Method handleFreqBins

lib/SoundReactivePlugin/src/SoundReactivePlugin.cpp:341–448

}

void SoundReactivePlugin::handleFreqBins(float* freqBins, size_t freqBinLen)
{
    float    octaveFreqBands[MAX_FREQ_BANDS];
    uint16_t freqBinIdx = 0U;
    float    peak       = 0.0F;
    float    avgDigital = 0.0F;
    uint8_t  bandIdx    = 0U;

    convertToOctaveFreqBands(octaveFreqBands, MAX_FREQ_BANDS, freqBins, freqBinLen);
    avgDigital = calculateAmplitudeAverage(octaveFreqBands, MAX_FREQ_BANDS);

    for (bandIdx = 0U; bandIdx < MAX_FREQ_BANDS; ++bandIdx)
    {
        /* If the ampltiude average is lower than the equivalent input noise (from datasheet),
         * the correction factors will be calculated. The amplitude average is used to detect
         * silence, which is necessary for this automatic calibration.
         */
        if (INMP441_NOISE_FLOOR_DIGITAL > static_cast<int32_t>(avgDigital))
        {
            constexpr const float WEIGHT_NEW_VALUE = 0.1F;
            constexpr const float WEIGHT_OLD_VALUE = 1.0F - WEIGHT_NEW_VALUE;
            constexpr const float NOISE_FLOOR      = static_cast<float>(INMP441_NOISE_FLOOR_DIGITAL);

            /* Calculate with weighted average to avoid jumping. */
            m_corrFactors[bandIdx]                 = WEIGHT_OLD_VALUE * m_corrFactors[bandIdx] + WEIGHT_NEW_VALUE * (NOISE_FLOOR / octaveFreqBands[bandIdx]);
        }

        /* Normalize */
        octaveFreqBands[bandIdx] *= m_corrFactors[bandIdx];

        /* Calculate the spectrum amplitude in dB SPL
         * The shown frequency spectrum amplitudes consider now the silent and loud parts better.
         *
         * = sensitivity [dB SPL] + 20 * log10(frequency amplitude digital / sensitivity digital)
         */
        octaveFreqBands[bandIdx]  = INMP441_SENSITIVITY_SPL + 20.0F * log10f(octaveFreqBands[bandIdx] / static_cast<float>(IMMP441_SENSITIVITY_DIGITAL));

        /* The amplitude shall consider only the dynamic range
         * by removing the equivalent input noise level.
         */
        if (INMP441_NOISE_SPL >= octaveFreqBands[bandIdx])
        {
            octaveFreqBands[bandIdx] = HEARING_THRESHOLD;
        }
        else
        {
            octaveFreqBands[bandIdx] -= INMP441_NOISE_SPL;
        }

        /* Determine peak over all frequency bands for automatic gain control. */
        if (octaveFreqBands[bandIdx] > peak)
        {
            peak = octaveFreqBands[bandIdx];
        }
    }

    /* Adapt the dynamic range on the y-axis, but limit it to a minimum,
     * otherwise the bar's will jump driven by silent tones.