[Question] Calling COM+ (MMDeviceEnumerator and IAudioMeterInformation)

[cocus]

Hello. Im trying to interface the MMDeviceEnumerator COM.
I've developed a Wrapper class for that interface in VB6 (source is here), and now im trying to get it working in QT.
Now im debugging it, and when it works, I will create a Class.

my MainWindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QMainWindow>
#include <QAxObject>
 
namespace Ui {
class MainWindow;
}
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
 
public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
 
private:
    QAxObject   *MMDevEnum;
    QAxObject   *IMMDevEnum;
    QAxObject   *IAudioMeter;
    Ui::MainWindow *ui;
};
 
#endif // MAINWINDOW_H

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QAxObject>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT
    
public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
    
private:
    QAxObject   *MMDevEnum;
    QAxObject   *IMMDevEnum;
    QAxObject   *IAudioMeter;
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

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my MainWindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
 
#include <QDebug>
#include <QAxObject>
#include <windows.h>
#include <InitGuid.h>
 
//#include "endpointvolume.h"
 
//typedef interface IAudioMeterInformation IAudioMeterInformation;
 
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
 
    qDebug() << "going to init";
 
    MMDevEnum = new QAxObject(this);
    MMDevEnum->setControl("{BCDE0395-E52F-467C-8E3D-C4579291692E}");
 
    qDebug() << "instantiated MMDevEnum";
 
    IMMDevEnum = new QAxObject(this);
    IMMDevEnum->setControl("{A95664D2-9614-4F35-A746-DE8DB63617E6}");
 
    IAudioMeter = new QAxObject(this);
    IAudioMeter->setControl("{C02216F6-8C67-4B5B-9D00-D008E73E0064}");
 
    MMDevEnum->dynamicCall("GetDefaultAudioEndpoint(0, 0, QAxBase::asVariant)", IMMDevEnum->asVariant());
 
    qDebug() << "OK";
 
    ui->setupUi(this);
}
 
MainWindow::~MainWindow()
{
    delete ui;
}

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QDebug>
#include <QAxObject>
#include <windows.h>
#include <InitGuid.h>

//#include "endpointvolume.h"

//typedef interface IAudioMeterInformation IAudioMeterInformation;

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{

    qDebug() << "going to init";

    MMDevEnum = new QAxObject(this);
    MMDevEnum->setControl("{BCDE0395-E52F-467C-8E3D-C4579291692E}");

    qDebug() << "instantiated MMDevEnum";

    IMMDevEnum = new QAxObject(this);
    IMMDevEnum->setControl("{A95664D2-9614-4F35-A746-DE8DB63617E6}");

    IAudioMeter = new QAxObject(this);
    IAudioMeter->setControl("{C02216F6-8C67-4B5B-9D00-D008E73E0064}");
   
    MMDevEnum->dynamicCall("GetDefaultAudioEndpoint(0, 0, QAxBase::asVariant)", IMMDevEnum->asVariant());

    qDebug() << "OK";

    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}

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As you can see, its just a little try.


However, it fails to instantiate IMMDevEnum and IAudioMeter.

In the MSDN, "GetDefaultAudioEndpoint" is defined as:

HRESULT GetDefaultAudioEndpoint(
  [in]   EDataFlow dataFlow,
  [in]   ERole role,
  [out]  IMMDevice **ppDevice
);
 
/*  Example (eRender = 0, eConsole = 0) 
 In the preceding code fragment, variable hr is of type HRESULT, pDevEnum is a pointer to an IMMDeviceEnumerator interface, and pDeviceOut is a pointer to an IMMDevice interface. 
*/
  hr = pDevEnum->GetDefaultAudioEndpoint(eRender, eConsole, &pDeviceOut);

HRESULT GetDefaultAudioEndpoint(
  [in]   EDataFlow dataFlow,
  [in]   ERole role,
  [out]  IMMDevice **ppDevice
);

/*  Example (eRender = 0, eConsole = 0) 
 In the preceding code fragment, variable hr is of type HRESULT, pDevEnum is a pointer to an IMMDeviceEnumerator interface, and pDeviceOut is a pointer to an IMMDevice interface. 
*/
  hr = pDevEnum->GetDefaultAudioEndpoint(eRender, eConsole, &pDeviceOut);

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Information about Interface IMMDeviceEnumerator can be found in the MSDN here.

I don't know why it doesnt work.

I think that both IMMDevEnum and IAudioMeter doesn´t need to be instantiated, but the Dynamic call still fails: "QAxBase::dynamicCallHelper: Object does not support automation".

Actually I use mingw, not MSVC.

Sorry for my bad english!

Thanks