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• Trying to capture display output for real-time analysis with OpenCV ; I need help with interfacing with the OS for input

  26 juillet 2024, par mirari

  I want to apply operations from the OpenCV computer vision library, in real time, to video captured from my computer display.
The idea in this particular case is to detect interesting features during gameplay in a popular game and provide the user with an enhanced experience ; but I could think of several other scenarios where one would want to have live access to this data as well. 
At any rate, for the development phase it might be acceptable using canned video, but for the final application performance and responsiveness are obviously critical.

  



  I am trying to do this on Ubuntu 10.10 as of now, and would prefer to use a UNIX-like system, but any options are of interest.
My C skills are very limited, so whenever talking to OpenCV through Python is possible, I try to use that instead.
Please note that I am trying to capture NOT from a camera device, but from a live stream of display output ; and I'm at a loss as to how to take the input. As far as I can tell, CaptureFromCAM works only for camera devices, and it seems to me that the requirement for real-time performance in the end result makes storage in file and reading back through CaptureFromFile a bad option.

  



  The most promising route I have found so far seems to be using ffmpeg with the x11grab option to capture from an X11 display ;
(e.g. the command
ffmpeg -f x11grab -sameq -r 25 -s wxga -i :0.0 out.mpg
captures 1366x768 of display 0 to 'out.mpg').
I imagine it should be possible to treat the output stream from ffmpeg as a file to be read by OpenCV (presumably by using the CaptureFromFile function) maybe by using pipes ; but this is all on a much higher level than I have ever dealt with before and I could really use some directions. 
Do you think this approach is feasible ? And more importantly can you think of a better one ? How would you do it ?

  


• avcodec/v4l2_m2m_dec : Fix decoding on Odroid XU4

  12 novembre 2019, par Andriy Gelman

  avcodec/v4l2_m2m_dec : Fix decoding on Odroid XU4
  c0c79461967 unintentianally changed the initialization flow of the
  
  decoder : It caused the capture buffers to be initialized on
  
  v4l2_m2m.c:180 in v4l2_configure_contexts(). This breaks h264 decoding
  
  on the Odroid XU4 (RPI4 was not affected).
  This commit postpones capture buffer initialization
  
  as before c0c79461967 to fix the issue.
  Signed-off-by : Andriy Gelman <andriy.gelman@gmail.com>
  
  Signed-off-by : Aman Gupta <aman@tmm1.net>
  

  • [DH] libavcodec/v4l2_m2m_dec.c

• Summer Hacking 2011

  28 avril 2011, par Multimedia Mike — General

  I recently learned that iD — you know, the famed game company — has a series of summer tech camps :

  
  
  

  All I care to know is : Where were programs like these when I was 7-18 years old ? Born too early, I tell ya.

  That reminds me that the Google Summer of Code, 2011 Edition is getting underway soon. I guess it’s like summertime computer camp for college-aged students. FFmpeg / libav is once again a part of the program with 10 slots awarded by Google. Here are the students, projects, and mentors.

  Wish them luck.