Am 05.08.2018 um 15:42 schrieb Gyan Doshi:
On 05-08-2018 06:41 PM, Michael Koch wrote:
I'd like to ask if it's possible to make an exponential decay effect
with FFmpeg.
Let's assume a pixel is fashing to luminance = 1 in just one frame.
Then in the output video I'd like to have the pixel flashing to 1
immediately, followed by an exponential decay with a time constant of
a few seconds.
The mathematics would be something like this:
luminance = 0.95 * luminance_in_last_frame; // exponential decay
if (luminance_in_new_frame > luminance)
luminance = luminance_in_new_frame;
So,
frame 0 --> luminance 0
frame 1 --> luminance 1
frame 2 --> as per exprs above
...
frame 2+T --> "
frame NEXT --> source luminance
...
frame LAST --> "
?
Or would the exponential decay restart each time a pixel of lum 1 is
encountered?
Every time when the input becomes brighter than the last output frame,
the output is set to the input value. If input is below the last output
value, then exponential decay.
I have a timelapse video of the night sky with meteors. Each meteor is
visible only in one frame. I'd like to make them visible a little
longer, decaying over several frames.
Example:
Input Output
0 0
1 1 // set to input value
0 0.95 // exponential decay begins
0 0.90
0.50 0.86
0.50 0.81 // until here
0.90 0.90 // now set again to input value, because input is
brighter
0.90 0.90 // keep at the same level
0.60 0.86 // exponential decay begins
0.60 0.81
0.60 0.77
Michael
--
**********************************************
ASTRO ELECTRONIC Dipl.-Ing. Michael Koch
Raabestr. 43 37412 Herzberg
www.astro-electronic.de
Tel. +49 5521 854265 Fax +49 5521 854266
**********************************************
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