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• Screencasting with hardware-accelerated gnome-3 [closed]

  30 octobre 2012, par Jeroen

  I am running Ubuntu 12.04 with gnome 3 shell, and I would like to create a screencast. I have tried using recordMyDesktop, Kazam Screencaster, and ffmpeg but all suffer from the same problem, which I think has to do with hardware acceleration in Gnome 3. The recorded videos all get very glitchy with blue space for all operations that use some sort of effect. Here is an example recording : http://www.stat.ucla.edu/ jeroen/files/screencast.mkv.

  The only method that does not seem to suffer from this, is the (largely undocumented) CTRL+SHIFT+R shortcut in gnome 3 that will start a recording. However, this feature is very buggy otherwise and often crashes when I enable audio input.

  My machine has a GeForce GT 120 with Apple LED Cinema monitor. I am using the proprietary nvidia drivers that ship with Ubuntu 12.04. Is there any way I can record the video as it appears on my screen ? I know I can avoid the problem by switching to gnome2 or unity 2d or anything that does not use effects, but I would prefer to make the recordings in my regular gnome 3 environment.

• Best Web Video Encoding Practices for IOS (FFMpeg)

  21 juin 2012, par MagicMushroom

  I am working on an online video repository system for a client, written mostly in PHP. At the moment I am building a mobile version of our desktop website. Our desktop site allows users to watch videos in the browser, much like YouTube.

  My client uploads videos through the manager interface I have created, and my application uses FFmpeg on the server to transcode his videos into several resolutions and bitrates. I am no expert on FFmpeg, and while I do not know the ins and outs of each individual setting, I do understand how it works as a whole. Right now, we are using the mp4 container format with the h.264 codec to encode our videos. Our command looks like :

  ffmpeg -y -i "INPUT FILE.mov" -f mp4 -s 640x480 -vcodec libx264 -preset fast -maxrate 1500 -bitrate 1000 -bufsize 4096 -acodec libfaac -ab 192 -ac 2 "OUTPUT_FILE.mp4" >> "FILE.log" 2>&1 &

  I'm hoping to gain information about best practices with encoding video for web streaming on IOS and other mobile devices using FFmpeg. What resolutions and settings make for good mobile streaming video ? How can I ensure maximum compatibility across the sea of Android devices ?

• Bash : bash script to download trimmed mp3 from youtube url

  25 août 2017, par Bhishan Poudel

  I would like to download the initially x seconds trimmed mp3 from a video url of youtube.
  I found that youtube-dl can download the video from youtube to local machine. But, when I looked at the man pages of youtube-dl, I could not find any trim options.

  So I tried to use the ffmpeg to trim downloaded mp3 file.
  Instead of doing this is two steps, I like to write one bash script which does the same thing.
  My attempt is given below.

  However, I was stuck at one place :
  "HOW TO GET THE VARIABLE NAME OF OUTPUT MP3 FILE FROM YOUTUBE-DL ?"
  The script is given below :

  # trim initial x seconds of mp3 file
  
  # e.g. mytrim https://www.youtube.com/watch?v=dD5RgCf1hrI 30
  
  function mytrim() {
  
      youtube-dl --extract-audio --embed-thumbnail --audio-format mp3 -o "%(title)s.%(ext)s" $1
  
      ffmpeg -ss $2 -i $OUTPUT_MP3 -acodec copy -y temp.mp3
  
      mv temp.mp3 $OUTPUT_MP3
  
      }

  How to get the variable value $OUTPUT_MP3 ?
  echo "%(title)s.%(ext)s" gives the verbatim output, does not give the output filename.

  How could we make the script work ?

  The help will be appreciated.