live AAC encoding with audio units

2
votes

I'm trying to do some streaming with Audio Unit Services and Audio Converter Service but I'm a bit stuck. My goal is to capture microphone input (PCM), convert it on the fly to AAC and send the packet over the network. It seems to works but the audio is terrible and the app crash after 4s

// init the Audio Unit

OSStatus status;
    AudioComponentDescription desc;
    desc.componentType = kAudioUnitType_Output;
    desc.componentSubType = kAudioUnitSubType_RemoteIO;
    desc.componentFlags = 0;
    desc.componentFlagsMask = 0;
    desc.componentManufacturer = kAudioUnitManufacturer_Apple;

    AudioComponent component = AudioComponentFindNext(NULL, &desc);
    status = AudioComponentInstanceNew(component, &_audioUnit);
    NSLog(@"status instance new: %lu",status);

    UInt32 flag = 1;
    status = AudioUnitSetProperty(_audioUnit,
                                  kAudioOutputUnitProperty_EnableIO,
                                  kAudioUnitScope_Input,
                                  1,
                                  &flag,
                                  sizeof(flag));
    NSLog(@"status AudioUnitSetProperty input: %lu",status);

    AudioStreamBasicDescription audioFormat;
    memset(&audioFormat, 0, sizeof(AudioStreamBasicDescription));
    audioFormat.mSampleRate         = 44100;
    audioFormat.mFormatID           = kAudioFormatLinearPCM;
    audioFormat.mFormatFlags        = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
    audioFormat.mFramesPerPacket    = 1;
    audioFormat.mChannelsPerFrame   = 1;
    audioFormat.mBitsPerChannel     = 16;
    audioFormat.mBytesPerPacket     =
    audioFormat.mBytesPerFrame      = audioFormat.mChannelsPerFrame * sizeof(SInt16);

    status = AudioUnitSetProperty(_audioUnit,
                                  kAudioUnitProperty_StreamFormat,
                                  kAudioUnitScope_Input,
                                  0,
                                  &audioFormat,
                                  sizeof(audioFormat));
    NSLog(@"status AudioUnitSetProperty audioFormat: %lu",status);

    AURenderCallbackStruct renderCallbackInfo;
    renderCallbackInfo.inputProc       = recordingCallback;
    renderCallbackInfo.inputProcRefCon = NULL;
    AudioUnitSetProperty(_audioUnit,
                         kAudioOutputUnitProperty_SetInputCallback,
                         kAudioUnitScope_Global,
                         1,
                         &renderCallbackInfo,
                         sizeof(renderCallbackInfo));

    float aBufferLength = 0.005; // In seconds
    AudioSessionSetProperty(kAudioSessionProperty_PreferredHardwareIOBufferDuration,
                            sizeof(aBufferLength), &aBufferLength);

    _converter = [[Converter alloc] initWithFormat];
    status = AudioUnitInitialize(_audioUnit);
    NSLog(@"status AudioUnit initialize: %lu",status);

//recording callback : 

static OSStatus recordingCallback(void *inRefCon,
                                  AudioUnitRenderActionFlags *ioActionFlags,
                                  const AudioTimeStamp *inTimeStamp,
                                  UInt32 inBusNumber,
                                  UInt32 inNumberFrames,
                                  AudioBufferList *ioData) {

    AudioBufferList bufferList;
    bufferList.mNumberBuffers = 1;
    bufferList.mBuffers[0].mNumberChannels = 1;
    bufferList.mBuffers[0].mData = NULL;
    bufferList.mBuffers[0].mDataByteSize = inNumberFrames * sizeof(SInt16);
    OSStatus status = AudioUnitRender(_audioUnit, ioActionFlags, inTimeStamp,1, inNumberFrames, &bufferList);
    AudioBuffer aac;

    pcm.mData = malloc(inNumberFrames * sizeof(SInt16));
    unsigned char * p = malloc(inNumberFrames * sizeof(SInt16));
    memcpy(p, bufferList.mBuffers[0].mData, inNumberFrames * sizeof(SInt16));
    memcpy(pcm.mData,p,bufferList.mBuffers[0].mDataByteSize); // dunno why i can't memcpy bufferlist data directly to pcm struct
    pcm.mDataByteSize = inNumberFrames * sizeof(SInt16);
    pcm.mNumberChannels = 1;
    int osstatus = [_converter convertAudioBuffer:&pcm EncodedAudioBuffer:&aac];

    // send to the network
    NSData* data = [[NSData alloc]initWithBytes:aac.mData length:aac.mDataByteSize];
    dispatch_async(myQueue, ^{_pts+=1024;[sender sendBuf2:data withTime:_pts];});
    return noErr;
}

// converter side : 

-(int) convertAudioBuffer:(AudioBuffer*)inSamples EncodedAudioBuffer:(AudioBuffer*) outData{
    memset(_buffer, 0, _converterSettings.maxPacketSize);

    _converterSettings.buffer = *inSamples;
    //_converterSettings.bytesToEncode = inSamples->mDataByteSize;

    UInt32 ioOutputDataPackets = 1;
    AudioStreamPacketDescription outPacketDesc[1];


    AudioBufferList convertedData;
    convertedData.mNumberBuffers = 1;
    convertedData.mBuffers[0].mNumberChannels = 1;
    convertedData.mBuffers[0].mDataByteSize = _converterSettings.maxPacketSize;
    convertedData.mBuffers[0].mData = _buffer;

    OSStatus error = AudioConverterFillComplexBuffer(_audioConverter,
                                                     MyAudioConverterCallback,
                                                     &_converterSettings,
                                                     &ioOutputDataPackets,
                                                     &convertedData,
                                                     outPacketDesc);
    if (error != noErr)
    {
        NSError *err = [NSError errorWithDomain:NSOSStatusErrorDomain code:error userInfo:nil];
        NSLog(@"%ld",convertedData.mBuffers[0].mDataByteSize);
    }
    NSLog(@"%ld",convertedData.mBuffers[0].mDataByteSize);
    /* Set the ouput data */
    outData->mNumberChannels    = convertedData.mBuffers[0].mNumberChannels;
    outData->mDataByteSize      = convertedData.mBuffers[0].mDataByteSize;
    outData->mData              = convertedData.mBuffers[0].mData;
    return 0;
}

proc callback : 

OSStatus MyAudioConverterCallback(AudioConverterRef inAudioConverter,
                                  UInt32 *ioDataPacketCount,
                                  AudioBufferList *ioData,
                                  AudioStreamPacketDescription **outDataPacketDescription,
                                  void *inUserData)
{   
    if (outDataPacketDescription)
    {
        *outDataPacketDescription = NULL;
    }
    Settings *audioConverterSettings = (Settings *)inUserData;
    ioData->mBuffers[0].mData = audioConverterSettings->buffer.mData;
    ioData->mBuffers[0].mDataByteSize = audioConverterSettings->buffer.mDataByteSize;
    ioData->mBuffers[0].mNumberChannels = audioConverterSettings->buffer.mNumberChannels;

    return noErr;
}

and finally the output : 

2013-07-16 16:58:57.192 AudioUnitAAC[84656:c07] status instance new: 0
2013-07-16 16:58:57.195 AudioUnitAAC[84656:c07] status AudioUnitSetProperty input: 0
2013-07-16 16:58:57.197 AudioUnitAAC[84656:c07] status AudioUnitSetProperty audioFormat: 0
2013-07-16 16:58:57.235 AudioUnitAAC[84656:c07] status AudioUnit initialize: 0
2013-07-16 16:58:58.182 AudioUnitAAC[84656:c07] start : 0
2013-07-16 16:58:58.200 AudioUnitAAC[84656:6e07] 4 bytes encoded
2013-07-16 16:58:58.211 AudioUnitAAC[84656:6e07] 152 bytes encoded
2013-07-16 16:58:58.223 AudioUnitAAC[84656:6e07] 169 bytes encoded
2013-07-16 16:58:58.235 AudioUnitAAC[84656:6e07] 157 bytes encoded
2013-07-16 16:58:58.246 AudioUnitAAC[84656:6e07] 160 bytes encoded
2013-07-16 16:58:58.258 AudioUnitAAC[84656:6e07] 164 bytes encoded
....

until it crashs for some random reason (AudioConverterFillComplexBuffer bad access, NSLog(@"%ld",convertedData.mBuffers[0].mDataByteSize) bad instruction...)

I'm new with apple audio core and any help would be appreciated :)

1
iosobjective-caudiocore-audio
Did you figure it out? I'm having the same issue on iOS 7.1 - Erik Villegas
nop, I had to get back with Audio Queues - HaneTV

1 Answers

0
votes

Thanks to this post I got it to work! I Changed:

pcm.mData = malloc(inNumberFrames * sizeof(SInt16));
unsigned char * p = malloc(inNumberFrames * sizeof(SInt16));
memcpy(p, bufferList.mBuffers[0].mData, inNumberFrames * sizeof(SInt16));
memcpy(pcm.mData,p,bufferList.mBuffers[0].mDataByteSize); // dunno why i can't memcpy bufferlist data directly to pcm struct
pcm.mDataByteSize = inNumberFrames * sizeof(SInt16);
pcm.mNumberChannels = 1;

to:

memset(&audioBuffer, 0, sizeof(AudioBufferList));
memset(&audioBuffer.mBuffers[0], 0, sizeof(AudioBuffer));
audioBuffer.mNumberBuffers = 1;
audioBuffer.mBuffers[0].mNumberChannels = bufferList->mBuffers[0].mNumberChannels;
audioBuffer.mBuffers[0].mDataByteSize = bufferList->mBuffers[0].mDataByteSize;
audioBuffer.mBuffers[0].mData = bufferList->mBuffers[0].mData;

And in the callback I do this:

ioData->mBuffers[0].mData = audioBuffer.mBuffers[0].mData;
ioData->mBuffers[0].mDataByteSize = audioBuffer.mBuffers[0].mDataByteSize;
ioData->mBuffers[0].mNumberChannels = audioBuffer.mBuffers[0].mNumberChannels;