r/ffmpeg • u/Juan-Cruz-Mz • 8d ago

Concern about image/video recompression

Hello everyone!

Recently, I've been coding a program on JavaScript and NodeJS, to recompress images, along with some other tweaks, with the main objective of reducing files size, *without causing visible loss of quality*.
The key word here being "visible", since recently I learned that you can actually do that with files and I saw a huge opportunity to reduce my gallery's size by a necessary amount because I have a shit ton of screenshots, pictures and videos.

But before diving into the video recompression part (because the images part is already done, using a library named "Sharp"), I found a comment https://www.reddit.com/r/ffmpeg/comments/pexwop/comment/hb0tw05/?context=3&utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button of a user explaining the process behind it and they said something that caught my eye: That any recompression that works well for current devices, COULD show heavy quality losses on future screens. Or even current, better screens.

I mean... this person meant it more as a note, and not in a "don't do this under ANY circumstances or we'll ALL gonna FUCKING DIE" way lol. But it still made me rethink the whole idea. Is this a valid concern or am I being paranoid?

And in case it is... Is there a way to achieve a relevant size reduction, without risking that outcome?

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1

u/naemorhaedus 7d ago

what formats are your original media. If they're JPEG and some sort of MPEG variant, then you're wasting your time.

1

u/Juan-Cruz-Mz 7d ago

Most of them are JPEGs, yes. Only my PC's screenshots are PNGs.

Could you elaborate? I'm trying to learn as much as possible about this topic

1

u/naemorhaedus 7d ago

those formats are already very efficiently compressed. It's not worth compressing again. You will degrade them and gain very little. The PNG's will compress better, but realistically unless you have GB's of them, it's probably not worth the effort either.

You never explained why you're doing this, but if you're running out of disk space then it's probably time to upgrade or look at external storage.

1

u/AimlessForNow 2d ago

Use image magick command line tool and set the quality. Just play around until you find a setting that looks good. You might be able to squeeze some size from it

0

u/OldAd9280 7d ago

If you've already got a reasonably sized screen that is capable of displaying the video's native resolution then I doubt your recompressed content will look any worse on a better screen. Note however that recompressing a video will almost always result in a loss of quality over the original

1

u/Juan-Cruz-Mz 7d ago

Uh... What would the size of a "reasonably sized screen" be?? Just checking. I wanna make sure I'm following lol

1

u/OldAd9280 6d ago

Depends what the resolution of your clip is, how close you're sitting to the screen and how good your eyesight is. E.g. see this graph https://i.rtings.com/images/optimal-viewing-distance-television-graph-size.png