// Takes the input audio channel |impulseP| as an input impulse response and calculates the average group delay.
// This represents the initial delay before the most energetic part of the impulse response.
// The sample-frame delay is removed from the |impulseP| impulse response, and this value is returned.
// The |length| of the passed in |impulseP| must be must be a power of 2.
static float extractAverageGroupDelay(float* impulseP, size_t length)
{
// Check for power-of-2.
MOZ_ASSERT(length && (length & (length - 1)) == 0);
FFTBlock estimationFrame(length);
estimationFrame.PerformFFT(impulseP);
float frameDelay = static_cast<float>(estimationFrame.ExtractAverageGroupDelay());
estimationFrame.GetInverse(impulseP);
return frameDelay;
}
// Takes the input AudioChannel as an input impulse response and calculates the average group delay.
// This represents the initial delay before the most energetic part of the impulse response.
// The sample-frame delay is removed from the impulseP impulse response, and this value is returned.
// the length of the passed in AudioChannel must be a power of 2.
static float extractAverageGroupDelay(AudioChannel* channel, size_t analysisFFTSize)
{
ASSERT(channel);
float* impulseP = channel->mutableData();
bool isSizeGood = channel->length() >= analysisFFTSize;
ASSERT(isSizeGood);
if (!isSizeGood)
return 0;
// Check for power-of-2.
ASSERT(1UL << static_cast<unsigned>(log2(analysisFFTSize)) == analysisFFTSize);
FFTFrame estimationFrame(analysisFFTSize);
estimationFrame.doFFT(impulseP);
float frameDelay = narrowPrecisionToFloat(estimationFrame.extractAverageGroupDelay());
estimationFrame.doInverseFFT(impulseP);
return frameDelay;
}
