[FFmpeg-user] Documentation of chromanr filter
astroelectronic at t-online.de
Sat Jul 11 10:27:23 EEST 2020
The documentation of the new chromanr filter, especially this sentence
for the "thres" option is hard to understand:
"Sum of absolute difference of U and V pixel components or current pixel
and neighbour pixels lower than this threshold will be used in averaging."
First of all I think "or" is a typo and should be "of". But even with
this change the sentence is still hard to understand.
The sum of absolute differences of what? Sum of absolute differences of
the U and V pixel components? That makes no sense.
This is how I think it might work:
Foreach neighbour pixel
A = absolute difference of U components of current pixel and
B = absolute difference of V components of current pixel and
if (A+B < threshold) then
use this neighbour pixel for averaging
If the above is correct, I suggest to change the sentence as follows:
"The algorithm calculates the absolute difference of the U components of
the current pixel and a neighbour pixel. The same is also calculated for
the V components. A neighbour pixel is used for averaging, if the sum of
both absolute differences is lower than the threshold."
Also the meaning of "stepw" and "steph" options is unclear:
-- Do these options refer to the pixels? If stepw=2 and steph=2 then
only a quarter of the pixels is analyzed, and the same U and V
components are used for 4 pixels?
-- Or do they refer to the selection of the neighbour pixels? If stepw=2
and steph=2 then only a quarter of the neighbour pixels is analyzed?
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