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• Continously read file in Ruby and save into pipe

  7 juillet 2016, par stiller_leser

  I am trying to continously read a file and save the output into a IO.pipe. The motivation being that ffmpeg which has been spawned before and given the r-end of the pipe as STDIN will then convert the video.
  This is what I have so far :

      r,w = IO.pipe
  
      ffmpeg_args = ' -i pipe:0 "test.mp4"'
  
      pid = Process.spawn('ffmpeg'+ffmpeg_args, {STDIN => r, STDERR => STDOUT})
  
      Process.detach pid
  
      File.open(@options['filename'], 'rb') do |file|
  
        while line = file.gets
  
          w.write line.read
  
        end
  
      end

  I had success with declaring the input file directly as STDIN for the process, but this lead to an early termination of ffmpeg since it had reached the end of the file. With the code above ffmpeg complains about invalid data.

  Is there any way this could be achieved ?

• Is it possible to save an audio stream with pure JavaScript in the browser ?

  8 juin 2016, par Konstantin

  I would like to make a webpage where visitors can save audio streams by clicking on links (not live streams, but links from a radio archive which uses streams), I want to do this without a server backend with pure JavaScript in the browser.
  I read somewhere about the JavaScript port of FFMpeg, which can encode and save video / audio in the browser utilizing so called blobs. However download library is huge, as far as I remember 17 MB. In fact I would need only stream copying the audio streams, not a real encoding process.
  I usually use similar commands to save a programme :

  ffmpeg -i http://stream.example.com/stream_20160518_0630.mp3 -c copy -t 3600 programme.mp3

  I wonder, is it possible to compile a subset of FFMpeg into JavaScript which provides only the really needed stream copying ?

• save matplotlib animation error

  27 juillet 2017, par Matt

  I created a program (see below) that takes position, force, and time from a pandas dataframe. The goal is to plot position vs force and animate it based on the time data associated with it.

  The animation is working well so far but I cannot save the animation, either as a gif or mp4. I have read countless solutions online for this sort of problem but none seem to work.

  I am using OS X El Capitan version 10.11.6 and python3.6. I used brew install ffmpeg and brew install mencoder. For both I get the error

   File "animation.py", line 73, in <module>
  
      ani.save('test.mp4', writer=writer)
  
    File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/matplotlib/animation.py", line 1009, in save
  
      for a in all_anim]):
  
    File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/matplotlib/animation.py", line 1009, in <listcomp>
  
      for a in all_anim]):
  
    File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/matplotlib/animation.py", line 1482, in new_saved_frame_seq
  
      return itertools.islice(self.new_frame_seq(), self.save_count)
  
  ValueError: Stop argument for islice() must be None or an integer: 0 &lt;= x &lt;= sys.maxsize.
  
  </listcomp></module>

  I used pip to install the rest of my packages so maybe that is the root of the problem ?

  import matplotlib.pyplot as plt
  
  import matplotlib.animation as animation
  
  import pandas
  
  import sys
  
  
  
  TABLE = pandas.read_csv("Data.csv")
  
  
  
  
  
  fig = plt.figure()
  
  ax1 = fig.add_subplot(1,1,1)
  
  
  
  xs=[]
  
  ys=[]
  
  
  
  def animate(interval):
  
  
  
      time = interval
  
  
  
      #convert to TIME series to int for handling purposes
  
      TABLE.TIME = TABLE.TIME.astype(int)
  
  
  
      if time in TABLE.TIME.unique(): 
  
  
  
          POSIT_series = TABLE[TABLE.TIME == time].POSIT
  
          POSIT_list = POSIT_series.tolist()
  
          x = POSIT_list[0]
  
  
  
          FORCE_series = TABLE[TABLE.TIME == time].FORCE
  
          FORCE_list = FORCE_series.tolist()
  
          y = FORCE_list[0]
  
  
  
          xs.append(x)
  
          ys.append(y)
  
  
  
          ax1.clear()
  
          ax1.plot(xs,ys)
  
      elif time > TABLE.TIME.max():
  
          sys.exit("Animation Done")
  
      return
  
  
  
  FRAMES= TABLE.TIME.astype(int).max()    
  
  plt.rcParams['animation.ffmpeg_path']='/usr/local/bin/ffmpeg'
  
  writer = animation.FFMpegWriter()
  
  ani = animation.FuncAnimation(fig, animate, interval=1, frames=FRAMES, repeat=False)
  
  plt.show()
  
  
  
  #same error for writer = 'mencoder' and writer ='ffpmeg
  
  ani.save('test.mp4', writer=writer)