content/media/webaudio/FFTBlock.cpp@97036ab72558
content/media/webaudio/FFTBlock.cpp
Tue, 06 Jan 2015 21:39:09 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Tue, 06 Jan 2015 21:39:09 +0100
- branch
- TOR_BUG_9701
- changeset 8
- 97036ab72558
- permissions
- -rw-r--r--
Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.
1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
2 /* vim:set ts=4 sw=4 sts=4 et cindent: */
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31 #include "FFTBlock.h"
33 #include <complex>
35 namespace mozilla {
37 typedef std::complex<double> Complex;
39 FFTBlock* FFTBlock::CreateInterpolatedBlock(const FFTBlock& block0, const FFTBlock& block1, double interp)
40 {
41 FFTBlock* newBlock = new FFTBlock(block0.FFTSize());
43 newBlock->InterpolateFrequencyComponents(block0, block1, interp);
45 // In the time-domain, the 2nd half of the response must be zero, to avoid circular convolution aliasing...
46 int fftSize = newBlock->FFTSize();
47 nsTArray<float> buffer;
48 buffer.SetLength(fftSize);
49 newBlock->GetInverseWithoutScaling(buffer.Elements());
50 AudioBufferInPlaceScale(buffer.Elements(), 1.0f / fftSize, fftSize / 2);
51 PodZero(buffer.Elements() + fftSize / 2, fftSize / 2);
53 // Put back into frequency domain.
54 newBlock->PerformFFT(buffer.Elements());
56 return newBlock;
57 }
59 void FFTBlock::InterpolateFrequencyComponents(const FFTBlock& block0, const FFTBlock& block1, double interp)
60 {
61 // FIXME : with some work, this method could be optimized
63 kiss_fft_cpx* dft = mOutputBuffer.Elements();
65 const kiss_fft_cpx* dft1 = block0.mOutputBuffer.Elements();
66 const kiss_fft_cpx* dft2 = block1.mOutputBuffer.Elements();
68 MOZ_ASSERT(mFFTSize == block0.FFTSize());
69 MOZ_ASSERT(mFFTSize == block1.FFTSize());
70 double s1base = (1.0 - interp);
71 double s2base = interp;
73 double phaseAccum = 0.0;
74 double lastPhase1 = 0.0;
75 double lastPhase2 = 0.0;
77 int n = mFFTSize / 2;
79 dft[0].r = static_cast<float>(s1base * dft1[0].r + s2base * dft2[0].r);
80 dft[n].r = static_cast<float>(s1base * dft1[n].r + s2base * dft2[n].r);
82 for (int i = 1; i < n; ++i) {
83 Complex c1(dft1[i].r, dft1[i].i);
84 Complex c2(dft2[i].r, dft2[i].i);
86 double mag1 = abs(c1);
87 double mag2 = abs(c2);
89 // Interpolate magnitudes in decibels
90 double mag1db = 20.0 * log10(mag1);
91 double mag2db = 20.0 * log10(mag2);
93 double s1 = s1base;
94 double s2 = s2base;
96 double magdbdiff = mag1db - mag2db;
98 // Empirical tweak to retain higher-frequency zeroes
99 double threshold = (i > 16) ? 5.0 : 2.0;
101 if (magdbdiff < -threshold && mag1db < 0.0) {
102 s1 = pow(s1, 0.75);
103 s2 = 1.0 - s1;
104 } else if (magdbdiff > threshold && mag2db < 0.0) {
105 s2 = pow(s2, 0.75);
106 s1 = 1.0 - s2;
107 }
109 // Average magnitude by decibels instead of linearly
110 double magdb = s1 * mag1db + s2 * mag2db;
111 double mag = pow(10.0, 0.05 * magdb);
113 // Now, deal with phase
114 double phase1 = arg(c1);
115 double phase2 = arg(c2);
117 double deltaPhase1 = phase1 - lastPhase1;
118 double deltaPhase2 = phase2 - lastPhase2;
119 lastPhase1 = phase1;
120 lastPhase2 = phase2;
122 // Unwrap phase deltas
123 if (deltaPhase1 > M_PI)
124 deltaPhase1 -= 2.0 * M_PI;
125 if (deltaPhase1 < -M_PI)
126 deltaPhase1 += 2.0 * M_PI;
127 if (deltaPhase2 > M_PI)
128 deltaPhase2 -= 2.0 * M_PI;
129 if (deltaPhase2 < -M_PI)
130 deltaPhase2 += 2.0 * M_PI;
132 // Blend group-delays
133 double deltaPhaseBlend;
135 if (deltaPhase1 - deltaPhase2 > M_PI)
136 deltaPhaseBlend = s1 * deltaPhase1 + s2 * (2.0 * M_PI + deltaPhase2);
137 else if (deltaPhase2 - deltaPhase1 > M_PI)
138 deltaPhaseBlend = s1 * (2.0 * M_PI + deltaPhase1) + s2 * deltaPhase2;
139 else
140 deltaPhaseBlend = s1 * deltaPhase1 + s2 * deltaPhase2;
142 phaseAccum += deltaPhaseBlend;
144 // Unwrap
145 if (phaseAccum > M_PI)
146 phaseAccum -= 2.0 * M_PI;
147 if (phaseAccum < -M_PI)
148 phaseAccum += 2.0 * M_PI;
150 dft[i].r = static_cast<float>(mag * cos(phaseAccum));
151 dft[i].i = static_cast<float>(mag * sin(phaseAccum));
152 }
153 }
155 double FFTBlock::ExtractAverageGroupDelay()
156 {
157 kiss_fft_cpx* dft = mOutputBuffer.Elements();
159 double aveSum = 0.0;
160 double weightSum = 0.0;
161 double lastPhase = 0.0;
163 int halfSize = FFTSize() / 2;
165 const double kSamplePhaseDelay = (2.0 * M_PI) / double(FFTSize());
167 // Remove DC offset
168 dft[0].r = 0.0f;
170 // Calculate weighted average group delay
171 for (int i = 1; i < halfSize; i++) {
172 Complex c(dft[i].r, dft[i].i);
173 double mag = abs(c);
174 double phase = arg(c);
176 double deltaPhase = phase - lastPhase;
177 lastPhase = phase;
179 // Unwrap
180 if (deltaPhase < -M_PI)
181 deltaPhase += 2.0 * M_PI;
182 if (deltaPhase > M_PI)
183 deltaPhase -= 2.0 * M_PI;
185 aveSum += mag * deltaPhase;
186 weightSum += mag;
187 }
189 // Note how we invert the phase delta wrt frequency since this is how group delay is defined
190 double ave = aveSum / weightSum;
191 double aveSampleDelay = -ave / kSamplePhaseDelay;
193 // Leave 20 sample headroom (for leading edge of impulse)
194 aveSampleDelay -= 20.0;
195 if (aveSampleDelay <= 0.0)
196 return 0.0;
198 // Remove average group delay (minus 20 samples for headroom)
199 AddConstantGroupDelay(-aveSampleDelay);
201 return aveSampleDelay;
202 }
204 void FFTBlock::AddConstantGroupDelay(double sampleFrameDelay)
205 {
206 int halfSize = FFTSize() / 2;
208 kiss_fft_cpx* dft = mOutputBuffer.Elements();
210 const double kSamplePhaseDelay = (2.0 * M_PI) / double(FFTSize());
212 double phaseAdj = -sampleFrameDelay * kSamplePhaseDelay;
214 // Add constant group delay
215 for (int i = 1; i < halfSize; i++) {
216 Complex c(dft[i].r, dft[i].i);
217 double mag = abs(c);
218 double phase = arg(c);
220 phase += i * phaseAdj;
222 dft[i].r = static_cast<float>(mag * cos(phase));
223 dft[i].i = static_cast<float>(mag * sin(phase));
224 }
225 }
227 } // namespace mozilla
