/Source/platform/audio/HRTFKernel.cpp
C++ | 133 lines | 68 code | 28 blank | 37 comment | 11 complexity | 620fdc4582f40ceec5c6fe6d4b8ef234 MD5 | raw file
Possible License(s): BSD-3-Clause, Unlicense, AGPL-1.0, Apache-2.0
- /*
- * 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 "config.h"
- #if ENABLE(WEB_AUDIO)
- #include "platform/audio/HRTFKernel.h"
- #include "platform/audio/AudioChannel.h"
- #include "platform/FloatConversion.h"
- #include "wtf/MathExtras.h"
- namespace blink {
- // Takes the input AudioChannel 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 AudioChannel must be a power of 2.
- static float extractAverageGroupDelay(AudioChannel* channel, size_t analysisFFTSize)
- {
- ASSERT(channel);
- float* impulseP = channel->mutableData();
- bool isSizeGood = channel->length() >= analysisFFTSize;
- ASSERT(isSizeGood);
- if (!isSizeGood)
- return 0;
- // Check for power-of-2.
- ASSERT(1UL << static_cast<unsigned>(log2(analysisFFTSize)) == analysisFFTSize);
- FFTFrame estimationFrame(analysisFFTSize);
- estimationFrame.doFFT(impulseP);
- float frameDelay = narrowPrecisionToFloat(estimationFrame.extractAverageGroupDelay());
- estimationFrame.doInverseFFT(impulseP);
- return frameDelay;
- }
- HRTFKernel::HRTFKernel(AudioChannel* channel, size_t fftSize, float sampleRate)
- : m_frameDelay(0)
- , m_sampleRate(sampleRate)
- {
- ASSERT(channel);
- // Determine the leading delay (average group delay) for the response.
- m_frameDelay = extractAverageGroupDelay(channel, fftSize / 2);
- float* impulseResponse = channel->mutableData();
- size_t responseLength = channel->length();
- // We need to truncate to fit into 1/2 the FFT size (with zero padding) in order to do proper convolution.
- size_t truncatedResponseLength = std::min(responseLength, fftSize / 2); // truncate if necessary to max impulse response length allowed by FFT
- // Quick fade-out (apply window) at truncation point
- unsigned numberOfFadeOutFrames = static_cast<unsigned>(sampleRate / 4410); // 10 sample-frames @44.1KHz sample-rate
- ASSERT(numberOfFadeOutFrames < truncatedResponseLength);
- if (numberOfFadeOutFrames < truncatedResponseLength) {
- for (unsigned i = truncatedResponseLength - numberOfFadeOutFrames; i < truncatedResponseLength; ++i) {
- float x = 1.0f - static_cast<float>(i - (truncatedResponseLength - numberOfFadeOutFrames)) / numberOfFadeOutFrames;
- impulseResponse[i] *= x;
- }
- }
- m_fftFrame = adoptPtr(new FFTFrame(fftSize));
- m_fftFrame->doPaddedFFT(impulseResponse, truncatedResponseLength);
- }
- PassOwnPtr<AudioChannel> HRTFKernel::createImpulseResponse()
- {
- OwnPtr<AudioChannel> channel = adoptPtr(new AudioChannel(fftSize()));
- FFTFrame fftFrame(*m_fftFrame);
- // Add leading delay back in.
- fftFrame.addConstantGroupDelay(m_frameDelay);
- fftFrame.doInverseFFT(channel->mutableData());
- return channel.release();
- }
- // Interpolates two kernels with x: 0 -> 1 and returns the result.
- PassOwnPtr<HRTFKernel> HRTFKernel::createInterpolatedKernel(HRTFKernel* kernel1, HRTFKernel* kernel2, float x)
- {
- ASSERT(kernel1 && kernel2);
- if (!kernel1 || !kernel2)
- return nullptr;
- ASSERT(x >= 0.0 && x < 1.0);
- x = std::min(1.0f, std::max(0.0f, x));
- float sampleRate1 = kernel1->sampleRate();
- float sampleRate2 = kernel2->sampleRate();
- ASSERT(sampleRate1 == sampleRate2);
- if (sampleRate1 != sampleRate2)
- return nullptr;
- float frameDelay = (1 - x) * kernel1->frameDelay() + x * kernel2->frameDelay();
- OwnPtr<FFTFrame> interpolatedFrame = FFTFrame::createInterpolatedFrame(*kernel1->fftFrame(), *kernel2->fftFrame(), x);
- return HRTFKernel::create(interpolatedFrame.release(), frameDelay, sampleRate1);
- }
- } // namespace blink
- #endif // ENABLE(WEB_AUDIO)