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• Remux video file and get the output bytes on the fly

  22 septembre 2014, par Miguel Botón

  I have been looking for a solution too many hours and maybe I didn’t use the proper keywords to find it but I give up. I hope somebody can help me with this.

  My goal is to create a small C code that remux a video file to another container (mp4 or whatever, not decided yet) and create a JNI interface to read the raw output bytes in my Java application.

  Create the JNI interface is not a problem and remux the video is pretty simple (and there is a great example at http://ffmpeg.org/doxygen/trunk/doc_2examples_2remuxing_8c-example.html), but I’m having a headache trying to figure out how I can tell FFmpeg to deliver the data when my application requests it.

  I was thinking in create a thread, where the remux would be done, and write the output data to a buffer where my application would read it. When the buffer is full the remux would be paused until it is flushed, but I don’t know how I can achieve that or if it would be a proper solution.

  I believe the best solution will involve creating an AVIOContext but I’m not very sure.

  Thank you very much in advance.

  EDIT :

  A solution I found, but I don’t like it at all, is to run the "ffmpeg" executable, tell it to write the output to "stdout" and read this output from my Java application using an InputStream.

• How to take screenshot (high fps) in Linux (programming)

  30 août 2014, par pirobtumen

  First of all I want to say that I’ve been reading a lot about this and I’ve learnt many ways to do it, but I haven’t been able to do it in linux.

  My project is an ambilight with arduino, so I need to take a screenshot of the desktop and analyze its colour.

  At the beginning I used Processing 2.0 with the class ’Robot’ from ’java.awt’. Initially I could take 5 frames per second and then I got 13fps. This works but I want more perfomance, so I start reading.

  In Windows or Mac you have libraries that let you access directly to the ’frameBuffer’, so you can take screenshot really ’easy’ and really fast.

  In Ubuntu I have tried python with Gtk, PIL, Qt... and the fastest way is GTK but I can only have about 15fps too.

  My problem is : I want to do it cross platform but I prefer that my program work in Linux at the beginning and then in Windows (I don’t like it too much :P).

  So, the first question : is python able to offer that perfomance ? Because I think that C++ can be a better option.

  And the second question : what do I need to do it ? I’ve read about Xlib (X11) but I can’t find documentation that let me take a screenshot. Also I know, for example, FFmpeg which is a powerful tool but I don’t know how to implement it.

  I hope that you could help me (and excuse me if I’ve made any mistakes).

• Programmatically specify rtmp s to be pulled from

  16 juillet 2014, par Stanislav

  I am sorry in advance if question might look a little bit silly, but I am very new to the current topic so hope you understand.

  Our current video streaming is performed with red5, and the client that receives the video is the flash client.

  My goal is to get the stream address of my red5 stream and programmatically send notification to nginx-rtmp to pull it.

  So let’s say I have the following nginx-rtmp configuration :

     application big {
  
         live on;
  
         exec_pull /home/stan/bin/ffmpeg -i rtmp://142.204.133.103/$app/${name}  -vcodec flv -an -f flv rtmp://localhost:1937/anotherapp/${name};
  
     }
  
  
  
     application anotherapp {
  
         live on;
  
    }

  Now I want notify nginx-rtmp and say : "Hey, here is rtmp ://142.204.133.103/red5app/livestream stream, can you please pull it, transcode and retransmit to "anotherapp" ?

  I can do it either from ActionScript3 or Java code, I just need a small example of how it’s usually done, because I got confused :(

  Thank you, guys.