如何在3D混音器单元（kAudioUnitSubType_SpatialMixer）中使用立体声源？

Question

有三个音频单元： equalizerUnit（kAudioUnitSubType_NBandEQ）， 3DmixerUnit（kAudioUnitSubType_SpatialMixer）， remoteIOUnit（kAudioUnitSubType_RemoteIO）。 使用AUGraph和Nodes（equalizerNode，3DmixerNode，remoteNode），它们可以正确连接到彼此： equalizerUnit - > mixerUnit - > remoteIOUnit。

一个问题，连接equalizerUnit和3DmixerUnit，我使用转换器单元（kAudioUnitSubType_AUConverter），在其输出上我设置AudioStreamBasicDescription：

    .mSampleRate = 44100.00,
    .mFormatID = kAudioFormatLinearPCM,
    .mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagsNativeEndian | kAudioFormatFlagIsPacked | kAudioFormatFlagIsNonInterleaved,
    .mFramesPerPacket = 1,
    .mChannelsPerFrame = 1,
    .mBytesPerFrame = 2,
    .mBitsPerChannel = 16,
    .mBytesPerPacket = 2

结果，我从Output Score 3DmixerUnit获得单声道声音。如何解决3DmixerUnit中的立体声问题？

我将不胜感激任何帮助！

附：一些编辑信息： 主要问题在于我需要一个立体声信号来申请3DmixerUnit的两个单声道输入。 Apple的3D混音器音频单元指南指出： 要使用立体声源，您可以将其左右声道视为两个独立的单声道声源，然后将立体声流的每一侧馈送到其自己的输入总线。 https://developer.apple.com/library/ios/qa/qa1695/_index.html 我无法弄清楚我的均衡器单元的立体声如何分成两个独立的单通道源。怎么做到这一点？

Answer 1

也许未来有人会通过解决这个问题来节省时间。

canonicalAudioStreamBasicDescription = (AudioStreamBasicDescription) {
    .mSampleRate = 44100.00,
    .mFormatID = kAudioFormatLinearPCM,
    .mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagsNativeEndian | kAudioFormatFlagIsPacked,
    .mFramesPerPacket = 1,
    .mChannelsPerFrame = 2,
    .mBytesPerFrame = 4,
    .mBitsPerChannel = 16,
    .mBytesPerPacket = 4
};
canonicalAudioStreamBasicDescription3Dmixer = (AudioStreamBasicDescription) {
    .mSampleRate = 44100.00,
    .mFormatID = kAudioFormatLinearPCM,
    .mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagsNativeEndian | kAudioFormatFlagIsPacked,
    .mFramesPerPacket = 1,
    .mChannelsPerFrame = 1,
    .mBytesPerFrame = 2,
    .mBitsPerChannel = 16,
    .mBytesPerPacket = 2
};
canonicalAudioStreamBasicDescriptionNonInterleaved = (AudioStreamBasicDescription) {
    .mSampleRate = 44100.00,
    .mFormatID = kAudioFormatLinearPCM,
    .mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagsNativeEndian | kAudioFormatFlagIsPacked | kAudioFormatFlagIsNonInterleaved,
    .mFramesPerPacket = 1,
    .mChannelsPerFrame = 2,
    .mBytesPerFrame = 2,
    .mBitsPerChannel = 16,
    .mBytesPerPacket = 2
};

 convertUnitDescription = (AudioComponentDescription) {
    .componentType = kAudioUnitType_FormatConverter,
    .componentSubType = kAudioUnitSubType_AUConverter,
    .componentFlags = 0,
    .componentFlagsMask = 0,
    .componentManufacturer = kAudioUnitManufacturer_Apple
};
splittertUnitDescription = (AudioComponentDescription) {
    .componentType = kAudioUnitType_FormatConverter,
    .componentSubType = kAudioUnitSubType_Splitter,
    .componentFlags = 0,
    .componentFlagsMask = 0,
    .componentManufacturer = kAudioUnitManufacturer_Apple
};
mixerDescription = (AudioComponentDescription){
    .componentType = kAudioUnitType_Mixer,
    .componentSubType = kAudioUnitSubType_SpatialMixer,
    .componentFlags = 0,
    .componentFlagsMask = 0,
    .componentManufacturer = kAudioUnitManufacturer_Apple
};

AUGraphAddNode(audioGraph, &mixerDescription, &mixerNode);
AUGraphNodeInfo(audioGraph, mixerNode, &mixerDescription, &mixerUnit);
AudioUnitSetProperty(mixerUnit, kAudioUnitProperty_MaximumFramesPerSlice, kAudioUnitScope_Global, 0, &maxFramesPerSlice, sizeof(maxFramesPerSlice));
UInt32 busCount = 2;
AudioUnitSetProperty(mixerUnit, kAudioUnitProperty_ElementCount, kAudioUnitScope_Input, 0, &busCount, sizeof(busCount));
Float64 graphSampleRate = 44100.0;
AudioUnitSetProperty(mixerUnit, kAudioUnitProperty_SampleRate, kAudioUnitScope_Output, 0, &graphSampleRate, sizeof(graphSampleRate));
AudioUnitSetParameter(mixerUnit, kSpatialMixerParam_Distance, kAudioUnitScope_Input, 0, 1.0, 0);
AudioUnitSetParameter(mixerUnit, kSpatialMixerParam_Azimuth, kAudioUnitScope_Input, 0, -90, 0);
AudioUnitSetParameter(mixerUnit, kSpatialMixerParam_Distance, kAudioUnitScope_Input, 1, 1.0, 0);
AudioUnitSetParameter(mixerUnit, kSpatialMixerParam_Azimuth, kAudioUnitScope_Input, 1, 90, 0);

AUNode splitterNode;
AudioUnit splittertUnit;
AUGraphAddNode(audioGraph, &splittertUnitDescription, &splitterNode);
AUGraphNodeInfo(audioGraph, splitterNode, &splittertUnitDescription, &splittertUnit);

AUNode convertNodeFromInterlevantToNonInterleaved;
AudioUnit convertUnitFromInterlevantToNonInterleaved;
AUGraphAddNode(audioGraph, &convertUnitDescription, &convertNodeFromInterlevantToNonInterleaved);
AUGraphNodeInfo(audioGraph, convertNodeFromInterlevantToNonInterleaved, &convertUnitDescription, &convertUnitFromInterlevantToNonInterleaved);
AudioUnitSetProperty(convertUnitFromInterlevantToNonInterleavedLeft, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &srcFormatFromEqualizer, sizeof(srcFormatFromEqualizer));
AudioUnitSetProperty(convertUnitFromInterlevantToNonInterleavedLeft, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, &canonicalAudioStreamBasicDescriptionNonInterleaved, sizeof(canonicalAudioStreamBasicDescriptionNonInterleaved));
AudioUnitSetProperty(convertUnitFromInterlevantToNonInterleavedLeft, kAudioUnitProperty_MaximumFramesPerSlice, kAudioUnitScope_Global, 0, &maxFramesPerSlice, sizeof(maxFramesPerSlice));

AUNode convertNodeFromInterlevantToNonInterleavedRight;
AudioUnit convertUnitFromInterlevantToNonInterleavedRight;
AUGraphAddNode(audioGraph, &convertUnitDescription, &convertNodeFromInterlevantToNonInterleavedRight);
AUGraphNodeInfo(audioGraph, convertNodeFromInterlevantToNonInterleavedRight, &convertUnitDescription, &convertUnitFromInterlevantToNonInterleavedRight);
AudioUnitSetProperty(convertUnitFromInterlevantToNonInterleavedRight, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &srcFormatFromEqualizer, sizeof(srcFormatFromEqualizer));
AudioUnitSetProperty(convertUnitFromInterlevantToNonInterleavedRight, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, &canonicalAudioStreamBasicDescriptionNonInterleaved, sizeof(canonicalAudioStreamBasicDescriptionNonInterleaved));
AudioUnitSetProperty(convertUnitFromInterlevantToNonInterleavedRight, kAudioUnitProperty_MaximumFramesPerSlice, kAudioUnitScope_Global, 0, &maxFramesPerSlice, sizeof(maxFramesPerSlice));

AUNode converterNodeFromNonInterleavedToMonoLeftChannel;
AudioUnit converUnitFromNonInterleavedToMonoLeftChannel;;
SInt32 left[1] = {0};
UInt32 leftSize = (UInt32)sizeof(left);
AUGraphAddNode(audioGraph, &convertUnitDescription, &converterNodeFromNonInterleavedToMonoLeftChannel);
AUGraphNodeInfo(audioGraph, converterNodeFromNonInterleavedToMonoLeftChannel, &convertUnitDescription, &converUnitFromNonInterleavedToMonoLeftChannel);
AudioUnitSetProperty(converUnitFromNonInterleavedToMonoLeftChannel, kAudioOutputUnitProperty_ChannelMap, kAudioUnitScope_Input, 0, &left, leftSize);
AudioUnitSetProperty(converUnitFromNonInterleavedToMonoLeftChannel, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &canonicalAudioStreamBasicDescriptionNonInterleaved, sizeof(canonicalAudioStreamBasicDescriptionNonInterleaved));
AudioUnitSetProperty(converUnitFromNonInterleavedToMonoLeftChannel, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, &canonicalAudioStreamBasicDescription3Dmixer, sizeof(canonicalAudioStreamBasicDescription3Dmixer));
AudioUnitSetProperty(converUnitFromNonInterleavedToMonoLeftChannel, kAudioUnitProperty_MaximumFramesPerSlice, kAudioUnitScope_Global, 0, &maxFramesPerSlice, sizeof(maxFramesPerSlice));

AUNode converterNodeFromNonInterleavedToMonoRightChannel;
AudioUnit converUnitFromNonInterleavedToMonoRightChannel;
SInt32 right[1] = {1};
UInt32 rightSize = (UInt32)sizeof(right);
AUGraphAddNode(audioGraph, &convertUnitDescription, &converterNodeFromNonInterleavedToMonoRightChannel);
AUGraphNodeInfo(audioGraph, converterNodeFromNonInterleavedToMonoRightChannel, &convertUnitDescription, &converUnitFromNonInterleavedToMonoRightChannel);
AudioUnitSetProperty(converUnitFromNonInterleavedToMonoRightChannel, kAudioOutputUnitProperty_ChannelMap, kAudioUnitScope_Input, 0, &right, rightSize);
AudioUnitSetProperty(converUnitFromNonInterleavedToMonoRightChannel, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &canonicalAudioStreamBasicDescriptionNonInterleaved, sizeof(canonicalAudioStreamBasicDescriptionNonInterleaved));
AudioUnitSetProperty(converUnitFromNonInterleavedToMonoRightChannel, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, &canonicalAudioStreamBasicDescription3Dmixer, sizeof(canonicalAudioStreamBasicDescription3Dmixer));
AudioUnitSetProperty(converUnitFromNonInterleavedToMonoRightChannel, kAudioUnitProperty_MaximumFramesPerSlice, kAudioUnitScope_Global, 0, &maxFramesPerSlice, sizeof(maxFramesPerSlice));

AUGraphConnectNodeInput(audioGraph, еqualizerNode, 0, splitterNode, 0);
AUGraphConnectNodeInput(audioGraph, splitterNode, 0, convertNodeFromInterlevantToNonInterleavedLeft, 0);
AUGraphConnectNodeInput(audioGraph, splitterNode, 1, convertNodeFromInterlevantToNonInterleavedRight, 0);
AUGraphConnectNodeInput(audioGraph, convertNodeFromInterlevantToNonInterleavedLeft, 0, converterNodeFromNonInterleavedToMonoLeftChannel, 0);
AUGraphConnectNodeInput(audioGraph, convertNodeFromInterlevantToNonInterleavedRight, 0, converterNodeFromNonInterleavedToMonoRightChannel, 0);
AUGraphConnectNodeInput(audioGraph, converterNodeFromNonInterleavedToMonoLeftChannel, 0, mixerNode, 0);
AUGraphConnectNodeInput(audioGraph, converterNodeFromNonInterleavedToMonoRightChannel, 0, mixerNode, 1);

就这样。完整工作的关键部分代码。