[FFmpeg-trac] #8124(ffmpeg:new): color option for perspective filter

FFmpeg trac at avcodec.org
Sun Sep 8 00:23:06 EEST 2019


#8124: color option for perspective filter
--------------------------------+---------------------------------------
             Reporter:  mkoch   |                     Type:  enhancement
               Status:  new     |                 Priority:  minor
            Component:  ffmpeg  |                  Version:  git-master
             Keywords:          |               Blocked By:
             Blocking:          |  Reproduced by developer:  0
Analyzed by developer:  0       |
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 Summary of the bug:
 When the "perspective" filter is used with parameter "sense=1", the size
 of the video becomes smaller and the outer area if filled with the pixel
 values from the border of the input video. It would be nice to have an
 option for filling the outer area with a color.

 This example shows the problem:

 rem  Make a chessboard video
 c:\ffmpeg\ffmpeg -f lavfi -i color=black:s=vga -vf
 geq=g='255*mod(floor(X/40)+floor(Y/40),2)' -t 5 -y in.mp4

 rem  Apply the perspective filter
 c:\ffmpeg\ffmpeg -i in.mp4 -lavfi
 "perspective=x0=150:y0=125:x1=500:y1=75:x2=100:y2=375:x3=480:y3=420:sense=1"
 -y out.mp4

 A known workaround is to pad the input video with a 1-pixel wide border
 (with alpha=0), before applying the perspective filter.
 This is useful if you have a video in which a flickering computer screen
 is visible, and you want to overlay another video over this computer
 screen.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/8124>
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