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• avconv/ffmpeg simultaneously stream from usb webcam and save video onto disk

  27 novembre 2017, par BojowyZajaczek

  I need to simultaneously stream/broadcast (over rtmp) and save video (with audio) from my USB webcam. The webcam is Logitech c920 which have hardware h.264 encoder.

  I don’t want to reencode the media, so I’m using the -c:v copy option.

  The whole script looks like below :

  #! /bin/bash
  
  
  
  SOURCEV="/dev/video0"
  
  SOURCEA="hw:1"
  
  
  
  FILE_TO_SAVE="Archive/file_to_save.mp4"
  
  YOUTUBE_URL="rtmp://x.rtmp.youtube.com/live2"
  
  KEY="my-secret-key"        
  
  
  
  avconv -f alsa -ac 2 -r 44100 -i $SOURCEA \
  
  -s 1920x1080 -r 24 -c:v h264 -i "$SOURCEV" \
  
  -ar "44100" -r:v 24 -c:a aac -c:v copy -s 1920x1080 -f mp4 "$FILE_TO_SAVE" \
  
  -g $FPS*4 -ar "44100" -b:a "128k" -ac 2 -r 24 -c:a aac -c:v copy -s 1920x1080 -f flv "$YOUTUBE_URL/$KEY"

  This method "works" - it means’ it can stream content and save it to disk, but the problem with this method is that file video relies on the stream. For example if the Internet connection is too slow, the saved file will have low FPS. If the Internet connection is interrupted the "recording" of video file is stopped.

  Can anyone help me with making this two streams independent ?

  The whole things is happening on raspberrypi 3 so computing power is highly limited.

• FFmpeg - What muxer do i need to save an AAC audio stream

  3 août 2022, par David Barishev

  I'm developing Android application, and im using ffmpeg for conversion of files.
  
I want my binary file to be as slim as possible since i don't have many input formats and output formats, and my operation is quite basic.And of course not to bloat the APK.

  



  In my program ffmpeg receives a file, and copys the audio stream (-acodec copy), the audio stream will always be aac (mp4a). What i need is to save the stream to file.
  
My command looks like this : ffmpeg -i {Input} -vn -acodec copy output.aac.

  



  What muxer do i need to for muxing aac to file ? I have tried flv,mp3,mov but i always get
  
Unable to find a suitable output format for 'output.aac', so these options are wrong.
  
I don't need an encoder for stream copy btw.

  



  Side note : this command work flawlessly on full installation of ffmpeg , but I don't know which muxer it uses. If there is a way to output the muxer it uses from regular ffmpeg run, it would work too.

  


• Unable to save Matplotlib animations using ffmpeg

  23 décembre 2017, par jtpointon

  I have installed ffmpeg and added it to path, and checked it works in command prompt, but I am still unable to save animations. I have tried creating a sin wave that will animate when I don’t try to save it, but throws an error when I do to demonstrate ;

  from __future__ import division
  
  
  
  import numpy as numpy
  
  from matplotlib import pyplot as pyplot
  
  from matplotlib import animation
  
  
  
  fig = pyplot.figure()
  
  ax = pyplot.axes(xlim=(0, 2), ylim=(-2, 2))
  
  line, = ax.plot([], [], lw=2)
  
  
  
  def init():
  
      line.set_data([], [])
  
      return line,
  
  
  
  def animate(i):
  
      x = numpy.linspace(0, 2, 1000)
  
      y = numpy.sin(2 * numpy.pi * (x - 0.01 * i))
  
      line.set_data(x, y)
  
      return line,
  
  
  
  anim = animation.FuncAnimation(fig, animate, init_func=init, frames=200, 
  
      interval=20, blit=True, repeat=False)
  
  
  
  FFwriter = animation.FFMpegWriter()
  
  anim.save('animation_testing.mp4', writer = FFwriter)
  
  
  
  pyplot.show()

  When I try to run this it throws the same errors over and over again, I assume as it iterates through each frame ;

  Traceback (most recent call last):
  
    File "c:\users\james\appdata\local\enthought\canopy\user\lib\site-
  
  packages\matplotlib\backends\backend_wx.py", line 212, in _on_timer
  
      TimerBase._on_timer(self)
  
    File "c:\users\james\appdata\local\enthought\canopy\user\lib\site-
  
  packages\matplotlib\backend_bases.py", line 1273, in _on_timer
  
      ret = func(*args, **kwargs)
  
    File "c:\users\james\appdata\local\enthought\canopy\user\lib\site-
  
  packages\matplotlib\animation.py", line 910, in _step
  
      still_going = Animation._step(self, *args)
  
    File "c:\users\james\appdata\local\enthought\canopy\user\lib\site-
  
  packages\matplotlib\animation.py", line 769, in _step
  
      self._draw_next_frame(framedata, self._blit)
  
    File "c:\users\james\appdata\local\enthought\canopy\user\lib\site-
  
  packages\matplotlib\animation.py", line 787, in _draw_next_frame
  
      self._pre_draw(framedata, blit)
  
    File "c:\users\james\appdata\local\enthought\canopy\user\lib\site-
  
  packages\matplotlib\animation.py", line 800, in _pre_draw
  
      self._blit_clear(self._drawn_artists, self._blit_cache)
  
    File "c:\users\james\appdata\local\enthought\canopy\user\lib\site-
  
  packages\matplotlib\animation.py", line 840, in _blit_clear
  
      a.figure.canvas.restore_region(bg_cache[a])
  
  KeyError: 

  Since it mentioned an error in _blit_clear I tried changing blit to False in FuncAnimation, but then it wouldn’t animate in the pyplot.show() when I didn’t try to save.

  I’m unsure as to where the error could be and so can’t work out how to fix this.

  I’m using Windows 10, python 2.7.6 and matplotlib version 1.4.2

  Many Thanks !