Using MediaInfo DLL with C# DLLImport

Question

Using MediaInfo DLL (64-bit), I am attempting to get the standard text output providing information about an mp4 file.

To wrap the dll, I have created a MediaInfo class, based on my (limited) understanding from the quickstart guide.

public class MediaInfo
{
    [DllImport("MediaInfo.dll")]
    private static extern IntPtr MediaInfo_New();

    [DllImport("MediaInfo.dll")]
    private static extern void MediaInfo_Open(string FileName);

    [DllImport("MediaInfo.dll")]
    private static extern IntPtr MediaInfo_Inform(IntPtr Handle);

    [DllImport("MediaInfo.DLL")]
    private static extern void MediaInfo_Close(IntPtr Handle);

    IntPtr Handle;

    public MediaInfo()
    {
        Handle = MediaInfo_New();
    }

    public void Open(string FileName)
    {
        MediaInfo_Open(FileName);
    }

    public string Inform()
    {   
        return Marshal.PtrToStringUni(MediaInfo_Inform(Handle));
    }

    public void Close()
    {
        MediaInfo_Close(Handle);
    }
}

And I am calling this class using the below console app:

static void Main(string[] args)
    {
        var objMediaInfo = new MediaInfo();
        objMediaInfo.Open("test.mp4");
        string result = objMediaInfo.Inform();
        objMediaInfo.Close();

        Console.WriteLine(result);
        Console.ReadKey();
    }

However, I am only getting a blank string in return. I have tried a few different media files.

I am aware there is already a fully developed wrapper for this, but I would like to keep this simple and lightweight.

Admin · Answer

Try this might work for you:

Changes

[System.Runtime.InteropServices.DllImport("MediaInfo.DLL")]
private static extern UIntPtr MediaInfo_Open(IntPtr Handle, string FileName);

[System.Runtime.InteropServices.DllImport("MediaInfo.DLL")]
private static extern IntPtr MediaInfo_Inform(IntPtr Handle, UIntPtr Reserved);

public System.UIntPtr Open(string FileName)
{
    return MediaInfo_Open(Handle, FileName);
}

public string Inform()
{
    return Marshal.PtrToStringUni(MediaInfo_Inform(Handle, (UIntPtr)0));
}

Clean up

Don't forget to delete the pointer (Handle) that created by _MediaInfo_New_. You need to add:

[DllImport("MediaInfo.dll")]
private static extern void MediaInfo_Delete(IntPtr Handle);

Thus:

~MediaInfo() { if (Handle == (IntPtr)0) return; MediaInfo_Delete(Handle); }

Implement

Then in your implementation, you must pass the full path of the media file not just its name:

static void Main(string[] args)
{
    var objMediaInfo = new MediaInfo();
    objMediaInfo.Open(@"TheFullPathOf	est.mp4");
    string result = objMediaInfo.Inform();
    objMediaInfo.Close();

    Console.WriteLine(result);
    Console.ReadKey();
}

Good luck.

Edit

Sorry for the incomplete answer. I forgot to include in my last post that you also need to set the Inform option through the MediaInfo_Option API, this is important step to define the returned data:

[System.Runtime.InteropServices.DllImport("MediaInfo.DLL")]
private static extern IntPtr MediaInfo_Option(IntPtr Handle, string option, string Value);

Create function for that:

public string Option(string option, string Value = "")
{
    return Marshal.PtrToStringUni(MediaInfo_Option(Handle, option, Value));
}

Finally, modify your implementation:

static void Main(string[] args)
{
    var objMediaInfo = new MediaInfo();
    objMediaInfo.Open(@"TheFullPathOf	est.mp4");
    objMediaInfo.Option("Complete"); //or mi.Option("Complete", "1") or mi.Option("Info_Parameters") try them..
    string result = objMediaInfo.Inform();
    objMediaInfo.Close();
    Console.WriteLine(result);
    Console.ReadKey();
}

Hope it works this time.

user_16288835 · Answer

namespace Test_MediaInfo{
  public partial class MainWindow : Window
  {

    public class MediaInfo
    {
      [DllImport("MediaInfo.dll")]
      private static extern IntPtr MediaInfo_New();

      [System.Runtime.InteropServices.DllImport("MediaInfo.DLL")]
      internal static extern IntPtr MediaInfo_Open(IntPtr Handle, [MarshalAs(UnmanagedType.LPWStr)] string FileName);

      [System.Runtime.InteropServices.DllImport("MediaInfo.DLL")]
      private static extern IntPtr MediaInfo_Option(IntPtr Handle, [MarshalAs(UnmanagedType.LPWStr)] string option, [MarshalAs(UnmanagedType.LPWStr)] string Value);

      [System.Runtime.InteropServices.DllImport("MediaInfo.DLL")]
      private static extern IntPtr MediaInfo_Inform(IntPtr Handle, UIntPtr Reserved);

      [System.Runtime.InteropServices.DllImport("MediaInfo.DLL")]
      private static extern void MediaInfo_Close(IntPtr Handle);

      [System.Runtime.InteropServices.DllImport("MediaInfo.dll")]
      private static extern void MediaInfo_Delete(IntPtr Handle);

      [DllImport("MediaInfo.dll")]
      private static extern IntPtr MediaInfoA_Option(IntPtr Handle, IntPtr Option, IntPtr Value);

      IntPtr Handle;
      public MediaInfo()
      {
        Handle = MediaInfo_New();
      }
      public System.IntPtr Open(string FileName)
      {
        return MediaInfo_Open(Handle, FileName);
      }
      public string Option(string option, string Value = "")
      {
        return Marshal.PtrToStringUni(MediaInfo_Option(Handle, option, Value));
      }
      public string Inform()
      {
        return Marshal.PtrToStringUni(MediaInfo_Inform(Handle, (UIntPtr)0));
      }
      public void Close()
      {
        MediaInfo_Close(Handle);
      }
      public void delete_pointeur()
      {
        MediaInfo_Delete(Handle);
      }

    }
    //---------------------------------------------------------------------------------
    public MainWindow()
      {
        InitializeComponent();
        btn_go_Click(null, null);
      }
    //---------------------------------------------------------------------------------
     private void btn_go_Click(object sender, RoutedEventArgs e)
    {
      string hhhh;
      string FileName = "";
    //  FileName = @"F:\mkv\American Nightmare 2 - Anarchy (2014).mkv";
      //   FileName = @"F:\mp4\Cinq cartes à abattre (1968).mp4";
      FileName = @"F:\avi\Danse avec les loups.avi";

      string[] msg = new string[15];

      var tmp = new MediaInfo();
      tmp.Open(FileName);
      tmp.Option("Inform", "General;%OverallBitRate/String%");    msg[0] = tmp.Inform();// 1 h 38 min
      tmp.Option("Inform", "General;%Format%");                   msg[1] = tmp.Inform();// MpEG-4
      tmp.Option("Inform", "General;%FileSize/String3%");         msg[2] = tmp.Inform();// 3.67 GiB
      tmp.Option("Inform", "General;%Duration/String2%");         msg[3] = tmp.Inform();// 1 h 38 min
      tmp.Option("Inform", "Video;%Width% x %Height%");           msg[4] = tmp.Inform();// 1920 x 1080    
      tmp.Option("Inform", "Video;%DisplayAspectRatio/String%");  msg[5] = tmp.Inform();// 16.9
      tmp.Option("Inform", "Video;%Format_Commercial%");          msg[6] = tmp.Inform();// AVC
      tmp.Option("Inform", "General;%FrameRate/String%");         msg[7] = tmp.Inform();// 60.000 FPS
      tmp.Option("Inform", "Video;%BitRate/String%");             msg[8] = tmp.Inform();// 5 165 kb/s
      tmp.Option("Inform", "Video;%CodecID/Hint%");               msg[9] = tmp.Inform();// DivX 3 low
      tmp.Option("Inform", "Audio;%SamplingRate/String%");        msg[10] = tmp.Inform();// 44.1 kHz
      tmp.Option("Inform", "Audio;%Language/String%, %Channel(s)% channels, %Codec/String%, %SamplingRate/String%, %BitRate/String%"); msg[11] = tmp.Inform(); // ,2 channels,, 44.1kHz, 160 kb/s
        tmp.Option("Inform", "Audio;%BitDepth/String%");          msg[12] = tmp.Inform();// 
      tmp.Option("Inform", "General;%Text_Language_List%");       msg[13] = tmp.Inform();// French / French / English
      tmp.Option("Inform", "Video;%CodecID%");                    msg[14] = tmp.Inform();// avc1
      hhhh = tmp.Option("Complete", "1");                         // end of session
      tmp.Close();
      tmp.delete_pointeur();

    }
    //---------------------------------------------------------------------------------
  }
}

Using MediaInfo DLL with C# DLLImport

2 Answers