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• Evolution #4628 (En cours) : Intégrer la fonction slugify

  17 février 2021, par cedric -

  L’inconvénient de la nommer slufigy c’est le risque de collision.
  Je recherche dans mes mails d’il y a 4 ans pour trouver pourquoi, mais à l’époque, on avait switché de slugify vers filtre_slugify_dist et une définition optionnelle de la fonction slufigy() https://git.spip.net/spip-contrib-extensions/spip-bonux/commit/9987b6f429211364492560f63d66a73f3b5d41b2

  Ça m’embêterait de faire ça dans le core.

  Donc soit on y va

  • pour slufigy() tout court, au risque de la collision,
  • ou un spip_slugify() peut-être qui sera plus sur, mais on perd la compat automatique avec les appels existants (cela dit bonux peut gérer le mappage de l’ancien vers le nouveau)
  • ou alors un autre nom ?

  Faites vos jeux, rien ne va plus...

• How to make high smooth, high resolution particle motion animations

  5 décembre 2019, par algae

  For some time I have been having trouble with producing short movies/animations/gifs which are of sufficiently high resolution. I’m going to use R to generate some frames as a random example, but if there is somewhere else I should be creating frames from to give better results I would be interested in that too.

  Creating frames

  The kinds of animations I’m interested involve some cloud of ’particles’ moving about the page. There are usually a large number of particles and I would like their motion be as smooth as possible. As a random example, consider the R code (using base graphics and not ggplot2 as it is far quicker for saving a large number of frames)

  N <- 500
  
  nFrames <- 250
  
  points <- pracma::randp(n=N, r=1)
  
  rot <- function(p, a) { return(cbind(p[,1]*cos(a) - p[,2]*sin(a), p[,1]*sin(a) + p[,2]*cos(a))) }
  
  cols <- colorRampPalette(c("red", "green", "blue"))(nFrames)
  
  ang <- seq(0, pi, length=N)
  
  
  
  # Save frames
  
  png(filename="%d.png")
  
  par(mar=c(0,0,0,0))
  
  for (i in seq(1,N,length=nFrames)) 
  
          plot(sqrt(i)*rot(points, ang[i]), xlim=sqrt(N)*c(-1,1),  ylim=sqrt(N)*c(-1,1), cex=0.5, pch=19, col=cols[i], asp=1, xaxs="i")
  
  
  
  dev.off()

  Frames to animation

  There are a number of tools available to chain each frame together into an animation (in R there are also things like gganimate which I have tried but did not find convenient or better than the following). I also don’t have any requirements for the resulting file size or time taken to get everything looking as crisp as possible.

  convert

  For short gif style animations a common solution is to do something like convert -delay 1 -loop 0 *.png g.gif which gives

  

  gifski

  Running gifski -o g.gif *.png produces

  

  There is an annoying amount of ’jitter’ happening in the transition between frames in both of the above (though less noticeable with gifski).

  ffmpeg

  Being gifs, the above will be have limited options for tweaking so I suspect part of the solution lies in using ffmpeg. All I would like to know is how to make the animation appear totally smooth without any kind of noticeable blurriness. Here the resulting movies tend to be quite smooth, but resolution is lacking.. e.g. after setting height=1080 and width=1080 in png() of the above code we can run

  fmpeg -i %d.png -s 1080x1080 -c:v libx264 -vf fps=250 -pix_fmt yuv444p out.mp4

  If the particles move on a time/space scale smaller than is visible to the naked eye, and we set the frames per second to be the total number of frames, the transition between frames should be seamless, right ? At around the 2 second mark in out.mp4 you will see some kind of frame drop and similarly right at the beginning. Why does this happen ?

  Questions

  1. Is there a standard documented approach to generating high quality animations/movies involving large numbers of ’point-like’ particles ? Do we need more an more frames ?
  2. How to improve resolution of movies using ffmpeg ? Should I change from .png format to something vectorised (if so, how) ?

  Running Fedora v31.

• how to make live streaming for multiple clients

  19 septembre 2014, par Abdulrahman Alcharbaji

  I have new project to do and I need some help to know where to start.
  I have more than 1000 DVR each with 4 channels, I need to be able to do live streaming for multiple clients, and clients could be android,iPhone or windows.
  Now throw searching i tried to check ffserver and ffmpeg but i couldn’t find much references to guide me throw a solution for my problem.
  NOTE : the DVRs streaming with h.264 encoding.

  So Please can anybody help me by guiding me for a start or some good references about this particular issue.

  Many Thnaks