From bffc1a38a7838fb96936cb926e5db07e63fc70e9 Mon Sep 17 00:00:00 2001
From: Philip Rosedale <philip@highfidelity.io>
Date: Thu, 18 Jun 2015 12:33:05 -0700
Subject: [PATCH 1/2] Separate DC offset rejection, and call it all the time

---
 libraries/audio-client/src/AudioClient.cpp    |  5 +++
 libraries/audio-client/src/AudioNoiseGate.cpp | 44 ++++++++++++-------
 libraries/audio-client/src/AudioNoiseGate.h   |  1 +
 3 files changed, 35 insertions(+), 15 deletions(-)

diff --git a/libraries/audio-client/src/AudioClient.cpp b/libraries/audio-client/src/AudioClient.cpp
index 84022d0fb9..aea4d66cae 100644
--- a/libraries/audio-client/src/AudioClient.cpp
+++ b/libraries/audio-client/src/AudioClient.cpp
@@ -786,6 +786,11 @@ void AudioClient::handleAudioInput() {
 
             delete[] inputAudioSamples;
 
+            //  Remove DC offset 
+            if (!_isStereoInput && !_audioSourceInjectEnabled) {
+                _inputGate.removeDCOffset(networkAudioSamples, numNetworkSamples);
+            }
+            
             // only impose the noise gate and perform tone injection if we are sending mono audio
             if (!_isStereoInput && !_audioSourceInjectEnabled && _isNoiseGateEnabled) {
                 _inputGate.gateSamples(networkAudioSamples, numNetworkSamples);
diff --git a/libraries/audio-client/src/AudioNoiseGate.cpp b/libraries/audio-client/src/AudioNoiseGate.cpp
index 77f230809f..062d21fb96 100644
--- a/libraries/audio-client/src/AudioNoiseGate.cpp
+++ b/libraries/audio-client/src/AudioNoiseGate.cpp
@@ -33,6 +33,33 @@ AudioNoiseGate::AudioNoiseGate() :
     
 }
 
+void AudioNoiseGate::removeDCOffset(int16_t* samples, int numSamples) {
+    //
+    //  DC Offset correction
+    //
+    //  Measure the DC offset over a trailing number of frames, and remove it from the input signal.
+    //  This causes the noise background measurements and server muting to be more accurate.  Many off-board
+    //  ADC's have a noticeable DC offset.  
+    //
+    const float DC_OFFSET_AVERAGING = 0.99f;
+    float measuredDcOffset = 0.0f;
+    //  Remove trailing DC offset from samples
+    for (int i = 0; i < numSamples; i++) {
+        measuredDcOffset += samples[i];
+        samples[i] -= (int16_t) _dcOffset;
+        //samples[i] = 0;
+    }
+    // Update measured DC offset
+    measuredDcOffset /= numSamples;
+    if (_dcOffset == 0.0f) {
+        // On first frame, copy over measured offset
+        _dcOffset = measuredDcOffset;
+    } else {
+        _dcOffset = DC_OFFSET_AVERAGING * _dcOffset + (1.0f - DC_OFFSET_AVERAGING) * measuredDcOffset;
+    }
+}
+
+
 void AudioNoiseGate::gateSamples(int16_t* samples, int numSamples) {
     //
     //  Impose Noise Gate
@@ -61,17 +88,12 @@ void AudioNoiseGate::gateSamples(int16_t* samples, int numSamples) {
     const int NOISE_GATE_WIDTH = 5;
     const int NOISE_GATE_CLOSE_FRAME_DELAY = 5;
     const int NOISE_GATE_FRAMES_TO_AVERAGE = 5;
-    const float DC_OFFSET_AVERAGING = 0.99f;
-    
-    //  Check clipping, adjust DC offset, and check if should open noise gate
-    float measuredDcOffset = 0.0f;
+
+    //  Check clipping, and check if should open noise gate
     _didClipInLastFrame = false;
     
     for (int i = 0; i < numSamples; i++) {
-        measuredDcOffset += samples[i];
-        samples[i] -= (int16_t) _dcOffset;
         thisSample = std::abs(samples[i]);
-        
         if (thisSample >= ((float) AudioConstants::MAX_SAMPLE_VALUE * CLIPPING_THRESHOLD)) {
             _didClipInLastFrame = true;
         }
@@ -83,14 +105,6 @@ void AudioNoiseGate::gateSamples(int16_t* samples, int numSamples) {
         }
     }
     
-    measuredDcOffset /= numSamples;
-    if (_dcOffset == 0.0f) {
-        // On first frame, copy over measured offset
-        _dcOffset = measuredDcOffset;
-    } else {
-        _dcOffset = DC_OFFSET_AVERAGING * _dcOffset + (1.0f - DC_OFFSET_AVERAGING) * measuredDcOffset;
-    }
-    
     _lastLoudness = fabs(loudness / numSamples);
     
     if (_quietestFrame > _lastLoudness) {
diff --git a/libraries/audio-client/src/AudioNoiseGate.h b/libraries/audio-client/src/AudioNoiseGate.h
index bfb9ec28d5..8cb1155938 100644
--- a/libraries/audio-client/src/AudioNoiseGate.h
+++ b/libraries/audio-client/src/AudioNoiseGate.h
@@ -21,6 +21,7 @@ public:
     AudioNoiseGate();
     
     void gateSamples(int16_t* samples, int numSamples);
+    void removeDCOffset(int16_t* samples, int numSamples);
     
     bool clippedInLastFrame() const { return _didClipInLastFrame; }
     float getMeasuredFloor() const { return _measuredFloor; }

From e46a8208728311b401e3f55bfec5cd617123521c Mon Sep 17 00:00:00 2001
From: Philip Rosedale <philip@highfidelity.io>
Date: Thu, 18 Jun 2015 12:37:50 -0700
Subject: [PATCH 2/2] remove debug

---
 libraries/audio-client/src/AudioNoiseGate.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/libraries/audio-client/src/AudioNoiseGate.cpp b/libraries/audio-client/src/AudioNoiseGate.cpp
index 062d21fb96..8766a20cdf 100644
--- a/libraries/audio-client/src/AudioNoiseGate.cpp
+++ b/libraries/audio-client/src/AudioNoiseGate.cpp
@@ -39,7 +39,7 @@ void AudioNoiseGate::removeDCOffset(int16_t* samples, int numSamples) {
     //
     //  Measure the DC offset over a trailing number of frames, and remove it from the input signal.
     //  This causes the noise background measurements and server muting to be more accurate.  Many off-board
-    //  ADC's have a noticeable DC offset.  
+    //  ADC's have a noticeable DC offset.
     //
     const float DC_OFFSET_AVERAGING = 0.99f;
     float measuredDcOffset = 0.0f;
@@ -47,7 +47,6 @@ void AudioNoiseGate::removeDCOffset(int16_t* samples, int numSamples) {
     for (int i = 0; i < numSamples; i++) {
         measuredDcOffset += samples[i];
         samples[i] -= (int16_t) _dcOffset;
-        //samples[i] = 0;
     }
     // Update measured DC offset
     measuredDcOffset /= numSamples;