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• Saving animations using ffmpeg and matplotlib

  2 juillet 2015, par PedroLago

  im new in here and new in python, im doing some animations with animation.FuncAnimation of matplotliib. The animation works perfectly but i´m having problems saving the animations. here is the part of the code of the animation.

  import numpy as np 
  
  import matplotlib.pyplot as plt
  
  import matplotlib.animation as animation
  
  
  
  fig, ax = plt.subplots()
  
  
  
  line,  = ax.plot(range(N),sin(x[0,:]),'o-')
  
  ax.axis([0,1,-1,1])
  
  
  
  def animate(i):
  
      line.set_ydata(sin(x[i,:]))  # update the data
  
      return line,
  
  
  
  def init():
  
      line.set_ydata(np.ma.array(x[0,:], mask=True))
  
      return line,
  
  
  
  ani = animation.FuncAnimation(fig, animate, np.arange(1, 10000),
  
      interval=25, init_func=init, blit=True)
  
  ani.save('2osc.mp4', writer="ffmpeg")
  
  plt.show()

  where x[ :, :] is previously set. ani.save is saving every frame of the animation as a .npg image instade of saving the movie. I dont know if this is how it is suposed to work and i have to do the movie with the .npg with another program or if im doing something wrong.
  Obs : i’ve previously installed ffmpeg and it seems to be working just fine.

• lavu/riscv : helper macro for VTYPE encoding

  5 octobre 2022, par Rémi Denis-Courmont

  lavu/riscv : helper macro for VTYPE encoding
  On most cases, the vector type (VTYPE) for the RISC-V Vector extension
  
  is supplied as an immediate value, with either of the VSETVLI or
  
  VSETIVLI instructions. There is however a third instruction VSETVL
  
  which takes the vector type from a general purpose register. That is so
  
  the type can be selected at run-time.
  This introduces a macro to load a (valid) vector type into a register.
  
  The syntax follows that of VSETVLI and VSETIVLI, with element size,
  
  group multiplier, then tail and mask policies.
  

  • [DH] libavutil/riscv/asm.S

• Best practices for developing scalable video transcoding server on Amazon Web Services ?

  6 septembre 2016, par undefined

  What do people think are the most important issues when developing an application that is going to allow users to upload video and images to a server and have them transcoded by FFMPEG and stored in amazon S3 ? I have a couple of options ;

  1) install FFMPEG on the same server that handles file uploads, when a video is uploaded and stored on EC2 instance, call FFMPEG to convert it then when done, write the file to S3 bucket and dispose of the original.

  How scalable is this ? What happens when many users upload at the same time ? How do I manage multiple processes at once ? How do I know when to start another instance and load balance this configuration ?

  2) Have one server for processing uploads (updating database, renaming files etc) and one server for doing transcoding. Again what is the best way to manage multiple processes ? should I be looking at Amazon SQS for this ? Can I tell the transcoding server to get the file from the upload server or should I copy the file to the transcoding server ? Should I just store all files on S3 and SQS can read from there. I am trying to have as little traffic as possible.

  I am running a linux box as the upload server and have FFMPEG running on this.

  Any advice on best practices for setting up such a configuration would be appreciated. Many thanks