The Tor Browser / file comparison
comparison: content/media/webaudio/blink/HRTFKernel.cpp
content/media/webaudio/blink/HRTFKernel.cpp
- branch
- TOR_BUG_9701
- changeset 15
- b8a032363ba2
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| -1:000000000000 | 0:e440e0e662ab |
|---|---|
| 1 /* | |
| 2 * Copyright (C) 2010 Google Inc. All rights reserved. | |
| 3 * | |
| 4 * Redistribution and use in source and binary forms, with or without | |
| 5 * modification, are permitted provided that the following conditions | |
| 6 * are met: | |
| 7 * | |
| 8 * 1. Redistributions of source code must retain the above copyright | |
| 9 * notice, this list of conditions and the following disclaimer. | |
| 10 * 2. Redistributions in binary form must reproduce the above copyright | |
| 11 * notice, this list of conditions and the following disclaimer in the | |
| 12 * documentation and/or other materials provided with the distribution. | |
| 13 * 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of | |
| 14 * its contributors may be used to endorse or promote products derived | |
| 15 * from this software without specific prior written permission. | |
| 16 * | |
| 17 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY | |
| 18 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED | |
| 19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE | |
| 20 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY | |
| 21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES | |
| 22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; | |
| 23 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND | |
| 24 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
| 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF | |
| 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
| 27 */ | |
| 28 | |
| 29 #include "HRTFKernel.h" | |
| 30 namespace WebCore { | |
| 31 | |
| 32 // Takes the input audio channel |impulseP| as an input impulse response and calculates the average group delay. | |
| 33 // This represents the initial delay before the most energetic part of the impulse response. | |
| 34 // The sample-frame delay is removed from the |impulseP| impulse response, and this value is returned. | |
| 35 // The |length| of the passed in |impulseP| must be must be a power of 2. | |
| 36 static float extractAverageGroupDelay(float* impulseP, size_t length) | |
| 37 { | |
| 38 // Check for power-of-2. | |
| 39 MOZ_ASSERT(length && (length & (length - 1)) == 0); | |
| 40 | |
| 41 FFTBlock estimationFrame(length); | |
| 42 estimationFrame.PerformFFT(impulseP); | |
| 43 | |
| 44 float frameDelay = static_cast<float>(estimationFrame.ExtractAverageGroupDelay()); | |
| 45 estimationFrame.GetInverse(impulseP); | |
| 46 | |
| 47 return frameDelay; | |
| 48 } | |
| 49 | |
| 50 HRTFKernel::HRTFKernel(float* impulseResponse, size_t length, float sampleRate) | |
| 51 : m_frameDelay(0) | |
| 52 , m_sampleRate(sampleRate) | |
| 53 { | |
| 54 // Determine the leading delay (average group delay) for the response. | |
| 55 m_frameDelay = extractAverageGroupDelay(impulseResponse, length); | |
| 56 | |
| 57 // The FFT size (with zero padding) needs to be twice the response length | |
| 58 // in order to do proper convolution. | |
| 59 unsigned fftSize = 2 * length; | |
| 60 | |
| 61 // Quick fade-out (apply window) at truncation point | |
| 62 // because the impulse response has been truncated. | |
| 63 unsigned numberOfFadeOutFrames = static_cast<unsigned>(sampleRate / 4410); // 10 sample-frames @44.1KHz sample-rate | |
| 64 MOZ_ASSERT(numberOfFadeOutFrames < length); | |
| 65 if (numberOfFadeOutFrames < length) { | |
| 66 for (unsigned i = length - numberOfFadeOutFrames; i < length; ++i) { | |
| 67 float x = 1.0f - static_cast<float>(i - (length - numberOfFadeOutFrames)) / numberOfFadeOutFrames; | |
| 68 impulseResponse[i] *= x; | |
| 69 } | |
| 70 } | |
| 71 | |
| 72 m_fftFrame = new FFTBlock(fftSize); | |
| 73 m_fftFrame->PadAndMakeScaledDFT(impulseResponse, length); | |
| 74 } | |
| 75 | |
| 76 // Interpolates two kernels with x: 0 -> 1 and returns the result. | |
| 77 nsReturnRef<HRTFKernel> HRTFKernel::createInterpolatedKernel(HRTFKernel* kernel1, HRTFKernel* kernel2, float x) | |
| 78 { | |
| 79 MOZ_ASSERT(kernel1 && kernel2); | |
| 80 if (!kernel1 || !kernel2) | |
| 81 return nsReturnRef<HRTFKernel>(); | |
| 82 | |
| 83 MOZ_ASSERT(x >= 0.0 && x < 1.0); | |
| 84 x = mozilla::clamped(x, 0.0f, 1.0f); | |
| 85 | |
| 86 float sampleRate1 = kernel1->sampleRate(); | |
| 87 float sampleRate2 = kernel2->sampleRate(); | |
| 88 MOZ_ASSERT(sampleRate1 == sampleRate2); | |
| 89 if (sampleRate1 != sampleRate2) | |
| 90 return nsReturnRef<HRTFKernel>(); | |
| 91 | |
| 92 float frameDelay = (1 - x) * kernel1->frameDelay() + x * kernel2->frameDelay(); | |
| 93 | |
| 94 nsAutoPtr<FFTBlock> interpolatedFrame( | |
| 95 FFTBlock::CreateInterpolatedBlock(*kernel1->fftFrame(), *kernel2->fftFrame(), x)); | |
| 96 return HRTFKernel::create(interpolatedFrame, frameDelay, sampleRate1); | |
| 97 } | |
| 98 | |
| 99 } // namespace WebCore |
