1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/content/media/webaudio/blink/HRTFKernel.cpp Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,99 @@
1.4 +/*
1.5 + * Copyright (C) 2010 Google Inc. All rights reserved.
1.6 + *
1.7 + * Redistribution and use in source and binary forms, with or without
1.8 + * modification, are permitted provided that the following conditions
1.9 + * are met:
1.10 + *
1.11 + * 1. Redistributions of source code must retain the above copyright
1.12 + * notice, this list of conditions and the following disclaimer.
1.13 + * 2. Redistributions in binary form must reproduce the above copyright
1.14 + * notice, this list of conditions and the following disclaimer in the
1.15 + * documentation and/or other materials provided with the distribution.
1.16 + * 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of
1.17 + * its contributors may be used to endorse or promote products derived
1.18 + * from this software without specific prior written permission.
1.19 + *
1.20 + * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
1.21 + * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
1.22 + * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
1.23 + * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
1.24 + * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
1.25 + * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
1.26 + * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
1.27 + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
1.28 + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
1.29 + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.30 + */
1.31 +
1.32 +#include "HRTFKernel.h"
1.33 +namespace WebCore {
1.34 +
1.35 +// Takes the input audio channel |impulseP| as an input impulse response and calculates the average group delay.
1.36 +// This represents the initial delay before the most energetic part of the impulse response.
1.37 +// The sample-frame delay is removed from the |impulseP| impulse response, and this value is returned.
1.38 +// The |length| of the passed in |impulseP| must be must be a power of 2.
1.39 +static float extractAverageGroupDelay(float* impulseP, size_t length)
1.40 +{
1.41 + // Check for power-of-2.
1.42 + MOZ_ASSERT(length && (length & (length - 1)) == 0);
1.43 +
1.44 + FFTBlock estimationFrame(length);
1.45 + estimationFrame.PerformFFT(impulseP);
1.46 +
1.47 + float frameDelay = static_cast<float>(estimationFrame.ExtractAverageGroupDelay());
1.48 + estimationFrame.GetInverse(impulseP);
1.49 +
1.50 + return frameDelay;
1.51 +}
1.52 +
1.53 +HRTFKernel::HRTFKernel(float* impulseResponse, size_t length, float sampleRate)
1.54 + : m_frameDelay(0)
1.55 + , m_sampleRate(sampleRate)
1.56 +{
1.57 + // Determine the leading delay (average group delay) for the response.
1.58 + m_frameDelay = extractAverageGroupDelay(impulseResponse, length);
1.59 +
1.60 + // The FFT size (with zero padding) needs to be twice the response length
1.61 + // in order to do proper convolution.
1.62 + unsigned fftSize = 2 * length;
1.63 +
1.64 + // Quick fade-out (apply window) at truncation point
1.65 + // because the impulse response has been truncated.
1.66 + unsigned numberOfFadeOutFrames = static_cast<unsigned>(sampleRate / 4410); // 10 sample-frames @44.1KHz sample-rate
1.67 + MOZ_ASSERT(numberOfFadeOutFrames < length);
1.68 + if (numberOfFadeOutFrames < length) {
1.69 + for (unsigned i = length - numberOfFadeOutFrames; i < length; ++i) {
1.70 + float x = 1.0f - static_cast<float>(i - (length - numberOfFadeOutFrames)) / numberOfFadeOutFrames;
1.71 + impulseResponse[i] *= x;
1.72 + }
1.73 + }
1.74 +
1.75 + m_fftFrame = new FFTBlock(fftSize);
1.76 + m_fftFrame->PadAndMakeScaledDFT(impulseResponse, length);
1.77 +}
1.78 +
1.79 +// Interpolates two kernels with x: 0 -> 1 and returns the result.
1.80 +nsReturnRef<HRTFKernel> HRTFKernel::createInterpolatedKernel(HRTFKernel* kernel1, HRTFKernel* kernel2, float x)
1.81 +{
1.82 + MOZ_ASSERT(kernel1 && kernel2);
1.83 + if (!kernel1 || !kernel2)
1.84 + return nsReturnRef<HRTFKernel>();
1.85 +
1.86 + MOZ_ASSERT(x >= 0.0 && x < 1.0);
1.87 + x = mozilla::clamped(x, 0.0f, 1.0f);
1.88 +
1.89 + float sampleRate1 = kernel1->sampleRate();
1.90 + float sampleRate2 = kernel2->sampleRate();
1.91 + MOZ_ASSERT(sampleRate1 == sampleRate2);
1.92 + if (sampleRate1 != sampleRate2)
1.93 + return nsReturnRef<HRTFKernel>();
1.94 +
1.95 + float frameDelay = (1 - x) * kernel1->frameDelay() + x * kernel2->frameDelay();
1.96 +
1.97 + nsAutoPtr<FFTBlock> interpolatedFrame(
1.98 + FFTBlock::CreateInterpolatedBlock(*kernel1->fftFrame(), *kernel2->fftFrame(), x));
1.99 + return HRTFKernel::create(interpolatedFrame, frameDelay, sampleRate1);
1.100 +}
1.101 +
1.102 +} // namespace WebCore
