我正在开发一个iOS项目，需要从麦克风捕获输入并将其转换为ULaw(以发送数据流)。我正在使用带有转换器节点的AUGraph来完成此任务。该图已成功创建并初始化，但是在我的渲染通知回调中，即使inNumberFrame包含值93，ioData缓冲区也始终包含NULL。由于格式转换器缓冲区的大小不正确，我认为这可能与某些东西有关，但我可以确定了解发生了什么事。
这是代码:
OSStatus status;
// ************************** DEFINE AUDIO STREAM FORMATS ******************************
double currentSampleRate;
currentSampleRate = [[AVAudioSession sharedInstance] sampleRate];
// Describe stream format
AudioStreamBasicDescription streamAudioFormat = {0};
streamAudioFormat.mSampleRate = 8000.00;
streamAudioFormat.mFormatID = kAudioFormatULaw;
streamAudioFormat.mFormatFlags = kAudioFormatFlagIsPacked | kAudioFormatFlagIsSignedInteger;
streamAudioFormat.mFramesPerPacket = 1;
streamAudioFormat.mChannelsPerFrame = 1;
streamAudioFormat.mBitsPerChannel = 8;
streamAudioFormat.mBytesPerPacket = 1;
streamAudioFormat.mBytesPerFrame = streamAudioFormat.mBytesPerPacket * streamAudioFormat.mFramesPerPacket;
// ************************** SETUP SEND AUDIO ******************************
AUNode ioSendNode;
AUNode convertToULAWNode;
AUNode convertToLPCMNode;
AudioUnit convertToULAWUnit;
AudioUnit convertToLPCMUnit;
status = NewAUGraph(&singleChannelSendGraph);
if (status != noErr)
{
NSLog(@"Unable to create send audio graph.");
return;
}
AudioComponentDescription ioDesc = {0};
ioDesc.componentType = kAudioUnitType_Output;
ioDesc.componentSubType = kAudioUnitSubType_VoiceProcessingIO;
ioDesc.componentManufacturer = kAudioUnitManufacturer_Apple;
ioDesc.componentFlags = 0;
ioDesc.componentFlagsMask = 0;
status = AUGraphAddNode(singleChannelSendGraph, &ioDesc, &ioSendNode);
if (status != noErr)
{
NSLog(@"Unable to add IO node.");
return;
}
AudioComponentDescription converterDesc = {0};
converterDesc.componentType = kAudioUnitType_FormatConverter;
converterDesc.componentSubType = kAudioUnitSubType_AUConverter;
converterDesc.componentManufacturer = kAudioUnitManufacturer_Apple;
converterDesc.componentFlags = 0;
converterDesc.componentFlagsMask = 0;
status = AUGraphAddNode(singleChannelSendGraph, &converterDesc, &convertToULAWNode);
if (status != noErr)
{
NSLog(@"Unable to add ULAW converter node.");
return;
}
status = AUGraphAddNode(singleChannelSendGraph, &converterDesc, &convertToLPCMNode);
if (status != noErr)
{
NSLog(@"Unable to add LPCM converter node.");
return;
}
status = AUGraphOpen(singleChannelSendGraph);
if (status != noErr)
{
return;
}
// get the io audio unit
status = AUGraphNodeInfo(singleChannelSendGraph, ioSendNode, NULL, &ioSendUnit);
if (status != noErr)
{
NSLog(@"Unable to get IO unit.");
return;
}
UInt32 enableInput = 1;
status = AudioUnitSetProperty (ioSendUnit,
kAudioOutputUnitProperty_EnableIO,
kAudioUnitScope_Input,
1, // microphone bus
&enableInput,
sizeof (enableInput)
);
if (status != noErr)
{
return;
}
UInt32 sizeASBD = sizeof(AudioStreamBasicDescription);
AudioStreamBasicDescription ioASBDin;
AudioStreamBasicDescription ioASBDout;
status = AudioUnitGetProperty(ioSendUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 1, &ioASBDin, &sizeASBD);
if (status != noErr)
{
NSLog(@"Unable to get IO stream input format.");
return;
}
status = AudioUnitGetProperty(ioSendUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, &ioASBDout, &sizeASBD);
if (status != noErr)
{
NSLog(@"Unable to get IO stream output format.");
return;
}
ioASBDin.mSampleRate = currentSampleRate;
ioASBDout.mSampleRate = currentSampleRate;
status = AudioUnitSetProperty(ioSendUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 1, &ioASBDin, sizeof(ioASBDin));
if (status != noErr)
{
NSLog(@"Unable to set IO stream output format.");
return;
}
status = AudioUnitSetProperty(ioSendUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &ioASBDin, sizeof(ioASBDin));
if (status != noErr)
{
NSLog(@"Unable to set IO stream input format.");
return;
}
// get the converter audio unit
status = AUGraphNodeInfo(singleChannelSendGraph, convertToULAWNode, NULL, &convertToULAWUnit);
if (status != noErr)
{
NSLog(@"Unable to get ULAW converter unit.");
return;
}
status = AudioUnitSetProperty(convertToULAWUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &ioASBDin, sizeof(ioASBDin));
if (status != noErr)
{
NSLog(@"Unable to set ULAW stream input format.");
return;
}
status = AudioUnitSetProperty(convertToULAWUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, &streamAudioFormat, sizeof(streamAudioFormat));
if (status != noErr)
{
NSLog(@"Unable to set ULAW stream output format.");
return;
}
// get the converter audio unit
status = AUGraphNodeInfo(singleChannelSendGraph, convertToLPCMNode, NULL, &convertToLPCMUnit);
if (status != noErr)
{
NSLog(@"Unable to get LPCM converter unit.");
return;
}
status = AudioUnitSetProperty(convertToLPCMUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &streamAudioFormat, sizeof(streamAudioFormat));
if (status != noErr)
{
NSLog(@"Unable to set LPCM stream input format.");
return;
}
status = AudioUnitSetProperty(convertToLPCMUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, &ioASBDin, sizeof(ioASBDin));
if (status != noErr)
{
NSLog(@"Unable to set LPCM stream output format.");
return;
}
status = AUGraphConnectNodeInput(singleChannelSendGraph, ioSendNode, 1, convertToULAWNode, 0);
if (status != noErr)
{
NSLog(@"Unable to set ULAW node input.");
return;
}
status = AUGraphConnectNodeInput(singleChannelSendGraph, convertToULAWNode, 0, convertToLPCMNode, 0);
if (status != noErr)
{
NSLog(@"Unable to set LPCM node input.");
return;
}
status = AUGraphConnectNodeInput(singleChannelSendGraph, convertToLPCMNode, 0, ioSendNode, 0);
if (status != noErr)
{
NSLog(@"Unable to set IO node input.");
return;
}
status = AudioUnitAddRenderNotify(convertToULAWUnit, &outputULAWCallback, (__bridge void*)self);
if (status != noErr)
{
NSLog(@"Unable to add ULAW render notify.");
return;
}
status = AUGraphInitialize(singleChannelSendGraph);
if (status != noErr)
{
NSLog(@"Unable to initialize send graph.");
return;
}
CAShow (singleChannelSendGraph);
}
图节点被初始化为:
Member Nodes:
node 1: 'auou' 'vpio' 'appl', instance 0x7fd5faf8fac0 O I
node 2: 'aufc' 'conv' 'appl', instance 0x7fd5fad05420 O I
node 3: 'aufc' 'conv' 'appl', instance 0x7fd5fad05810 O I
Connections:
node 1 bus 1 => node 2 bus 0 [ 1 ch, 44100 Hz, 'lpcm' (0x0000000C) 16-bit little-endian signed integer]
node 2 bus 0 => node 3 bus 0 [ 1 ch, 8000 Hz, 'ulaw' (0x0000000C) 8 bits/channel, 1 bytes/packet, 1 frames/packet, 1 bytes/frame]
node 3 bus 0 => node 1 bus 0 [ 1 ch, 44100 Hz, 'lpcm' (0x0000000C) 16-bit little-endian signed integer]
渲染通知回调:
static OSStatus outputULAWCallback(void *inRefCon,
AudioUnitRenderActionFlags *ioActionFlags,
const AudioTimeStamp *inTimeStamp,
UInt32 inBusNumber,
UInt32 inNumberFrames,
AudioBufferList *ioData)
{
AudioManager *audioManager = (__bridge AudioManager*)inRefCon;
if ((*ioActionFlags) & kAudioUnitRenderAction_PostRender)
{
if (!audioManager.mute && ioData->mBuffers[0].mData != NULL)
{
TPCircularBufferProduceBytes(audioManager.activeChannel == 0 ? audioManager.channel1StreamOutBufferPtr : audioManager.channel2StreamOutBufferPtr,
ioData->mBuffers[0].mData, ioData->mBuffers[0].mDataByteSize);
// do not want to playback our audio into local speaker
SilenceData(ioData);
}
}
return noErr;
}
注意:如果我直接将麦克风输入发送到输出(跳过转换器节点)，我会听到输出，因此我知道AUGraph在工作。
我有一个接收AUGraph设置，可以从流中接收ULaw，并通过转换器运行以播放扬声器，并且工作正常。
只是无法弄清楚转换器为什么会失败并且不返回任何数据。
有没有人对这种类型的问题有任何经验？
最佳答案
更新
因此，您在其他地方调用了AUGraphStart，但是ulaw转换器拒绝为您执行常规速率转换:(您可以在图形中添加另一个速率转换器，也可以简单地使用vpio单元为您执行此操作。更改此代码
ioASBDin.mSampleRate = currentSampleRate; // change me to 8000Hz
ioASBDout.mSampleRate = currentSampleRate; // delete me, I'm ignored
status = AudioUnitSetProperty(ioSendUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 1, &ioASBDin, sizeof(ioASBDin));
进入
ioASBDin.mSampleRate = streamAudioFormat.mSampleRate; // a.k.a 8000Hz
status = AudioUnitSetProperty(ioSendUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 1, &ioASBDin, sizeof(ioASBDin));
将使整个图形达到8kHz，并为您提供非null的ioData缓冲区:
AudioUnitGraph 0xCA51000:
Member Nodes:
node 1: 'auou' 'vpio' 'appl', instance 0x7b5bb320 O I
node 2: 'aufc' 'conv' 'appl', instance 0x7c878d50 O I
node 3: 'aufc' 'conv' 'appl', instance 0x7c875eb0 O I
Connections:
node 1 bus 1 => node 2 bus 0 [ 1 ch, 8000 Hz, 'lpcm' (0x0000000C) 16-bit little-endian signed integer]
node 2 bus 0 => node 3 bus 0 [ 1 ch, 8000 Hz, 'ulaw' (0x0000000C) 8 bits/channel, 1 bytes/packet, 1 frames/packet, 1 bytes/frame]
node 3 bus 0 => node 1 bus 0 [ 1 ch, 8000 Hz, 'lpcm' (0x0000000C) 16-bit little-endian signed integer]
CurrentState:
mLastUpdateError=0, eventsToProcess=F, isInitialized=T, isRunning=T (1)
旧答案
你需要
AUGraphStart您的图表mSampleRate更改为11025、22050或44100 那么您会在
kAudioUnitRenderAction_PostRender阶段看到非null的ioData。转换为8kHz甚至16kHz的律法似乎是音频转换器应该能够完成的工作。我不知道为什么它不起作用，但是当您将采样率设置为第2点中的值以外的任何值时，ulaw转换器会报告
kAUGraphErr_CannotDoInCurrentContext(-10863)错误，这对我来说毫无意义。