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• Command-line streaming webcam with audio from Ubuntu server in WebM format

  28 avril 2017, par mjtb

  I am trying to stream video and audio from my webcam connected to my headless Ubuntu server (running Maverick 10.10). I want to be able to stream in WebM format (VP8 video + OGG). Bandwidth is limited, and so the stream must be below 1Mbps.

  I have tried using FFmpeg. I am able to record WebM video from the webcam with the following :

  ffmpeg -s 640x360 \
  
  -f video4linux2 -i /dev/video0 -isync -vcodec libvpx -vb 768000 -r 10 -vsync 1 \
  
  -f alsa -ac 1 -i hw:1,0 -acodec libvorbis -ab 32000 -ar 11025 \
  
  -f webm /var/www/telemed/test.webm 

  However despite experimenting with all manner of vsync and async options, I can either get out of sync audio, or Benny Hill style fast-forward video with matching fast audio. I have also been unable to get this actually working with ffserver (by replacing the test.webm path and filename with the relevant feed filename).

  The objective is to get a live, audio + video feed which is viewable in a modern browser, in a tight bandwidth, using only open-source components. (None of that MP3 format legal chaff)

  My questions are therefore :
  How would you go about streaming webm from a webcam via Linux with in-sync audio ? What software you use ?

  Have you succeeded in encoding webm from a webcam with in-sync audio via FFmpeg ? If so, what command did you issue ?

  Is it worth persevering with FFmpeg + FFserver, or are there other more suitable command-line tools around (e.g. VLC which doesn’t seem too well built for encoding) ?

  Is something like Gstreamer + flumotion configurable from the command line ? If so, where do I find command line documentation because flumotion doc is rather light on command line details ?

  Thanks in advance !

• When using MacOS (iMac Intel) can I activate integrated graphics, but have ffmpeg/Video Toolbox use discrete graphics ?

  10 juin 2023, par Jann

  I have a 2019 Retina iMac with both integrated graphics (Intel HD Graphics CFL) and the Radeon Pro 560X. I never use this machine for anything except encoding videos as it is so old - and a desktop. So it generally sits on my desk handing ripping my Blurays and encoding them using a self-compiled version of ffmpeg.

  


  I use the video-toolbox hardware acceleration w/ffmpeg.

  


  If I tell the iMac to boot using integrated graphics, will ffmepg via video-toolbox use the Radeon card ? I ask cos when I boot using the Radeon card, then start an encode, screen sharing becomes unresponsive as the GPU is being used heavily by ffmpeg and the Radeon has issues driving the screen, doing acceleration on screen sharing AND encoding w/ffmpeg.

  


  TIA

  


  Jann

  


• ffmpeg : use drawtext with quote inside text

  18 octobre 2023, par Sulli

  I have a variable that takes its content from a file (I can't change the content of the file) :

  



  echo $variable
It's my variable


  



  I want to print that string on a video with ffmpeg :

  



  ffmpeg -nostdin -i input.mp4 -vf drawtext="text='$variable': fontcolor=white:box=1:boxcolor=black@0.8: x=h/70: y=h/5*4.2" -codec:a copy output.mp4


  



  when I do that, the quote inside $variable is not printed. I have read here that I need to escape the quote multiple times, some say 5 times, some say more.

  



  So I have tried to use

  



  variable=${variable//\'/'\\\\\'\'}


  



  to add between 1 and 10 backslashes, but it never worked : either nothing is printed, or \ are printed :

  



  It\s my variable


  



  Can someone tell me what is the correct syntax, or the correct number of backslashes I should add ?