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• avfilter/vf_bwdif : Add a filter_line3 method for optimisation

  4 juillet 2023, par John Cox

  avfilter/vf_bwdif : Add a filter_line3 method for optimisation
  Add an optional filter_line3 to the available optimisations.
  filter_line3 is equivalent to filter_line, memcpy, filter_line
  filter_line shares quite a number of loads and some calculations in
  
  common with its next iteration and testing shows that using aarch64
  
  neon filter_line3s performance is 30% better than two filter_lines
  
  and a memcpy.
  Adds a test for vf_bwdif filter_line3 to checkasm
  Rounds job start lines down to a multiple of 4. This means that if
  
  filter_line3 exists then filter_line will not sometimes be called
  
  once at the end of a slice depending on thread count. The final slice
  
  may do up to 3 extra lines but filter_edge is faster than filter_line
  
  so it is unlikely to create any noticable thread load variation.
  Signed-off-by : John Cox <jc@kynesim.co.uk>
  
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavfilter/bwdif.h
  • [DH] libavfilter/vf_bwdif.c
  • [DH] tests/checkasm/vf_bwdif.c

• can someone explain this difference between H.264 and H.265 ?

  19 janvier 2017, par Muhammad Abu bakr

  I have studied this in a research paper :

  "The off-the-shelf video codecs like H.264 handle all the movements equally. In our case there are some non moving region that lies in region of interest and need to be encode in high quality and there are some moving regions which don’t need such requirements. H.265 can help us in such circumstances."

  How H.265 deals with movements differently ?

• Saving the openGL context as a video output

  2 juin 2023, par psiyum

  I am currently trying to save the animation made in openGL to a video file. I have tried using openCV's videowriter but to no advantage. I have successfully been able to generate a snapshot and save it as bmp using the SDL library. If I save all snapshots and then generate the video using ffmpeg, that is like collecting 4 GB worth of images. Not practical.
How can I write video frames directly during rendering ?
Here the code i use to take snapshots when I require :

  



  void snapshot(){&#xA;SDL_Surface* snap = SDL_CreateRGBSurface(SDL_SWSURFACE,WIDTH,HEIGHT,24, 0x000000FF, 0x0000FF00, 0x00FF0000, 0);&#xA;char * pixels = new char [3 *WIDTH * HEIGHT];&#xA;glReadPixels(0, 0,WIDTH, HEIGHT, GL_RGB, GL_UNSIGNED_BYTE, pixels);&#xA;&#xA;for (int i = 0 ; i <height>pixels) &#x2B; snap->pitch * i, pixels &#x2B; 3 * WIDTH * (HEIGHT-i - 1), WIDTH*3 );&#xA;&#xA;delete [] pixels;&#xA;SDL_SaveBMP(snap, "snapshot.bmp");&#xA;SDL_FreeSurface(snap);&#xA;}&#xA;</height>

  



  I need the video output. I have discovered that ffmpeg can be used to create videos from C++ code but have not been able to figure out the process. Please help !

  



  EDIT : I have tried using openCV CvVideoWriter class but the program crashes ("segmentation fault") the moment it is declared.Compilation shows no errors ofcourse. Any suggestions to that ?

  



  SOLUTION FOR PYTHON USERS (Requires Python2.7,python-imaging,python-opengl,python-opencv, codecs of format you want to write to, I am on Ubuntu 14.04 64-bit) :

  



  def snap():
    pixels=[]
    screenshot = glReadPixels(0,0,W,H,GL_RGBA,GL_UNSIGNED_BYTE)
    snapshot = Image.frombuffer("RGBA",W,H),screenshot,"raw","RGBA",0,0)
    snapshot.save(os.path.dirname(videoPath) + "/temp.jpg")
    load = cv2.cv.LoadImage(os.path.dirname(videoPath) + "/temp.jpg")
    cv2.cv.WriteFrame(videoWriter,load)


  



  Here W and H are the window dimensions (width,height). What is happening is I am using PIL to convert the raw pixels read from the glReadPixels command into a JPEG image. I am loading that JPEG into the openCV image and writing to the videowriter. I was having certain issues by directly using the PIL image into the videowriter (which would save millions of clock cycles of I/O), but right now I am not working on that. Image is a PIL module cv2 is a python-opencv module.