How to create thumbnails from WMV video's
i want to display thumbnails for videos listed on my site, i want to fetch a single frame fro开发者_Go百科m a video (from a particular time) and display them as thumbnails.
Is that possible using .Net ? (C# or VB)
Yes that is possible. You need to use DirectShow.NET. I found this useful.
EDIT :
OK it looks like the library has changed since I used it... curse open source :)
I just translated to the following code and tested and it works fine for me(note that it assumes there is a wmv in c:\aaa called C4.wmv and the output will go to c:\aaa\out.bmp)
IGraphBuilder graphbuilder = (IGraphBuilder)new FilterGraph();
ISampleGrabber samplegrabber = (ISampleGrabber) new SampleGrabber();
graphbuilder.AddFilter((IBaseFilter)samplegrabber, "samplegrabber");
AMMediaType mt = new AMMediaType();
mt.majorType = MediaType.Video;
mt.subType = MediaSubType.RGB24;
mt.formatType = FormatType.VideoInfo;
samplegrabber.SetMediaType(mt);
int hr = graphbuilder.RenderFile("C:\\aaa\\c4.wmv", null);
IMediaEventEx mediaEvt = (IMediaEventEx)graphbuilder;
IMediaSeeking mediaSeek = (IMediaSeeking)graphbuilder;
IMediaControl mediaCtrl = (IMediaControl)graphbuilder;
IBasicAudio basicAudio = (IBasicAudio)graphbuilder;
IVideoWindow videoWin = (IVideoWindow)graphbuilder;
basicAudio.put_Volume(-10000);
videoWin.put_AutoShow(OABool.False);
samplegrabber.SetOneShot(true);
samplegrabber.SetBufferSamples(true);
long d = 0;
mediaSeek.GetDuration(out d);
long numSecs = d / 10000000;
long secondstocapture = (long)(numSecs * 0.10f);
DsLong rtStart, rtStop;
rtStart = new DsLong(secondstocapture * 10000000);
rtStop = rtStart;
mediaSeek.SetPositions(rtStart, AMSeekingSeekingFlags.AbsolutePositioning, rtStop, AMSeekingSeekingFlags.AbsolutePositioning);
mediaCtrl.Run();
EventCode evcode;
mediaEvt.WaitForCompletion(-1, out evcode);
VideoInfoHeader videoheader = new VideoInfoHeader();
AMMediaType grab = new AMMediaType();
samplegrabber.GetConnectedMediaType(grab);
videoheader =
(VideoInfoHeader)Marshal.PtrToStructure(grab.formatPtr,
typeof(VideoInfoHeader));
int width = videoheader.SrcRect.right;
int height = videoheader.SrcRect.bottom;
Bitmap b = new Bitmap(width, height, PixelFormat.Format24bppRgb);
uint bytesPerPixel = (uint)(24 >> 3);
uint extraBytes = ((uint)width * bytesPerPixel) % 4;
uint adjustedLineSize = bytesPerPixel * ((uint)width + extraBytes);
uint sizeOfImageData = (uint)(height) * adjustedLineSize;
BitmapData bd1 = b.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
int bufsize = (int)sizeOfImageData;
int n = samplegrabber.GetCurrentBuffer(ref bufsize, bd1.Scan0);
b.UnlockBits(bd1);
b.RotateFlip(RotateFlipType.RotateNoneFlipY);
b.Save("C:\\aaa\\out.bmp");
Marshal.ReleaseComObject(graphbuilder);
Marshal.ReleaseComObject(samplegrabber);
Also be aware that DirectShow is somethign of a framework in limbo... MS kind of recommend that you go to Media Foundation... I am an old school DirectX programmer that frankly doesn't do much with it any more.
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