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      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  * 1.  Redistributions of source code must retain the above copyright
      8  *    notice, this list of conditions and the following disclaimer.
      9  * 2.  Redistributions in binary form must reproduce the above copyright
     10  *    notice, this list of conditions and the following disclaimer in the
     11  *    documentation and/or other materials provided with the distribution.
     12  *
     13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
     14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     15  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     16  * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
     17  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
     18  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     19  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
     20  * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     21  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
     22  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     23  */
     24 
     25 #include "config.h"
     26 
     27 #if ENABLE(WEB_AUDIO)
     28 
     29 #include "core/platform/audio/HRTFPanner.h"
     30 
     31 #include <algorithm>
     32 #include "core/platform/audio/AudioBus.h"
     33 #include "core/platform/audio/FFTConvolver.h"
     34 #include "core/platform/audio/HRTFDatabase.h"
     35 #include "wtf/MathExtras.h"
     36 #include "wtf/RefPtr.h"
     37 
     38 using namespace std;
     39 
     40 namespace WebCore {
     41 
     42 // The value of 2 milliseconds is larger than the largest delay which exists in any HRTFKernel from the default HRTFDatabase (0.0136 seconds).
     43 // We ASSERT the delay values used in process() with this value.
     44 const double MaxDelayTimeSeconds = 0.002;
     45 
     46 const int UninitializedAzimuth = -1;
     47 const unsigned RenderingQuantum = 128;
     48 
     49 HRTFPanner::HRTFPanner(float sampleRate, HRTFDatabaseLoader* databaseLoader)
     50     : Panner(PanningModelHRTF)
     51     , m_databaseLoader(databaseLoader)
     52     , m_sampleRate(sampleRate)
     53     , m_crossfadeSelection(CrossfadeSelection1)
     54     , m_azimuthIndex1(UninitializedAzimuth)
     55     , m_elevation1(0)
     56     , m_azimuthIndex2(UninitializedAzimuth)
     57     , m_elevation2(0)
     58     , m_crossfadeX(0)
     59     , m_crossfadeIncr(0)
     60     , m_convolverL1(fftSizeForSampleRate(sampleRate))
     61     , m_convolverR1(fftSizeForSampleRate(sampleRate))
     62     , m_convolverL2(fftSizeForSampleRate(sampleRate))
     63     , m_convolverR2(fftSizeForSampleRate(sampleRate))
     64     , m_delayLineL(MaxDelayTimeSeconds, sampleRate)
     65     , m_delayLineR(MaxDelayTimeSeconds, sampleRate)
     66     , m_tempL1(RenderingQuantum)
     67     , m_tempR1(RenderingQuantum)
     68     , m_tempL2(RenderingQuantum)
     69     , m_tempR2(RenderingQuantum)
     70 {
     71     ASSERT(databaseLoader);
     72 }
     73 
     74 HRTFPanner::~HRTFPanner()
     75 {
     76 }
     77 
     78 size_t HRTFPanner::fftSizeForSampleRate(float sampleRate)
     79 {
     80     // The HRTF impulse responses (loaded as audio resources) are 512 sample-frames @44.1KHz.
     81     // Currently, we truncate the impulse responses to half this size, but an FFT-size of twice impulse response size is needed (for convolution).
     82     // So for sample rates around 44.1KHz an FFT size of 512 is good. We double the FFT-size only for sample rates at least double this.
     83     ASSERT(sampleRate >= 44100 && sampleRate <= 96000.0);
     84     return (sampleRate < 88200.0) ? 512 : 1024;
     85 }
     86 
     87 void HRTFPanner::reset()
     88 {
     89     m_convolverL1.reset();
     90     m_convolverR1.reset();
     91     m_convolverL2.reset();
     92     m_convolverR2.reset();
     93     m_delayLineL.reset();
     94     m_delayLineR.reset();
     95 }
     96 
     97 int HRTFPanner::calculateDesiredAzimuthIndexAndBlend(double azimuth, double& azimuthBlend)
     98 {
     99     // Convert the azimuth angle from the range -180 -> +180 into the range 0 -> 360.
    100     // The azimuth index may then be calculated from this positive value.
    101     if (azimuth < 0)
    102         azimuth += 360.0;
    103 
    104     HRTFDatabase* database = m_databaseLoader->database();
    105     ASSERT(database);
    106 
    107     int numberOfAzimuths = database->numberOfAzimuths();
    108     const double angleBetweenAzimuths = 360.0 / numberOfAzimuths;
    109 
    110     // Calculate the azimuth index and the blend (0 -> 1) for interpolation.
    111     double desiredAzimuthIndexFloat = azimuth / angleBetweenAzimuths;
    112     int desiredAzimuthIndex = static_cast<int>(desiredAzimuthIndexFloat);
    113     azimuthBlend = desiredAzimuthIndexFloat - static_cast<double>(desiredAzimuthIndex);
    114 
    115     // We don't immediately start using this azimuth index, but instead approach this index from the last index we rendered at.
    116     // This minimizes the clicks and graininess for moving sources which occur otherwise.
    117     desiredAzimuthIndex = max(0, desiredAzimuthIndex);
    118     desiredAzimuthIndex = min(numberOfAzimuths - 1, desiredAzimuthIndex);
    119     return desiredAzimuthIndex;
    120 }
    121 
    122 void HRTFPanner::pan(double desiredAzimuth, double elevation, const AudioBus* inputBus, AudioBus* outputBus, size_t framesToProcess)
    123 {
    124     unsigned numInputChannels = inputBus ? inputBus->numberOfChannels() : 0;
    125 
    126     bool isInputGood = inputBus &&  numInputChannels >= 1 && numInputChannels <= 2;
    127     ASSERT(isInputGood);
    128 
    129     bool isOutputGood = outputBus && outputBus->numberOfChannels() == 2 && framesToProcess <= outputBus->length();
    130     ASSERT(isOutputGood);
    131 
    132     if (!isInputGood || !isOutputGood) {
    133         if (outputBus)
    134             outputBus->zero();
    135         return;
    136     }
    137 
    138     HRTFDatabase* database = m_databaseLoader->database();
    139     ASSERT(database);
    140     if (!database) {
    141         outputBus->zero();
    142         return;
    143     }
    144 
    145     // IRCAM HRTF azimuths values from the loaded database is reversed from the panner's notion of azimuth.
    146     double azimuth = -desiredAzimuth;
    147 
    148     bool isAzimuthGood = azimuth >= -180.0 && azimuth <= 180.0;
    149     ASSERT(isAzimuthGood);
    150     if (!isAzimuthGood) {
    151         outputBus->zero();
    152         return;
    153     }
    154 
    155     // Normally, we'll just be dealing with mono sources.
    156     // If we have a stereo input, implement stereo panning with left source processed by left HRTF, and right source by right HRTF.
    157     const AudioChannel* inputChannelL = inputBus->channelByType(AudioBus::ChannelLeft);
    158     const AudioChannel* inputChannelR = numInputChannels > 1 ? inputBus->channelByType(AudioBus::ChannelRight) : 0;
    159 
    160     // Get source and destination pointers.
    161     const float* sourceL = inputChannelL->data();
    162     const float* sourceR = numInputChannels > 1 ? inputChannelR->data() : sourceL;
    163     float* destinationL = outputBus->channelByType(AudioBus::ChannelLeft)->mutableData();
    164     float* destinationR = outputBus->channelByType(AudioBus::ChannelRight)->mutableData();
    165 
    166     double azimuthBlend;
    167     int desiredAzimuthIndex = calculateDesiredAzimuthIndexAndBlend(azimuth, azimuthBlend);
    168 
    169     // Initially snap azimuth and elevation values to first values encountered.
    170     if (m_azimuthIndex1 == UninitializedAzimuth) {
    171         m_azimuthIndex1 = desiredAzimuthIndex;
    172         m_elevation1 = elevation;
    173     }
    174     if (m_azimuthIndex2 == UninitializedAzimuth) {
    175         m_azimuthIndex2 = desiredAzimuthIndex;
    176         m_elevation2 = elevation;
    177     }
    178 
    179     // Cross-fade / transition over a period of around 45 milliseconds.
    180     // This is an empirical value tuned to be a reasonable trade-off between
    181     // smoothness and speed.
    182     const double fadeFrames = sampleRate() <= 48000 ? 2048 : 4096;
    183 
    184     // Check for azimuth and elevation changes, initiating a cross-fade if needed.
    185     if (!m_crossfadeX && m_crossfadeSelection == CrossfadeSelection1) {
    186         if (desiredAzimuthIndex != m_azimuthIndex1 || elevation != m_elevation1) {
    187             // Cross-fade from 1 -> 2
    188             m_crossfadeIncr = 1 / fadeFrames;
    189             m_azimuthIndex2 = desiredAzimuthIndex;
    190             m_elevation2 = elevation;
    191         }
    192     }
    193     if (m_crossfadeX == 1 && m_crossfadeSelection == CrossfadeSelection2) {
    194         if (desiredAzimuthIndex != m_azimuthIndex2 || elevation != m_elevation2) {
    195             // Cross-fade from 2 -> 1
    196             m_crossfadeIncr = -1 / fadeFrames;
    197             m_azimuthIndex1 = desiredAzimuthIndex;
    198             m_elevation1 = elevation;
    199         }
    200     }
    201 
    202     // This algorithm currently requires that we process in power-of-two size chunks at least RenderingQuantum.
    203     ASSERT(1UL << static_cast<int>(log2(framesToProcess)) == framesToProcess);
    204     ASSERT(framesToProcess >= RenderingQuantum);
    205 
    206     const unsigned framesPerSegment = RenderingQuantum;
    207     const unsigned numberOfSegments = framesToProcess / framesPerSegment;
    208 
    209     for (unsigned segment = 0; segment < numberOfSegments; ++segment) {
    210         // Get the HRTFKernels and interpolated delays.
    211         HRTFKernel* kernelL1;
    212         HRTFKernel* kernelR1;
    213         HRTFKernel* kernelL2;
    214         HRTFKernel* kernelR2;
    215         double frameDelayL1;
    216         double frameDelayR1;
    217         double frameDelayL2;
    218         double frameDelayR2;
    219         database->getKernelsFromAzimuthElevation(azimuthBlend, m_azimuthIndex1, m_elevation1, kernelL1, kernelR1, frameDelayL1, frameDelayR1);
    220         database->getKernelsFromAzimuthElevation(azimuthBlend, m_azimuthIndex2, m_elevation2, kernelL2, kernelR2, frameDelayL2, frameDelayR2);
    221 
    222         bool areKernelsGood = kernelL1 && kernelR1 && kernelL2 && kernelR2;
    223         ASSERT(areKernelsGood);
    224         if (!areKernelsGood) {
    225             outputBus->zero();
    226             return;
    227         }
    228 
    229         ASSERT(frameDelayL1 / sampleRate() < MaxDelayTimeSeconds && frameDelayR1 / sampleRate() < MaxDelayTimeSeconds);
    230         ASSERT(frameDelayL2 / sampleRate() < MaxDelayTimeSeconds && frameDelayR2 / sampleRate() < MaxDelayTimeSeconds);
    231 
    232         // Crossfade inter-aural delays based on transitions.
    233         double frameDelayL = (1 - m_crossfadeX) * frameDelayL1 + m_crossfadeX * frameDelayL2;
    234         double frameDelayR = (1 - m_crossfadeX) * frameDelayR1 + m_crossfadeX * frameDelayR2;
    235 
    236         // Calculate the source and destination pointers for the current segment.
    237         unsigned offset = segment * framesPerSegment;
    238         const float* segmentSourceL = sourceL + offset;
    239         const float* segmentSourceR = sourceR + offset;
    240         float* segmentDestinationL = destinationL + offset;
    241         float* segmentDestinationR = destinationR + offset;
    242 
    243         // First run through delay lines for inter-aural time difference.
    244         m_delayLineL.setDelayFrames(frameDelayL);
    245         m_delayLineR.setDelayFrames(frameDelayR);
    246         m_delayLineL.process(segmentSourceL, segmentDestinationL, framesPerSegment);
    247         m_delayLineR.process(segmentSourceR, segmentDestinationR, framesPerSegment);
    248 
    249         bool needsCrossfading = m_crossfadeIncr;
    250 
    251         // Have the convolvers render directly to the final destination if we're not cross-fading.
    252         float* convolutionDestinationL1 = needsCrossfading ? m_tempL1.data() : segmentDestinationL;
    253         float* convolutionDestinationR1 = needsCrossfading ? m_tempR1.data() : segmentDestinationR;
    254         float* convolutionDestinationL2 = needsCrossfading ? m_tempL2.data() : segmentDestinationL;
    255         float* convolutionDestinationR2 = needsCrossfading ? m_tempR2.data() : segmentDestinationR;
    256 
    257         // Now do the convolutions.
    258         // Note that we avoid doing convolutions on both sets of convolvers if we're not currently cross-fading.
    259 
    260         if (m_crossfadeSelection == CrossfadeSelection1 || needsCrossfading) {
    261             m_convolverL1.process(kernelL1->fftFrame(), segmentDestinationL, convolutionDestinationL1, framesPerSegment);
    262             m_convolverR1.process(kernelR1->fftFrame(), segmentDestinationR, convolutionDestinationR1, framesPerSegment);
    263         }
    264 
    265         if (m_crossfadeSelection == CrossfadeSelection2 || needsCrossfading) {
    266             m_convolverL2.process(kernelL2->fftFrame(), segmentDestinationL, convolutionDestinationL2, framesPerSegment);
    267             m_convolverR2.process(kernelR2->fftFrame(), segmentDestinationR, convolutionDestinationR2, framesPerSegment);
    268         }
    269 
    270         if (needsCrossfading) {
    271             // Apply linear cross-fade.
    272             float x = m_crossfadeX;
    273             float incr = m_crossfadeIncr;
    274             for (unsigned i = 0; i < framesPerSegment; ++i) {
    275                 segmentDestinationL[i] = (1 - x) * convolutionDestinationL1[i] + x * convolutionDestinationL2[i];
    276                 segmentDestinationR[i] = (1 - x) * convolutionDestinationR1[i] + x * convolutionDestinationR2[i];
    277                 x += incr;
    278             }
    279             // Update cross-fade value from local.
    280             m_crossfadeX = x;
    281 
    282             if (m_crossfadeIncr > 0 && fabs(m_crossfadeX - 1) < m_crossfadeIncr) {
    283                 // We've fully made the crossfade transition from 1 -> 2.
    284                 m_crossfadeSelection = CrossfadeSelection2;
    285                 m_crossfadeX = 1;
    286                 m_crossfadeIncr = 0;
    287             } else if (m_crossfadeIncr < 0 && fabs(m_crossfadeX) < -m_crossfadeIncr) {
    288                 // We've fully made the crossfade transition from 2 -> 1.
    289                 m_crossfadeSelection = CrossfadeSelection1;
    290                 m_crossfadeX = 0;
    291                 m_crossfadeIncr = 0;
    292             }
    293         }
    294     }
    295 }
    296 
    297 double HRTFPanner::tailTime() const
    298 {
    299     // Because HRTFPanner is implemented with a DelayKernel and a FFTConvolver, the tailTime of the HRTFPanner
    300     // is the sum of the tailTime of the DelayKernel and the tailTime of the FFTConvolver, which is MaxDelayTimeSeconds
    301     // and fftSize() / 2, respectively.
    302     return MaxDelayTimeSeconds + (fftSize() / 2) / static_cast<double>(sampleRate());
    303 }
    304 
    305 double HRTFPanner::latencyTime() const
    306 {
    307     // The latency of a FFTConvolver is also fftSize() / 2, and is in addition to its tailTime of the
    308     // same value.
    309     return (fftSize() / 2) / static_cast<double>(sampleRate());
    310 }
    311 
    312 } // namespace WebCore
    313 
    314 #endif // ENABLE(WEB_AUDIO)
    315