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• avfilter/vf_drawtext : improve glyph shaping and positioning

  26 mai 2023, par yethie

  avfilter/vf_drawtext : improve glyph shaping and positioning
   text is now shaped using libharfbuz
  
   glyphs position is now accurate to 1/4 pixel in both directions
  
   the default line height is now the one defined in the font
  Adds libharfbuzz dependency.
  

  • [DH] configure
  • [DH] doc/filters.texi
  • [DH] libavfilter/vf_drawtext.c

• PHP-FFMpeg Video Stabilization using VidStab

  19 février 2016, par BakerStreet

  I’m using PHP-FFMpeg in a Laravel 5.2 application to stabilize videos with the help of VidStab. I have all the dependencies and everything installed correctly and I can follow the directions on the VidStab repo to stabilize my videos via the command line.

  My question is how could I do this nicely (the Laravel way) from within PHP ? I know I can add a custom filter to the Video object like this :

  $video = $ffmpeg->open('shaky_video.mp4');
  
  $video->addFilter(new CustomFilter('vidstabdetect=stepsize=6:shakiness=8:accuracy=9:result=transform.trf'));

  But how can I execute this command without the need for $video-save(), which I think is designed to output a video/audio file and not the trf analysis file ?

  I suppose I could just run a PHP exec() command, but I would like to keep this as much object oriented PHP as I can. Any suggestions ?

  Thanks in advance !

  ---

  I’ve tried this (added -f null - to filter and then tried running save() to execute the command), but it still creates the mp4 file instead of the trf file :

  $video = $ffmpeg->open('shaky_video.mp4');
  
  $video->addFilter(new CustomFilter('vidstabdetect=stepsize=6:shakiness=8:accuracy=9:result=transform.trf -f null -'));
  
  $video->save(new X264(), 'stabilized.mp4');

• 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 ?