Trying to setup an audio unit graph with a buffer of samples as the input -

i trying implement simple audio unit graph goes:

buffer of samples->low pass filter->generic output

where generic output copied new buffer processed further, saved disk, etc.

all of examples can find online having setting audio unit graph involve using generator kaudiounitsubtype_audiofileplayer input source... dealing buffer of samples acquired, examples not help... based on looking around in audiounitproperties.h file, looks should using using kaudiounitsubtype_scheduledsoundplayer?

i can't seem documentation on how hook up, quite stuck , hoping here can me out.

to simplify things, started out trying buffer of samples go straight system output, unable make work...

  #import "effectmachine.h"   #import <audiotoolbox/audiotoolbox.h>   #import "audiohelpers.h"   #import "buffer.h"    @interface effectmachine ()   @property (nonatomic, strong) buffer *buffer;   @end    typedef struct effectmachinegraph {       augraph   graph;       audiounit input;       audiounit lowpass;       audiounit output;   } effectmachinegraph;    @implementation effectmachine {       effectmachinegraph machine;   }    -(instancetype)initwithbuffer:(buffer *)buffer {       if (self = [super init]) {           self.buffer = buffer;            // buffer simple wrapper object holds 2 properties:           // pointer array of samples (as doubles) , size (number of samples)        }       return self;   }    -(void)process {       struct effectmachinegraph initialized = {0};       machine = initialized;        checkerror(newaugraph(&machine.graph),                  "newaugraph failed");        audiocomponentdescription outputcd = {0};       outputcd.componenttype = kaudiounittype_output;       outputcd.componentsubtype = kaudiounitsubtype_defaultoutput;       outputcd.componentmanufacturer = kaudiounitmanufacturer_apple;        aunode outputnode;       checkerror(augraphaddnode(machine.graph,                                 &outputcd,                                 &outputnode),                  "augraphaddnode[kaudiounitsubtype_genericoutput] failed");        audiocomponentdescription inputcd = {0};       inputcd.componenttype = kaudiounittype_generator;       inputcd.componentsubtype = kaudiounitsubtype_scheduledsoundplayer;       inputcd.componentmanufacturer = kaudiounitmanufacturer_apple;        aunode inputnode;       checkerror(augraphaddnode(machine.graph,                                 &inputcd,                                 &inputnode),                  "augraphaddnode[kaudiounitsubtype_scheduledsoundplayer] failed");        checkerror(augraphopen(machine.graph),                  "augraphopen failed");        checkerror(augraphnodeinfo(machine.graph,                                  inputnode,                                  null,                                  &machine.input),                  "augraphnodeinfo failed");        checkerror(augraphconnectnodeinput(machine.graph,                                          inputnode,                                          0,                                          outputnode,                                          0),                  "augraphconnectnodeinput");        checkerror(augraphinitialize(machine.graph),                  "augraphinitialize failed");        // prepare input        audiobufferlist iodata = {0};       iodata.mnumberbuffers = 1;       iodata.mbuffers[0].mnumberchannels = 1;       iodata.mbuffers[0].mdatabytesize = (uint32)(2 * self.buffer.size);       iodata.mbuffers[0].mdata = self.buffer.samples;        scheduledaudioslice slice = {0};       audiotimestamp timestamp  = {0};        slice.mtimestamp    = timestamp;       slice.mnumberframes = (uint32)self.buffer.size;       slice.mbufferlist   = &iodata;        checkerror(audiounitsetproperty(machine.input,                                       kaudiounitproperty_scheduleaudioslice,                                       kaudiounitscope_global,                                       0,                                       &slice,                                       sizeof(slice)),                  "audiounitsetproperty[kaudiounitproperty_schedulestarttimestamp] failed");        audiotimestamp starttimestamp = {0};       starttimestamp.mflags = kaudiotimestampsampletimevalid;       starttimestamp.msampletime = -1;        checkerror(audiounitsetproperty(machine.input,                                       kaudiounitproperty_schedulestarttimestamp,                                       kaudiounitscope_global,                                       0,                                       &starttimestamp,                                       sizeof(starttimestamp)),                  "audiounitsetproperty[kaudiounitproperty_schedulestarttimestamp] failed");        checkerror(augraphstart(machine.graph),                  "augraphstart failed");    //    augraphstop(machine.graph);  <-- commented out make sure wasn't stopping before finishing playing.   //    augraphuninitialize(machine.graph);   //    augraphclose(machine.graph);    } 

does know doing wrong here?

i think documentation you're looking for.

to summarize: setup augraph, setup audio units & add them graph, write & attach rendercallback function on first node in graph. run graph. note rendercallback app asked provide buffers of samples augraph. you'll need read buffers , fill buffers supplied rendercallback. think you're missing.

if you're on ios8, recommend avaudioengine, helps conceal of grungier boiler-platey details of graphs , effects

extras:

1. complete pre-ios8 example code on github
2. ios music player app reads audio mp3 library circular buffer , processes via augraph (using mixer & eq au). can see how rendercallback setup read buffer, etc.
3. amazing audio engine
4. novocaine audio library