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• ffmpeg convert white color to alpha

  11 janvier 2021, par tony

  Hello i took a picture with my camera :a drawing of a square frame on a white paper ; i'm trying to convert the white to transparent and keep the black color frame.

  


  So i started making 1 palette with only 2 colors to make the colors uniform and 1 palette to add the transparency

  


  ffmpeg -f lavfi -i "color=color=white:100x100" -f lavfi -i "color=color=black:100x100" -filter_complex "[0][1]hstack" -frames:v 1 blackwhite.png`
ffmpeg -i blackwhite.png -filter_complex "[0]split[a][b];[a]palettegen[pal1];[b]palettegen=reserve_transparent=on:transparency_color=white[pal2]" -map [pal1] palette1.png -map [pal2] palette2.png


  


  then i mapped the image png of the frame to convert the white to transparent and overlayed the result to a red background

  


  ffmpeg -i image.png -i palette1.png -i palette2.png -i background.png -filter_complex "[0:v][1:v]paletteuse=dither=bayer[a],[a]split[a1][a2];[a1][2:v]paletteuse=alpha_threshold=128[c];[3:v][c]overlay[d]" -map [a2] -c:v png out.png -map [d] -c:v png out1.png


  


  the png mapped to the first palette (as a test) comes as it should be, pure black and white,the second comes with no transparency at all and covers the background
what am i doing wrong ?

  


• Graph-based video processing for .NET

  23 octobre 2016, par Borv

  Does anyone know a good object-oriented library (preferably high-level, like C# or Java) for working with video and audio streams ?

  I wrote an app which fiddles with video and audio streams, feeds and such. The original task was simple :

  • grab an RTSP feed
  • display original feed(s) on the display
  • convert it to a series of h264 ts files
  • extract audio into separate MP3 files
  • upload videos and audio to the web site (preferably in real time, few minute delay is acceptable)

  As you may have already guessed it is about recording events (e.g. lectures) and publishing them on the web.

  To pull this out I needed some graph-based non-linear editing for media. Two weeks in, I tried ffmpeg, vlc and WMF. The only library I got to work is ffmpeg, and that comes with lots of "however". WMF required a lot of coding (and I abandoned this path), vlc looked great on paper, but I stumbled across some bugs with input splitting I could not get around (e.g. transcode:es combination flat out refused to work).

  So, the question. What are good non-linear editing libraries besides ffmpeg, vlc and wmf/directshow that allow for building video processing graphs with sources, sinks and filters ? Or perhaps good bindings over ffmpeg and vlc allowing to build such graphs ?

• ffmpeg : Crop webm file with circular .png mask [closed]

  26 mars 2021, par Beneos Battlemaps

  I tried everything for hours and can get it working by myself. I want to create animated Pen&Paper tokens for virtuale tabletops. I have a .webm video file with 720x720 pixel showing an animation of a render file created out of a png sequence via

  


  ffmpeg -framerate 24 -f image2 -i face.%04d.png -c:v libvpx-vp9 -pix_fmt yuva420p face1.mp4

  


  See here : https://webmshare.com/play/ZxZa0

  


  Now i want to overlay this .webm with an circle image as frame :

  


  overlay

  


  and crop the black part so its transparent in the end result as well as keeping the transparent area in the center for the video itself.

  


  So the endresult is from this :

  


  Face1

  


  to this :

  


  Face2

  


  Can you help me out with that ? If its easier i can split the steps, making first the alpha mask crop via png and adding the circle in it later.

  


  Beste regards in advance
-Ben