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• Debugging Video Frame Differences

  14 mai 2014, par jvenema

  I’m trying to decode an h264-encoded video frame using a decoder that has fairly limited capabilities (Broadway JS).

  Here’s the process I’m using for testing :

  1. Encode single image using h264 (output is 62KB) using OpenH264 from Cisco, write to disk
  2. Read file as binary in JS (loaded via XHR)
  3. Decode in JS using Broadway
  4. Display in canvas

  I actually have a functional example of this, but there’s a manual step at the moment between steps 1 and 2 - I have to call FFMPEG to force a small translation, and I can’t figure out why.

  I have successfully integrated Cisco’s Openh264 library into my project, and can encode the image as h264 and write it to disk. I’ve confirmed the encoding itself is valid by using FFMPEG to extract the frame back out as a JPEG (looks perfect).

  But, to make the frame decode properly in JS, I have to do a conversion using FFMPEG. It does some magic, the file size drops to 58KB, and voila, everything starts working.

  The Openh264 libraries only work with the baseline configuration, so I’m assuming I have some other random parameter set incorrectly. Problem is, if I use ffprobe to compare the frames - the settings are identical ! But the file sizes are different, so obviously something is different.

  So now the final question - what tool can I use to truly see what FFMPEG is doing behind the scenes here to make my "manually" encoded frame work ? Is there a tool that will let me compare all the details of two h264 frames ?

• Evolution #3123 (Nouveau) : #URL_ARTICLE et articles de redirection

  20 décembre 2013, par realet RealET

  Actuellement, #URL_ARTICLE génère l’URL de l’article, et c’est le moteur de SPIP qui au moment de charger la page détecte que c’est une redirection et la fait.
  Ce serait sans doute plus pertinent si #URL_ARTICLE générait directement l’URL de redirection.
  Autre formulation lue sur IRC : « c’est possible que l’URL des articles virtuels soit directement l’URL finale ? »

  Cette demande a initié une grosse discussion ici : http://thread.gmane.org/gmane.comp.web.spip.devel/57112

  Un des manques relevé est que SPIP fait une redirection 302 (temporaire) et qu’on ne peut pas faire de redirection 301 (permanente).

• Php exec ffmpeg not running in background

  12 décembre 2013, par mircea

  I am trying to start a ffmpeg process from a php script and I know it has been asked a lot of times but I tried many solutions and none of them seem to work, each time the php script never finishes unless I kill the ffmpeg process. At the moment I am using this script which indeed starts ffmpeg and writes info in the designated files but the php script is loading forever.

  What am I missing ?

  $cmd = 'cd cache && ffmpeg -y -i "rtsp://stream" -r 20 -f image2 a%6d.jpg >/dev/null 2>/dev/null &';
  
  
  
  exec(sprintf("%s > %s 2>&1 & echo $! >> %s", $cmd, 'log.txt', 'error.txt' . '.pid')); 

  A little more info : I am running FFMpeg 0.6.5, PHP 5.3.3 on CentOS 6.5

  Thank you for your time !