Open a microphone device with QAudioInput

Arthux

Hello everybody,

I try to open a microphone device under ubuntu like the tutorial : http://doc.qt.io/qt-5/qtmultimedia-multimedia-spectrum-example.html

void AudioRecorder::startListening(){
    if(m_audioInput == NULL){
        m_format.setChannelCount(1);
        m_format.setCodec("audio/pcm");
        m_format.setSampleSize(16);
        m_format.setSampleRate(48000);

        // Select the device that I want
        QList<QAudioDeviceInfo> availableDevices = QAudioDeviceInfo::availableDevices(QAudio::AudioInput);
        for(int i=0;i<availableDevices.size();i++){
            qDebug() << availableDevices.at(i).deviceName();
            if(!availableDevices.at(i).deviceName().compare("plughw:CARD=C525,DEV=0")){   //plughw:CARD=C525,DEV=0 plughw:CARD=r0,DEV=0
                m_audioInputDevice = availableDevices.at(i);
                qDebug() << "Selected device :" << m_audioInputDevice.deviceName();
                break;
            }
        }

        // Check format is OK
        if(!m_audioInputDevice.isFormatSupported(m_format)){
            qWarning() << "Default format not supported, trying to use the nearest.";
            m_format = m_audioInputDevice.nearestFormat(m_format);
            qDebug() << "Codec:" << m_format.codec();
            qDebug() << "Channel count:" << m_format.channelCount();
            qDebug() << "Sample size:" << m_format.sampleSize();
            qDebug() << "Sample rate:" << m_format.sampleRate();
        }

        if(m_format.isValid()){
            // Initialisation du micro
            m_audioInput = new QAudioInput(m_audioInputDevice,m_format,this);
            m_audioInput->setNotifyInterval(100);
            connect(m_audioInput,SIGNAL(stateChanged(QAudio::State)),this,SLOT(audioStateChanged(QAudio::State)));

            m_audioInputIODevice = m_audioInput->start();
            qDebug() << m_audioInput->error();
            connect(m_audioInputIODevice,SIGNAL(readyRead()),this,SLOT(audioDataReady()));

            qDebug() << "Start listening event" << m_audioInputIODevice << m_audioInput;
        }
        else {
            qCritical() << "Problem audio format";
        }
    }
}

The problem is the fonction "m_audioInput->start();" return always null pointer and I have an error for connect "connect(m_audioInputIODevice,SIGNAL(readyRead()),this,SLOT(audioDataReady()));" :

QObject::connect: Cannot connect (null)::readyRead() to AudioRecorder::audioDataReady()

Type variables are :

QAudioInput *m_audioInput;
QIODevice   *m_audioInputIODevice;
QAudioDeviceInfo    m_audioInputDevice;
QAudioFormat    m_format;

If someone can tell me where is my mistake ...

Thank a lot !

mrjj

Hi
I would also check the error stuff and see if it says
http://doc.qt.io/qt-5/qaudioinput.html#error
If it gives QAudio::OpenError
or why it cannot start.

I assume that
qtmultimedia-multimedia-spectrum-example
Does in fact fully work so its not a driver issue.

Arthux

I check the error with :

qDebug() << m_audioInput->error();

return :

NoError

I try to change the device and it works with alsa_input.pci-0000_00_1b.0.analog-stereo. But it's not the microphone that I want to used.
I think the microphone i want to used, it is not detected by alsa library ...

How can I do the detection of the microphone to alsa library ?

Knowing the microphone is detected with the alsamixer application ...

Arthux

In fact, when i use QAudioRecorder I must put "alsa:plughw:CARD=C525,DEV=0"and when i use QAudioInput I must put "alsa_input.usb-046d_HD_Webcam_C525_D01D63D0-00.analog-mono".

Why ? And have not always the "alsa_input.usb ..." for all input device ...

SGaist

Hi,

Did you try to enumarate all the available inputs ? Does the microphone appear in that list ?

Arthux

Yes :

"default"
"pulse"
"sysdefault:CARD=C525"
"front:CARD=C525,DEV=0"
"surround21:CARD=C525,DEV=0"
"surround40:CARD=C525,DEV=0"
"surround41:CARD=C525,DEV=0"
"surround50:CARD=C525,DEV=0"
"surround51:CARD=C525,DEV=0"
"surround71:CARD=C525,DEV=0"
"iec958:CARD=C525,DEV=0"
"dmix:CARD=C525,DEV=0"
"dsnoop:CARD=C525,DEV=0"
"hw:CARD=C525,DEV=0"
"plughw:CARD=C525,DEV=0"
"sysdefault:CARD=r0"
"front:CARD=r0,DEV=0"
"surround21:CARD=r0,DEV=0"
"surround40:CARD=r0,DEV=0"
"surround41:CARD=r0,DEV=0"
"surround50:CARD=r0,DEV=0"
"surround51:CARD=r0,DEV=0"
"surround71:CARD=r0,DEV=0"
"iec958:CARD=r0,DEV=0"
"dmix:CARD=r0,DEV=0"
"dsnoop:CARD=r0,DEV=0"
"hw:CARD=r0,DEV=0"
"plughw:CARD=r0,DEV=0"
"alsa_output.0.analog-stereo.monitor"
"alsa_input.usb-046d_HD_Webcam_C525_D01D63D0-00-C525.analog-mono"
default input device "alsa_output.0.analog-stereo.monitor"

I think pulseaudio create :

"alsa_output.0.analog-stereo.monitor"    // For stereo output
"alsa_input.usb-046d_HD_Webcam_C525_D01D63D0-00-C525.analog-mono"    // For the microphone of my webcam CARD=C525

But it does anything for the microphone CARD=r0 ....

I don't know why ... Do you how to create a device with pulseaudio ?