #include "AudioMixer.h"
@@ -26,7 +28,8 @@
 AudioMixerClientData::AudioMixerClientData(const QUuid& nodeID) :
     NodeData(nodeID),
     _outgoingMixedAudioSequenceNumber(0),
-    _downstreamAudioStreamStats()
+    _downstreamAudioStreamStats(),
+    _audioLimiter(new AudioLimiter(AudioConstants::SAMPLE_RATE, AudioConstants::STEREO))
 {
     // of the ~94 blocks in a second of audio sent from the AudioMixer, pick a random one to send out a stats packet on
     // this ensures we send out stats to this client around every second
@@ -38,6 +41,10 @@ AudioMixerClientData::AudioMixerClientData(const QUuid& nodeID) :
     _frameToSendStats = distribution(numberGenerator);
 }
 
+void AudioMixerClientData::clampAudioSamples(float* input, int16_t* output, int numFrames) {
+    _audioLimiter->render(input, output, numFrames);
+}
+
 AvatarAudioStream* AudioMixerClientData::getAvatarAudioStream() {
     QReadLocker readLocker { &_streamsLock };
     
diff --git a/assignment-client/src/audio/AudioMixerClientData.h b/assignment-client/src/audio/AudioMixerClientData.h
index ff4143cf08..e543c51b0c 100644
--- a/assignment-client/src/audio/AudioMixerClientData.h
+++ b/assignment-client/src/audio/AudioMixerClientData.h
@@ -21,6 +21,8 @@
 #include "PositionalAudioStream.h"
 #include "AvatarAudioStream.h"
 
+class AudioLimiter;
+
 class AudioMixerClientData : public NodeData {
     Q_OBJECT
 public:
@@ -61,6 +63,8 @@ public:
     // uses randomization to have the AudioMixer send a stats packet to this node around every second
     bool shouldSendStats(int frameNumber);
 
+    void clampAudioSamples(float* input, int16_t* output, int numFrames);
+
 signals:
     void injectorStreamFinished(const QUuid& streamIdentifier);
 
@@ -77,6 +81,8 @@ private:
     AudioStreamStats _downstreamAudioStreamStats;
 
     int _frameToSendStats { 0 };
+
+    std::unique_ptr<AudioLimiter> _audioLimiter;
 };
 
 #endif // hifi_AudioMixerClientData_h
diff --git a/libraries/audio/src/AudioConstants.h b/libraries/audio/src/AudioConstants.h
index 38fead87f1..dbbe434915 100644
--- a/libraries/audio/src/AudioConstants.h
+++ b/libraries/audio/src/AudioConstants.h
@@ -18,6 +18,9 @@
 
 namespace AudioConstants {
     const int SAMPLE_RATE = 24000;
+    const int MONO = 1;
+    const int STEREO = 2;
+
 
     typedef int16_t AudioSample;