[FFmpeg-user] scaling algorithms

[Michael Koch]

Hi all,

I have some questions about the scaling algorithms in FFmpeg.
https://www.ffmpeg.org/ffmpeg-scaler.html#sws_005fflags

1. Which is the default algorithm?

2. I have many pictures with resolution 5472x3648, which are combined to 
make a video with resolution 1800x1200. Any pixel in the video must be 
calculated from 3x3 pixels in the input pictures.
The input pictures contain stars in the night sky which are slowly 
moving. Most stars are so small that they are just one pixel.
If I use a "nearest neighbor" algorithm, then the star will blink on-off 
in the video.
If I use any averaging algorithm, then the contrast will go down because 
the star is averaged with the dark neighbor pixels.
Which is the best algorithm in this case? I need something like the 
maximum value out of the 3x3 neighborhood.

3. Please improve the documentation. For example: ‘experimental’ Select 
experimental scaling algorithm.
Wow, that sounds interesting, but what does it do?

Thanks,
Michael


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       ASTRO ELECTRONIC   Dipl.-Ing. Michael Koch
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