[FFmpeg-user] question about displace filter

[Michael Koch]

Finally I found a solution how to make curved text for a fulldome video. 
It's awfully slow because in the geq filter the same calculations are 
made for each frame again and again. But it works. Below is the Windows 
batch file.
Most probably the remap filter would make this process much faster, but 
I haven't yet figured out how to make the Xmap and Ymap files.

Michael



REM make a video with curved text for fulldome fade-in fade-out

set "DUR=10"            : duration of video
set "FPS=30"            : framerate
set "BACK=black"        : background color
set "FONT=arial.ttf"    : font
set "TEXT=my_text.txt"  : text file
set "COLOR=orange"      : text color
set "FSIZE=15"          : font size
set "POS_X=(w-tw)/2"    : X text position, for centered text: (w-tw)/2
set "POS_Y=h*0.9"       : Y text position
set "S=2"               : start time for text
set "E=8"               : end time for text
set "FI=2"              : fade-in duration (may be small, but not zero)
set "FO=2"              : fade-out duration (may be small, but not zero)
set "SIZE=1000"         : video size (quadratic)

c:/ffmpeg/ffmpeg ^
  -f lavfi ^
  -i color=c=%BACK% ^
  -r %FPS% ^
  -t %DUR% ^
  -aspect "1:1" ^
  -vf 
"scale=%SIZE%:%SIZE%,drawtext='fontfile=%FONT%:textfile=%TEXT%:fontcolor_expr=%COLOR%@%%{e\:clip(((t-%S%)/%FI%)*between(t,%S%,%S%+%FI%)+(%E%-t)/%FO%*between(t,%S%+%FI%,%E%),0,1)}:fontsize=%FSIZE%:x=%POS_X%:y=%POS_Y%',geq=p(if(gt(Y\,H*0.7)\,W/2+H/2*atan((X-W/2)/(Y-H/2))\,0)\,if(gt(Y\,H*0.7)\,H/2+hypot(X-W/2\,Y-H/2)\,0))" 
^
  -c:v mpeg4 ^
  -q:v 0 ^
  -y test.mp4

pause