iphone - Cocoa Touch 中的音调生成

Question

我需要生成一种可以控制频率和波形的音调。总体目标是创造一架基本的钢琴。有谁知道我怎样才能做到这一点？

我的开发平台是 iPhone 2.x

Answer 1

您总是可以从 sin 波开始。 :-)

#include <cmath>

typedef double Sample;
typedef double Time;

class MonoNote {
protected:
    Time start, duration;
    virtual void internalRender(double now, Sample *mono) = 0;
public:
    MonoNote(Time s, Time d) : start(s), duration(d) {}
    virtual ~MonoNote() {}
    void render(double now, Sample *mono) {
        if (start <= now && now < start + duration) {
            internalRender(now, mono);
        }
    }
};

class MonoSinNote : public MonoNote {
    Time freq;
    Sample amplitude;
protected:
    void internalRender(double now, Sample *mono) {
        const double v = sin(2*M_PI*(now - start) * freq);
        *mono += amplitude*v;
    }
public:
    MonoSinNote(Time s, Time d, Time f, Sample a) : MonoNote(s, d), freq(f), amplitude(a) {}
    ~MonoSinNote() {}
};