c++ - QAudioOutput - 应用程序大小不断增长

Question

我正在尝试每 20 毫秒写入一次 QAudioOutput 的缓冲区。当我尝试执行此代码时，我可以看到进程的大小每秒增加约 4-8 kB。我试图找到一些函数来清除 QIODevice 或 DAudioOuptut 的内部缓冲区，但没有成功。

我正在使用 Qt 5.2.1

在下面的例子中只写了silence(zeros)但是它有同样的效果:

#include <QLibraryInfo>
#include <QtCore/QCoreApplication>
#include <windows.h> // for Sleep
#include <QAudioOutput>
#include <QAudioDeviceInfo>
#include <QAudioFormat>
#include <array>

class QAudioOutput;

int main(int argc, char *argv[])
{
    // Create QApplication
    QCoreApplication app(argc, argv);
    app.setApplicationName("Audiotest");
    //Initialize device
    QIODevice * _output;
    QAudioDeviceInfo _device = QAudioDeviceInfo::defaultOutputDevice();
    QAudioFormat _format;
    _format.setSampleRate(44100);
    _format.setChannelCount(2);
    _format.setSampleSize(16);
    _format.setCodec("audio/pcm");  // This codec should be supported on all platforms and plugin implementation
    _format.setByteOrder(QAudioFormat::LittleEndian);
    _format.setSampleType(QAudioFormat::SignedInt);
    if (!_device.isFormatSupported(_format)) {
        printf("Default format not supported - trying to use nearest.\n");
        _format = _device.nearestFormat(_format);
    }
    QAudioOutput * _audioOutput = new QAudioOutput(_device, _format);
    _output = _audioOutput->start();
    std::array<char, 32768> _buffer;
    _buffer.fill(0);


    for (;;) {
        const int periodSize = _audioOutput->periodSize();
        const int chunks = _audioOutput->bytesFree() / periodSize;
        for (int i = 0; i < chunks; ++i) {
            const qint64 len = periodSize;
            if (len && _output) {
                _output->write(_buffer.data(), len);
            }
            if (len != periodSize) {
                break;
            }
        }
        Sleep(20);
    }
    return 0;
}

Answer 1

当你的循环运行时，没有其他事情发生。您的代码应该是异步的，并且您应该反转控制流。对音频输出设备的通知作出 react ，它已经处理了一定间隔的样本。

要接收第一个通知，您需要为设备准备一些数据。

// https://github.com/KubaO/stackoverflown/tree/master/questions/audio-37993427
#include <QtMultimedia>
#include <array>

int main(int argc, char ** argv) {
   QCoreApplication app{argc, argv};
   auto device = QAudioDeviceInfo::defaultOutputDevice();
   QAudioFormat format;
   format.setSampleRate(44100);
   format.setChannelCount(2);
   format.setSampleSize(16);
   format.setCodec("audio/pcm");
   format.setByteOrder(QAudioFormat::LittleEndian);
   format.setSampleType(QAudioFormat::SignedInt);
   if (!device.isFormatSupported(format))
      qFatal("Default format not supported");
   QAudioOutput audioOutput{device, format};
   auto output = audioOutput.start();
   qDebug() << audioOutput.state();
   std::array<char, 32768> buffer;
   buffer.fill(0);

   auto write = [&]{
      qDebug() << "notify";
      auto periodSize = audioOutput.periodSize();
      auto chunks = audioOutput.bytesFree() / periodSize;
      for (int i = 0; i < chunks; ++i) {
         if (periodSize && output) {
            auto len = output->write(buffer.data(), periodSize);
            if (len != periodSize)
               break;
         }
      }
   };

   audioOutput.setNotifyInterval(20);
   QObject::connect(&audioOutput, &QAudioOutput::notify, write);
   write();
   return app.exec();
}