cocoa - 无声音播放时核心音频 CPU 使用率高

Question

我刚刚开始学习核心音频，并制作了一个简单的测试应用程序，可以播放三个不同的钢琴音符。除了一件小事之外，看起来还不错。

首先，应用程序使用大约 7% 左右的 CPU(在事件监视器中可见)，我认为这是正常的，因为它正在运行实时 AUGraph。然而，随着演奏更多音符，CPU 使用率不断增加，即使当时可能没有播放声音。

时间表如下:

1. 启动应用程序。 CPU 使用率低至零。
2. 播放音符，中等 CPU 使用率。
3. 笔记完成且没有声音播放，CPU 使用率中等。

代码:

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    // Insert code here to initialize your application

    NewAUGraph(&audioGraph);

    AudioComponentDescription cd;
    AUNode outputNode;
    AudioUnit outputUnit;

    cd.componentManufacturer = kAudioUnitManufacturer_Apple;
    cd.componentFlags = 0;
    cd.componentFlagsMask = 0;
    cd.componentType = kAudioUnitType_Output;
    cd.componentSubType = kAudioUnitSubType_DefaultOutput;

    //AUGraphNewNode(audioGraph, &cd, 0, NULL, &outputNode);
    AUGraphAddNode(audioGraph, &cd, &outputNode);
    //AUGraphGetNodeInfo(audioGraph, outputNode, 0, 0, 0, &outputUnit);
    AUGraphNodeInfo(audioGraph, outputNode, &cd, &outputUnit);

    AUNode mixerNode;
    AudioUnit mixerUnit;

    cd.componentManufacturer = kAudioUnitManufacturer_Apple;
    cd.componentFlags = 0;
    cd.componentFlagsMask = 0;
    cd.componentType = kAudioUnitType_Mixer;
    cd.componentSubType = kAudioUnitSubType_StereoMixer;

    AUGraphAddNode(audioGraph, &cd, &mixerNode);
    AUGraphNodeInfo(audioGraph, mixerNode, &cd, &mixerUnit);

    AUGraphConnectNodeInput(audioGraph, mixerNode, 0, outputNode, 0);

    AUGraphOpen(audioGraph);
    AUGraphInitialize(audioGraph);
    AUGraphStart(audioGraph);

    AUNode synthNode;


    cd.componentManufacturer = kAudioUnitManufacturer_Apple;
    cd.componentFlags = 0;
    cd.componentFlagsMask = 0;
    cd.componentType = kAudioUnitType_MusicDevice;
    cd.componentSubType = kAudioUnitSubType_DLSSynth;

    AUGraphAddNode(audioGraph, &cd, &synthNode);
    AUGraphNodeInfo(audioGraph, synthNode, &cd, &synthUnit);

    AUGraphConnectNodeInput(audioGraph, synthNode, 0, mixerNode, 0);

    AUGraphUpdate(audioGraph, NULL);
    CAShow(audioGraph);

}

- (IBAction)playMusic:(id)sender {
    MusicDeviceMIDIEvent(synthUnit, 0x90, 60, 127, 0);
    sleep(1);
    MusicDeviceMIDIEvent(synthUnit, 0x90, 62, 127, 0);
    sleep(1);
    MusicDeviceMIDIEvent(synthUnit, 0x90, 64, 127, 0);
}

- (void)one:(id)sender {
    MusicDeviceMIDIEvent(synthUnit, 0x90, 60, 127, 0);
}

- (void)two:(id)sender {
    MusicDeviceMIDIEvent(synthUnit, 0x90, 62, 127, 0);
}

- (void)three:(id)sender {
    MusicDeviceMIDIEvent(synthUnit, 0x90, 64, 127, 0);
}

发生什么事了？我该如何解决这个问题？

谢谢。

Answer 1

好吧，我明白了!

基本上，我只是忘记停止演奏音符，尽管它们逐渐变得安静，但它们仍在演奏并使计算机正常工作。

可以通过将力度设置为 0 再次播放音符来解决此问题。因此，代码将如下所示:

- (IBAction)playMusic:(id)sender {
    MusicDeviceMIDIEvent(synthUnit, 0x90, 60, 127, 0);
    MusicDeviceMIDIEvent(synthUnit, 0x90, 60, 0, 0);
    sleep(1);
    MusicDeviceMIDIEvent(synthUnit, 0x90, 62, 127, 0);
    MusicDeviceMIDIEvent(synthUnit, 0x90, 62, 0, 0);
    sleep(1);
    MusicDeviceMIDIEvent(synthUnit, 0x90, 64, 127, 0);
    MusicDeviceMIDIEvent(synthUnit, 0x90, 64, 0, 0);
}

- (void)one:(id)sender {
    MusicDeviceMIDIEvent(synthUnit, 0x90, 60, 127, 0);
    MusicDeviceMIDIEvent(synthUnit, 0x90, 60, 0, 0);
}

- (void)two:(id)sender {
    MusicDeviceMIDIEvent(synthUnit, 0x90, 62, 127, 0);
    MusicDeviceMIDIEvent(synthUnit, 0x90, 62, 0, 0);
}

- (void)three:(id)sender {
    MusicDeviceMIDIEvent(synthUnit, 0x90, 64, 127, 0);
    MusicDeviceMIDIEvent(synthUnit, 0x90, 64, 0, 0);
}

我想如果我想让音符播放更长时间，我可以在开始和停止音符之间等待。

感谢您的所有帮助:@user757808 @Peter Hosey @mbykov