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• Overlay text on video with ffmpeg

  7 avril 2017, par ACIDSTEALTH

  I have some short mp4 video clips. Each one represents a response to a question or prompt. I would like to overlay the question/prompt text atop a grey semi-opaque banner. I need to be able to control the size, position, color, and opacity of the grey banner as well as the size, color, font family, justification, etc of the text that is overlaid atop it.

  I’ll prepend my question by stating that my experience with ffmpeg is limited to applying watermarks to videos via it’s Ruby wrapper streamio-ffmpeg. I know what I want to do is possible, I just don’t know where to begin. What I would like to know is how I can do this with ffmpeg. Specifically I am hoping for some sample code that I can learn from and adapt to my specific need, as well as how I can execute that code on a video within the context of a Rails app.

• ffmpeg- is there any limitation on number of drawtext filter used in a single command ?

  31 mars 2017, par hack

  i have to write different text on a number of images. The final filter command is quite large (> 500 draw text filters in a single command). I am writing this to a text file and using filter_complex_script to read it.
  If the number of frames and filter is small, it is working fine, but for a configuration with large number of images and draw text filters, it fails. Error is :

  Cannot find a valid font for the family Sans
  
  Error initializing filter 'drawtext' with args 'enable=between(n,180,180):fontsize=28:fontfile=C\:/Windows/Fonts/Arial.ttf:fontcolor=0x000000:text=109.0:x=581:y=527-th'
  
  Error initializing complex filters.
  
  No such file or directory

• ffmpeg for archval and convertability

  26 juillet 2021, par Satya

  I've got a couple hundred gigs of *.dv files. I'd like to convert them to H.264 or something else or even leave them alone. The purpose is archival, with an eye to maximum convertability especially to DVD. The content is family videos.

  


  Would this be fine ?

  


  ffmpeg -i input.dv \
    -c:v libx264 -preset slower \
    -crf 17 \
    -pix_fmt yuv420p \
    output.mp4


  


  I went with the slower preset because encoding time isn't an issue and I'd like a smaller file size. crf 17 is for least-lossy while being widely playable. I read somewhere that yuv420p is needed for some Quicktime players.

  


  Should I throw in -c:a aac for AAC audio ? The audio is voice only, no need for music-hall quality.

  


  I looked at https://trac.ffmpeg.org/wiki/Encode/H.264 for previous research and that's where I got those settings, but it is silent on the audio settings.