BlipBuffer.hh

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// Heavily based on:
//
// Band-limited sound synthesis and buffering
// Blip_Buffer 0.4.0
// http://www.slack.net/~ant/
 
#ifndef BLIPBUFFER_HH
#define BLIPBUFFER_HH
 
#include "FixedPoint.hh"
#include <array>
 
namespace openmsx {
 
class BlipBuffer
{
public:
        // Number of bits in phase offset. Fewer than 6 bits (64 phase offsets) results
        // in noticeable broadband noise when synthesizing high frequency square waves.
        static constexpr int BLIP_PHASE_BITS = 10;
 
        using TimeIndex = FixedPoint<BLIP_PHASE_BITS>;
 
        BlipBuffer();
 
        // Update amplitude of waveform at given time. Time is in output sample
        // units and since the last time readSamples() was called.
        void addDelta(TimeIndex time, float delta);
 
        // Read the given amount of samples into destination buffer.
        template<size_t PITCH>
        bool readSamples(float* out, size_t samples);
 
private:
        template<size_t PITCH>
        void readSamplesHelper(float* out, size_t samples);
 
private:
        static constexpr size_t BUFFER_SIZE = 1 << 14;
        static constexpr size_t BUFFER_MASK = BUFFER_SIZE - 1;
        std::array<float, BUFFER_SIZE> buffer;
        size_t offset = 0;
        ptrdiff_t availSamp = 0;
        float accum = 0.0f;
};
 
} // namespace openmsx
 
#endif