/content/media/webaudio/blink/HRTFKernel.cpp
C++ | 99 lines | 46 code | 15 blank | 38 comment | 11 complexity | a921b0bb6b5d327d00b0b94a33172b98 MD5 | raw file
Possible License(s): Apache-2.0, GPL-2.0, 0BSD, LGPL-3.0, LGPL-2.1, MPL-2.0-no-copyleft-exception, MPL-2.0, BSD-3-Clause, JSON
- /*
- * Copyright (C) 2010 Google Inc. All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the distribution.
- * 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of
- * its contributors may be used to endorse or promote products derived
- * from this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
- * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
- * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
- * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
- * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
- * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
- * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
- * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
- * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
- #include "HRTFKernel.h"
- namespace WebCore {
- // Takes the input audio channel |impulseP| as an input impulse response and calculates the average group delay.
- // This represents the initial delay before the most energetic part of the impulse response.
- // The sample-frame delay is removed from the |impulseP| impulse response, and this value is returned.
- // The |length| of the passed in |impulseP| must be must be a power of 2.
- static float extractAverageGroupDelay(float* impulseP, size_t length)
- {
- // Check for power-of-2.
- MOZ_ASSERT(length && (length & (length - 1)) == 0);
- FFTBlock estimationFrame(length);
- estimationFrame.PerformFFT(impulseP);
- float frameDelay = static_cast<float>(estimationFrame.ExtractAverageGroupDelay());
- estimationFrame.GetInverse(impulseP);
- return frameDelay;
- }
- HRTFKernel::HRTFKernel(float* impulseResponse, size_t length, float sampleRate)
- : m_frameDelay(0)
- , m_sampleRate(sampleRate)
- {
- // Determine the leading delay (average group delay) for the response.
- m_frameDelay = extractAverageGroupDelay(impulseResponse, length);
- // The FFT size (with zero padding) needs to be twice the response length
- // in order to do proper convolution.
- unsigned fftSize = 2 * length;
- // Quick fade-out (apply window) at truncation point
- // because the impulse response has been truncated.
- unsigned numberOfFadeOutFrames = static_cast<unsigned>(sampleRate / 4410); // 10 sample-frames @44.1KHz sample-rate
- MOZ_ASSERT(numberOfFadeOutFrames < length);
- if (numberOfFadeOutFrames < length) {
- for (unsigned i = length - numberOfFadeOutFrames; i < length; ++i) {
- float x = 1.0f - static_cast<float>(i - (length - numberOfFadeOutFrames)) / numberOfFadeOutFrames;
- impulseResponse[i] *= x;
- }
- }
- m_fftFrame = new FFTBlock(fftSize);
- m_fftFrame->PadAndMakeScaledDFT(impulseResponse, length);
- }
- // Interpolates two kernels with x: 0 -> 1 and returns the result.
- nsReturnRef<HRTFKernel> HRTFKernel::createInterpolatedKernel(HRTFKernel* kernel1, HRTFKernel* kernel2, float x)
- {
- MOZ_ASSERT(kernel1 && kernel2);
- if (!kernel1 || !kernel2)
- return nsReturnRef<HRTFKernel>();
-
- MOZ_ASSERT(x >= 0.0 && x < 1.0);
- x = mozilla::clamped(x, 0.0f, 1.0f);
-
- float sampleRate1 = kernel1->sampleRate();
- float sampleRate2 = kernel2->sampleRate();
- MOZ_ASSERT(sampleRate1 == sampleRate2);
- if (sampleRate1 != sampleRate2)
- return nsReturnRef<HRTFKernel>();
-
- float frameDelay = (1 - x) * kernel1->frameDelay() + x * kernel2->frameDelay();
-
- nsAutoPtr<FFTBlock> interpolatedFrame(
- FFTBlock::CreateInterpolatedBlock(*kernel1->fftFrame(), *kernel2->fftFrame(), x));
- return HRTFKernel::create(interpolatedFrame, frameDelay, sampleRate1);
- }
- } // namespace WebCore