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• OpenCV and Cloud Cameras

  8 mai 2014, par Alexander

  So as a bit of context ; this program was built originally to work with USB cameras - but a few things changed. I’m trying to convert it to work with networked cameras, but my presence here should make it quite apparent what my level of success has been. I still consider myself somewhat new at programming, and definately new at visual processing/OpenCV - so please forgive a few blunders if I make them. I’m going to try to provide as much detail as possible, so apologies for the length below.

  ---

  I’m using :

  • OpenCV 2.4.6.0
  • Microsoft Visual Studio Express 2012
  • C++
  • D-Link Cloud Camera 7100

  ---

  I am trying to access the DLink camera’s video feed through OpenCV.

  I can access the camera through it’s IP address with a browser without any issues. Unfourtunately ; my program is less cooperative. I’ve put it on two computers (excluding the computer it gets compiled on, which for unrelated/unchangable reasons cannot be placed on the same network the network camera is on) which both fail to grant my program access to the camera. One computer gives the OpenCV-generated error :

  warning : Error opening file (../../modules/highgui/src/cap_ffmpeg_impl.hpp:529)

  This error occurs with just about everything I try that doesn’t somehow generate more problems. The other computer (same code) generates no such error - it just doesn’t get the camera’s output either.

  For reference - the code in OpenCV’s cap_ffmpeg_impl.hpp around line 529 is as follows :

  522    bool CvCapture_FFMPEG::open( const char* _filename )
  
  523    {
  
  524        unsigned i;
  
  525        bool valid = false;
  
  526
  
  527        close();
  
  528
  
  529    #if LIBAVFORMAT_BUILD >= CALC_FFMPEG_VERSION(52, 111, 0)
  
  530        int err = avformat_open_input(&ic, _filename, NULL, NULL);
  
  531    #else
  
  532        int err = av_open_input_file(&ic, _filename, NULL, 0, NULL);
  
  533    #endif
  
  ...
  
  616    }

  ...for which I have no idea what I’m looking at.

  My entire program is rather large, so I’m editing it down as much as possible to help keep this readable - if I miss something you think is important please leave a comment telling me as much so I can throw it in...

  First up - this is one of the first things in main() so I don’t have to recompile every time I want to try a different value :

  3380    cout << "Please Enter Video Location: ";
  
  3381    cin >> videoFeedAddress;
  
  3382    cout << "videoFeedAddress: " << videoFeedAddress << endl;

  Just a simple string value.
  Next up - the actual place we’re having the problem ! Probably...

  Note that in the below code - if networkCam is false and a USB camera is connected there is no problem. The error here is caused by line 153.

  121    void displayCameraView()
  
  122    {
  
  123     if(camviewOn) // displayCameraView is triggered by a button the user can press as often as they want. Doesn't mean we want to let them break everything.
  
  124     {return;}
  
  125     else
  
  126     {
  
  127         CvCapture* cv_cap;
  
  128         VideoCapture cv_cap_IP;
  
  129         Mat color_img_IP;
  
  130         camviewOn = true;
  
  131         int capture;
  
  132         IplImage* color_img;
  
  133         if(!networkCam)
  
  134         {
  
  135             cv_cap = cvCaptureFromCAM(0);
  
  136             Sleep(100);
  
  137             if(!cv_cap)
  
  138             {
  
  139                 setExitError(1002);
  
  140                 if(textOutput){cout << "Video Error: Video input will not work.\n";}
  
  141                 MessageBox(hwnd, "Error opening camera.", "Error", MB_ICONEXCLAMATION);
  
  142                 cvReleaseCapture( &cv_cap );
  
  143                 cvDestroyWindow("Camera View");
  
  144                 return;
  
  145             }
  
  146             color_img = cvQueryFrame(cv_cap);
  
  147             clickPointStorage.create(((Mat)color_img).rows, ((Mat)color_img).cols, CV_8UC3);
  
  148         }
  
  149         else
  
  150         {
  
  151             ///*\
  
  152             
  
  153             cv_cap_IP.open(videoFeedAddress);
  
  154             Sleep(100);
  
  155             if(!cv_cap_IP.isOpened())
  
  156             {
  
  157                 setExitError(1002);
  
  158                 if(textOutput){cout << "Video Error: Video input will not work.\n";}
  
  159                 MessageBox(hwnd, "Error opening camera.", "Error", MB_ICONEXCLAMATION);
  
  160                 cvDestroyWindow("Camera View");
  
  161                 return;
  
  162             }
  
  163             clickPointStorage.create(color_img_IP.rows, color_img_IP.cols, CV_8UC3);
  
  164    
  
  165             //\*/
  
  166         }
  
  167         clickPointStorage.setTo(Scalar(0, 0, 0));
  
  168         cvNamedWindow("Camera View", 0); // create window
  
  169         cvSetMouseCallback("Camera View", CallBackFunc, NULL);
  
  170         IplImage* IplClickPointStorage = new IplImage(clickPointStorage);
  
  171         IplImage* Ipl_IP_Img;
  
  172         
  
  173         if(!networkCam)
  
  174         {
  
  175             for(;;)
  
  176             {
  
  177                 IplClickPointStorage = new IplImage(clickPointStorage);
  
  178                 cvAdd(cvQueryFrame(cv_cap), IplClickPointStorage, color_img); // get frame
  
  181                 cvShowImage("Camera View", color_img); // show frame
  
  182                 capture = cvWaitKey(10); // wait 10 ms or for key stroke
  
  183                 if(capture == 27 || capture == 13 || capture == 32){break;} // if ESC, Return, or space; close window.
  
  184             }
  
  185             /* clean up */
  
  186             cvReleaseCapture( &cv_cap );
  
  187             delete cv_cap;
  
  188             delete IplClickPointStorage;
  
  189         }
  
  190         else
  
  191         {
  
  192             ///*\
  
  193    
  
  194             for(;;)
  
  195             {
  
  196                 cv_cap_IP.read(color_img_IP);
  
  197                 IplClickPointStorage = new IplImage(clickPointStorage);
  
  198                 Ipl_IP_Img = new IplImage(color_img_IP);
  
  199                 cvAdd(Ipl_IP_Img, IplClickPointStorage, color_img);
  
  200                 cvShowImage("Camera View", color_img); // show frame
  
  201                 capture = cvWaitKey(10); // wait 10 ms or for key stroke
  
  202                 if(capture == 27 || capture == 13 || capture == 32){break;} // if ESC, Return, or space; close window.
  
  203             }
  
  204             cv_cap_IP.release();
  
  205             delete Ipl_IP_Img;
  
  206             delete IplClickPointStorage;
  
  207    
  
  208             //\*/
  
  209         }
  
  210         cvDestroyWindow("Camera View");
  
  211         camviewOn = false;
  
  212     }
  
  213     return;
  
  214    }

  As I said, on one computer I get the above error - both of them give me my own error from here :

  155             if(!cv_cap_IP.isOpened())
  
  156             {
  
  157                 setExitError(1002);
  
  158                 if(textOutput){cout << "Video Error: Video input will not work.\n";}
  
  159                 MessageBox(hwnd, "Error opening camera.", "Error", MB_ICONEXCLAMATION);
  
  160                 cvDestroyWindow("Camera View");
  
  161                 return;
  
  162             }

  ...which of course tells me cv_cap_IP is not open. One of my primary concerns is with the videoFeedAddress variable. No value I enter seems to get a different result.

  I searched the Googles - and come across a number of different "possible" answers - but none of them seem to work for me. If you attempt to google it yourself you may come across some of these :

  1. This is one of the first configurations my code was in. No dice.
  2. This one is talking about files - not cameras. It also mentions codecs - but I wouldn’t be able to watch it in a web browser if that were the problem, right ? (Correct me if I’m wrong here...)
  3. This one has the wrong error code/points to the wrong line of code !
  4. This one mentions compiling OpenCV with ffmpeg support - but I believe 2.4.6.0 already comes with that all set and ready ! Otherwise it’s not that different from what I’ve already tried.
  5. Now THIS one appears to be very similar to what I have, but the only proposed solution doesn’t really help as I had already located a list of connections. I do not believe this is a duplicate, because as per THIS meta discussion I had a lot more information and so didn’t feel comfortable taking over someone else’s question - especially if I end up needing to add even more information later.

  Back to the videoFeedAddress variable : I found THIS site that lists a number of possible addresses to connect to it. since there exists no 7100 anywhere in the list - and the install is the same for the DCS-7010L I used the addresses found next to the DCS-7010L listings. Most of them can be reached through the browser, confirming that they reach the camera - but they don’t seem to affect the outcome when I change them.

  As per many of the above links, I’ve tried many of them both with any without username:password, port number (554), and variations on ?.mjpg (the format) at the end.

  Any ideas ?

• AVFrame / AVPicture change color component

  26 avril 2014, par RoeeL

  Given a video stream (runs with SDL), I need to somehow make the video’s frames color green only, blue only and red only (depends on input).

  How can I do that ? How can I set the color component to be RED only for instance ? (R = 255, G = 0, B = 0)

  Didn’t manage to find anything on google. would love to get some assistance.

  thanks

• HTTP Live streaming iOS not refreshing the index .m3u8 file

  27 février 2013, par Emerson Fittipaldi

  I searched all similar questions on StackOverflow, but found none to answer my problem.

  I am trying to stream some movies from my Linux computer (openSuSE 12.1) to my iPad. I convert them with ffmpeg, segment them with my own segmenter, place them in the www folder of my apache2 server and also place inside the .m3u8 playlist. Til here - all is ok !

  I start playing the movie (HTML page with tag) and it plays nicely, but only the first five segments, which have been loaded with the first load of the playlist. The HTML page (the browser, or the player - no idea) does not refresh (re-download) the playlist from the server. Here is what my .m3u8 playlist file looks like :

  #EXTM3U
  
  #EXT-X-MEDIA-SEQUENCE:19
  
  #EXT-X-TARGETDURATION:8
  
  
  
  #EXTINF:8,
  
  http://192.168.1.4/segment_19.ts
  
  #EXTINF:8,
  
  http://192.168.1.4/segment_20.ts
  
  #EXTINF:8,
  
  http://192.168.1.4/segment_21.ts
  
  #EXTINF:8,
  
  http://192.168.1.4/segment_22.ts
  
  #EXTINF:8,
  
  http://192.168.1.4/segment_23.ts

  Segments are in the same folder as the playlist file, segments are correctly encoded (because I can see at least the first five ones :D). I also watch the access_log from the apache server and I see the first load of the playlist, then the consequent load of all 5 segments and it stops till there. It doesn't even try to further refresh the m3u8 file.

  If it matters - iOS 5.0, iPad 2, Wi-Fi version only, not jailbroken

  Ideas ? What am I doing wrong ?