[Interest] Receiving audio through USB frame grabber and playing it

[Anisha Kaul]

> HI,
>
> Following is the re-producable example:
>
> **header file:********************************************************
>
>     #ifndef AUDIOOUTPUT
>     #define AUDIOOUTPUT
>
>     #include <QQuickItem>
>     #include <QAudioOutput>
>     #include <QAudioInput>
>
>     class Output: public QObject
>     {
>     private:
>         Q_OBJECT
>
>     public:
>         Output();
>         ~Output() {}
>
>         QAudioOutput* audioOutpu;
>         QAudioInput* audioInpu;
>
>     public slots:
>         handleStateChanged(QAudio::State newState);
>         handleStateChanged0(QAudio::State newState);
>     };
>
>     #endif // AUDIOOUTPUT
>
>
> **Source file:*****************************************************
>
>     #include <QTimer>
>     #include "audiooutput.h"
>
>     Output::Output()
>     {
>         foreach (const QAudioDeviceInfo &deviceInfo, QAudioDeviceInfo::
> availableDevices(QAudio::AudioInput))
>             qDebug() << "Device name in: " << deviceInfo.deviceName();
>
>         foreach (const QAudioDeviceInfo &deviceInfo, QAudioDeviceInfo::
> availableDevices(QAudio::AudioOutput))
>             qDebug() << "Device name out: " << deviceInfo.deviceName();
>
>         QAudioDeviceInfo d;
>         QList<QAudioDeviceInfo> l = d.availableDevices(QAudio::
> AudioInput);
>
>         qDebug() << l.first().supportedCodecs();
>         qDebug() << l.first().supportedChannelCounts();
>         qDebug() << l.first().supportedSampleTypes();
>         qDebug() << l.first().supportedSampleRates();
>         qDebug() << l.first().supportedSampleSizes();
>
>         QAudioFormat desiredFormat;
>         desiredFormat.setChannelCount(5);
>         desiredFormat.setCodec("audio/pcm");
>         desiredFormat.setSampleType(QAudioFormat::SignedInt);
>         desiredFormat.setSampleRate(44100);
>         desiredFormat.setSampleSize(16);
>
>         QAudioDeviceInfo info(l.first());
>         if (!info.isFormatSupported(desiredFormat)) {
>                qWarning() << "Default format not supported, trying to use
> the nearest.";
>                desiredFormat = info.nearestFormat(desiredFormat);
>            }
>
>         audioInpu = new QAudioInput(l.first(), desiredFormat, this);
>         connect(audioInpu, SIGNAL(stateChanged(QAudio::State)), this,
> SLOT(handleStateChanged0(QAudio::State)));
>         audioInpu->setVolume(500);
>
>         QAudioDeviceInfo d1;
>         QList<QAudioDeviceInfo> l1 = d1.availableDevices(QAudio::
> AudioOutput);
>         qDebug() << "=============================
> =========================";
>         qDebug() << l1.first().supportedCodecs();
>         qDebug() << l1.first().supportedChannelCounts();
>         qDebug() << l1.first().supportedSampleTypes();
>         qDebug() << l1.first().supportedSampleRates();
>         qDebug() << l1.first().supportedSampleSizes();
>
>         QAudioFormat desiredFormat1;
>         desiredFormat1.setChannelCount(5);
>         desiredFormat1.setByteOrder(QAudioFormat::LittleEndian);
>         desiredFormat1.setCodec("audio/pcm");
>         desiredFormat1.setSampleType(QAudioFormat::SignedInt);
>         desiredFormat1.setSampleRate(44100);
>         desiredFormat1.setSampleSize(24);
>
>         QAudioDeviceInfo info1(l1.first());
>         if (!info1.isFormatSupported(desiredFormat1))
>         {
>                qWarning() << "Default format not supported, trying to use
> the nearest.";
>                desiredFormat1 = info1.nearestFormat(desiredFormat1);
>         }
>
>         audioOutpu = new QAudioOutput(desiredFormat1, this);
>         connect(audioOutpu, SIGNAL(stateChanged(QAudio::State)), this,
> SLOT(handleStateChanged(QAudio::State)));
>         audioOutpu->setVolume(500);
>
>         audioOutpu->start(audioInpu->start());
>     }
>
>     Output::handleStateChanged(QAudio::State newState)
>     {
>        switch (newState) {
>         case QAudio::ActiveState:
>             qDebug() << "active state out";
>         break;
>
>         case QAudio::IdleState:
>             qDebug() <<"IdleState out";
>             break;
>
>         case QAudio::StoppedState:
>             if (audioInpu->error() != QAudio::NoError)
>             {
>                 qDebug() << "\naudio stopped: " <<audioInpu->error();
>             }
>             break;
>
>         default:
>             // ... other cases as appropriate
>             break;
>        }
>     }
>
>     Output::handleStateChanged0(QAudio::State newState)
>     {
>         switch (newState) {
>             case QAudio::IdleState:
>                 qDebug() <<"IdleState inp";
>                 break;
>
>             case QAudio::StoppedState:
>                 if (audioInpu->error() != QAudio::NoError)
>                 {
>                     qDebug() << "\naudio stopped: " <<audioInpu->error();
>                 }
>                 break;
>
>             default:
>                 // ... other cases as appropriate
>                 break;
>         }
>     }
>
>
> **Output:********************************************
>
>     QML debugging is enabled. Only use this in a safe environment.
>     Device name in:  "Line (2- USB Audio Device)"
>     Device name out:  "Speakers (Realtek High Definiti"
>     ("audio/pcm")
>     (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
>     (SignedInt, UnSignedInt, Float)
>     (8000, 11025, 16000, 22050, 32000, 44100, 48000, 88200, 96000, 192000)
>     (8, 16, 24, 32, 48, 64)
>     ======================================================
>     ("audio/pcm")
>     (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
>     (SignedInt, UnSignedInt, Float)
>     (8000, 11025, 16000, 22050, 32000, 44100, 48000, 88200, 96000, 192000)
>     (8, 16, 24, 32, 48, 64)
>     IdleState inp
>
> ***************************************************
>
> As you can see that sample size for output is 24 and input is 16. The
> problem is that if I keep both these values same, no sound is produced.
> I have tried with different variations of sample sizes, but input works
> only with 16 and output only with 24.
>
> Works here means buzzing sound, real audio is not being heard in any case.
>
> Audio Input is being shown idle now. Output state is being shown active.
>
> The input and output devices are being detected as you can see in the
> output.
>
> **Problem is that I don't know how to pass the audio input to the
> speakers. I cannot hear anything other than a buzzing sound.**
>
> Please guide.
>
>

-- 
Anisha Kaul
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