2017-05-10 8:07 GMT+03:00 Gyan <gyando...@gmail.com>: > > On Wed, May 10, 2017 at 5:41 AM, SviMik <svi...@gmail.com> wrote: > > > > > Great answer, thank you for the idea! I have tried to run it, and it > > produced me a black screen (all zeroes), but I think it may be my fault > > somewhere. > > > > In the first geq filter, add a='p(X,Y)' after the b expression. Turns out > the geq initializes alpha to 1 if no expression is provided. Ideally, it > ought to pass through.
It works! Thank you so much! By the way, I got few pixels with >255 value, and it turns out the ffmpeg can't handle it itself - the pixel with r=266 value became r=10. So I had to add min() to the last geq to avoid overflow: r='min(255,255*p(X,Y)/alpha(X,Y))':g='min(255,255*p(X,Y)/alpha(X,Y))':b='min(255,255*p(X,Y)/alpha(X,Y))' Now it works like a charm. If you have any link for further reading about geq - it would be highly appreciated. For example, the min() function was just a guess, which turned out to be existing completely by chance. I still can't find a comprehensive list of geq features and functions. Does it have conditions? Can I declare variables? Is there a way to conditionally turn the whole filter on and off depending on some pixel color? Or (even better) count the clipping pixels and revert the whole frame to the original state if too many errors occurred? That would help to detect automatically when the filter needs to be applied instead of figuring the video fragments out manually. Sorry if I'm too annoying :) You can just throw me a link for reading. _______________________________________________ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
