How do I connect a Mixer with an AUGraph - objective-c

Question

I want to create an AUGraph that has the following AudioUnits:
1 * 440HZ sine wave generator
1 * 880HZ sine wave generator
1 * Mixer
1 * Output
If I connect my sine wave generators to my mixer, then the mixer to the output I get no sound.
If I connect a sine wave generator directly to the output I do get sound, probably because the Output unit connects to the sine wave generator callback.
Is there something I'm missing with how this should be connected?
Full code sample, Connect 1 * Joins 1 is not working, comment these out and run Connect 2 and Joins 2 to hear the sine wave working
//
// main.c
// TestAudioUnit
//
// Created by Chris Davis on 25/08/2013.
// Copyright (c) 2013 Chris Davis. All rights reserved.
//
#include <CoreFoundation/CoreFoundation.h>
#import <AudioToolbox/AudioToolbox.h>
typedef struct MyAUGraphPlayer
{
AudioStreamBasicDescription streamFormat;
AUGraph graph;
AUNode output;
AUNode mixer;
AUNode sine;
AudioUnit audioUnits[3];
AudioBufferList *inputBuffer;
Float64 firstInputSampleTime;
Float64 firstOutputSampleTime;
Float64 inToOutSampleTimeOffset;
} MyAUGraphPlayer;
OSStatus SineWaveRenderCallback(void * inRefCon,
AudioUnitRenderActionFlags * ioActionFlags,
const AudioTimeStamp * inTimeStamp,
UInt32 inBusNumber,
UInt32 inNumberFrames,
AudioBufferList * ioData)
{
// inRefCon is the context pointer we passed in earlier when setting the render callback
double currentPhase = *((double *)inRefCon);
// ioData is where we're supposed to put the audio samples we've created
Float32 * outputBuffer = (Float32 *)ioData->mBuffers[0].mData;
const double frequency = 880.0;
const double phaseStep = (frequency / 44100.) * (M_PI * 2.);
for(int i = 0; i < inNumberFrames; i++) {
outputBuffer[i] = sin(currentPhase);
currentPhase += phaseStep;
}
// If we were doing stereo (or more), this would copy our sine wave samples
// to all of the remaining channels
for(int i = 1; i < ioData->mNumberBuffers; i++) {
memcpy(ioData->mBuffers[i].mData, outputBuffer, ioData->mBuffers[i].mDataByteSize);
}
// writing the current phase back to inRefCon so we can use it on the next call
*((double *)inRefCon) = currentPhase;
return noErr;
}
int main(int argc, const char * argv[])
{
MyAUGraphPlayer *player = {0};
MyAUGraphPlayer p = {0};
player=&p;
NewAUGraph(&player->graph);
//Output
{
AudioComponentDescription description = {
.componentType = kAudioUnitType_Output,
.componentSubType = kAudioUnitSubType_DefaultOutput,
.componentManufacturer = kAudioUnitManufacturer_Apple
};
AUGraphAddNode(player->graph, &description, &player->output);
AudioComponent comp = AudioComponentFindNext(NULL, &description);
AudioComponentInstanceNew(comp, &player->audioUnits[0]);
AudioUnitInitialize(player->audioUnits[0]);
AudioStreamBasicDescription ASBD = {
.mSampleRate = 44100,
.mFormatID = kAudioFormatLinearPCM,
.mFormatFlags = kAudioFormatFlagsNativeFloatPacked,
.mChannelsPerFrame = 1,
.mFramesPerPacket = 1,
.mBitsPerChannel = sizeof(Float32) * 8,
.mBytesPerPacket = sizeof(Float32),
.mBytesPerFrame = sizeof(Float32)
};
AudioUnitSetProperty(player->audioUnits[0],
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Global,
0,
&ASBD,
sizeof(ASBD));
}
//Mixer
{
AudioComponentDescription description = {
.componentType = kAudioUnitType_Mixer,
.componentSubType = kAudioUnitSubType_StereoMixer,
.componentManufacturer = kAudioUnitManufacturer_Apple
};
AUGraphAddNode(player->graph, &description, &player->mixer);
AudioComponent comp = AudioComponentFindNext(NULL, &description);
AudioComponentInstanceNew(comp, &player->audioUnits[1]);
AudioUnitInitialize(player->audioUnits[1]);
}
//Sine
{
AudioComponentDescription description = {
.componentType = kAudioUnitType_Generator,
.componentSubType = kAudioUnitSubType_ScheduledSoundPlayer,
.componentManufacturer = kAudioUnitManufacturer_Apple
};
AUGraphAddNode(player->graph, &description, &player->sine);
AudioComponent comp = AudioComponentFindNext(NULL, &description);
AudioComponentInstanceNew(comp, &player->audioUnits[2]);
AudioUnitInitialize(player->audioUnits[2]);
}
//Connect 1
{
AURenderCallbackStruct callbackInfo = {
.inputProc = SineWaveRenderCallback,
.inputProcRefCon = player
};
AudioUnitSetProperty(player->audioUnits[1],
kAudioUnitProperty_SetRenderCallback,
kAudioUnitScope_Global,
0,
&callbackInfo,
sizeof(callbackInfo));
}
//Joins 1 - sine to mixer to outout
{
AUGraphConnectNodeInput(player->graph,
player->sine,
0,
player->mixer,
0);
AUGraphConnectNodeInput(player->graph,
player->mixer,
0,
player->output,
0);
}
//connect 2
/*{
AURenderCallbackStruct callbackInfo = {
.inputProc = SineWaveRenderCallback,
.inputProcRefCon = player
};
AudioUnitSetProperty(player->audioUnits[0],
kAudioUnitProperty_SetRenderCallback,
kAudioUnitScope_Global,
0,
&callbackInfo,
sizeof(callbackInfo));
}
//Joins 2 - sine direct to output
{
AUGraphConnectNodeInput(player->graph,
player->sine,
0,
player->output,
0);
}*/
AUGraphInitialize(player->graph);
player->firstOutputSampleTime = -1;
AudioOutputUnitStart(player->audioUnits[0]);
AUGraphStart(player->graph);
printf("enter key to stop\n");
getchar();
return 0;
}

Answer 1

This code correctly plays the sine wave, however, I get lots of errors from CoreAudio during setup:
//
// main.c
// TestAudioUnit
//
// Created by Chris Davis on 25/08/2013.
// Copyright (c) 2013 Chris Davis. All rights reserved.
//
#include <CoreFoundation/CoreFoundation.h>
#import <AudioToolbox/AudioToolbox.h>
typedef struct MyAUGraphPlayer
{
AudioStreamBasicDescription streamFormat;
AUGraph graph;
AUNode output;
AUNode mixer;
AUNode sine;
AudioUnit audioUnits[3];
AudioBufferList *inputBuffer;
Float64 firstInputSampleTime;
Float64 firstOutputSampleTime;
Float64 inToOutSampleTimeOffset;
} MyAUGraphPlayer;
OSStatus SineWaveRenderCallback(void * inRefCon,
AudioUnitRenderActionFlags * ioActionFlags,
const AudioTimeStamp * inTimeStamp,
UInt32 inBusNumber,
UInt32 inNumberFrames,
AudioBufferList * ioData)
{
// inRefCon is the context pointer we passed in earlier when setting the render callback
double currentPhase = *((double *)inRefCon);
// ioData is where we're supposed to put the audio samples we've created
Float32 * outputBuffer = (Float32 *)ioData->mBuffers[0].mData;
const double frequency = 880.0;
const double phaseStep = (frequency / 44100.) * (M_PI * 2.);
for(int i = 0; i < inNumberFrames; i++) {
outputBuffer[i] = sin(currentPhase);
currentPhase += phaseStep;
}
// If we were doing stereo (or more), this would copy our sine wave samples
// to all of the remaining channels
for(int i = 1; i < ioData->mNumberBuffers; i++) {
memcpy(ioData->mBuffers[i].mData, outputBuffer, ioData->mBuffers[i].mDataByteSize);
}
// writing the current phase back to inRefCon so we can use it on the next call
*((double *)inRefCon) = currentPhase;
return noErr;
}
int main(int argc, const char * argv[])
{
MyAUGraphPlayer *player = {0};
MyAUGraphPlayer p = {0};
player=&p;
NewAUGraph(&player->graph);
OSStatus result = 0;
AudioStreamBasicDescription ASBD = {
.mSampleRate = 44100,
.mFormatID = kAudioFormatLinearPCM,
.mFormatFlags = kAudioFormatFlagsNativeFloatPacked,
.mChannelsPerFrame = 2,
.mFramesPerPacket = 1,
.mBitsPerChannel = sizeof(Float32) * 8,
.mBytesPerPacket = sizeof(Float32),
.mBytesPerFrame = sizeof(Float32)
};
//Output
{
AudioComponentDescription description = {
.componentType = kAudioUnitType_Output,
.componentSubType = kAudioUnitSubType_DefaultOutput,
.componentManufacturer = kAudioUnitManufacturer_Apple
};
result = AUGraphAddNode(player->graph, &description, &player->output);
printf("err: %d\n", result);
AudioComponent comp = AudioComponentFindNext(NULL, &description);
result = AudioComponentInstanceNew(comp, &player->audioUnits[0]);
printf("err: %d\n", result);
result = AudioUnitInitialize(player->audioUnits[0]);
printf("err: %d\n", result);
}
//Mixer
{
AudioComponentDescription description = {
.componentType = kAudioUnitType_Mixer,
.componentSubType = kAudioUnitSubType_StereoMixer,
.componentManufacturer = kAudioUnitManufacturer_Apple
};
result = AUGraphAddNode(player->graph, &description, &player->mixer);
printf("err: %d\n", result);
AudioComponent comp = AudioComponentFindNext(NULL, &description);
result = AudioComponentInstanceNew(comp, &player->audioUnits[1]);
printf("err: %d\n", result);
}
//Sine
{
AudioComponentDescription description = {
.componentType = kAudioUnitType_Generator,
.componentSubType = kAudioUnitSubType_ScheduledSoundPlayer,
.componentManufacturer = kAudioUnitManufacturer_Apple
};
result = AUGraphAddNode(player->graph, &description, &player->sine);
printf("err: %d\n", result);
AudioComponent comp = AudioComponentFindNext(NULL, &description);
result = AudioComponentInstanceNew(comp, &player->audioUnits[2]);
printf("err: %d\n", result);
result = AudioUnitInitialize(player->audioUnits[2]);
printf("err: %d\n", result);
}
result = AUGraphConnectNodeInput(player->graph,
player->sine,
0,
player->mixer,
0);
printf("err: %d\n", result);
result = AUGraphConnectNodeInput(player->graph,
player->mixer,
0,
player->output,
0);
printf("err: %d\n", result);
result = AUGraphOpen(player->graph);
printf("err: %d\n", result);
UInt32 numbuses = 1;
result = AudioUnitSetProperty(player->audioUnits[1], kAudioUnitProperty_ElementCount, kAudioUnitScope_Input, 0, &numbuses, sizeof(numbuses));
printf("err: %d\n", result);
for (UInt32 i = 0; i <= numbuses; ++i) {
// setup render callback struct
AURenderCallbackStruct rcbs;
rcbs.inputProc = &SineWaveRenderCallback;
rcbs.inputProcRefCon = &player;
printf("set AUGraphSetNodeInputCallback\n");
// set a callback for the specified node's specified input
result = AUGraphSetNodeInputCallback(player->graph, player->mixer, i, &rcbs);
printf("AUGraphSetNodeInputCallback err: %d\n", result);
printf("set input bus %d, client kAudioUnitProperty_StreamFormat\n", (unsigned int)i);
// set the input stream format, this is the format of the audio for mixer input
result = AudioUnitSetProperty(player->audioUnits[1], kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, i, &ASBD, sizeof(ASBD));
printf("err: %d\n", result);
}
result = AudioUnitSetProperty(player->audioUnits[1], kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, &ASBD, sizeof(ASBD));
printf("err: %d\n", result);
OSStatus status = AUGraphInitialize(player->graph);
printf("err: %d\n", status);
player->firstOutputSampleTime = -1;
AudioOutputUnitStart(player->audioUnits[0]);
AUGraphStart(player->graph);
printf("enter key to stop\n");
getchar();
return 0;
}