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• run ffmpeg commands from my own project

  28 octobre 2013, par bruno

  I'm starting a project where I want ppl to upload videos of a talk and a the video of slides for that talk and want to merge them (to play at the same time) and then show results.

  My question is :
  Is it possible to do that from code ? if it is, can you point me to the right doc ?
  I was able to do it running command line, but as I want this to run on a server with different ppl uploading their videos I think this would not be the best approach.
  I have a preference for Java if it's possible to do it, but I can manage to use other languages what do you guys suggest ?

  The idea would be to have a service where I can point the urls of the videos stored in my server and it would merge them and save file where I can later stream. With different ppl uploading videos at the same time and being able to watch the result in a reasonable amount of time.

  I used this tutorial to test :
  https://trac.ffmpeg.org/wiki/Create%20a%20mosaic%20out%20of%20several%20input%20videos

  Thanks for your time

• Anomalie #3523 : Gestion des plugins avec spip 3.0.20

  5 août 2015, par Gilles VINCENT

  en ajoutant la directive
  

  opcache.validate_timestamps=0

  à ma config php, comme conseillé dans http://wiki.mikejung.biz/PHP_OPcache pour un serveur en production, la page de gestion des plugins refonctionne à nouveau correctement. De plus, la valeur
  

  opcache.revalidate_freq=60

  (valeur par défaut fournie lors de l’install) est vraiment longue.
  Si je commente cette ligne dans le fichier de config, le phpinfo() indique une valeur plus raisonnable de 2 seulement.
  Je pense que le chargement méga long venait de cette constante.

  La différence de comportement avec la config "pour développement" entre une 3.0.19 et une 3.0.20 reste encore surprenante.
  Si j’ai le temps, je creuserai dans une semaine à mon retour de vacance, car tout le monde ne peut as jouer avec ces paramètres du serveur... :/

• How to parallelize this for loop for rapidly converting YUV422 to RGB888 ?

  16 avril 2015, par vineet

  I am using v4l2 api to grab images from a Microsoft Lifecam and then transferring these images over TCP to a remote computer. I am also encoding the video frames into a MPEG2VIDEO using ffmpeg API. These recorded videos play too fast which is probably because not enough frames have been captured and due to incorrect FPS settings.

  The following is the code which converts a YUV422 source to a RGB888 image. This code fragment is the bottleneck in my code as it takes nearly 100 - 150 ms to execute which means I can’t log more than 6 - 10 FPS at 1280 x 720 resolution. The CPU usage is 100% as well.

  for (int line = 0; line < image_height; line++) {
  
      for (int column = 0; column < image_width; column++) {
  
          *dst++ = CLAMP((double)*py + 1.402*((double)*pv - 128.0));                                                  // R - first byte           
  
          *dst++ = CLAMP((double)*py - 0.344*((double)*pu - 128.0) - 0.714*((double)*pv - 128.0));    // G - next byte
  
          *dst++ = CLAMP((double)*py + 1.772*((double)*pu - 128.0));                                                            // B - next byte
  
  
  
          vid_frame->data[0][line * frame->linesize[0] + column] = *py; 
  
  
  
          // increment py, pu, pv here
  
  
  
      }

  ’dst’ is then compressed as jpeg and sent over TCP and ’vid_frame’ is saved to the disk.

  How can I make this code fragment faster so that I can get atleast 30 FPS at 1280x720 resolution as compared to the present 5-6 FPS ?

  I’ve tried parallelizing the for loop across three threads using p_thread, processing one third of the rows in each thread.

  for (int line = 0; line < image_height/3; line++) // thread 1
  
  for (int line = image_height/3; line < 2*image_height/3; line++) // thread 2
  
  for (int line = 2*image_height/3; line < image_height; line++) // thread 3

  This gave me only a minor improvement of 20-30 milliseconds per frame.
  What would be the best way to parallelize such loops ? Can I use GPU computing or something like OpenMP ? Say spwaning some 100 threads to do the calculations ?

  I also noticed higher frame rates with my laptop webcam as compared to the Microsoft USB Lifecam.

  Here are other details :

  • Ubuntu 12.04, ffmpeg 2.6
  • AMG-A8 quad core processor with 6GB RAM
  • Encoder settings :
    • codec : AV_CODEC_ID_MPEG2VIDEO
    • bitrate : 4000000
    • time_base : (AVRational)1, 20
    • pix_fmt : AV_PIX_FMT_YUV420P
    • gop : 10
    • max_b_frames : 1