opencv rtsp connection using vlc library

RTSP(Real Time Streaming Protocol) is video streaming, it usually sent from network camera.

VideoCapture function in opencv also can get rtsp video, but difficult to receive a stable image.
This is simple example using videocapture.
...

int main()
{

 VideoCapture cap("rtsp://192.168.0.50");

 namedWindow("fish", 0);
 Mat fishEye;
 while (1)
 {
  cap >> fishEye;
  if (fishEye.empty())
   return 0;

  imshow("fish", fishEye);
  if (waitKey(10) > 0)
   break;
 }

 return 0;

}

...

We can receive more reliable RTSP using VLC library.
Of course, there are many different ways(LIVE555, FFmpeg, Qt api...).

#include < windows.h>
#include < vlc/vlc.h>

#include < opencv2\opencv.hpp>    
#include < opencv2\core.hpp>  
#include < opencv2\highgui.hpp>   

#pragma comment(lib, "libvlc.lib")

#ifdef _DEBUG
#pragma comment(lib, "opencv_core300d.lib")  
#pragma comment(lib, "opencv_highgui300d.lib")
#pragma comment(lib, "opencv_imgproc300d.lib")
#pragma comment(lib, "opencv_imgcodecs300d.lib")
#else
#pragma comment(lib, "opencv_core300.lib")  
#pragma comment(lib, "opencv_highgui300.lib")
#pragma comment(lib, "opencv_imgproc300.lib")
#pragma comment(lib, "opencv_imgcodecs300.lib")
#endif

using namespace cv;
using namespace std;

struct ctx
{
 Mat* image;
 HANDLE mutex;
 uchar* pixels;
};
bool isRunning = true;

Size getsize(const char* path)
{
 libvlc_instance_t *vlcInstance;
 libvlc_media_player_t *mp;
 libvlc_media_t *media;

 char *vlc_argv[6];
 vlc_argv[0] = new char[3];
 strcpy_s(vlc_argv[0], 3, "-I");
 vlc_argv[1] = new char[6];
 strcpy_s(vlc_argv[1], 6, "dummy"); // Don't use any interface
 vlc_argv[2] = new char[16];
 strcpy_s(vlc_argv[2], 16, "--ignore-config"); // Don't use VLC's config
 vlc_argv[3] = new char[128];
 strcpy_s(vlc_argv[3], 128, "--plugin-path=/plugins");
 int vlc_argc = 4;

 vlcInstance = libvlc_new(vlc_argc, vlc_argv);

 for (int i = 0; i < vlc_argc; i++)
  delete[] vlc_argv[i];

 media = libvlc_media_new_location(vlcInstance, path);
 mp = libvlc_media_player_new_from_media(media);

 libvlc_media_release(media);
 libvlc_video_set_callbacks(mp, NULL, NULL, NULL, NULL);
 libvlc_video_set_format(mp, "RV24", 100, 100, 100 * 24 / 8); // pitch = width * BitsPerPixel / 8
 //libvlc_video_set_format(mp, "RV32", 100, 100, 100 * 4);
 libvlc_media_player_play(mp);

 Sleep(2000);//wait a while so that something get rendered so that size info is available
 unsigned int width = 640, height = 480;

 for (int i = 0; i < 30 && height == 0; i++)
 {
  Sleep(50);
  libvlc_video_get_size(mp, 0, &width, &height);

  if (width != 0 && height != 0)
   break;
 }


 if (width == 0 || height == 0)
 {
  width = 640;
  height = 480;
 }

 libvlc_media_player_stop(mp);
 libvlc_release(vlcInstance);
 libvlc_media_player_release(mp);
 return Size(width, height);
}


void *lock(void *data, void**p_pixels)
{
 struct ctx *ctx = (struct ctx*)data;
 WaitForSingleObject(ctx->mutex, INFINITE);
 *p_pixels = ctx->pixels;
 return NULL;

}

void display(void *data, void *id){
 (void)data;
 assert(id == NULL);
}

void unlock(void *data, void *id, void *const *p_pixels)
{

 struct ctx *ctx = (struct ctx*)data;
 Mat frame = *ctx->image;
 if (frame.data)
 {
  imshow("frame", frame);
  if (waitKey(1) == 27)
  {
   isRunning = false;
   //exit(0);
  }
 }
 ReleaseMutex(ctx->mutex);
}


int main()
{
 string url = "rtsp://...";
 //vlc sdk does not know the video size until it is rendered, so need to play it a bit so that size is     known
 Size sz = getsize(url.c_str());

 // VLC pointers
 libvlc_instance_t *vlcInstance;
 libvlc_media_player_t *mp;
 libvlc_media_t *media;

 char *vlc_argv[6];
 vlc_argv[0] = new char[3];
 strcpy_s(vlc_argv[0], 3, "-I");
 vlc_argv[1] = new char[6];
 strcpy_s(vlc_argv[1], 6, "dummy"); // Don't use any interface
 vlc_argv[2] = new char[16];
 strcpy_s(vlc_argv[2], 16, "--ignore-config"); // Don't use VLC's config
 vlc_argv[3] = new char[128];
 strcpy_s(vlc_argv[3], 128, "--plugin-path=/plugins");
 int vlc_argc = 4;

 vlcInstance = libvlc_new(vlc_argc, vlc_argv);

 for (int i = 0; i < vlc_argc; i++)
  delete[] vlc_argv[i];

 media = libvlc_media_new_location(vlcInstance, url.c_str());
 mp = libvlc_media_player_new_from_media(media);
 libvlc_media_release(media);


 struct ctx* context = (struct ctx*)malloc(sizeof(*context));
 context->mutex = CreateMutex(NULL, FALSE, NULL);
 context->image = new Mat(sz.height, sz.width, CV_8UC3);
 context->pixels = (unsigned char *)context->image->data;

 libvlc_video_set_callbacks(mp, lock, unlock, display, context);
 libvlc_video_set_format(mp, "RV24", sz.width, sz.height, sz.width * 24 / 8); // pitch = width *     BitsPerPixel / 8
 //libvlc_video_set_format(mp, "RV32", sz.width, sz.height, sz.width * 4);

 libvlc_media_player_play(mp);
 while (isRunning)
 {
  //imshow("rtsp", *(context->image));
  Sleep(1);  
 }

 libvlc_media_player_stop(mp);
 libvlc_release(vlcInstance);
 libvlc_media_player_release(mp);
 free(context);

 return 0;
}

This example code is referenced in here
http://stackoverflow.com/questions/23529620/opencv-and-network-cameras-or-how-to-spy-on-the-neighbors

To use this example code, you should install VLC player, and set dependency referencing include, lib, dll and plugins.
And If you are using opencv 64 bits then you also install 64-bit vlc.

Test video