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• Compiling ffmpeg for android on windows OS

  22 octobre 2015, par Srini5

  After searching a lot on web I didn’t got any proper tutorial which can explain step by step approach of compiling ffmpeg for android on a windows OS. Lots of people suggested to drop windows and compile it on a Ubuntu machine. And I got many tutorial on how to compile on a Linux based machine using android NDK. Is there any tutorial or blog post which can explain how to do it on a windows machine. Or anybody know how to do the same in a windows machine.

• How to debug into CvCapture_FFMPEG from opencv codes ,avoid cap_ffmpeg.cpp load "opencv_ffmpeg.dll"

  19 juin 2014, par Ericking

  I had got ffmpeg source and build their libs and dlls within my include,lib,bin folders,and I import it into my Opencv project/opencv_highgui, and give the project right property settings.
  At the same time, I delete opencv_ffmpeg.dll in Opencv Origin folder.
  But it still cant step into ffmpeg source. In debug mode,it just stoped when it go into class CvCaptrue_FFMPEG_proxy’s virtual open()function.
  So my question is :
  1.how to step into ffmpeg codes ?
  2.how to build the opencv_ffmpeg.dll for debug ?

• IO.copy_stream performance in ruby

  19 juillet 2016, par stiller_leser

  I am trying to continously read a file in ruby (which is growing over time and needs to be processed in a separate process). Currently I am archiving this with the following bit of code :

  r,w = IO.pipe
  
  pid = Process.spawn('ffmpeg'+ffmpeg_args, {STDIN => r, STDERR => STDOUT})
  
  Process.detach pid
  
  while true do
  
    IO.copy_stream(open(@options['filename']), w)
  
    sleep 1
  
  end

  However - while working - I can’t imagine that this is the most performant way of doing it. An alternative would be to use the following variation :

  step = 1024*4
  
  copied = 0
  
  pid = Process.spawn('ffmpeg'+ffmpeg_args, {STDIN => r, STDERR => STDOUT})
  
  Process.detach pid
  
  while true do
  
    IO.copy_stream(open(@options['filename']), w, step, copied)
  
    copied += step
  
    sleep 1
  
  end

  which would only continously copy parts of the file (the issue here being if the step should ever overreach the end of the file). Other approaches such a simple read-file led to ffmpeg failing when there was no new data. With this solution the frames are dropped if no new data is available (which is what I need).

  Is there a better way (more performant) to archive something like that ?

  EDIT :

  Using the method proposed by @RaVeN I am now using the following code :

  open(@options['filename'], 'rb') do |stream|
  
    stream.seek(0, IO::SEEK_END)
  
    queue = INotify::Notifier.new
  
    queue.watch(@options['filename'], :modify) do
  
      w.write stream.read
  
    end
  
    queue.run
  
  end

  However now ffmpeg complaints about invalid data. Is there another method than read ?