Direct show doesn't change webcam resolution

EDN Admin · Nov 13, 2011

<div style="font:normal normal normal 13px/normal Verdana,Arial,Tahoma,Calibri,Geneva,sans-serif; color:#222222; padding:8px; margin:0px
Hi, 
 
I have two Microsoft LifeCam Studio webcams that need to have a still image taken when required. I have managed to put this code together that works for all except changing the resolution. The weird thing that I dont understand is that the equivalent code
for the form works in C# but not in vb. 
 
The code is built up of 3 parts, a form with a picturebox and a button, the class written in C# that uses directshow and another class that acts between them (the form is just temporary until it works). 
 
My form written in vb (it does need the dispose event to close the camera adding but Ive left this out) 
<div style="color:Black;background-color:White; <pre>
<span style="color:Blue; Imports SnapShot

<span style="color:Blue; Public <span style="color:Blue; Class Form1

<span style="color:Blue; Private cam <span style="color:Blue; As Class1

<span style="color:Blue; Private <span style="color:Blue; Sub Button1_Click(<span style="color:Blue; ByVal sender <span style="color:Blue; As System.Object, <span style="color:Blue; ByVal e <span style="color:Blue; As System.EventArgs) <span style="color:Blue; Handles Button1.Click
cam.takeImage(<span style="color:#A31515; "C:UsersProgrammingDesktopme.jpg")
<span style="color:Blue; End <span style="color:Blue; Sub

<span style="color:Blue; Private <span style="color:Blue; Sub Form1_Load(<span style="color:Blue; ByVal sender <span style="color:Blue; As <span style="color:Blue; Object, <span style="color:Blue; ByVal e <span style="color:Blue; As System.EventArgs) <span style="color:Blue; Handles <span style="color:Blue; Me.Load
cam = 
 
 
The "middle" class, based upon the directshow example. 
<div style="color:Black;background-color:White; <pre>
<span style="color:Blue; using System;<span style="color:Blue; using System.Collections.Generic;
<span style="color:Blue; using System.Text;
<span style="color:Blue; using System.Windows.Forms;
<span style="color:Blue; using System.Runtime.InteropServices;
<span style="color:Blue; using System.Drawing;
<span style="color:Blue; using System.Drawing.Imaging;

<span style="color:Blue; namespace SnapShot
{
<span style="color:Blue; public <span style="color:Blue; class Class1
{
<span style="color:Blue; private Capture cam;
IntPtr m_ip = IntPtr.Zero;

<span style="color:Blue; public Class1(<span style="color:Blue; int VIDEODEVICE, Control pictureBox2)
{
cam = <span style="color:Blue; new Capture(VIDEODEVICE, 1024, 768, 24, pictureBox2);
}

<span style="color:Blue; public <span style="color:Blue; void dispose()
{
<span style="color:Blue; if (m_ip != IntPtr.Zero)
{
Marshal.FreeCoTaskMem(m_ip);
m_ip = IntPtr.Zero;
}
}

<span style="color:Blue; public <span style="color:Blue; void takeImage(String name)
{
<span style="color:Green; // Release any previous buffer
<span style="color:Blue; if (m_ip != IntPtr.Zero)
{
Marshal.FreeCoTaskMem(m_ip);
m_ip = IntPtr.Zero;
}

<span style="color:Green; // capture image
m_ip = cam.Click();
Bitmap b = <span style="color:Blue; new Bitmap(cam.Width, cam.Height, cam.Stride, PixelFormat.Format24bppRgb, m_ip);


 
 
 
The class that uses direct show, from the samples:
<div style="font:normal normal normal 13px/normal Verdana,Arial,Tahoma,Calibri,Geneva,sans-serif; color:#222222; padding:8px; margin:0px
<div style="color:Black;background-color:White; <pre>
<span style="color:Green; /****************************************************************************While the underlying libraries are covered by LGPL, this sample is released
as public domain. It is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE.
*****************************************************************************/

<span style="color:Blue; using System;
<span style="color:Blue; using System.Drawing;
<span style="color:Blue; using System.Drawing.Imaging;
<span style="color:Blue; using System.Collections;
<span style="color:Blue; using System.Runtime.InteropServices;
<span style="color:Blue; using System.Threading;
<span style="color:Blue; using System.Diagnostics;
<span style="color:Blue; using System.Windows.Forms;


<span style="color:Blue; internal 
<span style="color:Blue; private IFilterGraph2 m_FilterGraph = <span style="color:Blue; null;

<span style="color:Green; // Used to snap picture on Still pin
<span style="color:Blue; private IAMVideoControl m_VidControl = 
<span style="color:Blue; private ManualResetEvent m_PictureReady = 
<span style="color:Blue; private <span style="color:Blue; int m_videoWidth;
<span style="color:Blue; private 
<span style="color:Blue; private IntPtr m_ipBuffer = IntPtr.Zero;

<span style="color:Blue; #if DEBUG
<span style="color:Green; // Allow you to "Connect to remote graph" from GraphEdit
DsROTEntry m_rot = <span style="color:Blue; null;
<span style="color:Blue; #endif
<span style="color:Blue; #endregion

<span style="color:Blue; #region APIs
[DllImport(<span style="color:#A31515; "Kernel32.dll", EntryPoint=<span style="color:#A31515; "RtlMoveMemory")]
<span style="color:Blue; private <span style="color:Blue; static <span style="color:Blue; extern <span style="color:Blue; void CopyMemory(IntPtr Destination, IntPtr Source, [MarshalAs(UnmanagedType.U4)] <span style="color:Blue; int Length);
<span style="color:Blue; #endregion

<span style="color:Green; // Zero based device index and device params and output window
<span style="color:Blue; public Capture(<span style="color:Blue; int iDeviceNum, <span style="color:Blue; int iWidth, <span style="color:Blue; int iHeight, <span style="color:Blue; short iBPP, Control hControl)
{
DsDevice [] capDevices;

 capDevices.Length)
{
<span style="color:Blue; throw <span style="color:Blue; new Exception(<span style="color:#A31515; "No video capture devices found at that index!");
}

<span style="color:Blue; try
{
<span style="color:Green; // Set up the capture graph
SetupGraph( capDevices[iDeviceNum], iWidth, iHeight, iBPP, hControl);

<span style="color:Green; // tell the callback to ignore new images
m_PictureReady = <span style="color:Blue; new ManualResetEvent(
<span style="color:Blue; public <span style="color:Blue; void Dispose()
{
<span style="color:Blue; #if DEBUG
<span style="color:Blue; if (m_rot != <span style="color:Blue; null)
{
m_rot.Dispose();
}
<span style="color:Blue; #endif
CloseInterfaces();
<span style="color:Blue; if (m_PictureReady != 
<span style="color:Gray; ///<span style="color:Green; Get the image from the Still pin. The returned image can turned into a bitmap with
<span style="color:Gray; ///<span style="color:Green; Bitmap b = new Bitmap(cam.Width, cam.Height, cam.Stride, PixelFormat.Format24bppRgb, m_ip);
<span style="color:Gray; ///<span style="color:Green; If the image is upside down, you can fix it with


<span style="color:Blue; public IntPtr Click()
{
<span style="color:Blue; int hr;

<span style="color:Green; // get ready to wait for new image
m_PictureReady.Reset();
m_ipBuffer = Marshal.AllocCoTaskMem(Math.Abs(m_stride) * m_videoHeight);

<span style="color:Blue; try
{
m_WantOne = <span style="color:Blue; true;

<span style="color:Green; // If we are using a still pin, ask for a picture
<span style="color:Blue; if (m_VidControl != <span style="color:Blue; null)
{
<span style="color:Green; // Tell the camera to send an image
hr = m_VidControl.SetMode(m_pinStill, VideoControlFlags.Trigger);
DsError.ThrowExceptionForHR( hr );
}

<span style="color:Green; // Start waiting
<span style="color:Blue; if ( ! m_PictureReady.WaitOne(9000, <span style="color:Blue; false) )
{
<span style="color:Blue; throw <span style="color:Blue; new Exception(<span style="color:#A31515; "Timeout waiting to get picture");
}
}
<span style="color:Blue; catch
{
Marshal.FreeCoTaskMem(m_ipBuffer);
m_ipBuffer = IntPtr.Zero;
<span style="color:Blue; throw;
}

<span style="color:Green; // Got one
<span style="color:Blue; return m_ipBuffer;
}

<span style="color:Blue; public <span style="color:Blue; int Width
{
<span style="color:Blue; get
{
<span style="color:Blue; return m_videoWidth;
}
}
<span style="color:Blue; public <span style="color:Blue; int Height
{
<span style="color:Blue; get
{
<span style="color:Blue; return m_videoHeight;
}
}
<span style="color:Blue; public 
<span style="color:Blue; private <span style="color:Blue; void SetupGraph(DsDevice dev, <span style="color:Blue; int iWidth, <span style="color:Blue; int iHeight, <span style="color:Blue; short iBPP, Control hControl)
{
<span style="color:Blue; int hr;

ISampleGrabber sampGrabber = <span style="color:Blue; null;
IBaseFilter capFilter = <span style="color:Blue; null;
IPin pCaptureOut = <span style="color:Blue; null;
IPin pSampleIn = <span style="color:Blue; null;
IPin pRenderIn = <span style="color:Blue; null;

<span style="color:Green; // Get the graphbuilder object
m_FilterGraph = <span style="color:Blue; new FilterGraph() <span style="color:Blue; as IFilterGraph2;

<span style="color:Blue; try
{
<span style="color:Blue; #if DEBUG
m_rot = <span style="color:Blue; new DsROTEntry(m_FilterGraph);
<span style="color:Blue; #endif
<span style="color:Green; // add the video input device
hr = m_FilterGraph.AddSourceFilterForMoniker(dev.Mon, <span style="color:Blue; null, dev.Name, <span style="color:Blue; out capFilter);
DsError.ThrowExceptionForHR( hr );

<span style="color:Green; // Find the still pin
m_pinStill = DsFindPin.ByCategory(capFilter, PinCategory.Still, 0);

<span style="color:Green; // Didnt find one. Is there a preview pin?
<span style="color:Blue; if (m_pinStill == <span style="color:Blue; null)
{
m_pinStill = DsFindPin.ByCategory(capFilter, PinCategory.Preview, 0);
}

<span style="color:Green; // Still havent found one. Need to put a splitter in so we have
<span style="color:Green; // one stream to capture the bitmap from, and one to display. Ok, we
<span style="color:Green; // dont *have* to do it that way, but we are going to anyway.
<span style="color:Blue; if (m_pinStill == <span style="color:Blue; null)
{
IPin pRaw = <span style="color:Blue; null;
IPin pSmart = <span style="color:Blue; null;

<span style="color:Green; // There is no still pin
m_VidControl = <span style="color:Blue; null;

<span style="color:Green; // Add a splitter
IBaseFilter iSmartTee = (IBaseFilter)<span style="color:Blue; new SmartTee();

<span style="color:Blue; try
{
hr = m_FilterGraph.AddFilter(iSmartTee, <span style="color:#A31515; "SmartTee");
DsError.ThrowExceptionForHR( hr );

<span style="color:Green; // Find the find the capture pin from the video device and the
<span style="color:Green; // input pin for the splitter, and connnect them
pRaw = DsFindPin.ByCategory(capFilter, PinCategory.Capture, 0);
pSmart = DsFindPin.ByDirection(iSmartTee, PinDirection.Input, 0);

hr = m_FilterGraph.Connect(pRaw, pSmart);
DsError.ThrowExceptionForHR( hr );

<span style="color:Green; // Now set the capture and still pins (from the splitter)
m_pinStill = DsFindPin.ByName(iSmartTee, <span style="color:#A31515; "Preview");
pCaptureOut = DsFindPin.ByName(iSmartTee, <span style="color:#A31515; "Capture");

<span style="color:Green; // If any of the default config items are set, perform the config
 0)
{
SetConfigParms(pRaw, iWidth, iHeight, iBPP);
}
}
<span style="color:Blue; finally
{
<span style="color:Blue; if (pRaw != <span style="color:Blue; null)
{
Marshal.ReleaseComObject(pRaw);
}
<span style="color:Blue; if (pRaw != pSmart)
{
Marshal.ReleaseComObject(pSmart);
}
<span style="color:Blue; if (pRaw != iSmartTee)
{
Marshal.ReleaseComObject(iSmartTee);
}
}
}
<span style="color:Blue; else
{
<span style="color:Green; // Get a control pointer (used in Click())
m_VidControl = capFilter <span style="color:Blue; as IAMVideoControl;

pCaptureOut = DsFindPin.ByCategory(capFilter, PinCategory.Capture, 0);

 0)
{
SetConfigParms(m_pinStill, iWidth, iHeight, iBPP);
}
}

<span style="color:Green; // Get the SampleGrabber interface
sampGrabber = <span style="color:Blue; new SampleGrabber() <span style="color:Blue; as ISampleGrabber;

<span style="color:Green; // Configure the sample grabber
IBaseFilter baseGrabFlt = sampGrabber <span style="color:Blue; as IBaseFilter;
ConfigureSampleGrabber(sampGrabber);
pSampleIn = DsFindPin.ByDirection(baseGrabFlt, PinDirection.Input, 0);

<span style="color:Green; // Get the default video renderer
IBaseFilter pRenderer = <span style="color:Blue; new VideoRendererDefault() <span style="color:Blue; as IBaseFilter;
hr = m_FilterGraph.AddFilter(pRenderer, <span style="color:#A31515; "Renderer");
DsError.ThrowExceptionForHR( hr );

pRenderIn = DsFindPin.ByDirection(pRenderer, PinDirection.Input, 0);

<span style="color:Green; // Add the sample grabber to the graph
hr = m_FilterGraph.AddFilter( baseGrabFlt, <span style="color:#A31515; "Ds.NET Grabber" );
DsError.ThrowExceptionForHR( hr );

<span style="color:Blue; if (m_VidControl == <span style="color:Blue; null)
{
<span style="color:Green; // Connect the Still pin to the sample grabber
hr = m_FilterGraph.Connect(m_pinStill, pSampleIn);
DsError.ThrowExceptionForHR( hr );

<span style="color:Green; // Connect the capture pin to the renderer
hr = m_FilterGraph.Connect(pCaptureOut, pRenderIn);
DsError.ThrowExceptionForHR( hr );
}
<span style="color:Blue; else
{
<span style="color:Green; // Connect the capture pin to the renderer
hr = m_FilterGraph.Connect(pCaptureOut, pRenderIn);
DsError.ThrowExceptionForHR( hr );

<span style="color:Green; // Connect the Still pin to the sample grabber
hr = m_FilterGraph.Connect(m_pinStill, pSampleIn);
DsError.ThrowExceptionForHR( hr );
}

<span style="color:Green; // Learn the video properties
SaveSizeInfo(sampGrabber);
ConfigVideoWindow(hControl);

<span style="color:Green; // Start the graph
IMediaControl mediaCtrl = m_FilterGraph <span style="color:Blue; as IMediaControl;
hr = mediaCtrl.Run();
DsError.ThrowExceptionForHR( hr );
}
<span style="color:Blue; finally
{
<span style="color:Blue; if (sampGrabber != <span style="color:Blue; null)
{
Marshal.ReleaseComObject(sampGrabber);
sampGrabber = <span style="color:Blue; null;
}
<span style="color:Blue; if (pCaptureOut != <span style="color:Blue; null)
{
Marshal.ReleaseComObject(pCaptureOut);
pCaptureOut = <span style="color:Blue; null;
}
<span style="color:Blue; if (pRenderIn != <span style="color:Blue; null)
{
Marshal.ReleaseComObject(pRenderIn);
pRenderIn = <span style="color:Blue; null;
}
<span style="color:Blue; if (pSampleIn != <span style="color:Blue; null)
{
Marshal.ReleaseComObject(pSampleIn);
pSampleIn = <span style="color:Blue; null;
}
}
}

<span style="color:Blue; private <span style="color:Blue; void SaveSizeInfo(ISampleGrabber sampGrabber)
{
<span style="color:Blue; int hr;

<span style="color:Green; // Get the media type from the SampleGrabber
AMMediaType media = <span style="color:Blue; new AMMediaType();

hr = sampGrabber.GetConnectedMediaType( media );
DsError.ThrowExceptionForHR( hr );

<span style="color:Blue; if( (media.formatType != FormatType.VideoInfo) || (media.formatPtr == IntPtr.Zero) )
{
<span style="color:Blue; throw <span style="color:Blue; new NotSupportedException( <span style="color:#A31515; "Unknown Grabber Media Format" );
}

<span style="color:Green; // Grab the size info
VideoInfoHeader videoInfoHeader = (VideoInfoHeader) Marshal.PtrToStructure( media.formatPtr, <span style="color:Blue; typeof(VideoInfoHeader) );
m_videoWidth = videoInfoHeader.BmiHeader.Width;
m_videoHeight = videoInfoHeader.BmiHeader.Height;
m_stride = m_videoWidth * (videoInfoHeader.BmiHeader.BitCount / 8);

DsUtils.FreeAMMediaType(media);
media = <span style="color:Blue; null;
}

<span style="color:Green; // Set the video window within the control specified by hControl
<span style="color:Blue; private <span style="color:Blue; void ConfigVideoWindow(Control hControl)
{
<span style="color:Blue; int hr;

IVideoWindow ivw = m_FilterGraph <span style="color:Blue; as IVideoWindow;

<span style="color:Green; // Set the parent
hr = ivw.put_Owner(hControl.Handle);
DsError.ThrowExceptionForHR( hr );

<span style="color:Green; // Turn off captions, etc
hr = ivw.put_WindowStyle(WindowStyle.Child | WindowStyle.ClipChildren | WindowStyle.ClipSiblings);
DsError.ThrowExceptionForHR( hr );

<span style="color:Green; // Yes, make it visible
hr = ivw.put_Visible( OABool.True );
DsError.ThrowExceptionForHR( hr );

<span style="color:Green; // Move to upper left corner
Rectangle rc = hControl.ClientRectangle;
hr = ivw.SetWindowPosition( 0, 0, rc.Right, rc.Bottom );
DsError.ThrowExceptionForHR( hr );
}

<span style="color:Blue; private <span style="color:Blue; void ConfigureSampleGrabber(ISampleGrabber sampGrabber)
{
<span style="color:Blue; int hr;
AMMediaType media = <span style="color:Blue; new AMMediaType();

<span style="color:Green; // Set the media type to Video/RBG24
media.majorType = MediaType.Video;
media.subType = MediaSubType.RGB24;
media.formatType = FormatType.VideoInfo;
hr = sampGrabber.SetMediaType( media );
DsError.ThrowExceptionForHR( hr );

DsUtils.FreeAMMediaType(media);
media = <span style="color:Blue; null;

<span style="color:Green; // Configure the samplegrabber
hr = sampGrabber.SetCallback( <span style="color:Blue; this, 1 );
DsError.ThrowExceptionForHR( hr );
}

<span style="color:Green; // Set the Framerate, and video size
<span style="color:Blue; private <span style="color:Blue; void SetConfigParms(IPin pStill, <span style="color:Blue; int iWidth, <span style="color:Blue; int iHeight, <span style="color:Blue; short iBPP)
{
<span style="color:Blue; int hr;
AMMediaType media;
VideoInfoHeader v;

IAMStreamConfig videoStreamConfig = pStill <span style="color:Blue; as IAMStreamConfig;

<span style="color:Green; // Get the existing format block
hr = videoStreamConfig.GetFormat(<span style="color:Blue; out media);
DsError.ThrowExceptionForHR(hr);

<span style="color:Blue; try
{
<span style="color:Green; // copy out the videoinfoheader
v = 0)
{
v.BmiHeader.Width = iWidth;
}

 0)
{
v.BmiHeader.Height = iHeight;
}

 0)
{
v.BmiHeader.BitCount = iBPP;
}

<span style="color:Green; // Copy the media structure back
Marshal.StructureToPtr( v, media.formatPtr, <span style="color:Blue; false );

<span style="color:Green; // Set the new format
hr = videoStreamConfig.SetFormat( media );
DsError.ThrowExceptionForHR( hr );
}

<span style="color:Blue; private <span style="color:Blue; void CloseInterfaces()
{
<span style="color:Blue; int hr;

<span style="color:Blue; try
{
<span style="color:Blue; if( m_FilterGraph != <span style="color:Blue; null )
{
IMediaControl mediaCtrl = m_FilterGraph <span style="color:Blue; as IMediaControl;

<span style="color:Green; // Stop the graph
hr = mediaCtrl.Stop();
}
}
<span style="color:Blue; catch (Exception ex)
{
Debug.WriteLine(ex);
}

<span style="color:Blue; if (m_FilterGraph != <span style="color:Blue; null)
{
Marshal.ReleaseComObject(m_FilterGraph);
m_FilterGraph = <span style="color:Blue; null;
}

<span style="color:Blue; if (m_VidControl != <span style="color:Blue; null)
{
Marshal.ReleaseComObject(m_VidControl);
m_VidControl = <span style="color:Blue; null;
}

<span style="color:Blue; if (m_pinStill != 
<span style="color:Blue; int ISampleGrabberCB.SampleCB( 
<span style="color:Blue; int ISampleGrabberCB.BufferCB( <span style="color:Blue; double SampleTime, IntPtr pBuffer, <span style="color:Blue; int BufferLen )
{
<span style="color:Green; // Note that we depend on only being called once per call to Click. Otherwise
<span style="color:Green; // a second call can overwrite the previous image.
Debug.Assert(BufferLen == Math.Abs(m_stride) * m_videoHeight, <span style="color:#A31515; "Incorrect buffer length");

<span style="color:Blue; if (m_WantOne)
{
m_WantOne = <span style="color:Blue; false;
Debug.Assert(m_ipBuffer != IntPtr.Zero, <span style="color:#A31515; "Unitialized buffer");

<span style="color:Green; // Save the buffer
CopyMemory(m_ipBuffer, pBuffer, BufferLen);


 
 
 
Many thanks, 
 
Chris

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Direct show doesn't change webcam resolution

EDN Admin

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