我正在编写一个 iOS 应用程序，它从麦克风捕获音频，使用高通滤波器对其进行过滤，然后通过扬声器播放。
AudioUnitRender当我在 iPhone 4S 上运行渲染回调函数时调用渲染回调函数时出现 -50 OSStatus 错误，但它在模拟器上运行良好。
我正在使用一个AUGraph，它有一个RemoteIO单元、一个HighPassFilter效果单元和一个AUConverter单元来使 HPF 和输出之间的 ASBD 匹配。转换器AudioUnit实例称为converterUnit.
这是代码。
static OSStatus renderInput(void *inRefCon, AudioUnitRenderActionFlags *ioActionFlags, const AudioTimeStamp *inTimeStamp, UInt32 inBusNumber, UInt32 inNumberFrames, AudioBufferList *ioData)
{
AudioController *THIS = (AudioController*)inRefCon;
AudioBuffer buffer;
AudioStreamBasicDescription converterOutputASBD;
UInt32 converterOutputASBDSize = sizeof(converterOutputASBD);
AudioUnitGetProperty([THIS converterUnit], kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, &converterOutputASBD, &converterOutputASBDSize);
buffer.mDataByteSize = inNumberFrames * converterOutputASBD.mBytesPerFrame;
buffer.mNumberChannels = converterOutputASBD.mChannelsPerFrame;
buffer.mData = malloc(buffer.mDataByteSize);
AudioBufferList bufferList;
bufferList.mNumberBuffers = 1;
bufferList.mBuffers[0] = buffer;
OSStatus result = AudioUnitRender([THIS converterUnit], ioActionFlags, inTimeStamp, inBusNumber, inNumberFrames, &bufferList);
...
}
我认为 -50 错误意味着其中一个参数是错误的。唯一可能出错的参数是[THIS converterUnit]and &bufferList，因为所有其余参数都作为参数交给我。我检查了converterUnit 实例，它被正确分配和初始化（更重要的是，如果这是问题所在，它也不会在模拟器上运行）。唯一需要检查的参数是bufferList. 到目前为止，我从调试中可以看出 RemoteIO 的输出元素的输入 ASBD 以及inNumberFrames手机和模拟器中的不同。但是，我认为这对我来说并没有改变，因为我AudioBuffer buffer根据调用产生的 ASBD创建和分配内存AudioUnitGetProperty([THIS ioUnit], kAudioUnitProperty_StreamFormat, ...)。
任何帮助将不胜感激，我在这里有点绝望..
你们真棒。
干杯。
更新：
这是音频控制器类的定义：
@interface AudioController : NSObject
{
AUGraph mGraph;
AudioUnit mEffects;
AudioUnit ioUnit;
AudioUnit converterUnit;
}
@property (readonly, nonatomic) AudioUnit mEffects;
@property (readonly, nonatomic) AudioUnit ioUnit;
@property (readonly, nonatomic) AudioUnit converterUnit;
@property (nonatomic) float* volumenPromedio;
-(void)initializeAUGraph;
-(void)startAUGraph;
-(void)stopAUGraph;
@end
，这是 AUGraph 的初始化代码（在 中定义AudioController.mm）：
- (void)initializeAUGraph
{
NSError *audioSessionError = nil;
AVAudioSession *mySession = [AVAudioSession sharedInstance];
[mySession setPreferredHardwareSampleRate: kGraphSampleRate
error: &audioSessionError];
[mySession setCategory: AVAudioSessionCategoryPlayAndRecord
error: &audioSessionError];
[mySession setActive: YES error: &audioSessionError];
OSStatus result = noErr;
// create a new AUGraph
result = NewAUGraph(&mGraph);
AUNode outputNode;
AUNode effectsNode;
AUNode converterNode;
// effects component
AudioComponentDescription effects_desc;
effects_desc.componentType = kAudioUnitType_Effect;
effects_desc.componentSubType = kAudioUnitSubType_HighPassFilter;
effects_desc.componentFlags = 0;
effects_desc.componentFlagsMask = 0;
effects_desc.componentManufacturer = kAudioUnitManufacturer_Apple;
// output component
AudioComponentDescription output_desc;
output_desc.componentType = kAudioUnitType_Output;
output_desc.componentSubType = kAudioUnitSubType_RemoteIO;
output_desc.componentFlags = 0;
output_desc.componentFlagsMask = 0;
output_desc.componentManufacturer = kAudioUnitManufacturer_Apple;
// stream format converter component
AudioComponentDescription converter_desc;
converter_desc.componentType = kAudioUnitType_FormatConverter;
converter_desc.componentSubType = kAudioUnitSubType_AUConverter;
converter_desc.componentFlags = 0;
converter_desc.componentFlagsMask = 0;
converter_desc.componentManufacturer = kAudioUnitManufacturer_Apple;
// Add nodes to the graph
result = AUGraphAddNode(mGraph, &output_desc, &outputNode);
[self hasError:result:__FILE__:__LINE__];
result = AUGraphAddNode(mGraph, &effects_desc, &effectsNode);
[self hasError:result:__FILE__:__LINE__];
result = AUGraphAddNode(mGraph, &converter_desc, &converterNode);
// manage connections in the graph
// Connect the io unit node's input element's output to the effectsNode input
result = AUGraphConnectNodeInput(mGraph, outputNode, 1, effectsNode, 0);
// Connect the effects node's output to the converter node's input
result = AUGraphConnectNodeInput(mGraph, effectsNode, 0, converterNode, 0);
// open the graph
result = AUGraphOpen(mGraph);
// Get references to the audio units
result = AUGraphNodeInfo(mGraph, effectsNode, NULL, &mEffects);
result = AUGraphNodeInfo(mGraph, outputNode, NULL, &ioUnit);
result = AUGraphNodeInfo(mGraph, converterNode, NULL, &converterUnit);
// Enable input on remote io unit
UInt32 flag = 1;
result = AudioUnitSetProperty(ioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Input, 1, &flag, sizeof(flag));
// Setup render callback struct
AURenderCallbackStruct renderCallbackStruct;
renderCallbackStruct.inputProc = &renderInput;
renderCallbackStruct.inputProcRefCon = self;
result = AUGraphSetNodeInputCallback(mGraph, outputNode, 0, &renderCallbackStruct);
// Get fx unit's input current stream format...
AudioStreamBasicDescription fxInputASBD;
UInt32 sizeOfASBD = sizeof(AudioStreamBasicDescription);
result = AudioUnitGetProperty(mEffects, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &fxInputASBD, &sizeOfASBD);
// ...and set it on the io unit's input scope's output
result = AudioUnitSetProperty(ioUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Output,
1,
&fxInputASBD,
sizeof(fxInputASBD));
// Set fx unit's output sample rate, just in case
Float64 sampleRate = 44100.0;
result = AudioUnitSetProperty(mEffects,
kAudioUnitProperty_SampleRate,
kAudioUnitScope_Output,
0,
&sampleRate,
sizeof(sampleRate));
AudioStreamBasicDescription fxOutputASBD;
// get fx audio unit's output ASBD...
result = AudioUnitGetProperty(mEffects, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, &fxOutputASBD, &sizeOfASBD);
// ...and set it to the converter audio unit's input
result = AudioUnitSetProperty(converterUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &fxOutputASBD, sizeof(fxOutputASBD));
AudioStreamBasicDescription ioUnitsOutputElementInputASBD;
// now get io audio unit's output element's input ASBD...
result = AudioUnitGetProperty(ioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &ioUnitsOutputElementInputASBD, &sizeOfASBD);
// ...set the sample rate...
ioUnitsOutputElementInputASBD.mSampleRate = 44100.0;
// ...and set it to the converter audio unit's output
result = AudioUnitSetProperty(converterUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, &ioUnitsOutputElementInputASBD, sizeof(ioUnitsOutputElementInputASBD));
// initialize graph
result = AUGraphInitialize(mGraph);
}
我使用渲染回调函数（而不是使用AUGraphConnectNodeInput方法）在转换器的输出和远程 io 单元的输出元素的输入之间建立连接的原因是因为我需要在样本被处理后立即对样本进行一些计算高通滤波器。渲染回调让我有机会在AudioUnitRender调用后立即查看样本缓冲区，并在那里进行所述计算。
更新 2：
通过调试，我发现设备和模拟器上远程 IO 输出总线的输入 ASBD 存在差异。它不应该有什么不同（我根据来自先前AudioUnitGetProperty([THIS ioUnit], kAudioUnitProperty_StreamFormat, ...)调用的数据分配和初始化 AudioBufferList），但这是我在设备和模拟器中看到的唯一不同之处。
这是设备上远程 IO 输出总线的输入 ASBD：
Float64 mSampleRate 44100
UInt32 mFormatID 1819304813
UInt32 mFormatFlags 41
UInt32 mBytesPerPacket 4
UInt32 mFramesPerPacket 1
UInt32 mBytesPerFrame 4
UInt32 mChannelsPerFrame 2
UInt32 mBitsPerChannel 32
UInt32 mReserved 0
，这是在模拟器上：
Float64 mSampleRate 44100
UInt32 mFormatID 1819304813
UInt32 mFormatFlags 12
UInt32 mBytesPerPacket 4
UInt32 mFramesPerPacket 1
UInt32 mBytesPerFrame 4
UInt32 mChannelsPerFrame 2
UInt32 mBitsPerChannel 16
UInt32 mReserved 0