Method setCoefficients

examples/sound_effects/SoundEffects.cpp:742–801

    using Processing::Processing;

    void setCoefficients(const Coefficients& coefficients)
    {
        auto& music = getMusic();

        struct State
        {
            float xnz1{};
            float xnz2{};
            float ynz1{};
            float ynz2{};
        };

        // We use a mutable lambda to tie the lifetime of the state and coefficients to the lambda itself
        // This is necessary since the Echo object will be destroyed before the Music object
        // While the Music object exists, it is possible that the audio engine will try to call
        // this lambda hence we need to always have usable coefficients and state until the Music and the
        // associated lambda are destroyed
        music.setEffectProcessor(
            [coefficients,
             enabled = getEnabled(),
             state   = std::vector<State>()](const float*  inputFrames,
                                           unsigned int& inputFrameCount,
                                           float*        outputFrames,
                                           unsigned int& outputFrameCount,
                                           unsigned int  frameChannelCount) mutable
            {
                // IMPORTANT: The channel count of the audio engine currently sourcing data from this sound
                // will always be provided in frameChannelCount, this can be different from the channel count
                // of the audio source so make sure to size your buffers according to the engine and not the source
                // Ensure we have as many state objects as the audio engine has channels
                if (state.size() < frameChannelCount)
                    state.resize(frameChannelCount - state.size());

                for (auto frame = 0u; frame < outputFrameCount; ++frame)
                {
                    for (auto channel = 0u; channel < frameChannelCount; ++channel)
                    {
                        auto& channelState = state[channel];

                        const auto xn = inputFrames ? inputFrames[channel] : 0.f; // Read silence if no input data available
                        const auto yn = coefficients.a0 * xn + coefficients.a1 * channelState.xnz1 +
                                        coefficients.a2 * channelState.xnz2 - coefficients.b1 * channelState.ynz1 -
                                        coefficients.b2 * channelState.ynz2;

                        channelState.xnz2 = channelState.xnz1;
                        channelState.xnz1 = xn;
                        channelState.ynz2 = channelState.ynz1;
                        channelState.ynz1 = yn;

                        outputFrames[channel] = *enabled ? yn : xn;
                    }

                    inputFrames += (inputFrames ? frameChannelCount : 0u);
                    outputFrames += frameChannelCount;
                }

                // We processed data 1:1
                inputFrameCount = outputFrameCount;