[FFmpeg-user] remap filter, unmapped pixels

[Michael Koch]

Am 20.02.2020 um 11:07 schrieb Paul B Mahol:
> On 2/20/20, Michael Koch <astroelectronic at t-online.de> wrote:
>> I'd like to understand how the new "fill" option in the remap filter works.
>> What is an "unmapped pixel"? How is it possible that pixels are
>> unmapped, if the xmap and ymap files have the same size as the output
>> image? Is a pixel "unmapped" if it has invalid coordinates (negative or
>> too big) in the xmap or ymap files?
> Previously all unmapped pixels were set to black for rgba or dark
> green for y420p.
> It is very obvious to understand even for every little kid in the block.

Finally I got it working. A pixel can be declared as "unmapped" by 
setting the values to 65535 in the xmap and ymap files. However using a 
negative value (for example -1) doesn't work. In this case the pixel is 
mapped to the top left pixel of the input image.
This behaviour might be obvious for little kids, but not for me. Should 
be added to documentation.

Michael