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• How can I programmatically write and read random video watermarks ?

  13 novembre 2017, par GreenTriangle

  I spent a few minutes trying to think of a clearer way to word my title, but I couldn’t manage it, sorry.

  I want to essentially canary trap video files : I am (hypothetically, this is not real but a personal exercise) offering them up to 5,000 different people, and if one gets leaked, I want to know who leaked it. Metadata is too easily emoved, so what I’d like to do is add a random and subtle watermark to each file, and store information about that in a database.

  For example : on Joe Smith’s copy, a 10x10 pixel 80% transparent red square in the upper left corner for 5 frames. On Diane Brown’s copy, a full-width 5-pixel 90% transparent black bar on the bottom edge for 15 frames. Then, if I find a leaked copy, I could check it against the database.

  I know this still isn’t foolproof : cropping would break co-ordinates, hue/brightness transforms would break colour reading, cutting time would break timestamps. But if I did want to do this anyway, what would be a good strategy for it ?

  My idea was to generate PNG overlays randomly, split the video into parts with mkvtoolnix/ffmpeg, re-encode the middle part with ffmpeg + overlay filter, and then rejoin them. But is this silly when there’s a "proper" way to do it ? And what would I be doing to read the watermarks, which I can’t even really conceive of ?

• runtime error when linking ffmpeg libraries in qt creator

  6 juillet 2012, par dxthegreat

  I'm quite new around here but i hear that if you want a question answered, stackoverflow is the place to ask it >.<. So i hope that my question isn't too trivial that everyone will get annoyed at my lack of research (I've tried googling for two days already D= no progress !)
  I've also asked this question in the Qt forums, but i figured i'd ask here too.

  so...

  For the last few days I’ve been fiddling around with opengl and the like, trying to write a video player.

  However, when i try to import the ffmpeg libraries (avcodec, avformat, avutils etc), an error occurs on runtime (the program compiles fine). When compiled and run in debug mode, the error message gives me only a memory address and error code 135 (DLL not found).

  This error occurs when i include a function from those libraries in my code (e.g. av_register_all()) and it occurs regardless of whether the function is actually called.

  So i’m thinking that I’m doing something wrong when linking these libraries.
  I’m currently using :
  Windows vista (32bit),
  Qt creator 2.4.1 based on Qt 4.7.4 (32bit),
  Zeranoe’s FFmpeg build git-3233ad4 (2012-06-30)

  My .pro file consists of :

  QT       += core gui opengl
  
  
  
  TARGET = test
  
  TEMPLATE = app
  
  
  
  
  
  SOURCES += main.cpp\
  
          mainwindow.cpp \
  
      glwidget.cpp
  
  
  
  HEADERS += mainwindow.h \
  
      glwidget.h \
  
  
  
  FORMS    += mainwindow.ui
  
  
  
  
  
  LIBS += -L"$$_PRO_FILE_PWD_/libraries/ffmpeg/libs/" -lavcodec -lavformat -lavutil
  
  INCLUDEPATH += libraries/ffmpeg/includes

  I’ve tried many variations to the LIBS += line and checked my filepath many times. However, the DLL not found error occurs in all of these variations =(.

  Is there something I’m forgetting when doing these includes ?

  Thanks in advance >.<,
  (young and naive) aspiring dev

• Revision 109827 : Ajout d’options sur les saisies, et y++ - checkboxes et radios : pouvoir ...

  6 avril 2018, par nicolas.dorigny@… — Log

  Ajout d’options sur les saisies, et y++
   checkboxes et radios : pouvoir désactiver certains choix (disable_choix)
   checkboxes : nombre maximal de choix possibles (maximum_choix)
   textarea : nombre maximal de caractères (longueur_max)
  avec une vérification côté client (navigateur) en JS
  TODO :
   vérifications en PHP
   traduire la chaine en JS dans saisies/textarea.html, ligne 34 (chaine de texte avec une variable), pour l’instant en français "en dur"