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/Source/WebCore/platform/audio/HRTFKernel.cpp

https://bitbucket.org/codefirex/external_webkit
C++ | 146 lines | 76 code | 30 blank | 40 comment | 12 complexity | dbc62fa6366a108fffe67f546a42b95d MD5 | raw file
  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 "config.h"
 30
 31#if ENABLE(WEB_AUDIO)
 32
 33#include "HRTFKernel.h"
 34
 35#include "AudioChannel.h"
 36#include "Biquad.h"
 37#include "FFTFrame.h"
 38#include "FloatConversion.h"
 39#include <wtf/MathExtras.h>
 40
 41using namespace std;
 42
 43namespace WebCore {
 44
 45// Takes the input AudioChannel as an input impulse response and calculates the average group delay.
 46// This represents the initial delay before the most energetic part of the impulse response.
 47// The sample-frame delay is removed from the impulseP impulse response, and this value  is returned.
 48// the length of the passed in AudioChannel must be a power of 2.
 49static float extractAverageGroupDelay(AudioChannel* channel, size_t analysisFFTSize)
 50{
 51    ASSERT(channel);
 52
 53    float* impulseP = channel->mutableData();
 54
 55    bool isSizeGood = channel->length() >= analysisFFTSize;
 56    ASSERT(isSizeGood);
 57    if (!isSizeGood)
 58        return 0;
 59
 60    // Check for power-of-2.
 61    ASSERT(1UL << static_cast<unsigned>(log2(analysisFFTSize)) == analysisFFTSize);
 62
 63    FFTFrame estimationFrame(analysisFFTSize);
 64    estimationFrame.doFFT(impulseP);
 65
 66    float frameDelay = narrowPrecisionToFloat(estimationFrame.extractAverageGroupDelay());
 67    estimationFrame.doInverseFFT(impulseP);
 68
 69    return frameDelay;
 70}
 71
 72HRTFKernel::HRTFKernel(AudioChannel* channel, size_t fftSize, float sampleRate, bool bassBoost)
 73    : m_frameDelay(0)
 74    , m_sampleRate(sampleRate)
 75{
 76    ASSERT(channel);
 77
 78    // Determine the leading delay (average group delay) for the response.
 79    m_frameDelay = extractAverageGroupDelay(channel, fftSize / 2);
 80
 81    float* impulseResponse = channel->mutableData();
 82    size_t responseLength = channel->length();
 83
 84    if (bassBoost) {
 85        // Run through some post-processing to boost the bass a little -- the HRTF's seem to be a little bass-deficient.
 86        // FIXME: this post-processing should have already been applied to the HRTF file resources.  Once the files are put into this form,
 87        // then this code path can be removed along with the bassBoost parameter.
 88        Biquad filter;
 89        filter.setLowShelfParams(700.0 / nyquist(), 6.0); // boost 6dB at 700Hz
 90        filter.process(impulseResponse, impulseResponse, responseLength);
 91    }
 92
 93    // We need to truncate to fit into 1/2 the FFT size (with zero padding) in order to do proper convolution.
 94    size_t truncatedResponseLength = min(responseLength, fftSize / 2); // truncate if necessary to max impulse response length allowed by FFT
 95
 96    // Quick fade-out (apply window) at truncation point
 97    unsigned numberOfFadeOutFrames = static_cast<unsigned>(sampleRate / 4410); // 10 sample-frames @44.1KHz sample-rate
 98    ASSERT(numberOfFadeOutFrames < truncatedResponseLength);
 99    if (numberOfFadeOutFrames < truncatedResponseLength) {
100        for (unsigned i = truncatedResponseLength - numberOfFadeOutFrames; i < truncatedResponseLength; ++i) {
101            float x = 1.0f - static_cast<float>(i - (truncatedResponseLength - numberOfFadeOutFrames)) / numberOfFadeOutFrames;
102            impulseResponse[i] *= x;
103        }
104    }
105
106    m_fftFrame = adoptPtr(new FFTFrame(fftSize));
107    m_fftFrame->doPaddedFFT(impulseResponse, truncatedResponseLength);
108}
109
110PassOwnPtr<AudioChannel> HRTFKernel::createImpulseResponse()
111{
112    OwnPtr<AudioChannel> channel = adoptPtr(new AudioChannel(fftSize()));
113    FFTFrame fftFrame(*m_fftFrame);
114
115    // Add leading delay back in.
116    fftFrame.addConstantGroupDelay(m_frameDelay);
117    fftFrame.doInverseFFT(channel->mutableData());
118
119    return channel.release();
120}
121
122// Interpolates two kernels with x: 0 -> 1 and returns the result.
123PassRefPtr<HRTFKernel> HRTFKernel::createInterpolatedKernel(HRTFKernel* kernel1, HRTFKernel* kernel2, float x)
124{
125    ASSERT(kernel1 && kernel2);
126    if (!kernel1 || !kernel2)
127        return 0;
128
129    ASSERT(x >= 0.0 && x < 1.0);
130    x = min(1.0f, max(0.0f, x));
131
132    float sampleRate1 = kernel1->sampleRate();
133    float sampleRate2 = kernel2->sampleRate();
134    ASSERT(sampleRate1 == sampleRate2);
135    if (sampleRate1 != sampleRate2)
136        return 0;
137
138    float frameDelay = (1 - x) * kernel1->frameDelay() + x * kernel2->frameDelay();
139
140    OwnPtr<FFTFrame> interpolatedFrame = FFTFrame::createInterpolatedFrame(*kernel1->fftFrame(), *kernel2->fftFrame(), x);
141    return HRTFKernel::create(interpolatedFrame.release(), frameDelay, sampleRate1);
142}
143
144} // namespace WebCore
145
146#endif // ENABLE(WEB_AUDIO)