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• Streaming audio from C++ [closed]

  27 août 2022, par Oliver Hawker

  I have a C++ audio application that generates audio, which I intend to stream over a network using RTSP and FFmpeg (or it's libs directly). Fundamentally, the audio is not coming from a file or device but is generated internally by the application.

  


  So far, I have looked at the following approaches :

  


  


  1. Spin up an FFmpeg process inside my application using FFmpeg-kit, and pipe data in to it using a named pipe
— Written in objective C, so I'd need a wrapper around it to call from C++.
— Feels like an awful lot of overhead for something so simple, I am dubious that it's necessary.

     


  


  2. Leverage libavformat etc. directly.
— I can imagine that the pipeline would look like a regular encode pipeline using raw frames, which I can sort-of see how it would work, but I'm struggling to mix this example with something that also transmits over RTSP.

     


  


  3. Make something myself that transmits raw samples over UDP
— Bandwidth-heavy and probably unnecessary

     


  


  


  Does anybody know of a tutorial, starting point, reference implementation or other project I could look at for some guidance ? Any solution I have come up with seems ridiculously heavyweight for something so simple.

  


  Thanks all.

  


• Animation speed adjustment using ffmpeg in Python

  5 novembre 2015, par neither-nor

  I’m been for years using stock ffmpeg script to sequentially snitch together temporal plots in Python. However, I cannot figure out the trivial issue of how to, for instance, slow down the animation speed so that the resultant video file has a longer duration.

  Example :

  import matplotlib.pyplot as plt
  
  import os, sys
  
  
  
  for t in range(100):
  
      plt.cla()
  
      plt.text(0.5, 0.5, 'time %02d'%(t+1))
  
      plt.draw()
  
  
  
      fname = '_tmp%02d.png'%(t+1)
  
      plt.savefig(fname)
  
  
  
  os.system("ffmpeg -i _tmp%02d.png -pix_fmt yuv420p -r 20 -b:v 20M flipbook.mp4")
  
  os.system("rm _tmp*.png")    

  The resulting "flip book" takes 4s and the time stamp increases steadily. However, I tried to make the animation last twice as long by testing the following :

  1. Change 20 after -r to 1 : this still lasts 4s but now the time stamp "leaps" nonlinearly

  2. Change 20M to 1M : no discernible effect

  I can’t find much information about this line of code, either the usage of each flag or how to modify aspects of it (e.g.,speed).

• New builds for PHP 5.4 and PHP 5.3

  29 novembre 2012, par Mikko Koppanen — Imagick

  It’s been a while since I last updated this blog (September 2009 to be exact). Time flies ! Anyway, here comes the actual content : updated imagick binaries for PHP 5.3 and PHP 5.4. The download package also includes ImageMagick 6.8.0 binaries compiled with VC9 (Visual Studio 2008). I noticed that the official ImageMagick builds are now Visual Studio 2010 and that wouldn’t work well with PHP compiled with 2008.

  I am not sure if I am violating any license in distributing ImageMagick binaries but if I do, please let me know and I will remove them. The binaries are just stock ImageMagick 6.8.0, which you can download from http://imagemagick.org/.

  In order to get things running you should add the ImageMagick DLL directory into PATH, add the imagick extension to php.ini and things should be running. At least hopefully.

  The download link for the binaries is here : imagick-php54-php53.tgz.