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Delete the old noise gate

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This commit is contained in:
Ken Cooke 2017-05-23 15:53:38 -07:00
parent f3797798d3
commit 3d67978caa
2 changed files with 0 additions and 212 deletions
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164
libraries/audio/src/AudioNoiseGate.cpp
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//
// AudioNoiseGate.cpp
// libraries/audio
//
// Created by Stephen Birarda on 2014-12-16.
// Copyright 2014 High Fidelity, Inc.
//
// Distributed under the Apache License, Version 2.0.
// See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
//
#include "AudioNoiseGate.h"
#include <cstdlib>
#include <string.h>
#include "AudioConstants.h"
const float AudioNoiseGate::CLIPPING_THRESHOLD = 0.90f;
AudioNoiseGate::AudioNoiseGate() :
_lastLoudness(0.0f),
_didClipInLastBlock(false),
_dcOffset(0.0f),
_measuredFloor(0.0f),
_sampleCounter(0),
_isOpen(false),
_blocksToClose(0) {}
void AudioNoiseGate::removeDCOffset(int16_t* samples, int numSamples) {
//
// DC Offset correction
//
// Measure the DC offset over a trailing number of blocks, 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 block, 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
//
// The Noise Gate is used to reject constant background noise by measuring the noise
// floor observed at the microphone and then opening the 'gate' to allow microphone
// signals to be transmitted when the microphone samples average level exceeds a multiple
// of the noise floor.
//
// NOISE_GATE_HEIGHT: How loud you have to speak relative to noise background to open the gate.
// Make this value lower for more sensitivity and less rejection of noise.
// NOISE_GATE_WIDTH: The number of samples in an audio block for which the height must be exceeded
// to open the gate.
// NOISE_GATE_CLOSE_BLOCK_DELAY: Once the noise is below the gate height for the block, how many blocks
// will we wait before closing the gate.
// NOISE_GATE_BLOCKS_TO_AVERAGE: How many audio blocks should we average together to compute noise floor.
// More means better rejection but also can reject continuous things like singing.
// NUMBER_OF_NOISE_SAMPLE_BLOCKS: How often should we re-evaluate the noise floor?
float loudness = 0;
int thisSample = 0;
int samplesOverNoiseGate = 0;
const float NOISE_GATE_HEIGHT = 7.0f;
const int NOISE_GATE_WIDTH = 5;
const int NOISE_GATE_CLOSE_BLOCK_DELAY = 5;
const int NOISE_GATE_BLOCKS_TO_AVERAGE = 5;
// Check clipping, and check if should open noise gate
_didClipInLastBlock = false;
for (int i = 0; i < numSamples; i++) {
thisSample = std::abs(samples[i]);
if (thisSample >= ((float) AudioConstants::MAX_SAMPLE_VALUE * CLIPPING_THRESHOLD)) {
_didClipInLastBlock = true;
}
loudness += thisSample;
// Noise Reduction: Count peaks above the average loudness
if (thisSample > (_measuredFloor * NOISE_GATE_HEIGHT)) {
samplesOverNoiseGate++;
}
}
_lastLoudness = fabs(loudness / numSamples);
// If Noise Gate is enabled, check and turn the gate on and off
float averageOfAllSampleBlocks = 0.0f;
_sampleBlocks[_sampleCounter++] = _lastLoudness;
if (_sampleCounter == NUMBER_OF_NOISE_SAMPLE_BLOCKS) {
float smallestSample = std::numeric_limits<float>::max();
for (int i = 0; i <= NUMBER_OF_NOISE_SAMPLE_BLOCKS - NOISE_GATE_BLOCKS_TO_AVERAGE; i += NOISE_GATE_BLOCKS_TO_AVERAGE) {
float thisAverage = 0.0f;
for (int j = i; j < i + NOISE_GATE_BLOCKS_TO_AVERAGE; j++) {
thisAverage += _sampleBlocks[j];
averageOfAllSampleBlocks += _sampleBlocks[j];
}
thisAverage /= NOISE_GATE_BLOCKS_TO_AVERAGE;
if (thisAverage < smallestSample) {
smallestSample = thisAverage;
}
}
averageOfAllSampleBlocks /= NUMBER_OF_NOISE_SAMPLE_BLOCKS;
_measuredFloor = smallestSample;
_sampleCounter = 0;
}
_closedInLastBlock = false;
_openedInLastBlock = false;
if (samplesOverNoiseGate > NOISE_GATE_WIDTH) {
_openedInLastBlock = !_isOpen;
_isOpen = true;
_blocksToClose = NOISE_GATE_CLOSE_BLOCK_DELAY;
} else {
if (--_blocksToClose == 0) {
_closedInLastBlock = _isOpen;
_isOpen = false;
}
}
if (!_isOpen) {
// First block after being closed gets faded to silence, we fade across
// the entire block on fading out. All subsequent blocks are muted by being slammed
// to zeros
if (_closedInLastBlock) {
float fadeSlope = (1.0f / numSamples);
for (int i = 0; i < numSamples; i++) {
float fadedSample = (1.0f - ((float)i * fadeSlope)) * (float)samples[i];
samples[i] = (int16_t)fadedSample;
}
} else {
memset(samples, 0, numSamples * sizeof(int16_t));
}
_lastLoudness = 0;
}
if (_openedInLastBlock) {
// would be nice to do a little crossfade from silence, but we only want to fade
// across the first 1/10th of the block, because we don't want to miss early
// transients.
int fadeSamples = numSamples / 10; // fade over 1/10th of the samples
float fadeSlope = (1.0f / fadeSamples);
for (int i = 0; i < fadeSamples; i++) {
float fadedSample = (float)i * fadeSlope * (float)samples[i];
samples[i] = (int16_t)fadedSample;
}
}
}

48
libraries/audio/src/AudioNoiseGate.h
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//
// AudioNoiseGate.h
// libraries/audio
//
// Created by Stephen Birarda on 2014-12-16.
// Copyright 2014 High Fidelity, Inc.
//
// Distributed under the Apache License, Version 2.0.
// See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
//
#ifndef hifi_AudioNoiseGate_h
#define hifi_AudioNoiseGate_h
#include <stdint.h>
const int NUMBER_OF_NOISE_SAMPLE_BLOCKS = 300;
class AudioNoiseGate {
public:
AudioNoiseGate();
void gateSamples(int16_t* samples, int numSamples);
void removeDCOffset(int16_t* samples, int numSamples);
bool clippedInLastBlock() const { return _didClipInLastBlock; }
bool closedInLastBlock() const { return _closedInLastBlock; }
bool openedInLastBlock() const { return _openedInLastBlock; }
bool isOpen() const { return _isOpen; }
float getMeasuredFloor() const { return _measuredFloor; }
float getLastLoudness() const { return _lastLoudness; }
static const float CLIPPING_THRESHOLD;
private:
float _lastLoudness;
bool _didClipInLastBlock;
float _dcOffset;
float _measuredFloor;
float _sampleBlocks[NUMBER_OF_NOISE_SAMPLE_BLOCKS];
int _sampleCounter;
bool _isOpen;
bool _closedInLastBlock { false };
bool _openedInLastBlock { false };
int _blocksToClose;
};
#endif // hifi_AudioNoiseGate_h