我目前有一个简单的需求,即编写一个iOS应用程序,使用AudioUnits从音频文件读取并输出到扬声器。不使用高级API的原因是,在某些时候,我需要处理从音频文件传出的样本,并最终将其发送到网络上。
我已经有一个可以工作的代码,它可以读取音频文件并播放到扬声器中。唯一的问题是,回调函数没有起作用。回调函数从未被调用,也没有收到任何注册时的错误提示。非常感谢您的帮助(我是Core Audio的初学者,这是我在stackoverflow上的第一个问题,因此请原谅任何基础性的错误/疏忽)。我用于初始化图形的代码片段已附上。
void createMyAUGraph (MyAUGraphPlayerST *player) {
// Create a new AUGraph
CheckError(NewAUGraph(&player->graph), "New AUGraph failed");
// Generate description for output
AudioComponentDescription outputcd = {0};
outputcd.componentType = kAudioUnitType_Output;
outputcd.componentSubType = kAudioUnitSubType_RemoteIO;
outputcd.componentManufacturer = kAudioUnitManufacturer_Apple;
outputcd.componentFlags = 0;
outputcd.componentFlagsMask = 0;
// Add new node
AUNode outputNode;
CheckError(AUGraphAddNode(player->graph, &outputcd, &outputNode), "Add output node failed");
// Node for file player
AudioComponentDescription fileplayercd = {0};
fileplayercd.componentType = kAudioUnitType_Generator;
fileplayercd.componentSubType = kAudioUnitSubType_AudioFilePlayer;
fileplayercd.componentManufacturer = kAudioUnitManufacturer_Apple;
// Add new node
AUNode fileNode;
CheckError(AUGraphAddNode(player->graph, &fileplayercd, &fileNode), "Add file node failed");
// Open graph
CheckError(AUGraphOpen(player->graph), "Graph open failed");
// Retrive AudioUnit
CheckError(AUGraphNodeInfo(player->graph, outputNode, NULL, &player->outputAU), "file unit retrive failed");
CheckError(AUGraphNodeInfo(player->graph, fileNode, NULL, &player->fileAU), "file unit retrive failed");
// connect nodes
CheckError(AUGraphConnectNodeInput(player->graph, fileNode, 0, outputNode, 0), "failed to connect nodes");
// some other setup
UInt32 flag = 1;
CheckError(AudioUnitSetProperty(player->outputAU,
kAudioOutputUnitProperty_EnableIO,
kAudioUnitScope_Output,
0,
&flag,
sizeof (flag)), "Set io property failed");
// Register render callback
AURenderCallbackStruct output_cb;
output_cb.inputProc = recording_cb;
output_cb.inputProcRefCon = player;
CheckError(AudioUnitSetProperty(player->outputAU, kAudioUnitProperty_SetRenderCallback, kAudioUnitScope_Global, 0, &output_cb, sizeof (output_cb)), "callback register failed");
// initialize graph
CheckError(AUGraphInitialize(player->graph), "graph initialization failed");
}