Core Audio的渲染回调不会改变输出音频[重复]

Posted 2023-02-25

【中文标题】Core Audio的渲染回调不会改变输出音频[重复]

【英文标题】：Core Audio's render callback does not change output audio [duplicate]

【发布时间】：2015-08-13 19:27:34

【问题描述】：

在使用核心音频时，我无法使用渲染回调更改输出或使其静音。

这是我的 IO 初始化函数：

- (void)setupIOUnit

    // Create a new instance of AURemoteIO

    AudioComponentDescription desc;
    desc.componentType = kAudioUnitType_Output;
    desc.componentSubType = kAudioUnitSubType_RemoteIO;
    desc.componentManufacturer = kAudioUnitManufacturer_Apple;
    desc.componentFlags = 0;
    desc.componentFlagsMask = 0;

    AudioComponent comp = AudioComponentFindNext(NULL, &desc);
    AudioComponentInstanceNew(comp, &rioUnit);


    //  Enable input and output on AURemoteIO
    //  Input is enabled on the input scope of the input element
    //  Output is enabled on the output scope of the output element

    UInt32 one = 1;
    AudioUnitSetProperty(rioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Input, 1, &one, sizeof(one));
    AudioUnitSetProperty(rioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Output, 0, &one, sizeof(one));

    AudiostreamBasicDescription audioFormat;
    audioFormat.mSampleRate         = 44100.00;
    audioFormat.mFormatID           = kAudioFormatLinearPCM;
    audioFormat.mFormatFlags        = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
    audioFormat.mFramesPerPacket    = 1;
    audioFormat.mChannelsPerFrame   = 1;
    audioFormat.mBitsPerChannel     = 16;
    audioFormat.mBytesPerPacket     = 2;
    audioFormat.mBytesPerFrame      = 2;

    AudioUnitSetProperty(rioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 1, &audioFormat, sizeof(audioFormat));
    AudioUnitSetProperty(rioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &audioFormat, sizeof(audioFormat));

    // Set the MaximumFramesPerSlice property. This property is used to describe to an audio unit the maximum number
    // of samples it will be asked to produce on any single given call to AudioUnitRender
    UInt32 maxFramesPerSlice = 4096;
    AudioUnitSetProperty(rioUnit, kAudioUnitProperty_MaximumFramesPerSlice, kAudioUnitScope_Global, 0, &maxFramesPerSlice, sizeof(UInt32));

    // Get the property value back from AURemoteIO. We are going to use this value to allocate buffers accordingly
    UInt32 propSize = sizeof(UInt32);
    AudioUnitGetProperty(rioUnit, kAudioUnitProperty_MaximumFramesPerSlice, kAudioUnitScope_Global, 0, &maxFramesPerSlice, &propSize);

    // Set the render callback on AURemoteIO
    AURenderCallbackStruct renderCallback;
    renderCallback.inputProc = performRender;
    renderCallback.inputProcRefCon = NULL;
    AudioUnitSetProperty(rioUnit, kAudioUnitProperty_SetRenderCallback, kAudioUnitScope_Input, 0, &renderCallback, sizeof(renderCallback));
    NSLog(@"render set now");
    // Initialize the AURemoteIO instance
    AudioUnitInitialize(rioUnit);
    [self startIOUnit];
    return;

这是我的渲染函数：

// Render callback function
static OSStatus performRender (void                         *inRefCon,
                           AudioUnitRenderActionFlags   *ioActionFlags,
                           const AudioTimeStamp         *inTimeStamp,
                           UInt32                       inBusNumber,
                           UInt32                       inNumberFrames,
                           AudioBufferList              *ioData)

    OSStatus err = noErr;
    err = AudioUnitRender(rioUnit, ioActionFlags, inTimeStamp, 1, inNumberFrames, ioData);
    if (ioData->mBuffers[0].mDataByteSize >= 12) 
        NSData *myAudioData = [NSData dataWithBytes: ioData->mBuffers[0].mData length:12];
        NSLog(@"aa playback's first 12 bytes: %@", myAudioData);
    

    for (UInt32 i=0; i<ioData->mNumberBuffers; ++i) 
        memset(ioData->mBuffers[i].mData, 0, ioData->mBuffers[i].mDataByteSize);
    

    return err;

这不会使输出声音静音，我仍然可以从我的流媒体应用中听到声音。发生这种情况的可能情况有哪些？我的声音怎么没静音？

任何见解都会有所帮助

【参考方案1】：

您能否澄清一下您所说的“我仍然可以从我的流媒体应用程序中听到声音”的意思？您是指通过麦克风传来的声音，还是应用程序中发生了其他事情？

FWIW：您显然正在适应 Apple 的 aurioTouch 示例，如果我将您的 setupIOUnit 方法和渲染回调放入该项目并运行它，静音工作正常 - 即，您似乎没有用您的代码破坏任何东西'已经张贴在这里。这表明问题出在代码的其他地方。