Qt audio loopback delay

Hello. Please tell me how to remove the delay when sending voice from the microphone to the speakers.
(OS Linux Mint 18.1, pulseaudio)

Code:

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#include <iostream>
#include <cassert>
#include <QCoreApplication>
#include <QAudioInput>
#include <QAudioOutput>
#include <QBuffer>
#include <QDebug>
 
int main(int argc, char *argv[])
{
    QCoreApplication app(argc, argv);
 
    QBuffer rdBuff;
    QBuffer wrBuff;
    wrBuff.open(QBuffer::WriteOnly);
    rdBuff.open(QBuffer::ReadOnly);
 
    QObject::connect(&wrBuff, &QIODevice::bytesWritten, [&wrBuff, &rdBuff](qint64)
    {
        // remove all data that was already read
        rdBuff.buffer().remove(0, rdBuff.pos());
 
        // set pointer to the beginning of the unread data
        const auto res = rdBuff.seek(0);
        assert(res);
 
        // write new data
        rdBuff.buffer().append(wrBuff.buffer());
 
        // remove all data that was already written
        wrBuff.buffer().clear();
        wrBuff.seek(0);
    });
 
    const auto decideAudioFormat = [](const QAudioDeviceInfo& devInfo)
    {
        QAudioFormat format;
        format.setSampleRate(8000);
        format.setChannelCount(1);
        format.setSampleSize(16);
        format.setCodec("audio/pcm");
        format.setByteOrder(QAudioFormat::LittleEndian);
        format.setSampleType(QAudioFormat::SignedInt);
 
 
        if (devInfo.isFormatSupported(format))
        {
            return format;
        }
    };
 
    QAudioInput audioInput(decideAudioFormat(QAudioDeviceInfo::defaultInputDevice()));
    QAudioOutput audioOutput(decideAudioFormat(QAudioDeviceInfo::defaultOutputDevice()));
 
    audioInput.start(&wrBuff);
    audioOutput.start(&rdBuff);
    return app.exec();
}

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