CODEWITHSUNDEEP
iphoneobjective-ccore-audiosignal-processingpiano
amccloud
amccloud

Reputation: 91

Tone Generation in Cocoa Touch

I need to generate a tone that I can manipulate frequency and wave. The overall goal is to create a basic piano. Does anyone know how I can achieve this?

My development platform is the iPhone 2.x

Upvotes: 9

Views: 7137

Answers (6)

face
face

Reputation: 46

Check out Mobilesynth...an open source synthesizer in the app store: http://code.google.com/p/mobilesynth/

Upvotes: 3

Peter N Lewis
Peter N Lewis

Reputation: 17811

Check out the DefaultOutputUnit sample code which plays a sine wave.

/Developer/Examples/CoreAudio/SimpleSDK/DefaultOutputUnit

Upvotes: 2

Nosredna
Nosredna

Reputation: 86206

Piano is strange. Robert Moog wrote about it in Keyboard Magazine in March 1980. The fundamental (lowest frequency partial) is in tune, but each higher harmonic is brighter (or "sharper" or higher-pitched) than it should be, and by an increasing amount.

The second through ninth harmonics are louder than the fundamental. The tenth through twentieth are about as loud.

The fundamental swells up in volume and then dives, then it comes back. The other partials have characteristic up and down shapes. The partials exchange energy so the overall volume acts as you would expect. Buts it's a swarm of partials trading energy. I'd guess if you got the lowest few right and the weird inharmonic spread right you'd do OK.

You could watch the action in a software spectrum analyzer and learn what you need to know. Additive synthesis is probably how I'd take on the problem.

Upvotes: 7

Alex Reynolds
Alex Reynolds

Reputation: 96937

Apple Developer Forums has a thread on this ("Audio Synthesis") that might provide some insight.

Upvotes: 2

Frank Krueger
Frank Krueger

Reputation: 70983

You could always start with sin waves. :-)

#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() {}
};

Upvotes: 7

Roland Rabien
Roland Rabien

Reputation: 8836

Check out http://mda.smartelectronix.com/. They are a series of open source VST plugins. Look at the source for Piano, ePiano or DX10. It's about as simple as you are going to find.

Upvotes: 2

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