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1 // Copyright 2016 The Chromium Authors. All rights reserved. | 1 // Copyright 2016 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 #include "modules/webaudio/IIRDSPKernel.h" | 5 #include "modules/webaudio/IIRDSPKernel.h" |
6 | 6 |
7 #include "wtf/MathExtras.h" | 7 #include "wtf/MathExtras.h" |
8 | 8 |
9 namespace blink { | 9 namespace blink { |
10 | 10 |
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33 // Convert from frequency in Hz to normalized frequency (0 -> 1), | 33 // Convert from frequency in Hz to normalized frequency (0 -> 1), |
34 // with 1 equal to the Nyquist frequency. | 34 // with 1 equal to the Nyquist frequency. |
35 for (int k = 0; k < nFrequencies; ++k) | 35 for (int k = 0; k < nFrequencies; ++k) |
36 frequency[k] = clampTo<float>(frequencyHz[k] / nyquist); | 36 frequency[k] = clampTo<float>(frequencyHz[k] / nyquist); |
37 | 37 |
38 m_iir.getFrequencyResponse(nFrequencies, frequency.data(), magResponse, | 38 m_iir.getFrequencyResponse(nFrequencies, frequency.data(), magResponse, |
39 phaseResponse); | 39 phaseResponse); |
40 } | 40 } |
41 | 41 |
42 double IIRDSPKernel::tailTime() const { | 42 double IIRDSPKernel::tailTime() const { |
43 // TODO(rtoy): This is true mathematically (infinite impulse response), but pe
rhaps it should be | 43 // TODO(rtoy): This is true mathematically (infinite impulse response), but |
44 // limited to a smaller value, possibly based on the actual filter coefficient
s. To do that, we | 44 // perhaps it should be limited to a smaller value, possibly based on the |
45 // would probably need to find the pole, r, with largest magnitude and select
some threshold, | 45 // actual filter coefficients. To do that, we would probably need to find the |
46 // eps, such that |r|^n < eps for all n >= N. N is then the tailTime for the
filter. If the | 46 // pole, r, with largest magnitude and select some threshold, eps, such that |
47 // the magnitude of r is greater than or equal to 1, the infinity is the right
answer. (There is | 47 // |r|^n < eps for all n >= N. N is then the tailTime for the filter. If the |
48 // no constraint on the IIR filter that it be stable.) | 48 // the magnitude of r is greater than or equal to 1, the infinity is the right |
| 49 // answer. (There is no constraint on the IIR filter that it be stable.) |
49 return std::numeric_limits<double>::infinity(); | 50 return std::numeric_limits<double>::infinity(); |
50 } | 51 } |
51 | 52 |
52 double IIRDSPKernel::latencyTime() const { | 53 double IIRDSPKernel::latencyTime() const { |
53 return 0; | 54 return 0; |
54 } | 55 } |
55 | 56 |
56 } // namespace blink | 57 } // namespace blink |
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