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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

• What does matplotlib need to know about ffmpeg's installation

  8 décembre 2016, par fffred

  My installation of ffmpeg and matplotlib seem to be problematic :

  In [9]: matplotlib.animation.writers["ffmpeg"]
  
  ---------------------------------------------------------------------------
  
  RuntimeError                              Traceback (most recent call last)
  
   ........
  
       58     def __getitem__(self, name):
  
       59         if not self.avail:
  
  ---> 60             raise RuntimeError("No MovieWriters available!")
  
       61         return self.avail[name]
  
       62 
  
  
  
  RuntimeError: No MovieWriters available!

  It looks like ffmpeg (or any other writer) has not been found. However, I have built it from source and installed it in ~/.local. This is included in the $PATH, and I verified that the command ffmpeg is working from the terminal.

  Is there something I should watch out when installing ffmpeg ? Is there something else to do ?

  Config :

  • Python 2.7.3
  • matplotlib 1.2.0
  • ffmpeg N-82786-gc188f35
  • Red Hat 6.7

  Note : I would like to avoid re-installing everything from scratch. I do not have root access and the only thing I installed manually is ffmpeg.