Simultaneously record and play audio

learnthetruth

Hi all,

I want to record and play audio at the same time with Qt.

I have read through the provided examples and I have also read through this: https://www.codeproject.com/Articles/421287/Cross-Platform-Microphone-Audio-Processing-Utility

I have tried to piece together a bar minimal program. This is the best I have - this program records the audio and saves it to a .wav file but I have been unable to figure out how to play the audio back at the time it is being recorded:

    QAudioRecorder *m_audioRecorder = new QAudioRecorder;
    QAudioProbe *m_probe = new QAudioProbe;

    int i = 0;
    int audioSampleRate;
    for(int sampleRate: m_audioRecorder->supportedAudioSampleRates()){
        if(i == 0){
            audioSampleRate = sampleRate;
            i++;
        }
    }


    QAudioEncoderSettings settings;
    settings.setCodec(m_audioRecorder->audioInputs().first());
    settings.setSampleRate(audioSampleRate);
    settings.setChannelCount(1);
    settings.setEncodingMode(QMultimedia::ConstantQualityEncoding);

    QString fileName = QLatin1String("february.wav");
 bool output_location_set = m_audioRecorder->setOutputLocation(QUrl::fromLocalFile(fileName));


    QAudioFormat formatOut;
    formatOut.setSampleRate(22050);
    formatOut.setChannelCount(1);
    formatOut.setSampleRate(16);
    formatOut.setCodec("audio/pcm");
    formatOut.setByteOrder(QAudioFormat::LittleEndian);
    formatOut.setSampleType(QAudioFormat::SignedInt);

    QAudioOutput *audioOut;
    audioOut = new QAudioOutput(deviceOut, formatOut, 0);
    audioOut->setVolume(1);
    audioOut->start();

    QThread::sleep(10);

    QTextStream(stdout) << "	period of sleep is completed" << endl;
    m_audioRecorder->stop();
    QTextStream(stdout) << "	recording has stopped" << endl;

Any idea as to what to do or how to move forward or what I'm doing wrong ?

Please and thank you!

learnthetruth

@learnthetruth I have also read through and tried to implement this: https://forum.qt.io/topic/10399/how-to-record-and-play-sound-simultaneously/2

But I feel that it is an outdated post in some aspects. And not entirely fitting my circumstances. I don't need a GUI and this appears to use a function from the widgets module

wrosecrans

@learnthetruth Which Widgets specific function are you talking about? Skimming that thread, nothing widgets/GUI specific jumps out at me.

Basically, don't sleep. Use something like a QTimer that will trigger a signal where you can tell the input and output devices to stop. The event loop needs to be able to be active, and service the devices for the recording/playback to work.

learnthetruth

Okay, but then no recording happens. :(

jsulm

@learnthetruth Please show your code

learnthetruth

@jsulm

Okay, first file is the .h file and the next one is the .cpp file

#ifndef MYAUDIORECORDER_H
#define MYAUDIORECORDER_H

#include <QAudioFormat>
#include <QAudioDeviceInfo>
#include <QTextStream>
#include <QAudioInput>
#include <QAudioOutput>
#include <QObject>
#include <QAudioRecorder>
#include <QAudioProbe>
#include <QUrl>
#include <QThread>

class MyAudioRecorder : public QObject
{
    Q_OBJECT

public:
    MyAudioRecorder();

    int audioSampleRate;
    QAudioEncoderSettings settings;

    QAudioFormat formatIn;
    QAudioFormat formatOut;

    QAudioInput *m_audioInput;
    QAudioOutput *m_audioOutput;

    QAudioDeviceInfo m_InputDevice;
    QAudioDeviceInfo m_OutputDevice;

    QIODevice *m_input;
    QIODevice *m_output;

    QAudioDeviceInfo deviceIn;
    QAudioDeviceInfo deviceOut;

    QAudioRecorder *m_audioRecorder;
    QAudioProbe *m_probe;

    void getFormat();
    void createAudioInput();
    void createAudioOutput();
    void beginAudio();

};

#endif // MYAUDIORECORDER_H

#include "myaudiorecorder.h"

MyAudioRecorder::MyAudioRecorder() {
getFormat();
createAudioInput();
createAudioOutput();
}

void MyAudioRecorder::getFormat(){
formatIn.setSampleSize(8);
formatIn.setCodec("audio/pcm");
formatIn.setByteOrder(QAudioFormat::LittleEndian);
formatIn.setSampleType(QAudioFormat::UnSignedInt);

formatOut.setSampleSize(16);
formatOut.setCodec("audio/pcm");
formatOut.setByteOrder(QAudioFormat::LittleEndian);
formatOut.setSampleType(QAudioFormat::UnSignedInt);


// QAudioDeviceInfo deviceIn = QAudioDeviceInfo::defaultInputDevice();
deviceIn = QAudioDeviceInfo::availableDevices(QAudio::AudioInput).at(2);
if(!deviceIn.isFormatSupported(formatIn)){
    QTextStream(stdout) << " default formatIn not supported " << endl;
    formatIn = deviceIn.nearestFormat(formatIn);
} else {
    QTextStream(stdout) << " default formatIn supported " << endl;
    QTextStream(stdout) << " deviceIn.deviceName(): " << deviceIn.deviceName() << endl;
}

// QAudioDeviceInfo deviceOut = QAudioDeviceInfo::defaultOutputDevice();
deviceOut = QAudioDeviceInfo::availableDevices(QAudio::AudioOutput).at(1);
if(!deviceOut.isFormatSupported(formatOut)) {
    QTextStream(stdout) << "default formatOut not supported " << endl;
    formatOut = deviceOut.nearestFormat(formatOut);
} else {
    QTextStream(stdout) << " default formatOut supported " << endl;
    QTextStream(stdout) << " deviceOut.deviceName(): " << deviceOut.deviceName() << endl;
}

}

void MyAudioRecorder::createAudioInput(){
m_audioInput = new QAudioInput(m_InputDevice, formatIn, 0);
}

void MyAudioRecorder::createAudioOutput(){
m_audioOutput = new QAudioOutput(m_OutputDevice, formatOut, 0);
}

void MyAudioRecorder::beginAudio(){
m_output = m_audioOutput->start();
m_input = m_audioInput->start();
}

SGaist

Hi,

I don't see anywhere code to connect your input to your output.

learnthetruth

Okay. I have a working solution - though the output produces a lot of static with the audio from the microphone (note: the .h file is the same as what has been previously posted)

Anyone know how to fix the static output problem?

#include "testrecord.h"

TestRecord::TestRecord() {
    getFormat();
    createAudioInput();
    createAudioOutput();
}


void TestRecord::getFormat(){
    formatIn.setSampleSize(8);
    formatIn.setCodec("audio/pcm");
    formatIn.setByteOrder(QAudioFormat::LittleEndian);
    formatIn.setSampleType(QAudioFormat::UnSignedInt);

    deviceIn = QAudioDeviceInfo::defaultInputDevice();
    if(!deviceIn.isFormatSupported(formatIn)){
        QTextStream(stdout) << " default formatIn not supported " << endl;
        formatIn = deviceIn.nearestFormat(formatIn);
    }

    deviceOut = QAudioDeviceInfo::defaultOutputDevice();
    if(!deviceOut.isFormatSupported(formatOut)) {
        QTextStream(stdout) << "1. default formatOut not supported " << endl;
        formatOut = deviceOut.nearestFormat(formatOut);
    }

}

void TestRecord::createAudioInput(){
    m_InputDevice = QAudioDeviceInfo::defaultInputDevice();
    m_audioInput = new QAudioInput(m_InputDevice, formatIn, 0);
}

void TestRecord::createAudioOutput(){
    m_OutputDevice = QAudioDeviceInfo::defaultOutputDevice();
    m_audioOutput = new QAudioOutput(m_OutputDevice, formatOut, 0);
}

void TestRecord::beginAudio(){
    m_output = m_audioOutput->start();
    m_audioInput->start(m_output);
}