gecko/content/media/webaudio/blink/HRTFElevation.cpp

/*
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#include "HRTFElevation.h"

#include "speex/speex_resampler.h"
#include "mozilla/PodOperations.h"
#include "AudioSampleFormat.h"

#include "IRC_Composite_C_R0195-incl.cpp"

using namespace std;
using namespace mozilla;
 
namespace WebCore {

const int elevationSpacing = irc_composite_c_r0195_elevation_interval;
const int firstElevation = irc_composite_c_r0195_first_elevation;
const int numberOfElevations = MOZ_ARRAY_LENGTH(irc_composite_c_r0195);

const unsigned HRTFElevation::NumberOfTotalAzimuths = 360 / 15 * 8;

const int rawSampleRate = irc_composite_c_r0195_sample_rate;

// Number of frames in an individual impulse response.
const size_t ResponseFrameSize = 256;

size_t HRTFElevation::fftSizeForSampleRate(float sampleRate)
{
    // The IRCAM HRTF impulse responses were 512 sample-frames @44.1KHz,
    // but these have been truncated to 256 samples.
    // An FFT-size of twice impulse response size is used (for convolution).
    // So for sample rates of 44.1KHz an FFT size of 512 is good.
    // We double the FFT-size only for sample rates at least double this.
    // If the FFT size is too large then the impulse response will be padded
    // with zeros without the fade-out provided by HRTFKernel.
    MOZ_ASSERT(sampleRate > 1.0 && sampleRate < 1048576.0);

    // This is the size if we were to use all raw response samples.
    unsigned resampledLength =
        floorf(ResponseFrameSize * sampleRate / rawSampleRate);
    // Keep things semi-sane, with max FFT size of 1024 and minimum of 4.
    // "size |= 3" ensures a minimum of 4 (with the size++ below) and sets the
    // 2 least significant bits for rounding up to the next power of 2 below.
    unsigned size = min(resampledLength, 1023U);
    size |= 3;
    // Round up to the next power of 2, making the FFT size no more than twice
    // the impulse response length.  This doubles size for values that are
    // already powers of 2.  This works by filling in 7 bits to right of the
    // most significant bit.  The most significant bit is no greater than
    // 1 << 9, and the least significant 2 bits were already set above.
    size |= (size >> 1);
    size |= (size >> 2);
    size |= (size >> 4);
    size++;
    MOZ_ASSERT((size & (size - 1)) == 0);

    return size;
}

nsReturnRef<HRTFKernel> HRTFElevation::calculateKernelForAzimuthElevation(int azimuth, int elevation, SpeexResamplerState* resampler, float sampleRate)
{
    int elevationIndex = (elevation - firstElevation) / elevationSpacing;
    MOZ_ASSERT(elevationIndex >= 0 && elevationIndex <= numberOfElevations);

    int numberOfAzimuths = irc_composite_c_r0195[elevationIndex].count;
    int azimuthSpacing = 360 / numberOfAzimuths;
    MOZ_ASSERT(numberOfAzimuths * azimuthSpacing == 360);

    int azimuthIndex = azimuth / azimuthSpacing;
    MOZ_ASSERT(azimuthIndex * azimuthSpacing == azimuth);

    const int16_t (&impulse_response_data)[ResponseFrameSize] =
        irc_composite_c_r0195[elevationIndex].azimuths[azimuthIndex];

    // When libspeex_resampler is compiled with FIXED_POINT, samples in
    // speex_resampler_process_float are rounded directly to int16_t, which
    // only works well if the floats are in the range +/-32767.  On such
    // platforms it's better to resample before converting to float anyway.
#ifdef MOZ_SAMPLE_TYPE_S16
#  define RESAMPLER_PROCESS speex_resampler_process_int
    const int16_t* response = impulse_response_data;
    const int16_t* resampledResponse;
#else
#  define RESAMPLER_PROCESS speex_resampler_process_float
    float response[ResponseFrameSize];
    ConvertAudioSamples(impulse_response_data, response, ResponseFrameSize);
    float* resampledResponse;
#endif

    // Note that depending on the fftSize returned by the panner, we may be truncating the impulse response.
    const size_t resampledResponseLength = fftSizeForSampleRate(sampleRate) / 2;

    nsAutoTArray<AudioDataValue, 2 * ResponseFrameSize> resampled;
    if (sampleRate == rawSampleRate) {
        resampledResponse = response;
        MOZ_ASSERT(resampledResponseLength == ResponseFrameSize);
    } else {
        resampled.SetLength(resampledResponseLength);
        resampledResponse = resampled.Elements();
        speex_resampler_skip_zeros(resampler);

        // Feed the input buffer into the resampler.
        spx_uint32_t in_len = ResponseFrameSize;
        spx_uint32_t out_len = resampled.Length();
        RESAMPLER_PROCESS(resampler, 0, response, &in_len,
                          resampled.Elements(), &out_len);

        if (out_len < resampled.Length()) {
            // The input should have all been processed.
            MOZ_ASSERT(in_len == ResponseFrameSize);
            // Feed in zeros get the data remaining in the resampler.
            spx_uint32_t out_index = out_len;
            in_len = speex_resampler_get_input_latency(resampler);
            out_len = resampled.Length() - out_index;
            RESAMPLER_PROCESS(resampler, 0, nullptr, &in_len,
                              resampled.Elements() + out_index, &out_len);
            out_index += out_len;
            // There may be some uninitialized samples remaining for very low
            // sample rates.
            PodZero(resampled.Elements() + out_index,
                    resampled.Length() - out_index);
        }

        speex_resampler_reset_mem(resampler);
    }

#ifdef MOZ_SAMPLE_TYPE_S16
    nsAutoTArray<float, 2 * ResponseFrameSize> floatArray;
    floatArray.SetLength(resampledResponseLength);
    float *floatResponse = floatArray.Elements();
    ConvertAudioSamples(resampledResponse,
                        floatResponse, resampledResponseLength);
#else
    float *floatResponse = resampledResponse;
#endif
#undef RESAMPLER_PROCESS

    return HRTFKernel::create(floatResponse, resampledResponseLength, sampleRate);
}

// The range of elevations for the IRCAM impulse responses varies depending on azimuth, but the minimum elevation appears to always be -45.
//
// Here's how it goes:
static int maxElevations[] = {
        //  Azimuth
        //
    90, // 0  
    45, // 15 
    60, // 30 
    45, // 45 
    75, // 60 
    45, // 75 
    60, // 90 
    45, // 105 
    75, // 120 
    45, // 135 
    60, // 150 
    45, // 165 
    75, // 180 
    45, // 195 
    60, // 210 
    45, // 225 
    75, // 240 
    45, // 255 
    60, // 270 
    45, // 285 
    75, // 300 
    45, // 315 
    60, // 330 
    45 //  345 
};

nsReturnRef<HRTFElevation> HRTFElevation::createBuiltin(int elevation, float sampleRate)
{
    if (elevation < firstElevation ||
        elevation > firstElevation + numberOfElevations * elevationSpacing ||
        (elevation / elevationSpacing) * elevationSpacing != elevation)
        return nsReturnRef<HRTFElevation>();
        
    // Spacing, in degrees, between every azimuth loaded from resource.
    // Some elevations do not have data for all these intervals.
    // See maxElevations.
    static const unsigned AzimuthSpacing = 15;
    static const unsigned NumberOfRawAzimuths = 360 / AzimuthSpacing;
    static_assert(AzimuthSpacing * NumberOfRawAzimuths == 360,
                  "Not a multiple");
    static const unsigned InterpolationFactor =
        NumberOfTotalAzimuths / NumberOfRawAzimuths;
    static_assert(NumberOfTotalAzimuths ==
                  NumberOfRawAzimuths * InterpolationFactor, "Not a multiple");

    HRTFKernelList kernelListL;
    kernelListL.SetLength(NumberOfTotalAzimuths);

    SpeexResamplerState* resampler = sampleRate == rawSampleRate ? nullptr :
        speex_resampler_init(1, rawSampleRate, sampleRate,
                             SPEEX_RESAMPLER_QUALITY_DEFAULT, nullptr);

    // Load convolution kernels from HRTF files.
    int interpolatedIndex = 0;
    for (unsigned rawIndex = 0; rawIndex < NumberOfRawAzimuths; ++rawIndex) {
        // Don't let elevation exceed maximum for this azimuth.
        int maxElevation = maxElevations[rawIndex];
        int actualElevation = min(elevation, maxElevation);

        kernelListL[interpolatedIndex] = calculateKernelForAzimuthElevation(rawIndex * AzimuthSpacing, actualElevation, resampler, sampleRate);
            
        interpolatedIndex += InterpolationFactor;
    }

    if (resampler)
        speex_resampler_destroy(resampler);

    // Now go back and interpolate intermediate azimuth values.
    for (unsigned i = 0; i < NumberOfTotalAzimuths; i += InterpolationFactor) {
        int j = (i + InterpolationFactor) % NumberOfTotalAzimuths;

        // Create the interpolated convolution kernels and delays.
        for (unsigned jj = 1; jj < InterpolationFactor; ++jj) {
            float x = float(jj) / float(InterpolationFactor); // interpolate from 0 -> 1

            kernelListL[i + jj] = HRTFKernel::createInterpolatedKernel(kernelListL[i], kernelListL[j], x);
        }
    }
    
    return nsReturnRef<HRTFElevation>(new HRTFElevation(&kernelListL, elevation, sampleRate));
}

nsReturnRef<HRTFElevation> HRTFElevation::createByInterpolatingSlices(HRTFElevation* hrtfElevation1, HRTFElevation* hrtfElevation2, float x, float sampleRate)
{
    MOZ_ASSERT(hrtfElevation1 && hrtfElevation2);
    if (!hrtfElevation1 || !hrtfElevation2)
        return nsReturnRef<HRTFElevation>();
        
    MOZ_ASSERT(x >= 0.0 && x < 1.0);
    
    HRTFKernelList kernelListL;
    kernelListL.SetLength(NumberOfTotalAzimuths);

    const HRTFKernelList& kernelListL1 = hrtfElevation1->kernelListL();
    const HRTFKernelList& kernelListL2 = hrtfElevation2->kernelListL();
    
    // Interpolate kernels of corresponding azimuths of the two elevations.
    for (unsigned i = 0; i < NumberOfTotalAzimuths; ++i) {
        kernelListL[i] = HRTFKernel::createInterpolatedKernel(kernelListL1[i], kernelListL2[i], x);
    }

    // Interpolate elevation angle.
    double angle = (1.0 - x) * hrtfElevation1->elevationAngle() + x * hrtfElevation2->elevationAngle();
    
    return nsReturnRef<HRTFElevation>(new HRTFElevation(&kernelListL, static_cast<int>(angle), sampleRate));
}

void HRTFElevation::getKernelsFromAzimuth(double azimuthBlend, unsigned azimuthIndex, HRTFKernel* &kernelL, HRTFKernel* &kernelR, double& frameDelayL, double& frameDelayR)
{
    bool checkAzimuthBlend = azimuthBlend >= 0.0 && azimuthBlend < 1.0;
    MOZ_ASSERT(checkAzimuthBlend);
    if (!checkAzimuthBlend)
        azimuthBlend = 0.0;
    
    unsigned numKernels = m_kernelListL.Length();

    bool isIndexGood = azimuthIndex < numKernels;
    MOZ_ASSERT(isIndexGood);
    if (!isIndexGood) {
        kernelL = 0;
        kernelR = 0;
        return;
    }
    
    // Return the left and right kernels,
    // using symmetry to produce the right kernel.
    kernelL = m_kernelListL[azimuthIndex];
    int azimuthIndexR = (numKernels - azimuthIndex) % numKernels;
    kernelR = m_kernelListL[azimuthIndexR];

    frameDelayL = kernelL->frameDelay();
    frameDelayR = kernelR->frameDelay();

    int azimuthIndex2L = (azimuthIndex + 1) % numKernels;
    double frameDelay2L = m_kernelListL[azimuthIndex2L]->frameDelay();
    int azimuthIndex2R = (numKernels - azimuthIndex2L) % numKernels;
    double frameDelay2R = m_kernelListL[azimuthIndex2R]->frameDelay();

    // Linearly interpolate delays.
    frameDelayL = (1.0 - azimuthBlend) * frameDelayL + azimuthBlend * frameDelay2L;
    frameDelayR = (1.0 - azimuthBlend) * frameDelayR + azimuthBlend * frameDelay2R;
}

} // namespace WebCore