objective c - How to play a signal with AudioUnit (iOS)? -

i need generate signal , play iphone's speakers or headset.

to generate interleaved signal. need instantiate audiounit inherited class object next info: 2 channels, 44100 khz sample rate, buffer size store few frames.

then need write callback method take chink of signal , pit iphone's output buffer.

the problem have no idea how write audiounit inherited class. can't understand apple's documentation regarding it, , examples find either read file , play huge lag or use depricated constructions.

i start think stupid or something. please, help...

to play audio iphone's hardware audiounit, don't derive audiounit coreaudio c framework - instead give render callback in feed unit audio samples. following code sample shows how. need replace asserts real error handling , you'll want change or @ least inspect audio unit's sample format using kaudiounitproperty_streamformat selector. format happens 48khz floating point interleaved stereo.

static osstatus rendercallback(                void* inrefcon,                audiounitrenderactionflags* ioactionflags,                const audiotimestamp* intimestamp,                uint32 inbusnumber,                uint32 innumberframes,                audiobufferlist* iodata) {     // inrefcon contains cookie      // write innumberframes iodata->mbuffers[i].mdata here      return noerr; }  audiounit createaudiounit() {     audiounit   au;     osstatus err;      audiocomponentdescription desc;     desc.componenttype = kaudiounittype_output;     desc.componentsubtype = kaudiounitsubtype_remoteio;     desc.componentmanufacturer = kaudiounitmanufacturer_apple;     desc.componentflags = 0;     desc.componentflagsmask = 0;      audiocomponent comp = audiocomponentfindnext(null, &desc);     assert(0 != comp);      err = audiocomponentinstancenew(comp, &au);     assert(0 == err);       aurendercallbackstruct input;     input.inputproc = rendercallback;     input.inputprocrefcon = 0;  // put cookie here      err = audiounitsetproperty(au, kaudiounitproperty_setrendercallback, kaudiounitscope_input, 0, &input, sizeof(input));     assert(0 == err);      err = audiounitinitialize(au);     assert(0 == err);      err = audiooutputunitstart(au);     assert(0 == err);      return au; }