hart_nyquist_signal.hpp

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#pragma once
 
#include <cmath>
#include <memory>
 
#include "hart_exceptions.hpp"
#include "hart_precision.hpp"
#include "signals/hart_signal.hpp"
#include "hart_utils.hpp"
 
namespace hart
{
 
/// @brief Produces a Nyquist signal
/// @details Regardless of sample rate, outputs an alternating squence like:
/// {+1, -1, +1, -1, +1, ...} at 0 dB sample peak.
/// @ingroup Signals
template<typename SampleType>
class NyquistSignal:
    public Signal<SampleType, NyquistSignal<SampleType>>
{
public:
    NyquistSignal() = default;
    bool supportsNumChannels (size_t /* numChannels */) const override { return true; };
    void prepare (double /* sampleRateHz */, size_t /* numOutputChannels */, size_t /*maxBlockSizeFrames*/) override {}
 
    void renderNextBlock (AudioBuffer<SampleType>& output) override
    {
        hassert (output.getNumChannels() >= 1);
        const size_t numFrames = output.getNumFrames();
 
        for (size_t channel = 0; channel < output.getNumChannels(); ++channel)
        {
            SampleType* channelData = output[channel];
 
            const SampleType evenFrameValues = m_nextBlockStartValue;
            const SampleType oddFrameValues = -m_nextBlockStartValue;
 
            for (size_t frame = 0; frame < numFrames; frame += 2)
                channelData[frame] = evenFrameValues;
 
            for (size_t frame = 1; frame < numFrames; frame += 2)
                channelData[frame] = oddFrameValues;
        }
 
        if (numFrames % 2 != 0)
            m_nextBlockStartValue = -m_nextBlockStartValue;
    }
 
    void reset() override
    {
        m_nextBlockStartValue = 1.0;
    }
 
    HART_DEFINE_GENERIC_REPRESENT (NyquistSignal);
 
private:
    SampleType m_nextBlockStartValue = 1.0;
};
 
HART_SIGNAL_DECLARE_ALIASES_FOR (NyquistSignal)
 
}  // namespace hart