[FFmpeg-user] rounding error in v360

[Michael Koch]

There is a rounding or +-1 error in the v360 filter when converting from 
double_fisheye to equirectangular. The error is visible with or without 
interpolation. Can be reproduced as follows:

ffmpeg -f lavfi -i color=black:s=160x80 -lavfi 
geq=r='255*mod(trunc(4*X/W),2)':g='255*trunc(2*X/W)':b='255*trunc(2*Y/H)' 
-frames 1 -y test.png

ffmpeg -i test.png -lavfi 
v360=dfisheye:e:ih_fov=180:iv_fov=180:interp=near -y eq.png

Michael