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| 1 /* | 1 /* |
| 2 * Copyright (C) 2013 Google Inc. All rights reserved. | 2 * Copyright (C) 2013 Google Inc. All rights reserved. |
| 3 * | 3 * |
| 4 * Redistribution and use in source and binary forms, with or without | 4 * Redistribution and use in source and binary forms, with or without |
| 5 * modification, are permitted provided that the following conditions are | 5 * modification, are permitted provided that the following conditions are |
| 6 * met: | 6 * met: |
| 7 * | 7 * |
| 8 * * Redistributions of source code must retain the above copyright | 8 * * Redistributions of source code must retain the above copyright |
| 9 * notice, this list of conditions and the following disclaimer. | 9 * notice, this list of conditions and the following disclaimer. |
| 10 * * Redistributions in binary form must reproduce the above | 10 * * Redistributions in binary form must reproduce the above |
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| 29 */ | 29 */ |
| 30 | 30 |
| 31 #include "platform/audio/DownSampler.h" | 31 #include "platform/audio/DownSampler.h" |
| 32 #include "wtf/MathExtras.h" | 32 #include "wtf/MathExtras.h" |
| 33 | 33 |
| 34 namespace blink { | 34 namespace blink { |
| 35 | 35 |
| 36 DownSampler::DownSampler(size_t inputBlockSize) | 36 DownSampler::DownSampler(size_t inputBlockSize) |
| 37 : m_inputBlockSize(inputBlockSize), | 37 : m_inputBlockSize(inputBlockSize), |
| 38 m_reducedKernel(DefaultKernelSize / 2), | 38 m_reducedKernel(DefaultKernelSize / 2), |
| 39 m_convolver(inputBlockSize / 2) // runs at 1/2 source sample-rate | 39 m_convolver(inputBlockSize / 2), // runs at 1/2 source sample-rate |
| 40 , | |
| 41 m_tempBuffer(inputBlockSize / 2), | 40 m_tempBuffer(inputBlockSize / 2), |
| 42 m_inputBuffer(inputBlockSize * 2) { | 41 m_inputBuffer(inputBlockSize * 2) { |
| 43 initializeKernel(); | 42 initializeKernel(); |
| 44 } | 43 } |
| 45 | 44 |
| 46 void DownSampler::initializeKernel() { | 45 void DownSampler::initializeKernel() { |
| 47 // Blackman window parameters. | 46 // Blackman window parameters. |
| 48 double alpha = 0.16; | 47 double alpha = 0.16; |
| 49 double a0 = 0.5 * (1.0 - alpha); | 48 double a0 = 0.5 * (1.0 - alpha); |
| 50 double a1 = 0.5; | 49 double a1 = 0.5; |
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| 140 m_inputBuffer.zero(); | 139 m_inputBuffer.zero(); |
| 141 } | 140 } |
| 142 | 141 |
| 143 size_t DownSampler::latencyFrames() const { | 142 size_t DownSampler::latencyFrames() const { |
| 144 // Divide by two since this is a linear phase kernel and the delay is at the | 143 // Divide by two since this is a linear phase kernel and the delay is at the |
| 145 // center of the kernel. | 144 // center of the kernel. |
| 146 return m_reducedKernel.size() / 2; | 145 return m_reducedKernel.size() / 2; |
| 147 } | 146 } |
| 148 | 147 |
| 149 } // namespace blink | 148 } // namespace blink |
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