objective c - AUHAL with USB audio device -

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i've got usb audio device (presonus audiobox) , want able switch audio output of program between usb device , default output device (the internal speakers). apple documentation tells me have use auhal:

if need connect [..] hardware device other default output device, need use auhal.

source

normally, make device description , if exists. wrote function test this:

-(osstatus) showauhaldevices {     //show available auhal devices     // create description     audiocomponentdescription test_desc;     test_desc.componenttype = kaudiounittype_output;     test_desc.componentsubtype = kaudiounitsubtype_haloutput;     test_desc.componentmanufacturer = kaudiounitmanufacturer_apple;     test_desc.componentflags = 0;     test_desc.componentflagsmask = 0;      // determine number of available components     uint32 count = audiocomponentcount(&test_desc);      // print result     osstatus err = noerr;     cfstringref compname;     audiocomponent test_comp;      (uint32 = 0; < count; i++)     {         test_comp = audiocomponentfindnext(nil, &test_desc);         err = audiocomponentcopyname(test_comp, &compname);         nslog(@"audio component number %u/%u: %@", (i+1), count, compname);     }      return err; }

the problem here cannot set test_desc.componentmanufacturer = kaudiounitmanufacturer_apple; manufacturer apple, usb device doesn't show in list printed in log.

what missing? , far know, not driver issue.

thanks in advance.

edit

i've set properties zero, usb device still doesn't show between 98 different components. can find [avcapturedevice deviceswithmediatype:avmediatypeaudio] though, can set input, not output..

componentmanufacture can set 0 treat wildcard (as can componenttype , componentsubtype).

//show available auhal devices // create description audiocomponentdescription test_desc; test_desc.componenttype = kaudiounittype_output; test_desc.componentsubtype = kaudiounitsubtype_haloutput; test_desc.componentmanufacturer = 0; test_desc.componentflags = 0; test_desc.componentflagsmask = 0;

additionally, usage of audiocomponentfindnext wrong in how pass nil first parameter. first parameter should component wish begin search from. pass nil first time , result of first call second time , on.

audiocomponent test_comp = nullptr;  (uint32 = 0; < count; i++) {     test_comp = audiocomponentfindnext(test_comp, &test_desc);     ... }

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