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Merge pull request #5161 from PhilipRosedale/master

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Always test and remove DC Offset
This commit is contained in:
Howard Stearns 2015-06-22 12:09:08 -07:00
commit 240272be11
3 changed files with 34 additions and 15 deletions
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5
libraries/audio-client/src/AudioClient.cpp
View file

@ -795,6 +795,11 @@ 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);

43
libraries/audio-client/src/AudioNoiseGate.cpp
View file

@ -33,6 +33,32 @@ 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;
}
// 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 +87,12 @@ 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 +104,6 @@ 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) {

1
libraries/audio-client/src/AudioNoiseGate.h
View file

@ -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; }