在Spotify iOS SDK中混合两个AUNodes

Question

我正在尝试使用动态处理器和一堆过滤器来压缩 Spotify 方法中的特定频段connectOutputBus但是当我混合kAudioUnitSubType_MultiChannelMixer中的节点时，只有第一个添加的节点的声音出来。

OBS：我实际上在sourceNodeCopy上使用过滤器来删除将在souceNode上压缩的频率，但为了简短起见，我省略了它们。

代码如下：

override func connectOutputBus(_ sourceOutputBusNumber: UInt32, ofNode  sourceNode: AUNode, toInputBus destinationInputBusNumber: UInt32, ofNode destinationNode: AUNode, in graph: AUGraph!) throws {
let sourceNodeCopy = sourceNode //original node without the harsh freq
//create a filter for the harsh frequencies
var filterDescription = AudioComponentDescription()
filterDescription.componentType = kAudioUnitType_Effect
filterDescription.componentSubType = kAudioUnitSubType_BandPassFilter
filterDescription.componentManufacturer = kAudioUnitManufacturer_Apple
filterDescription.componentFlags = 0
filterDescription.componentFlagsMask = 0
AUGraphAddNode(graph, &filterDescription, &filterNode!) // Add the filter node
AUGraphNodeInfo(graph, filterNode!, nil, &filterUnit!) // Get the Audio Unit from the node
AudioUnitInitialize(filterUnit!) // Initialize the audio unit
// Set filter params
AudioUnitSetParameter(filterUnit!, kBandpassParam_CenterFrequency, kAudioUnitScope_Global, 0, 10038, 0)
//create a processor to compress the frequency
var dynamicProcessorDescription = AudioComponentDescription()
dynamicProcessorDescription.componentType = kAudioUnitType_Effect
dynamicProcessorDescription.componentSubType = kAudioUnitSubType_DynamicsProcessor
dynamicProcessorDescription.componentManufacturer = kAudioUnitManufacturer_Apple
dynamicProcessorDescription.componentFlags = 0
dynamicProcessorDescription.componentFlagsMask = 0
// Add the dynamic processor node
AUGraphAddNode(graph, &dynamicProcessorDescription, &dynamicProcessorNode)
AUGraphNodeInfo(graph, dynamicProcessorNode, nil, &dynamicProcessorUnit)
AudioUnitInitialize(dynamicProcessorUnit!)
// Set compressor params
AudioUnitSetParameter(dynamicProcessorUnit!, kDynamicsProcessorParam_Threshold, kAudioUnitScope_Global, 0, -35, 0)
AudioUnitSetParameter(dynamicProcessorUnit!, kDynamicsProcessorParam_AttackTime, kAudioUnitScope_Global, 0, 0.02, 0)
AudioUnitSetParameter(dynamicProcessorUnit!, kDynamicsProcessorParam_ReleaseTime, kAudioUnitScope_Global, 0, 0.04, 0)
AudioUnitSetParameter(dynamicProcessorUnit!, kDynamicsProcessorParam_HeadRoom, kAudioUnitScope_Global, 0, 0, 0)
//mixer
var mixerDescription = AudioComponentDescription()
mixerDescription.componentType = kAudioUnitType_Mixer
mixerDescription.componentSubType = kAudioUnitSubType_MultiChannelMixer
mixerDescription.componentManufacturer = kAudioUnitManufacturer_Apple
mixerDescription.componentFlags = 0
mixerDescription.componentFlagsMask = 0
AUGraphAddNode(graph, &mixerDescription, &audioEffectsController.mixerNode)
AUGraphNodeInfo(graph, audioEffectsController.mixerNode, nil,
&audioEffectsController.mixerUnit)
AudioUnitInitialize(audioEffectsController.mixerUnit!)
AudioUnitSetParameter(mixerUnit!, kMultiChannelMixerParam_Volume, kAudioUnitScope_Input, 0, 1.0, 0);
AudioUnitSetParameter(mixerUnit!, kMultiChannelMixerParam_Volume, kAudioUnitScope_Output, 0, 1.0, 0);

//connect the nodes
AUGraphConnectNodeInput(graph, sourceNode, sourceOutputBusNumber, filterNode, 0)
AUGraphConnectNodeInput(graph, filterNode, sourceOutputBusNumber, dynamicProcessorNode, 0)
AUGraphConnectNodeInput(graph, sourceNodeCopy, sourceOutputBusNumber, mixerNode, 0)
AUGraphConnectNodeInput(graph, fiterNode, sourceOutputBusNumber, mixerNode, 0)
//connect the mixer to the output
AUGraphConnectNodeInput(graph, audioEffectsController.mixerNode, 0, destinationNode, destinationInputBusNumber)

Answer 1

在你的代码中，你像这样连接节点

AUGraphConnectNodeInput(graph, sourceNodeCopy, sourceOutputBusNumber, mixerNode, 0)
AUGraphConnectNodeInput(graph, fiterNode, sourceOutputBusNumber, mixerNode, 0)

如果这样做，则将sourceNodeCopy和filterNode连接到MixerNode的同一输入 (0(。但只能连接一个...

你应该试试这个

AUGraphConnectNodeInput(graph, sourceNodeCopy, sourceOutputBusNumber, mixerNode, 0)
AUGraphConnectNodeInput(graph, fiterNode, sourceOutputBusNumber, mixerNode, 1)