Не работает функция cvWriteFrame

    private: System::Void button1_Click(System::Object^  sender, System::EventArgs^  e) {
    
                 
    const char *filename = "C:\\Users\\валера\\Pictures\\Video.avi";
 
    
                 Graphics^ graph;           
  Bitmap^ bitmap;
     //cvNamedWindow("original",CV_WINDOW_AUTOSIZE);
         bitmap = gcnew Bitmap (Screen::PrimaryScreen->Bounds.Width,Screen::PrimaryScreen->Bounds.Height);  
      CvSize size = cvSize(Screen::PrimaryScreen->Bounds.Width, Screen::PrimaryScreen->Bounds.Height);
     
     CvVideoWriter *writer = cvCreateVideoWriter(filename, CV_FOURCC('D','I','V','X'), 25, size, 1);
       
     
     assert(writer!=0);  
   while(true){
     
  
    graph = Graphics::FromImage(bitmap);     
         graph->CopyFromScreen(0,0,0,0,bitmap->Size); 
System::Drawing::Rectangle Rect(0,0,bitmap->Width,bitmap->Height);
         
        Bitmap ^ bitmap1 = bitmap->Clone(Rect, Imaging::PixelFormat::Format32bppRgb);
 
 
           System::Drawing::Imaging::BitmapData^ bmData = bitmap->LockBits(
            System::Drawing::Rectangle(0, 0, bitmap1->Width, bitmap1->Height) ,
            System::Drawing::Imaging::ImageLockMode::ReadWrite,bitmap1-> PixelFormat);
        
            frame = cvCreateImage(cvSize(bitmap1->Width , bitmap1->Height) , IPL_DEPTH_8U , 4);
        frame->imageData = (char*)bmData->Scan0.ToPointer();
            cvNamedWindow("original",CV_WINDOW_AUTOSIZE);    
             
        
        cvWriteFrame(writer, frame);
                 // cvShowImage( "original", frame );
 
                  cvWaitKey(5);
   bitmap->UnlockBits(bmData);
   }
                  cvReleaseCapture( &capture );
             cvReleaseVideoWriter(&writer);
       // cvDestroyWindow("capture");
   
   }

bitmap = gcnew Bitmap (Screen::PrimaryScreen->Bounds.Width,Screen::PrimaryScreen->Bounds.Height, Imaging::PixelFormat::Format24bppRgb);