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• How does record functionality in vlc works [on hold]

  14 décembre 2013, par quartz

  I am curious about how does "record" functionality of vlc works.
  1) Does it work like screen capture software like "recordmydesktop" ?
  or
  2) Does it save in-memory the frames and latter combine it with tools like ffmpeg ?
  or
  3) Does it simply copy the required information from original video to new video file ?

  Or something else ?

  I want to know these informations because I am developing some simulation tool using a rendering engine. I want my render output to be stored directly in a video file rather than displayed on monitor. If I know these informations, I think it will help.

  Just give me hints, I don't need complete answer.
  This question is not too broad, since I asked specifically about record functionality of vlc media player.

• 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 ?

• Generating thumbnail from video using php classes

  4 janvier 2014, par user2582858

  I was using the exec command to generate thumbnails via ffmpeg..
  My method was :

  exec("ffmpeg -f image2 -i /home/phedra/imgs/image/img%03d.png -r 12 -s 610x489 /home/phedra/imgs/video/out.avi", $out);

  but my senior team member told me that using exec command is not a good practice because it is a dangerous command and It may harm server.. So find any other technique.. I struggled alot but didnt find any comprehensive method other than this..
  Can anybody tell me anyother way to generate thumbnail from video using php class from scratch (With an example if possible), so that I could understand completely, Moreover also tell me the library link to download and settings for server if any setting needed to be done before using that technque(My server system is based on Ubuntu and the framework for developement is codeignitter)..

  (Third party api tool for generating thumbnail is also welcome but the necessary thing is that it must be free :))