Audio Unit 实现音频录制功能
录制音频流程图
使用Audio Unit录制的时候，过程相对简单，我们使用一个Audio Unit就可以完成了，步骤如下：
- 设置好AudioComponentDescription，确定我们使用的Audio Unit类型
- 获取Audio Unit实例，我们有两种获取方式，通过AUGraph获取，通过AudioComponent获取。
- 设置Audio Unit的属性，告诉系统我们需要使用Audio Unit的哪些功能以及需要采集什么样的数据。
- 开始录制和结束录制的控制。
- 从回调函数中取得音频数据。
初始化
- (instancetype)initWithAsbd:(AudioStreamBasicDescription)asbd {
self = [super init];
if (self) {
_asbd = asbd;
_queue = dispatch_queue_create("zf.audioRecorder", DISPATCH_QUEUE_SERIAL);
[self setupAcd];
dispatch_async(_queue, ^{
// [self createInputUnit];
[self getAudioUnits];
[self setupAudioUnits];
});
}
return self;
}
设置AudioComponentDescription
- (void)setupAcd {
_ioUnitDesc.componentType = kAudioUnitType_Output;
//vpio模式
_ioUnitDesc.componentSubType = kAudioUnitSubType_VoiceProcessingIO;
_ioUnitDesc.componentManufacturer = kAudioUnitManufacturer_Apple;
_ioUnitDesc.componentFlags = 0;
_ioUnitDesc.componentFlagsMask = 0;
}
获取Audio Unit实例
通过AUGraph获取实例
- (void)getAudioUnits {
OSStatus status = NewAUGraph(&_graph);
printf("create graph %d \n", (int)status);
AUNode ioNode;
status = AUGraphAddNode(_graph, &_ioUnitDesc, &ioNode);
printf("add ioNote %d \n", (int)status);
//instantiate the audio units
status = AUGraphOpen(_graph);
printf("open graph %d \n", (int)status);
//obtain references to the audio unit instances
status = AUGraphNodeInfo(_graph, ioNode, NULL, &_ioUnit);
printf("get ioUnit %d \n", (int)status);
}
通过AudioComponent获取实例
- (void)createInputUnit {
AudioComponent comp = AudioComponentFindNext(NULL, &_ioUnitDesc);
if (comp == NULL) {
printf("can't get AudioComponent");
}
OSStatus status = AudioComponentInstanceNew(comp, &(_ioUnit));
printf("creat audio unit %d \n", (int)status);
}
设置Audio Unit属性
- (void)setupAudioUnits {
OSStatus status;
//音频输入默认是关闭的，需要开启 0:关闭，1:开启
UInt32 enableInput = 1; // to enable input
UInt32 propertySize;
status = AudioUnitSetProperty(_ioUnit,
kAudioOutputUnitProperty_EnableIO,
kAudioUnitScope_Input,
1,
&enableInput,
sizeof(enableInput));
printf("enable input %d \n", (int)status);
//关闭音频输出
UInt32 disableOutput = 0; // to disable output
status = AudioUnitSetProperty(_ioUnit,
kAudioOutputUnitProperty_EnableIO,
kAudioUnitScope_Output,
0,
&disableOutput,
sizeof(disableOutput));
printf("disable output %d \n", (int)status);
//设置stram format
propertySize = sizeof (AudioStreamBasicDescription);
status = AudioUnitSetProperty(_ioUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Output,
1,
&_asbd,
propertySize);
printf("set input format %d \n", (int)status);
//检查是否设置成功
AudioStreamBasicDescription deviceFormat;
status = AudioUnitGetProperty(_ioUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Output,
1,
&deviceFormat,
&propertySize);
printf("get input format %d \n", (int)status);
//设置最大采集帧数
UInt32 maxFramesPerSlice = 4096;
propertySize = sizeof(UInt32);
status = AudioUnitSetProperty(_ioUnit,
kAudioUnitProperty_MaximumFramesPerSlice,
kAudioUnitScope_Global,
0,
&maxFramesPerSlice,
propertySize);
printf("set max frame per slice: %d, %d \n", (int)maxFramesPerSlice, (int)status);
AudioUnitGetProperty(_ioUnit,
kAudioUnitProperty_MaximumFramesPerSlice,
kAudioUnitScope_Global,
0,
&maxFramesPerSlice,
&propertySize);
printf("get max frame per slice: %d, %d \n", (int)maxFramesPerSlice, (int)status);
//设置回调
AURenderCallbackStruct callbackStruct;
callbackStruct.inputProc = &inputCallback;
callbackStruct.inputProcRefCon = (__bridge void *_Nullable)(self);
status = AudioUnitSetProperty(_ioUnit,
kAudioOutputUnitProperty_SetInputCallback,
kAudioUnitScope_Input,
0,
&callbackStruct,
sizeof(callbackStruct));
printf("set render callback %d \n", (int)status);
}
开始录制
注释的部分是不使用AUGraph的方式。
- (void)startRecord {
dispatch_async(_queue, ^{
OSStatus status;
// status = AudioUnitInitialize(self.ioUnit);
// printf("AudioUnitInitialize %d \n", (int)status);
// status = AudioOutputUnitStart(self.ioUnit);
// printf("AudioOutputUnitStart %d \n", (int)status);
status = AUGraphInitialize(self.graph);
printf("AUGraphInitialize %d \n", (int)status);
status = AUGraphStart(self.graph);
printf("AUGraphStart %d \n", (int)status);
});
}
停止录制
- (void)stopRecord {
dispatch_async(_queue, ^{
OSStatus status;
status = AUGraphStop(self.graph);
printf("AUGraphStop %d \n", (int)status);
});
}
数据回调AURenderCallback
OSStatus inputCallback(void *inRefCon,
AudioUnitRenderActionFlags *ioActionFlags,
const AudioTimeStamp *inTimeStamp,
UInt32 inBusNumber,
UInt32 inNumberFrames,
AudioBufferList *__nullable ioData) {
ZFAudioUnitRecorder *recorder = (__bridge ZFAudioUnitRecorder *)inRefCon;
AudioBuffer buffer;
/**
on this point we define the number of channels, which is mono
for the iphone. the number of frames is usally 512 or 1024.
*/
UInt32 size = inNumberFrames * recorder.asbd.mBytesPerFrame;
buffer.mDataByteSize = size; // sample size
buffer.mNumberChannels = 1; // one channel
buffer.mData = malloc(size); // buffer size
// we put our buffer into a bufferlist array for rendering
AudioBufferList bufferList;
bufferList.mNumberBuffers = 1;
bufferList.mBuffers[0] = buffer;
OSStatus status = noErr;
status = AudioUnitRender(recorder.ioUnit, ioActionFlags, inTimeStamp, 1, inNumberFrames, &bufferList);
if (status != noErr) {
printf("AudioUnitRender %d \n", (int)status);
return status;
}
if ([recorder.delegate respondsToSelector:@selector(audioRecorder:didRecoredAudioData:length:)]) {
[recorder.delegate audioRecorder:recorder didRecoredAudioData:buffer.mData length:buffer.mDataByteSize];
}
free(buffer.mData);
return status;
}
- 回调函数中并没有真正获取到数据，还需要调用AudioUnitRender去取数据。
- 我们使用了malloc开辟了一块内存空间，我们需要用free释放调。
完整代码请到项目地址下载
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