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Using the DirectShow Video Mixing Renderer 9 filter

, 1 Feb 2005
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This article describes how to dynamically mix two video files (.mpeg, .mpg, .avi and .dat). Mixing involves alpha-blending and stretching/shrinking and positioning of the two video streams, individually, using DirectShow's VMR9 filter.

Sample Image - DirectShowVMR91.jpg

Introduction

This article shows the steps involved in creating and configuring DirectShow’s Video Mixing Renderer Filter 9 (VMR9). The two video streams, one on top of the other, are rendered on a single surface. This surface, in our case, is a PictureBox control. Each stream's alpha value, position and height/width can be adjusted at runtime.

How VMR9 is different

The following diagrams show the difference between rendering two videos with VMR9 and without VMR9.

Without VMR9

Rendering without VMR9

We notice that simply rendering two videos will result in two separate Video Renderers, which means that the videos are being played on two separate surfaces.

With VMR9

Rendering with VMR9

In this case, the VMR9 filter directs both video streams into its own input pins. This means there is only one renderer, and thus a single rendering surface for both video streams.

The Working

To enhance reusability and readability factors, the functionality of the VMR9 filter has been encapsulated inside a class named myVMR9.

The myVMR9 class

This class has the following private data members:

  • VMR9NormalizedRect *r;
  • IVMRWindowlessControl9 *pWC;
  • IVMRMixerControl9 *pMix;
  • IGraphBuilder *pGB;
  • IBaseFilter *pVmr;
  • IVMRFilterConfig9 *pConfig;
  • IMediaControl *pMC;
  • IMediaSeeking *pMS;

The constructor

The constructor receives a PictureBox's coordinates of type System::Drawing::Rectangle, along with its handler of type HWND. These two attributes are used by VMR9 for rendering purposes.

public: myVMR9(System::Drawing::Rectangle rect, HWND hwnd)
{
    // initialize video coordinates with normal values
    r = new VMR9NormalizedRect;
    r->left = 0;
    r->top = 0;
    r->right = 1;
    r->bottom = 1;

    pWC = NULL;
    pMix = NULL;
    pGB = NULL;
    pVmr = NULL;
    pConfig = NULL;
    pMC = NULL;
    pMS = NULL;
    // create an instance of the Filter Graph Manager
    CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER, 
        IID_IGraphBuilder, (void **)&pGB);
    // create an instance of the VMR9 filter
    CoCreateInstance(CLSID_VideoMixingRenderer9, NULL, CLSCTX_INPROC,
        IID_IBaseFilter, (void**)&pVmr);
    // add the VMR9 filter to the Graph Manager
    pGB->AddFilter(pVmr, L"Video");    
    // get a pointer to the IVMRFilterConfig9 interface
    pVmr->QueryInterface(IID_IVMRFilterConfig9, (void**)&pConfig);
    // make sure VMR9 is in windowless mode
    pConfig->SetRenderingMode(VMR9Mode_Windowless);
    // get a pointer to the IVMRWindowlessControl9 interface 
    pVmr->QueryInterface(IID_IVMRWindowlessControl9, (void**)&pWC);
    // explicitly convert System::Drawing::Rectangle type to RECT type
    RECT rcDest = {0};
    rcDest.bottom = rect.Bottom;
    rcDest.left = rect.Left;
    rcDest.right = rect.Right;
    rcDest.top = rect.Top;

    // set destination rectangle for the video
    pWC->SetVideoPosition(NULL, &rcDest);

    // specify the container window that the video should be clipped to    
    pWC->SetVideoClippingWindow(hwnd);
    // IVMRMixerControl manipulates video streams
    pVmr->QueryInterface(IID_IVMRMixerControl9, (void**)&pMix);
    // IMediaSeeking seeks to a position in the video stream
    pGB->QueryInterface(IID_IMediaSeeking, (void **)&pMS);
    // IMediaControl controls flow of data through the graph
    pGB->QueryInterface(IID_IMediaControl, (void **)&pMC);
}

The methods

HRESULT play()
{
    pMC->Run(); return
    S_OK;
}

HRESULT pause()
{
    pMC->Pause();
    return S_OK;
}

HRESULT stop()
{
    LONGLONG pos = 0;
    pMC->Stop();
    pMS->SetPositions(&pos, AM_SEEKING_AbsolutePositioning, 
                      NULL,AM_SEEKING_NoPositioning);
    pMC->Pause();
    return S_OK;
}

HRESULT close()
{
    // make sure resources are freed
    SAFE_RELEASE(pWC);
    SAFE_RELEASE(pMix);
    SAFE_RELEASE(pGB);
    SAFE_RELEASE(pVmr);
    SAFE_RELEASE(pConfig);
    SAFE_RELEASE(pMC);
    SAFE_RELEASE(pMS);
    return S_OK;
}

HRESULT setAlpha(DWORD stream, float alpha)
{
    // set alpha of specified video stream
    pMix->SetAlpha(stream, alpha);
    return S_OK;
}

HRESULT setX(DWORD stream, float x)
{
    // video displacement along x-axis
    r->right = x + (r->right - r->left);
    r->left = x;
    pMix->SetOutputRect(stream, r);
    return S_OK;
}

HRESULT setY(DWORD stream, float y)
{
    // video displacement along y-axis
    r->bottom = y + (r->bottom - r->top);
    r->top = y;
    pMix->SetOutputRect(stream, r);
    return S_OK;
}

HRESULT setW(DWORD stream, float w)
{
    // video stretching/shrinking along x-axis
    r->right = r->left + w;
    pMix->SetOutputRect(stream, r);
    return S_OK;
}

HRESULT setH(DWORD stream, float h)
{
    // video stretching/shrinking along y-axis
    r->bottom = r->top + h;
    pMix->SetOutputRect(stream, r);
    return S_OK;
}

HRESULT renderFiles(String* file1, String* file2)
{
    // convert String type to LPCSTR type and render the videos
    LPCTSTR lFile;
    lFile = 
      static_cast<LPCTSTR>(const_cast<void*>(static_cast<const void*>
      (System::Runtime::InteropServices::Marshal::StringToHGlobalAuto(file1))));
    pGB->RenderFile((LPCWSTR)lFile, NULL);
    lFile = 
      static_cast<LPCTSTR>(const_cast<void*>(static_cast<const void*>
      (System::Runtime::InteropServices::Marshal::StringToHGlobalAuto(file2))));
    pGB->RenderFile((LPCWSTR)lFile, NULL);
    System::Runtime::InteropServices::Marshal::FreeHGlobal
      (static_cast<IntPtr>(const_cast<void*>
      (static_cast<const void*>(lFile))));
    pMC->StopWhenReady();
    return S_OK;
}

Now that the VMR9's functionality has been separated from the GUI, Button and TrackBar handlers can simply create a pointer to a myVMR9 object and call the required methods.

Sample screenshot

Additional Information

  • The second video stream opened is on top of the first one, i.e., file-2 video is rendered on top of file-1 video. Therefore, if the first video's alpha value is a 100% and the second video's alpha value is 50%, then both videos will be equally (50%) visible.
  • It should be noted that the values of Width and Height of trackbars can run into negative values. So when a video stream's width is -100%, it is laterally inverted. Similarly, when a video stream's height is -100%, the video is upside down.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

About the Author

Sameer Ahmed
Software Developer
Pakistan Pakistan
No Biography provided

Comments and Discussions

 
AnswerRe: Send the result of VMR9 to an .avi file Pinmembertanvon malik25-Sep-07 21:14 
Generalgreenish lines on video using VMR9 Pinmembershovit25-Oct-06 20:29 
GeneralFull Screen [modified] Pinmemberalanmark5-Oct-06 4:02 
Questionenumerate pins PinmemberFariha Atta1-Oct-06 17:57 
AnswerRe: enumerate pins PinmemberSameer Ahmed2-Oct-06 11:08 
GeneralSound PinmemberTharkunius26-Sep-06 23:38 
GeneralRe: Sound PinmemberSameer Ahmed2-Oct-06 10:29 
QuestionUrgent !!! No errors in code but still cant see the video :-( [modified] Pinmember~Jabeen~3-Sep-06 21:21 
Assalamoalikum!
 
i have tried your code as the way it is
 
It gives no errors but i cant see the video ... now i am stuck Confused | :confused:
 
My scenario is that i have a preview mode and a capture mode
 
I have implemented "preview mode" through VMR in the preview window.
 
It works fine through it.
 
Now about the problem i am facing i have a child window that starts showing the same preview on button click in it( say "capture window").
 
I had implemented this scenario through GRABBER but i want to do it through VMR although i am running an instance of appilication in the same application and on the same dialog
 

Through your code i got no errors through out i mean till
m_hr=pMC->Run();
i get no errors still i cant preview the video
 
more over i am getting the rectangle of the child window as
 

RECT rcDest;
::GetClientRect (hWnd,&rcDest);

 

still i cant preview it Frown | :( how to proceed???
 

 

 
Thanks and regards
 

 
if you want to look through Code then its like
 

/*
 
m_DlghWnd: the handle of the dialog which have both child windows that is preview (for which i have written the code through VMR) and the capture window which will show the image stream on button click
 

hWnd: it is the handle of the child window in which i want to start the preview stream
 

Requirement: Both windows should be previewed after the button click
 
*/
 
HRESULT CCameraPreview::TestVideo(HWND m_DlghWnd,HWND hWnd)
{
 
r = new VMR9NormalizedRect;
r->left = 0;
r->top = 0;
r->right = 1;
r->bottom = 1;
 
pWC = NULL;
pMix = NULL;
pGB = NULL;
pVmr = NULL;
pConfig = NULL;
pMC = NULL;
pMS = NULL;
 
// create an instance of the Filter Graph Manager
m_hr=CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER,
IID_IGraphBuilder, (void **)&pGB);
// create an instance of the VMR9 filter
m_hr=CoCreateInstance(CLSID_VideoMixingRenderer9, NULL, CLSCTX_INPROC,
IID_IBaseFilter, (void**)&pVmr);
// add the VMR9 filter to the Graph Manager
m_hr=pGB->AddFilter(pVmr, L"Video");
// get a pointer to the IVMRFilterConfig9 interface
m_hr=pVmr->QueryInterface(IID_IVMRFilterConfig9, (void**)&pConfig);
// make sure VMR9 is in windowless mode
m_hr=pConfig->SetRenderingMode(VMR9Mode_Windowless);
// get a pointer to the IVMRWindowlessControl9 interface
m_hr=pVmr->QueryInterface(IID_IVMRWindowlessControl9, (void**)&pWC);
// explicitly convert System::Drawing::Rectangle type to RECT type
 

RECT rcDest;
::GetClientRect (hWnd,&rcDest);

 
// set destination rectangle for the video
m_hr=pWC->SetVideoPosition(NULL, &rcDest);
 
// specify the container window that the video should be clipped to
m_hr=pWC->SetVideoClippingWindow(hWnd);
// IVMRMixerControl manipulates video streams
m_hr=pVmr->QueryInterface(IID_IVMRMixerControl9, (void**)&pMix);
// IMediaSeeking seeks to a position in the video stream
m_hr=pGB->QueryInterface(IID_IMediaSeeking, (void **)&pMS);
// IMediaControl controls flow of data through the graph
m_hr=pGB->QueryInterface(IID_IMediaControl, (void **)&pMC);
m_hr=pMC->Run();
return m_hr;

 

 
-- modified at 3:45 Monday 4th September, 2006

 
Jabeen

AnswerRe: Urgent !!! No errors in code but still cant see the video :-( PinmemberSameer Ahmed5-Sep-06 1:58 
Questionvideo mixing problem [modified] Pinmemberfariha atta17-Aug-06 16:06 
AnswerRe: video mixing problem [modified] PinmemberSameer Ahmed17-Aug-06 18:22 
GeneralRe: video mixing problem Pinmemberfariha atta18-Aug-06 5:04 
GeneralRe: vmr9 PinmemberSameer Ahmed15-Aug-06 23:55 
Questionproblem in implementing a filter graph thru Filter Graph Manager Pinmemberfariha atta28-Jul-06 16:22 
AnswerRe: problem in implementing a filter graph thru Filter Graph Manager PinmemberSameer Ahmed29-Jul-06 1:36 
GeneralFull screen switching mode Pinmembergabrilestrimtu9-Jun-06 7:45 
GeneralRe: Full screen switching mode Pinmemberjimerino18-Apr-07 7:35 
Generalsir,i got some error complied in .net Pinmemberchenhuasheng8-May-06 18:44 
GeneralText Mixing Pinmemberjeykumars27-Apr-06 23:11 
GeneralRe: Text Mixing PinmemberSameer Ahmed28-Apr-06 2:06 
GeneralRe: AoA Sameer! PinmemberSameer Ahmed29-Jul-06 1:49 
GeneralGreat stuff PinmemberRYoung4-Mar-06 7:36 
GeneralRe: Great stuff PinmemberSameer Ahmed4-Mar-06 8:14 
Generaloops PinmemberGraceNetwork23-Feb-06 6:35 
Questionoutput render video to file? PinmemberGraceNetwork22-Feb-06 14:10 

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