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Proper detection of digital clipping on the unprocessed audio input.

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Triggered when 3+ consecutive samples > -0.1 dBFS.
This commit is contained in:
Ken Cooke 2019-02-06 16:08:30 -08:00
parent f9afe6fe43
commit 918e2fc7ab
1 changed files with 54 additions and 10 deletions
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64
libraries/audio-client/src/AudioClient.cpp
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@ -170,6 +170,57 @@ static void channelDownmix(int16_t* source, int16_t* dest, int numSamples) {
}
}
static float computeLoudness(int16_t* samples, int numSamples, int numChannels, bool& isClipping) {
const int32_t CLIPPING_THRESHOLD = 32392; // -0.1 dBFS
const int32_t CLIPPING_DETECTION = 3; // consecutive samples over threshold
float scale = numSamples ? 1.0f / numSamples : 0.0f;
int32_t loudness = 0;
isClipping = false;
if (numChannels == 2) {
int32_t oversLeft = 0;
int32_t oversRight = 0;
for (int i = 0; i < numSamples/2; i++) {
int32_t left = std::abs((int32_t)samples[2*i+0]);
int32_t right = std::abs((int32_t)samples[2*i+1]);
loudness += left;
loudness += right;
if (left > CLIPPING_THRESHOLD) {
isClipping |= (++oversLeft >= CLIPPING_DETECTION);
} else {
oversLeft = 0;
}
if (right > CLIPPING_THRESHOLD) {
isClipping |= (++oversRight >= CLIPPING_DETECTION);
} else {
oversRight = 0;
}
}
} else {
int32_t overs = 0;
for (int i = 0; i < numSamples; i++) {
int32_t sample = std::abs((int32_t)samples[i]);
loudness += sample;
if (sample > CLIPPING_THRESHOLD) {
isClipping |= (++overs >= CLIPPING_DETECTION);
} else {
overs = 0;
}
}
}
return (float)loudness * scale;
}
static inline float convertToFloat(int16_t sample) {
return (float)sample * (1 / 32768.0f);
}
@ -1170,17 +1221,10 @@ void AudioClient::handleMicAudioInput() {
_inputRingBuffer.readSamples(inputAudioSamples.get(), inputSamplesRequired);
// detect loudness and clipping on the raw input
int32_t loudness = 0;
bool didClip = false;
for (int i = 0; i < inputSamplesRequired; ++i) {
const int32_t CLIPPING_THRESHOLD = (int32_t)(AudioConstants::MAX_SAMPLE_VALUE * 0.9f);
int32_t sample = std::abs((int32_t)inputAudioSamples.get()[i]);
loudness += sample;
didClip |= (sample > CLIPPING_THRESHOLD);
}
_lastInputLoudness = (float)loudness / inputSamplesRequired;
bool isClipping = false;
_lastInputLoudness = computeLoudness(inputAudioSamples.get(), inputSamplesRequired, _inputFormat.channelCount(), isClipping);
if (didClip) {
if (isClipping) {
_timeSinceLastClip = 0.0f;
} else if (_timeSinceLastClip >= 0.0f) {
_timeSinceLastClip += AudioConstants::NETWORK_FRAME_SECS;