Capture to Play Object Interfacing for C

The following code demonstrates how to grap samples from the capture object and feed them to the play object. It is intended to demonstrate the basic function set that would be required to remote the playback of media samples.

// define helper macros for using the interfaces under C 
#ifndef COBJMACROS 
   #define COBJMACROS 
#endif 
 
// include the LEAD Multimedia TOOLKIT header 
#include "ltmm.h" 
 
#include <tchar.h> 
#include <stdio.h> 
#include <math.h> 
#include <assert.h> 
 
#define UNUSED_PARAMETER(x) (void) (x) 
 
#define SZ_WNDCLASS_PLAY _T("PLAY WNDCLASS") 
#define WM_PLAYNOTIFY (WM_USER + 1000)  
 
HINSTANCE g_hInstance;    // application instance handle 
HWND g_hwndPlay;      // video frame window 
IltmmPlay* g_pPlay;      // play object interface pointer 
IltmmCapture* g_pCapture;   // capture object interface pointer 
IltmmSampleTarget* g_pTarget;   // target object, used with capture 
IltmmSampleSource* g_pSource;   // source object, used with play 
 
// 
// PlayWndProc 
// video frame window procedure 
// 
LRESULT CALLBACK PlayWndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)  
{ 
   switch (message)  
   { 
   case WM_CREATE:  
      g_hwndPlay = hwnd;  
 
      // window is the video window frame 
      IltmmPlay_put_VideoWindowFrame(g_pPlay, (long) hwnd);  
 
      // assign the media source 
      IltmmPlay_put_SourceObject(g_pPlay, (IUnknown*) g_pSource);  
#ifdef _DEBUG 
      { 
         IUnknown* punk;  
         IltmmPlay_get_SourceObject(g_pPlay, &punk);  
         assert(punk != NULL);  
         if(punk)  
            IUnknown_Release(punk);  
      } 
#endif 
 
      return 0;  
      break;  
   case WM_DESTROY:  
      PostQuitMessage(0);  
      break;  
   } 
   return DefWindowProc(hwnd, message, wParam, lParam);  
} 
 
int APIENTRY WinMain(HINSTANCE hInstance,  
                     HINSTANCE hPrevInstance,  
                     LPSTR     lpCmdLine,  
                     int       nCmdShow)  
{ 
   MSG msg;  
   HRESULT hr;  
   WNDCLASSEX wcex;  
   IltmmDevices* pDevices;  
   VARIANT var;  
   IltmmMediaTypeDisp* pMediaType;  
   BSTR bstr;  
   long index;  
   IltmmCompressors* pCompressors;  
 
 
   UNUSED_PARAMETER(lpCmdLine); 
   UNUSED_PARAMETER(hPrevInstance);    
 
   g_hInstance = hInstance;  
 
   // initialize the COM library 
   hr = CoInitialize(NULL);  
   if(FAILED(hr))  
      goto error;  
 
 
   // register the video frame window class 
   wcex.cbSize = sizeof(WNDCLASSEX);  
   wcex.style         = CS_HREDRAW | CS_VREDRAW;  
   wcex.lpfnWndProc   = PlayWndProc;  
   wcex.cbClsExtra    = 0;  
   wcex.cbWndExtra    = 0;  
   wcex.hInstance      = g_hInstance;  
   wcex.hIcon         = NULL;  
   wcex.hCursor      = LoadCursor(NULL, IDC_ARROW);  
   wcex.hbrBackground   = (HBRUSH) (COLOR_APPWORKSPACE + 1);  
   wcex.lpszMenuName   = NULL;  
   wcex.lpszClassName   = SZ_WNDCLASS_PLAY;  
   wcex.hIconSm      = NULL;  
 
   if(!RegisterClassEx(&wcex))  
      goto error;  
 
 
   // create the play object 
   hr = CoCreateInstance(&CLSID_ltmmPlay, NULL, CLSCTX_INPROC_SERVER, &IID_IltmmPlay, (void**) &g_pPlay);  
   if(FAILED(hr))  
      goto error;  
 
   // create the capture object 
   hr = CoCreateInstance(&CLSID_ltmmCapture, NULL, CLSCTX_INPROC_SERVER, &IID_IltmmCapture, (void**) &g_pCapture);  
   if(FAILED(hr))  
      goto error;  
 
   // create the target object 
   hr = CoCreateInstance(&CLSID_ltmmSampleTarget, NULL, CLSCTX_INPROC_SERVER, &IID_IltmmSampleTarget, (void**) &g_pTarget);  
   if(FAILED(hr))  
      goto error;  
 
   // create the source object 
   hr = CoCreateInstance(&CLSID_ltmmSampleSource, NULL, CLSCTX_INPROC_SERVER, &IID_IltmmSampleSource, (void**) &g_pSource);  
   if(FAILED(hr))  
      goto error;  
 
   // do not use preview 
   IltmmCapture_put_Preview(g_pCapture, VARIANT_FALSE);  
 
   // select the first video device 
   IltmmCapture_get_VideoDevices(g_pCapture, &pDevices);  
   IltmmDevices_put_Selection(pDevices, 0);  
   IUnknown_Release(pDevices);  
 
   // select the LEAD video compressor 
   IltmmCapture_get_VideoCompressors(g_pCapture, &pCompressors);  
   bstr = SysAllocString(L"@device:sw:{33D9A760-90C8-11D0-BD43-00A0C911CE86}\\LEAD MCMP/MJPEG Codec (2.0)"); 
   IltmmCompressors_Find(pCompressors, bstr, &index);  
   SysFreeString(bstr);  
   IltmmCompressors_put_Selection(pCompressors, index);  
   IUnknown_Release(pCompressors);  
 
   // set the capture output object 
   IltmmCapture_put_TargetObject(g_pCapture, (IUnknown*) g_pTarget);  
#ifdef _DEBUG 
   { 
      IUnknown* punk;  
      IltmmCapture_get_TargetObject(g_pCapture, &punk);  
      assert(punk != NULL);  
      if(punk)  
         IUnknown_Release(punk);  
   } 
#endif 
   // start running 
   hr = IltmmCapture_StartCapture(g_pCapture, ltmmCapture_Mode_Video);  
   if(FAILED(hr))  
      goto error;  
 
   // retreive the video media type 
 
   IltmmSampleTarget_GetConnectedMediaType(g_pTarget, &pMediaType);  
 
   // could just assign the media type to the source object,  
   // but let us get the portable type instead 
   IltmmMediaTypeDisp_GetPortableType(pMediaType, &var);    
 
   // have the portable type, so do not need this anymore 
   IUnknown_Release(pMediaType);  
 
   // create a new media type 
   CoCreateInstance(&CLSID_ltmmMediaType, NULL, CLSCTX_INPROC_SERVER, &IID_IltmmMediaTypeDisp, (void**) &pMediaType);  
 
   // initialize it with the portable type 
   IltmmMediaTypeDisp_SetPortableType(pMediaType, var);  
 
   // assign it to the source object 
   IltmmSampleSource_SetMediaType(g_pSource, pMediaType);  
 
#ifdef _DEBUG 
   { 
      IltmmMediaTypeDisp* punk; 
      IltmmSampleSource_GetMediaType(g_pSource, &punk); 
      assert(punk != NULL); 
      if(punk) 
         IUnknown_Release(punk); 
   } 
#endif 
   // release the media type 
   IUnknown_Release(pMediaType);  
 
   // done with portable type 
   VariantClear(&var);  
 
   // create the video frame window 
   if(!CreateWindow(SZ_WNDCLASS_PLAY, _T("Play"), WS_OVERLAPPEDWINDOW | WS_CLIPCHILDREN,  
      CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, NULL, NULL, g_hInstance, NULL))  
      goto error;  
 
   ShowWindow(g_hwndPlay, nCmdShow);  
 
   UpdateWindow(g_hwndPlay);  
 
   // process until done 
   for(;;) 
   { 
      if(PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE))  
      { 
         if(!GetMessage(&msg, NULL, 0, 0))  
            break;  
         TranslateMessage(&msg);  
         DispatchMessage(&msg);  
      } 
      else 
      { 
         IltmmMediaSampleDisp* pSample;  
 
         // fetch a sample 
         hr = IltmmSampleTarget_GetSample(g_pTarget, 1000, &pSample);  
         if(FAILED(hr))  
            break;  
         // deliver it 
         hr = IltmmSampleSource_DeliverSample(g_pSource, 1000, pSample);  
         IUnknown_Release(pSample);  
         if(FAILED(hr))  
            goto error;  
      } 
   } 
   IltmmCapture_StopCapture(g_pCapture);  
   IltmmSampleSource_DeliverEndOfStream(g_pSource, 1000);  
   IltmmPlay_Stop(g_pPlay);  
error:  
   if(g_pSource)  
      IUnknown_Release(g_pSource);  
   if(g_pTarget)  
      IUnknown_Release(g_pTarget);  
   if(g_pCapture)  
      IUnknown_Release(g_pCapture);  
   if(g_pPlay)  
      IUnknown_Release(g_pPlay);  
 
   CoUninitialize(); 
 
   return 0;    
} 

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