如何动态地向AUGraph添加新乐器

Question

我目前正在创建一个音乐应用程序，您可以在其中添加新乐器作为音乐序列的曲目。

以下是我添加新曲目时的内容：

MusicPlayerStop(_musicPlayer);

status = MusicSequenceNewTrack(sequence, &tracks[tracksCount]);

timeDiff = 32.f/_tempo;

[self setLoopDuration:currentLoopDuration forPattern:tracks[tracksCount]];

AudioComponentDescription samplerNodeDesc;
samplerNodeDesc.componentManufacturer = (OSType)kAudioUnitManufacturer_Apple;
samplerNodeDesc.componentType = (OSType)kAudioUnitType_MusicDevice;
samplerNodeDesc.componentSubType = (OSType)kAudioUnitSubType_Sampler;
samplerNodeDesc.componentFlags = 0;
samplerNodeDesc.componentFlagsMask = 0;


status = AUGraphAddNode(graph, &samplerNodeDesc, &auNodes[tracksCount]);
status = AUGraphNodeInfo(graph, auNodes[tracksCount], 0, &audioUnits[tracksCount]);


status = AUGraphConnectNodeInput(graph, auNodes[tracksCount], 0, filterNode, 0);
status = MusicTrackSetDestNode(tracks[tracksCount], auNodes[tracksCount]);

int trackId = tracksCount;

tracksCount++;

MusicPlayerStart(_musicPlayer);


return trackId;

以下根本不会产生音频，我可以在这做什么。

非常感谢！

Answer 1

您需要致电AUGraphUpdate(graph, nil);或者，如果你希望图形被阻塞直到它已经添加，你就会为它提供一个指向布尔值的指针，调用线程将等待音频线程添加音频单元。

Boolean updated;
AUGraphUpdate(graph, &updated); //will block until end of next audio cycle

if (updated){
    printf("hooray\n");
}