Retrieve media info using C#

video-info.cs

/*
 * http://stackoverflow.com/questions/6215185/getting-length-of-video
 */

using DirectShowLib;
using DirectShowLib.DES;
using System.Runtime.InteropServices;

...

var mediaDet = (IMediaDet)new MediaDet();
DsError.ThrowExceptionForHR(mediaDet.put_Filename(FileName));

// find the video stream in the file
int index;
var type = Guid.Empty;
for (index = 0; index < 1000 && type != MediaType.Video; index++)
{
    mediaDet.put_CurrentStream(index);
    mediaDet.get_StreamType(out type);
}

// retrieve some measurements from the video
double frameRate;
mediaDet.get_FrameRate(out frameRate);

var mediaType = new AMMediaType();
mediaDet.get_StreamMediaType(mediaType);
var videoInfo = (VideoInfoHeader)Marshal.PtrToStructure(mediaType.formatPtr, typeof(VideoInfoHeader));
DsUtils.FreeAMMediaType(mediaType);
var width = videoInfo.BmiHeader.Width;
var height = videoInfo.BmiHeader.Height;

double mediaLength;
mediaDet.get_StreamLength(out mediaLength);
var frameCount = (int)(frameRate * mediaLength);
var duration = frameCount / frameRate;

///////////////////////////////
// Version 2
///////////////////////////////

using WMPLib;

WindowsMediaPlayer wmp = new WindowsMediaPlayerClass();
IWMPMedia mediainfo = wmp.newMedia(file);
var duration = mediainfo.duration;
...