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228 lines
7.3 KiB
C++
228 lines
7.3 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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/* vim:set ts=4 sw=4 sts=4 et cindent: */
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/*
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* Copyright (C) 2010 Google Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of
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* its contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "FFTBlock.h"
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#include <complex>
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namespace mozilla {
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typedef std::complex<double> Complex;
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FFTBlock* FFTBlock::CreateInterpolatedBlock(const FFTBlock& block0, const FFTBlock& block1, double interp)
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{
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FFTBlock* newBlock = new FFTBlock(block0.FFTSize());
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newBlock->InterpolateFrequencyComponents(block0, block1, interp);
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// In the time-domain, the 2nd half of the response must be zero, to avoid circular convolution aliasing...
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int fftSize = newBlock->FFTSize();
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nsTArray<float> buffer;
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buffer.SetLength(fftSize);
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newBlock->GetInverseWithoutScaling(buffer.Elements());
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AudioBufferInPlaceScale(buffer.Elements(), 1.0f / fftSize, fftSize / 2);
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PodZero(buffer.Elements() + fftSize / 2, fftSize / 2);
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// Put back into frequency domain.
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newBlock->PerformFFT(buffer.Elements());
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return newBlock;
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}
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void FFTBlock::InterpolateFrequencyComponents(const FFTBlock& block0, const FFTBlock& block1, double interp)
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{
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// FIXME : with some work, this method could be optimized
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kiss_fft_cpx* dft = mOutputBuffer.Elements();
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const kiss_fft_cpx* dft1 = block0.mOutputBuffer.Elements();
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const kiss_fft_cpx* dft2 = block1.mOutputBuffer.Elements();
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MOZ_ASSERT(mFFTSize == block0.FFTSize());
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MOZ_ASSERT(mFFTSize == block1.FFTSize());
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double s1base = (1.0 - interp);
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double s2base = interp;
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double phaseAccum = 0.0;
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double lastPhase1 = 0.0;
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double lastPhase2 = 0.0;
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int n = mFFTSize / 2;
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dft[0].r = static_cast<float>(s1base * dft1[0].r + s2base * dft2[0].r);
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dft[n].r = static_cast<float>(s1base * dft1[n].r + s2base * dft2[n].r);
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for (int i = 1; i < n; ++i) {
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Complex c1(dft1[i].r, dft1[i].i);
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Complex c2(dft2[i].r, dft2[i].i);
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double mag1 = abs(c1);
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double mag2 = abs(c2);
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// Interpolate magnitudes in decibels
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double mag1db = 20.0 * log10(mag1);
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double mag2db = 20.0 * log10(mag2);
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double s1 = s1base;
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double s2 = s2base;
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double magdbdiff = mag1db - mag2db;
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// Empirical tweak to retain higher-frequency zeroes
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double threshold = (i > 16) ? 5.0 : 2.0;
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if (magdbdiff < -threshold && mag1db < 0.0) {
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s1 = pow(s1, 0.75);
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s2 = 1.0 - s1;
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} else if (magdbdiff > threshold && mag2db < 0.0) {
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s2 = pow(s2, 0.75);
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s1 = 1.0 - s2;
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}
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// Average magnitude by decibels instead of linearly
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double magdb = s1 * mag1db + s2 * mag2db;
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double mag = pow(10.0, 0.05 * magdb);
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// Now, deal with phase
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double phase1 = arg(c1);
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double phase2 = arg(c2);
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double deltaPhase1 = phase1 - lastPhase1;
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double deltaPhase2 = phase2 - lastPhase2;
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lastPhase1 = phase1;
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lastPhase2 = phase2;
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// Unwrap phase deltas
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if (deltaPhase1 > M_PI)
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deltaPhase1 -= 2.0 * M_PI;
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if (deltaPhase1 < -M_PI)
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deltaPhase1 += 2.0 * M_PI;
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if (deltaPhase2 > M_PI)
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deltaPhase2 -= 2.0 * M_PI;
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if (deltaPhase2 < -M_PI)
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deltaPhase2 += 2.0 * M_PI;
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// Blend group-delays
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double deltaPhaseBlend;
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if (deltaPhase1 - deltaPhase2 > M_PI)
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deltaPhaseBlend = s1 * deltaPhase1 + s2 * (2.0 * M_PI + deltaPhase2);
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else if (deltaPhase2 - deltaPhase1 > M_PI)
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deltaPhaseBlend = s1 * (2.0 * M_PI + deltaPhase1) + s2 * deltaPhase2;
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else
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deltaPhaseBlend = s1 * deltaPhase1 + s2 * deltaPhase2;
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phaseAccum += deltaPhaseBlend;
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// Unwrap
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if (phaseAccum > M_PI)
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phaseAccum -= 2.0 * M_PI;
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if (phaseAccum < -M_PI)
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phaseAccum += 2.0 * M_PI;
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dft[i].r = static_cast<float>(mag * cos(phaseAccum));
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dft[i].i = static_cast<float>(mag * sin(phaseAccum));
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}
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}
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double FFTBlock::ExtractAverageGroupDelay()
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{
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kiss_fft_cpx* dft = mOutputBuffer.Elements();
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double aveSum = 0.0;
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double weightSum = 0.0;
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double lastPhase = 0.0;
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int halfSize = FFTSize() / 2;
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const double kSamplePhaseDelay = (2.0 * M_PI) / double(FFTSize());
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// Remove DC offset
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dft[0].r = 0.0f;
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// Calculate weighted average group delay
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for (int i = 1; i < halfSize; i++) {
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Complex c(dft[i].r, dft[i].i);
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double mag = abs(c);
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double phase = arg(c);
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double deltaPhase = phase - lastPhase;
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lastPhase = phase;
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// Unwrap
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if (deltaPhase < -M_PI)
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deltaPhase += 2.0 * M_PI;
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if (deltaPhase > M_PI)
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deltaPhase -= 2.0 * M_PI;
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aveSum += mag * deltaPhase;
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weightSum += mag;
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}
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// Note how we invert the phase delta wrt frequency since this is how group delay is defined
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double ave = aveSum / weightSum;
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double aveSampleDelay = -ave / kSamplePhaseDelay;
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// Leave 20 sample headroom (for leading edge of impulse)
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aveSampleDelay -= 20.0;
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if (aveSampleDelay <= 0.0)
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return 0.0;
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// Remove average group delay (minus 20 samples for headroom)
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AddConstantGroupDelay(-aveSampleDelay);
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return aveSampleDelay;
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}
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void FFTBlock::AddConstantGroupDelay(double sampleFrameDelay)
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{
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int halfSize = FFTSize() / 2;
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kiss_fft_cpx* dft = mOutputBuffer.Elements();
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const double kSamplePhaseDelay = (2.0 * M_PI) / double(FFTSize());
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double phaseAdj = -sampleFrameDelay * kSamplePhaseDelay;
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// Add constant group delay
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for (int i = 1; i < halfSize; i++) {
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Complex c(dft[i].r, dft[i].i);
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double mag = abs(c);
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double phase = arg(c);
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phase += i * phaseAdj;
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dft[i].r = static_cast<float>(mag * cos(phase));
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dft[i].i = static_cast<float>(mag * sin(phase));
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}
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}
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} // namespace mozilla
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