content/media/webaudio/blink/HRTFKernel.cpp@6474c204b198 (annotated)
content/media/webaudio/blink/HRTFKernel.cpp
Wed, 31 Dec 2014 06:09:35 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Wed, 31 Dec 2014 06:09:35 +0100
- changeset 0
- 6474c204b198
- permissions
- -rw-r--r--
Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.
| michael@0 | 1 | /* |
| michael@0 | 2 | * Copyright (C) 2010 Google Inc. All rights reserved. |
| michael@0 | 3 | * |
| michael@0 | 4 | * Redistribution and use in source and binary forms, with or without |
| michael@0 | 5 | * modification, are permitted provided that the following conditions |
| michael@0 | 6 | * are met: |
| michael@0 | 7 | * |
| michael@0 | 8 | * 1. Redistributions of source code must retain the above copyright |
| michael@0 | 9 | * notice, this list of conditions and the following disclaimer. |
| michael@0 | 10 | * 2. Redistributions in binary form must reproduce the above copyright |
| michael@0 | 11 | * notice, this list of conditions and the following disclaimer in the |
| michael@0 | 12 | * documentation and/or other materials provided with the distribution. |
| michael@0 | 13 | * 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of |
| michael@0 | 14 | * its contributors may be used to endorse or promote products derived |
| michael@0 | 15 | * from this software without specific prior written permission. |
| michael@0 | 16 | * |
| michael@0 | 17 | * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY |
| michael@0 | 18 | * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED |
| michael@0 | 19 | * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
| michael@0 | 20 | * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY |
| michael@0 | 21 | * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES |
| michael@0 | 22 | * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
| michael@0 | 23 | * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND |
| michael@0 | 24 | * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| michael@0 | 25 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| michael@0 | 26 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| michael@0 | 27 | */ |
| michael@0 | 28 | |
| michael@0 | 29 | #include "HRTFKernel.h" |
| michael@0 | 30 | namespace WebCore { |
| michael@0 | 31 | |
| michael@0 | 32 | // Takes the input audio channel |impulseP| as an input impulse response and calculates the average group delay. |
| michael@0 | 33 | // This represents the initial delay before the most energetic part of the impulse response. |
| michael@0 | 34 | // The sample-frame delay is removed from the |impulseP| impulse response, and this value is returned. |
| michael@0 | 35 | // The |length| of the passed in |impulseP| must be must be a power of 2. |
| michael@0 | 36 | static float extractAverageGroupDelay(float* impulseP, size_t length) |
| michael@0 | 37 | { |
| michael@0 | 38 | // Check for power-of-2. |
| michael@0 | 39 | MOZ_ASSERT(length && (length & (length - 1)) == 0); |
| michael@0 | 40 | |
| michael@0 | 41 | FFTBlock estimationFrame(length); |
| michael@0 | 42 | estimationFrame.PerformFFT(impulseP); |
| michael@0 | 43 | |
| michael@0 | 44 | float frameDelay = static_cast<float>(estimationFrame.ExtractAverageGroupDelay()); |
| michael@0 | 45 | estimationFrame.GetInverse(impulseP); |
| michael@0 | 46 | |
| michael@0 | 47 | return frameDelay; |
| michael@0 | 48 | } |
| michael@0 | 49 | |
| michael@0 | 50 | HRTFKernel::HRTFKernel(float* impulseResponse, size_t length, float sampleRate) |
| michael@0 | 51 | : m_frameDelay(0) |
| michael@0 | 52 | , m_sampleRate(sampleRate) |
| michael@0 | 53 | { |
| michael@0 | 54 | // Determine the leading delay (average group delay) for the response. |
| michael@0 | 55 | m_frameDelay = extractAverageGroupDelay(impulseResponse, length); |
| michael@0 | 56 | |
| michael@0 | 57 | // The FFT size (with zero padding) needs to be twice the response length |
| michael@0 | 58 | // in order to do proper convolution. |
| michael@0 | 59 | unsigned fftSize = 2 * length; |
| michael@0 | 60 | |
| michael@0 | 61 | // Quick fade-out (apply window) at truncation point |
| michael@0 | 62 | // because the impulse response has been truncated. |
| michael@0 | 63 | unsigned numberOfFadeOutFrames = static_cast<unsigned>(sampleRate / 4410); // 10 sample-frames @44.1KHz sample-rate |
| michael@0 | 64 | MOZ_ASSERT(numberOfFadeOutFrames < length); |
| michael@0 | 65 | if (numberOfFadeOutFrames < length) { |
| michael@0 | 66 | for (unsigned i = length - numberOfFadeOutFrames; i < length; ++i) { |
| michael@0 | 67 | float x = 1.0f - static_cast<float>(i - (length - numberOfFadeOutFrames)) / numberOfFadeOutFrames; |
| michael@0 | 68 | impulseResponse[i] *= x; |
| michael@0 | 69 | } |
| michael@0 | 70 | } |
| michael@0 | 71 | |
| michael@0 | 72 | m_fftFrame = new FFTBlock(fftSize); |
| michael@0 | 73 | m_fftFrame->PadAndMakeScaledDFT(impulseResponse, length); |
| michael@0 | 74 | } |
| michael@0 | 75 | |
| michael@0 | 76 | // Interpolates two kernels with x: 0 -> 1 and returns the result. |
| michael@0 | 77 | nsReturnRef<HRTFKernel> HRTFKernel::createInterpolatedKernel(HRTFKernel* kernel1, HRTFKernel* kernel2, float x) |
| michael@0 | 78 | { |
| michael@0 | 79 | MOZ_ASSERT(kernel1 && kernel2); |
| michael@0 | 80 | if (!kernel1 || !kernel2) |
| michael@0 | 81 | return nsReturnRef<HRTFKernel>(); |
| michael@0 | 82 | |
| michael@0 | 83 | MOZ_ASSERT(x >= 0.0 && x < 1.0); |
| michael@0 | 84 | x = mozilla::clamped(x, 0.0f, 1.0f); |
| michael@0 | 85 | |
| michael@0 | 86 | float sampleRate1 = kernel1->sampleRate(); |
| michael@0 | 87 | float sampleRate2 = kernel2->sampleRate(); |
| michael@0 | 88 | MOZ_ASSERT(sampleRate1 == sampleRate2); |
| michael@0 | 89 | if (sampleRate1 != sampleRate2) |
| michael@0 | 90 | return nsReturnRef<HRTFKernel>(); |
| michael@0 | 91 | |
| michael@0 | 92 | float frameDelay = (1 - x) * kernel1->frameDelay() + x * kernel2->frameDelay(); |
| michael@0 | 93 | |
| michael@0 | 94 | nsAutoPtr<FFTBlock> interpolatedFrame( |
| michael@0 | 95 | FFTBlock::CreateInterpolatedBlock(*kernel1->fftFrame(), *kernel2->fftFrame(), x)); |
| michael@0 | 96 | return HRTFKernel::create(interpolatedFrame, frameDelay, sampleRate1); |
| michael@0 | 97 | } |
| michael@0 | 98 | |
| michael@0 | 99 | } // namespace WebCore |
