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• Revision 98537 : 3 notices PHP en moins lors de la création d’une Page unique. Le champ ...

  23 juin 2016, par marcimat@… — Log

  3 notices PHP en moins lors de la création d’une Page unique.
  Le champ $erreurchamp_page ? n’est pas toujours présent, tout comme $argcontexte ?page ?.

• Is there an alternative to libmediainfo ?

  8 novembre 2014, par Alexander Alexandrowitsch Klim

  In my upcoming application I’d like to get information about an A/V file. libmediainfo’s dev doc is quite hard-to-study for me (and it uses wchar_t -.-").

  Is there a better alternative ?

  Acceptance criteria :

  • platform independent (I’m going to dev on GNU OS)
  • works w/ C++11
  • supports 8bit (char) for all strings and I/O (doesn’t require wchar_t) w/o re-compiling the whole library.

  Maybe I’d prefer libav if its doc weren’t so poor.

• QOpenGLWidget video rendering perfomance in multiple processes

  24 novembre 2018, par MasterAler

  My problem may seem vague without code, but it actually isn’t.

  So, there I’ve got an almost properly-working widget, which renders video frames.

  Qt 5.10 and QOpenGLWidget subclassing worked fine, I didn’t make any sophisticated optimizations — there are two textures and a couple of shaders, converting YUV pixel format to RGB — glTexImage2D() + shaders, no buffers.

  Video frames are obtained from FFMPEG, it shows great performance due to hardware acceleration... when there is only one video window.

  The piece of software is a "video wall" — multiple independent video windows on the same screen. Of course, multi-threading would be the preferred solution, but legacy holds for now, I can’t change it.

  So, 1 window with Full HD video consumes 2% CPU & 8-10% GPU regardless of the size of the window. But 7-10 similar windows, launched from the same executable at the same time consume almost all the CPU. My math says that 2 x 8 != 100...

  My best guesses are :

  • This is a ffmpeg decoder issue, hardware acceleration still is not magic, some hardware pipeline stalls
  • 7-8-9 independent OpenGL contexts cost a lot more than 1 cost x N
  • I’m not using PUBO or some other complex techniques to improve OpenGL rendering. It still explains nothing, but at least it is a guess

  The behavior is the same on Ubuntu, where decoding uses different codec (I mean that using GPU accelerated or CPU accelerated codecs makes no difference !), so, it makes more probable that I’m missing something about OpenGL... or not, because launching 6-7 Qt examples with dynamic textures shows normal growth of CPU usages — it is approximately a sum for the number of windows.

  Anyway, it becomes quite tricky for me to profile the case, so I hope someone could have been solving the similar problem before and could share his experience with me. I’d be appreciated for any ideas, how to deal with the described riddle.

  I can add any pieces of code if that helps.