在remoteIO音频设备上渲染回调不接收音频样本

Question

我一直在尝试获取kAudioUnitSubType_RemoteIO播放的样本以及从kAudioUnitSubType_AudioFilePlayer接收的样本。

为了获得这些样本，我在remoteIO Audio Unit（总线0）的输出上配置了kAudioUnitProperty_SetRenderCallback。虽然我成功播放音频，但这个渲染回调似乎没有收到样本。据我了解，remoteIO回调从FilePlayer音频单元（总线1）拉取（呈现）可用数据（存储在缓冲区中）。

有谁知道出了什么问题？

 NewAUGraph(player.graph)

 // Add file player node
 var cd = AudioComponentDescription(componentType: OSType(kAudioUnitType_Generator),
    componentSubType: OSType(kAudioUnitSubType_AudioFilePlayer),
    componentManufacturer: OSType(kAudioUnitManufacturer_Apple),
    componentFlags: 0, componentFlagsMask: 0)
 AUGraphAddNode(player.graph, &cd, &player.filePlayerNode)

 // Add output node
 var rioNode = AUNode()
 cd.componentType = OSType(kAudioUnitType_Output)
 cd.componentSubType = OSType(kAudioUnitSubType_RemoteIO)
 AUGraphAddNode(player.graph, &cd, &rioNode)

 AUGraphOpen(player.graph)
 AUGraphNodeInfo(player.graph, player.filePlayerNode, nil, &player.filePlayerAU)
 AUGraphNodeInfo(player.graph, rioNode, nil, &player.rioAU)

 AUGraphConnectNodeInput(player.graph, player.filePlayerNode, 0, outputNode, 0)


 // The callback is configures as
 var callbackStruct = AURenderCallbackStruct(inputProc: InputRenderProc, inputProcRefCon: &player)
 CheckError(AudioUnitSetProperty(player.rioAU,
    kAudioUnitProperty_SetRenderCallback,
    kAudioUnitScope_Output,
    0,
    &callbackStruct,
    UInt32(sizeof(callbackStruct.dynamicType))),
    operation: "Couldn't set RIO's render callback")


 AUGraphInitialize(player.graph)

渲染回调（不接收任何数据，也没有任何错误）：

 let InputRenderProc: AURenderCallback = {(inRefCon, ioActionFlags, inTimeStamp, inBusNumber, inNumberFrames, ioData)  -> OSStatus in
    let player = UnsafeMutablePointer<StatePlayer>(inRefCon).memory

    // Just obtain samples from buffer
     var bus1: UInt32 = 1
    CheckError(AudioUnitRender(player.filePlayerAU, ioActionFlags, inTimeStamp, bus1, inNumberFrames, ioData),
        operation: "Couldn't render from filePlayer Audio Unit")

    return noErr
 }