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• Adding a watermark to a GIF with reasonable quality using FFMPEG

  27 novembre 2017, par Neo Herakles

  so I got this code to add a logo onto a folder full of GIFs

  @echo off
  
  setlocal
  
  for %%G in ("%~dp0webm\*.gif") do (
  
      ffmpeg -i %%G -i watermark.png -filter_complex "[0:v]scale=trunc(iw/2)*2:trunc(ih/2)*2[v0];[1:v][v0]scale2ref=trunc(iw/5):trunc(ih/16)[logo][0v];[0v][logo]overlay=W-w-3:H-h-4 [v]" -map "[v]" "C:\Users\Propietario\Desktop\Conversion\gif\%%~nG.gif"
  
      )
  
  )
  
  endlocal
  
  pause

  However, the output quality is rather low, similar to an issue I had with converting from video to GIF which was solved by creating a palette.

  ffmpeg -i input.gif -filter_complex palettegen[PAL];[0:v]fifo[v0];[v0][PAL]paletteuse output.gif

  Issue is, both solutions use -filter_complex so I don’t know exactly how to combine the two in a way in which I’ll be able to turn GIFs into watermarked GIFs with reasonable quality.

• How can I programmatically write and read random video watermarks ?

  13 novembre 2017, par GreenTriangle

  I spent a few minutes trying to think of a clearer way to word my title, but I couldn’t manage it, sorry.

  I want to essentially canary trap video files : I am (hypothetically, this is not real but a personal exercise) offering them up to 5,000 different people, and if one gets leaked, I want to know who leaked it. Metadata is too easily emoved, so what I’d like to do is add a random and subtle watermark to each file, and store information about that in a database.

  For example : on Joe Smith’s copy, a 10x10 pixel 80% transparent red square in the upper left corner for 5 frames. On Diane Brown’s copy, a full-width 5-pixel 90% transparent black bar on the bottom edge for 15 frames. Then, if I find a leaked copy, I could check it against the database.

  I know this still isn’t foolproof : cropping would break co-ordinates, hue/brightness transforms would break colour reading, cutting time would break timestamps. But if I did want to do this anyway, what would be a good strategy for it ?

  My idea was to generate PNG overlays randomly, split the video into parts with mkvtoolnix/ffmpeg, re-encode the middle part with ffmpeg + overlay filter, and then rejoin them. But is this silly when there’s a "proper" way to do it ? And what would I be doing to read the watermarks, which I can’t even really conceive of ?

• Trim video around pixel color at specified coordinate [closed]

  22 février 2020, par Modf

  I have some videos I would like to trim programatically. They have a keyboard/mouse overlay. The overlay changes colour in response to keypresses, for example, when left mouse is pressed, it looks like this :

  

  I want to remove all frames from the video except those that are within one second of a left mouse press frame (as pictured above, where the left mouse button is now filled with the yellow colour).

  Can this be achieved with ffmpeg filters ?