ios - 发布 iOS 音频单元

Question

我正在尝试制作一个应用程序间音频 iOS 应用程序，看起来我在 AudioOutputUnitPublish 方法上遇到了问题。方法如下:

- (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 表示参数无效...但我似乎无法弄清楚哪个参数无效。谁能帮我调试这里？谢谢!

---

编辑:

只是想发布更多代码以便其他人可以帮助我:

我有两个音频单元，希望还有第三个 - MIDISynth(目前处于非事件状态)、MultiChannelMixer 和 RemoteIO 音频单元。我有一个连接到混音器音频单元的渲染回调。我猜我在我的 AUGraph 中连接有问题(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的地方)。希望有人能指出我做错了什么!

代码如下:

- (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;
 }

Answer 1

AudioComponentDescription 中的最后一个字段，componentFlagsMask，应该是 0，而不是 1。(参见 documentation。看起来至少有一个 tutorial 错误地将此字段识别为组件版本。 )

我不确定这是否是问题的唯一原因。其余代码看起来没问题，但我想项目的其他地方可能存在问题，例如。具有能力。