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• stream flv over tcp using ffmpeg

  16 août 2017, par Naseeb Panghal

  I am using FC23 machine and FFMPEG version is 2.8.10

  Using below command, I can stream flv over tcp successfully and able to receive it successfully at receiver side as well. I play it using vlc player. Both audio and video are played well.

  ./ffmpeg -f x11grab -s 1920x1080 -framerate 15 -i :0.0 -f alsa -ac 2 -i hw:1 -vcodec libx264 -r 30 -pix_fmt yuv420p -tune zerolatency -preset ultrafast -acodec aac -strict -2 -ar 48000 -ab 96k -f flv -metadata streamName=naseeb.sdp tcp ://127.0.0.1:6666

  But in actually i need to do this using an application. So i wrote an application in ’C’ language.
  I have done following things in the application.

  1. open `AVOutputFormat` using below API
  
      fmt = av_guess_format("flv", NULL , NULL);
  
   2. Get `AVFormatContext` using below API
  
      avformat_alloc_output_context2(&oc, fmt, NULL, NULL);
  
   3. Then added streams(audio and video) using required APIs
  
   4. Then open codecs using required APIs
  
   5. Then set the output using below API
  
      ret = avio_open(&oc->pb, filename, AVIO_FLAG_WRITE);

  When i need to write flv into a file on system then i provide filename in step 5 as muxer.flv.
  When i need to stream flv over tcp then i provide filename as tcp://127.0.0.1:6666.

  when i play muxer.flv using vlc player both video and audio are played well but when it is streamed over network then Green frames are shown for video and audio works very well. I am wondering what extra setting is required when i need to stream it over network ?

  I have no doubt on Receiver side as it works very well with ffmpeg utility(command mentioned above).
  Currently i have downloaded ffmpeg 2.8.10 source code and looking into ffmpeg.c file for some extra setting. Till now i have not found anything helpful. Please suggest something why Green frames shown when flv is sent on network where it works well when dump on system hard disk.

• Evolution #3986 (Nouveau) : Class .btn plutôt que .submit

  15 août 2017, par tetue tetue

  Les boutons générés par SPIP portent nativement le sélecteur .submit, même s’ils ne sont pas des submit. Si nommer ainsi ce sélecteur CSS nous a semblé pertinent à l’époque, l’on peut trouver mieux aujourd’hui.

  Les frameworks actuels utilisent un nom plus générique, évoquant le bouton, tout simplement. Sur la vingtaine que j’ai étudié, 9 utilisent .button, 6 l’abréviation .btn, tandis que les autres l’emploient en suffixe ou radical : .ym-button, .btn-info. C’est dire si ce nommage est répandu !

  Afin de bénéficier plus facilement de styles de boutons distribués par ailleurs, je propose de renommer cette classe, soit avec le plus courant .button, soit avec l’abréviation .btn qui a le mérite d’être anglo-française et plus rapide à écrire.

  Remplacer class="submit
  par class="btn submit
  en conservant submit dans un premier temps pour rétro-compatibilité.

• How to searialize GOPs to bytes and desearialize using FFmpeg ?

  20 avril 2017, par Ye Li

  I’m working on an experiment which needs to read GOPs from a media file (e.g. mp4) and send over a network via UDP sockets. What I’ll need to do are as follows :

  At the source node :

  1, Read a GOP and searialize it into a buffer of bytes (i.e., pointed by uint8_t*) ;

  2, Split the buffer into equal-size packets, perform channel coding amongst the packets and send coded packets via UDP sockets ;

  At the receiver side :

  3, Receive UDP packets and recover the packets into a buffer of bytes. Note that our channel coding scheme can ensure that the content of the buffer is identical to that at the source side, so don’t worry about the lossy nature of UDP ;

  4, Desearialize the buffer to reconstruct GOP ;

  5, Play the GOP.

  And repeat 1-5.

  I have very little experience with FFmpeg APIs. Could someone please point to me which API functions (if exist) I would probably need to look to complete the Steps 1,4,5 ?
  Thanks sincerely.