cocoa - 音频单元 : getting generated audio into a render callback

Question

我一直在尝试通过将 AURenderCallbackStruct 附加到音频单元的输入来操作 kAudioUnitType_Generator 音频单元生成的样本，但没有成功。我设法使用以下简单图表在 OS X 上实现此功能:

(input callback) -> multichannel mixer -> (intput callback) -> default output

但是我失败了以下(甚至更简单)以发电机组开头的图表:

speech synthesis -> (intput callback) -> default output           | fails in render callback with kAudioUnitErr_Uninitialized
audiofile player -> (intput callback) -> default output           | fails when scheduling file region with kAudioUnitErr_Uninitialized

我已经尝试了几乎所有我能想到的方法，从设置 ASBD 格式到采样率，但我总是遇到这些错误。有谁知道如何设置一个图表，我们可以在其中操作来自这些漂亮的生成器单元的样本？

下面是尝试使用语音合成时失败的渲染回调函数和图形实例化方法。当然，除了设置文件播放之外，音频文件播放器几乎是相同的。如果我删除回调并在其位置添加 AUGraphConnectNodeInput，这两种设置都可以工作...

static OSStatus RenderCallback(void *inRefCon,
                                    AudioUnitRenderActionFlags *ioActionFlags,
                                    const AudioTimeStamp *inTimeStamp,
                                    UInt32 inBusNumber,
                                    UInt32 inNumberFrames,
                                    AudioBufferList *ioData) {

    AppDelegate *app = (AppDelegate *)inRefCon;
    AudioUnit inputUnit = app->_speechUnit;
    OSStatus status = noErr;

    status = AudioUnitRender(inputUnit, ioActionFlags, inTimeStamp, 0, inNumberFrames, ioData);
    // *** ERROR *** kAudioUnitErr_Uninitialized, code: -10867

    // ... insert processing code here...

    return status;
}

- (int)createSynthGraph {
    AUGRAPH_CHECK( NewAUGraph( &_graph ) );

    AUNode speechNode, outputNode;

    // speech synthesizer
    AudioComponentDescription speechCD = {0};
    speechCD.componentType = kAudioUnitType_Generator;
    speechCD.componentSubType = kAudioUnitSubType_SpeechSynthesis;
    speechCD.componentManufacturer = kAudioUnitManufacturer_Apple;

    // output device (speakers)
    AudioComponentDescription outputCD = {0};
    outputCD.componentType = kAudioUnitType_Output;
    outputCD.componentSubType = kAudioUnitSubType_DefaultOutput;
    outputCD.componentManufacturer = kAudioUnitManufacturer_Apple;

    AUGRAPH_CHECK( AUGraphAddNode( _graph, &outputCD, &outputNode ) );
    AUGRAPH_CHECK( AUGraphAddNode( _graph, &speechCD, &speechNode ) );

    AUGRAPH_CHECK( AUGraphOpen( _graph ) );
    AUGRAPH_CHECK( AUGraphNodeInfo( _graph, outputNode, NULL, &_outputUnit ) );
    AUGRAPH_CHECK( AUGraphNodeInfo( _graph, speechNode, NULL, &_speechUnit ) );

    // setup stream formats:
    AudioStreamBasicDescription streamFormat = [self streamFormat];
    AU_CHECK( AudioUnitSetProperty( _speechUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, &streamFormat, sizeof(streamFormat) ) );

    // setup callback:
    AURenderCallbackStruct callback;
    callback.inputProc = RenderCallback;
    callback.inputProcRefCon = self;
    AUGRAPH_CHECK( AUGraphSetNodeInputCallback ( _graph, outputNode, 0, &callback ) );

    // init and start
    AUGRAPH_CHECK( AUGraphInitialize( _graph ) );
    AUGRAPH_CHECK( AUGraphStart( _graph ) );
    return 0;
}

Answer 1

您必须使用 AUGraphConnectNodeInput 将这些节点连接在一起。 AUGraph 不会初始化其中的 AudioUnit，除非它们已连接。图中未连接到其他单元的单元将不会被初始化。

您还可以尝试在启动图表之前手动初始化它们。