Qt QAudioOutput mode

I have a question about how to use QAudioOutput to directly record a sample with a specific sampling rate to a sound output device. I write an emulator that emulates sound chips based on a frame, and then receives a buffer containing a frame, which stands for sound samples that I would like to record on the audio output. Currently, to test my sound output routine, I allocate a huge (5-minute) buffer for entering random numbers, for example:

Title:

uint16_t *audio_outputBuffer;
uint32_t audio_bytesRemainingToRead;
QAudioOutput *audio_outputStream;
QIODevice *audio_outputDevice;

Implementation:

audio_outputBuffer = (uint16_t *) malloc((96000 * 4) * 300);
int i = 0;

uint16_t *tempAudioBuffer = audio_outputBuffer;
for(i = 0; i < ((96000 * 4) * 150); i++) {
    *tempAudioBuffer = (uint16_t) rand() & 0xFFFF;
    tempAudioBuffer++;
}

audio_bytesRemainingToRead = (96000 * 4) * 300;

Then I set up my audio device with some basic parameters:

// Set up the format
QAudioFormat format;
format.setFrequency(96000); // Usually this is specified through an UI option
format.setChannels(2);
format.setSampleSize(16);
format.setCodec("audio/pcm");
format.setByteOrder(QAudioFormat::LittleEndian);
format.setSampleType(QAudioFormat::UnSignedInt);

// There code here to notify the user of inability to match the format and choose an action, which is omitted for clarity

// Create audio output stream, set up signals
audio_outputStream = new QAudioOutput(format, this);

connect(audio_outputStream, SIGNAL(stateChanged(QAudio::State)), this, SLOT(audio_stateChanged(QAudio::State)));

audio_outputDevice = audio_outputStream->start();

Then, in my timer procedure, which QTimer calls at 60 FPS, I do the following code to write a “chunk” of audio data to the QAudioOutput buffer:

if(audio_outputDevice->isOpen() && audio_outputStream->state() != QAudio::StoppedState) {
    qint64 bytesOfAudioWrittenToDevice = audio_outputDevice->write((char *) audio_outputBuffer, audio_outputStream->periodSize());
    audio_bytesRemainingToRead -= bytesOfAudioWrittenToDevice;
    qDebug() << "Wrote" << bytesOfAudioWrittenToDevice << "bytes of audio to output device. Remaining bytes to read:" << audio_bytesRemainingToRead;
    qDebug() << "Free bytes in audio output:" << audio_outputStream->bytesFree();
}

As soon as I started the audio output process, I get the following output on the console:

Current audio state: 3 Error: 0 
Wrote 2048 bytes of audio to output device. Remaining bytes to read: 115197952 
Free bytes in audio output: 6144 
Current audio state: 0 Error: 0 
Wrote 2048 bytes of audio to output device. Remaining bytes to read: 115195904 
Free bytes in audio output: 4096 
Wrote 2048 bytes of audio to output device. Remaining bytes to read: 115193856 
Free bytes in audio output: 2048
Wrote 2048 bytes of audio to output device. Remaining bytes to read: 115191808 
Free bytes in audio output: 0 (This and the above line is repeated forever)

, QAudioOutput , " , ".

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(, Qt 4.8.1, Mac OS X 10.7.4.)

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