[FFmpeg-user] why reducing the resolution a percentage doesn't reduce the video the same proportion?

Phil Rhodes phil_rhodes at rocketmail.com
Tue Mar 14 14:07:40 EET 2023

 Hi Natalia
This gets complicated, but in general it depends on the compression settings. "libx265" is capable of doing many different things. It's probably best if you look up some examples of how that works because it's too much to explain here, and examples will help.
Also, it depends what you mean by 50% of the resolution. If your original video is 100x100 pixels and you reduce it to 50x50, then you have half the resolution, but you only have one quarter the pixels.
    On Tuesday, 14 March 2023 at 09:37:36 GMT, Natalia Molinero Mingorance <eng.nataliamolinero at gmail.com> wrote:  
 I'm using this command:

-y -r -i $inVideoUri -movflags faststart -c:v libx265 -s
$videoResolution -c:a copy -preset ultrafast  $outPutUri"

However, if "videoResolution" is a 50% of the original video resolution,
the resulting file size is not 50% of the original one. I assume there are
some headers or metadata added during the process but I would like to know
how to estimate the final video size.
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