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• How can I get my saved mp4 to exactly match the output of plot.show() ?

  10 mai 2019, par Jimmy

  When I try to save the results of an animation to mp4 using ffmpeg, I am getting a jumbled mess.

  plt.show() shows exactly what I want it to show in the animation. However, when I save it using ffmpeg, the result is very different from what plt.show() returns. I have tried various arguments for fps etc. but nothing has helped.

  %matplotlib
  
  import pandas as pd
  
  import matplotlib as mpl ## uncomment this if you are running this on a Mac
  
  #mpl.use('TkAgg')         ## and want to use blit=True
  
  import matplotlib.pyplot as plt 
  
  import matplotlib.animation as animation 
  
  import numpy as np 
  
  import csv
  
  
  
  people = ('','Jim', 'Dan')
  
  plt.rcdefaults()
  
  fig, ax = plt.subplots()
  
  y_pos = np.arange(len(people))
  
  
  
  ax.set_xlim(0,10)
  
  ax.set_yticks(y_pos)
  
  ax.set_yticklabels(people)
  
  ax.invert_yaxis() 
  
  ax.set_xlabel('Skill')
  
  titleList=['Basketball','Hockey','Baseball']
  
  df=[[0,5,7],[0,4,9],[0,2,6]]
  
  def animate(i):
  
     # Example data
  
      while i<3:
  
          ax.set_yticks(y_pos)
  
          ax.set_yticklabels(people)
  
          ax.set_xlabel(titleList[i])
  
          performance=df[i]
  
  
  
          title = ax.text(0.5,0.95,str(titleList[i]), bbox={'facecolor':'w', 'alpha':0.5, 'pad':5},transform=ax.transAxes, ha="center")
  
  
  
          rects = ax.barh(y_pos, performance, align='center',
  
                  color='blue', ecolor='None')
  
          return [rect for rect in rects] + [title]
  
  
  
  
  
  ani = animation.FuncAnimation(fig,animate, frames=3, blit=True
  
                              ,interval=2000,repeat=False)
  
  
  
  plt.rcParams['animation.ffmpeg_path'] = 'C:\\ffmpeg\\bin\\ffmpeg.exe'
  
  Writer = animation.writers['ffmpeg']
  
  ani.save('test.mp4')
  
  plt.show() 

  The result is a very fast video where all the data gets written over (similar to the plt.show() results when blit=False).

• How to set sample format when using sox with ffmpeg ?

  18 décembre 2020, par Finch

  I am trying to convert a 44.1k 16bit flac file into 48k 32 bit (float) wav file.

  


  This is the command I use :

  


  'ffmpeg -i in.flac -af aresample=resampler=soxr:precision=28:out_sample_fmt=fltp:out_sample_rate=48000 out.wav'

  


  No matter which value I use for out_sample_fmt like s32, flt, fltp the output out.wav is only 16 bit.

  


  What am I doing wrong here ? How to get the highest quality (as in resampling) 32 bit floating point wav file with ffmpeg using soxr ?

  


• avcodec/aactab : Make AAC encoder and decoders actually init-threadsafe

  22 novembre 2020, par Andreas Rheinhardt

  avcodec/aactab : Make AAC encoder and decoders actually init-threadsafe
  Commit 1a29804558c13ef512d9ef73a9b0d782af4fa5f2 guarded several
  
  initializations of static data in the AAC decoders with an AVOnce and
  
  set the FF_CODEC_CAP_INIT_THREADSAFE flag, believing the former to be
  
  sufficient for the latter. It wasn't, because several of these static
  
  tables are shared with other components, so that there might be data
  
  races if they are initialized from multiple threads. This affected
  
  initializing the ff_sine_* tables as well as initializing the
  
  ff_aac_pow*sf_tab tables (shared between both decoders and encoder) as
  
  well as ff_aac_kbd_* tables (shared between encoder and floating point
  
  decoder).
  Commit 3d62e7a30fa552be52d12b31e3e0f79153aff891 set the
  
  FF_CODEC_CAP_INIT_THREADSAFE flag for the AAC encoder. More explicitly,
  
  this commit used the same AVOnce to guard initializing ff_aac_pow*sf_tab
  
  in the encoder and to guard initializing the static data of each
  
  decoder ; the ensuing catastrophe was "fixed" in commit
  
  ec0719264cb9a9d5cbaf225da48929aea24997a3 by using a single AVOnce
  
  for each codec again. But the codec cap has not been removed and
  
  therefore the encoder claimed to be init-threadsafe, but wasn't, because
  
  of the same tables as above.
  The ff_sine_* tables as well as ff_aac_pow*sf_tab tables have already
  
  been fixed ; this commit deals with the ff_aac_kbd_* tables, making the
  
  encoder as well as the floating-point decoder init-threadsafe (the
  
  fixed-point decoder is it already).
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavcodec/aactab.c