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POHow do I scan every frame from ISampleGrabber using directshow.net
 

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  1. POHow do I scan every frame from ISampleGrabber using directshow.net
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    <p>I have a program which currently displays a preview of a usb webcam and then displays a frame within a picturebox when a button is pressed. This is done by using the directshow DxSnap sample thus using the ISampleGrabberCB interface.</p> <p>Would it be possible for each frame to be scanned automatically without the use of a button?</p> <p>I tried to do this with a timer however the result ended with bad image quality from both preview and the captured image.</p> <p>Would this be achieved by using the IsampleGrabberCB.BufferCB function?</p> <p>The way I am currently getting frames using is a button consists of:</p> <pre><code>int ISampleGrabberCB.BufferCB(double sampleTime, IntPtr buffer, int bufferLength) { Debug.Assert(bufferLength == Math.Abs(pitch) * videoHeight, "Wrong Buffer Length"); if (gotFrame) { gotFrame = false; Debug.Assert(imageBuffer != IntPtr.Zero, "Remove Buffer"); CopyMemory(imageBuffer, buffer, bufferLength); pictureReady.Set(); } return 0; } public void getFrameFromWebcam() { if (iPtr != IntPtr.Zero) { Marshal.FreeCoTaskMem(iPtr); iPtr = IntPtr.Zero; } //Get Image iPtr = sampleGrabberCallBack.getFrame(); Bitmap bitmapOfFrame = new Bitmap(sampleGrabberCallBack.width, sampleGrabberCallBack.height, sampleGrabberCallBack.capturePitch, PixelFormat.Format32bppRgb, iPtr); bitmapOfFrame.RotateFlip(RotateFlipType.RotateNoneFlipY); pictureBox3.Image = bitmapOfFrame; barcodeReader(bitmapOfFrame); } public IntPtr getFrame() { int hr; pictureReady.Reset(); imageBuffer = Marshal.AllocCoTaskMem(Math.Abs(pitch) * videoHeight); try { gotFrame = true; if (videoControl != null) { hr = videoControl.SetMode(stillPin, VideoControlFlags.Trigger); DsError.ThrowExceptionForHR(hr); } if (!pictureReady.WaitOne(9000, false)) { throw new Exception("Timeout waiting to get picture"); } } catch { Marshal.FreeCoTaskMem(imageBuffer); imageBuffer = IntPtr.Zero; } return imageBuffer; } </code></pre>
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