如何从WMV视频的

Question

创建缩略图我想要显示我的网站上列出的视频的缩略图，我想从视频（从特定时间）获取单帧并将它们显示为缩略图。

使用.Net可以吗？ （C＃或VB）

Answer 1

是的，这是可能的。你需要使用DirectShow.NET。我发现this有用。

编辑：

确定它看起来像，因为我用它的库已经改变了......诅咒开源:)

我刚翻译成下面的代码和测试，它为我工作正常（注意，假定存在一个在C WMV：\ AAA称为C4.wmv和输出将转至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); 

另外要注意，DirectShow是somethign的框架中冷静...... MS有点建议你去媒体基金会......我是一个老派的DirectX坦率地说，这个程序员不再那么做了。