我正在尝试制作一个应用程序间音频 iOS 应用程序，看起来我的AudioOutputUnitPublish方法有问题。这是方法：
- (void)publishOutputAudioUnit {
AudioComponentDescription desc = {kAudioUnitType_RemoteInstrument,
'iasp','rfoo', 0, 1};
OSStatus result = AudioOutputUnitPublish(&desc, CFSTR("MyMusicApp"),
1, outputUnit);
if (result != noErr)
NSLog(@"AudioOutputUnitPublish instrument result: %d", (int)result);
desc = { kAudioUnitType_RemoteGenerator, 'iasp', 'rfoo', 0, 1 };
result = AudioOutputUnitPublish(&desc, CFSTR("MyMusicApp"), 1, outputUnit);
if (result != noErr)
NSLog(@"AudioOutputUnitPublish generator result: %d", (int)result);
}
这是我的 plist 信息：
<key>AudioComponents</key>
<array>
<dict>
<key>manufacturer</key>
<string>rfoo</string>
<key>name</key>
<string>MyMusicApp</string>
<key>subtype</key>
<string>iasp</string>
<key>type</key>
<string>aurg</string>
<key>version</key>
<integer>1</integer>
</dict>
<dict>
<key>manufacturer</key>
<string>rfoo</string>
<key>name</key>
<string>MyMusicApp</string>
<key>subtype</key>
<string>iasp</string>
<key>type</key>
<string>auri</string>
<key>version</key>
<integer>1</integer>
</dict>
</array>
这是我得到的结果：
AudioOutputUnitPublish instrument result: -50
AudioOutputUnitPublish generator result: -50
我知道 OSStatus 代码 -50 意味着有一个无效参数......但我似乎无法弄清楚哪个是无效的。谁能帮我在这里调试？谢谢！
编辑 ：
只是想发布更多代码，以便其他人可以帮助我更多：
我有两个音频单元，希望还有第三个 - MIDISynth（目前处于非活动状态）、MultiChannelMixer 和 RemoteIO 音频单元。我有一个渲染回调附加到混音器音频单元。我猜我在我的 AUGraph 中连接了一些错误（我见过的所有示例都没有将音频渲染回调附加到音频单元，所以这可能是我做错了什么）。希望有人能发现我做错了什么！
这是代码：
- (AUGraph)createAUGraphWithSynth:(AudioUnit *)sUnit mixUnit:(AudioUnit *)mixUnit remoteUnit:(AudioUnit *)remUnit {
// Initializations
AUGraph graph = 0;
OSStatus result = noErr;
// Create graph nodes
AUNode mixerNode, ioNode;
// Create Component Descriptor
AudioComponentDescription cd;
cd.componentManufacturer = kAudioUnitManufacturer_Apple;
cd.componentFlags = 0;
cd.componentFlagsMask = 0;
// Init AUGraph
Check(result = NewAUGraph(&graph));
// Init Mixer unit
cd.componentType = kAudioUnitType_Mixer;
cd.componentSubType = kAudioUnitSubType_MultiChannelMixer;
Check(result = AUGraphAddNode(graph, &cd, &mixerNode));
// Init io Unit
cd.componentType = kAudioUnitType_Output;
cd.componentSubType = kAudioUnitSubType_RemoteIO;
Check(result = AUGraphAddNode(graph, &cd, &ioNode));
// Open AUGraph
Check(AUGraphOpen(graph));
// Get mixer unit
Check(AUGraphNodeInfo(graph, mixerNode, NULL, mixUnit));
// Get io unit
Check(AUGraphNodeInfo(graph, ioNode, NULL, remUnit));
// Set number of input busses
UInt32 numBuses = 1;
UInt32 size = sizeof(numBuses);
Check(AudioUnitSetProperty(*mixUnit,
kAudioUnitProperty_ElementCount,
kAudioUnitScope_Input,
0, &numBuses, size));
AudioStreamBasicDescription desc;
const int four_bytes_per_float = 4;
const int eight_bits_per_byte = 8;
for (int i = 0; i < numBuses; ++i) {
AURenderCallbackStruct callbackStruct;
callbackStruct.inputProc = outputCallback;
callbackStruct.inputProcRefCon = (__bridge void *)self;
Check(AUGraphSetNodeInputCallback(graph, mixerNode, i, &callbackStruct));
UInt32 size = sizeof(desc);
Check(AudioUnitGetProperty(*mixUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Input,
0, &desc, &size));
memset(&desc, 0, sizeof(desc));
desc.mSampleRate = SAMPLE_RATE;
desc.mFormatID = kAudioFormatLinearPCM;
desc.mFormatFlags = kAudioFormatFlagsNativeFloatPacked
| kAudioFormatFlagIsNonInterleaved;
desc.mBytesPerPacket = four_bytes_per_float;
desc.mFramesPerPacket = 1;
desc.mBytesPerFrame = four_bytes_per_float;
desc.mBitsPerChannel = four_bytes_per_float * eight_bits_per_byte;
desc.mChannelsPerFrame = 2;
Check(AudioUnitSetProperty(*remUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Input,
0, &desc, sizeof(desc)));
}
Check(AudioUnitSetProperty(*mixUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Output,
0, &desc, sizeof(desc)));
Check(AudioUnitGetProperty(*mixUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Output,
0, &desc, &size));
memset(&desc, 0, sizeof(desc));
desc.mSampleRate = SAMPLE_RATE;
desc.mFormatID = kAudioFormatLinearPCM;
desc.mFormatFlags = kAudioFormatFlagsNativeFloatPacked
| kAudioFormatFlagIsNonInterleaved;
desc.mBytesPerPacket = four_bytes_per_float;
desc.mFramesPerPacket = 1;
desc.mBytesPerFrame = four_bytes_per_float;
desc.mBitsPerChannel = four_bytes_per_float * eight_bits_per_byte;
desc.mChannelsPerFrame = 2;
Check(AudioUnitSetProperty(*mixUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Output,
0, &desc, sizeof(desc)));
// Must configure remote io unit:
Check(AudioUnitSetProperty(*remUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Output,
1, &desc, sizeof(desc)));
// Connect nodes (synth->output)
Check(AUGraphConnectNodeInput(graph, mixerNode, 0, ioNode, 0));
return graph;
}