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Author Topic: The Generic Computer Advice Thread  (Read 177429 times)

milo christiansen

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Re: The Generic Computer Advice Thread
« Reply #3645 on: May 07, 2018, 09:48:41 am »

No, it does not. You need some kind of converter.

However, why do you want to do that? Converting to PNG does not magically recover the quality lost to JPG.
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scriver

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Re: The Generic Computer Advice Thread
« Reply #3646 on: May 07, 2018, 10:19:14 am »

Of course not, but it stops further loss of quality.
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wierd

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Re: The Generic Computer Advice Thread
« Reply #3647 on: May 07, 2018, 10:40:28 am »

Pretty much all cameras use jpeg compression. They do this for a number of reasons.

1) it lets them use lacklustre ccds that aren't the most consistent (jpeg compression averages regions, and blurs out the anomalous pixels)

2) it let's them use cheaper/slower nand, because a jpeg is smaller than raw pixels.

3) there are cots hw accelerated jpeg compression chips they can leverage to get jpeg format data from a CCD very quickly and cheaply.

I too have longed for a high quality camera that can optionally capture as PNG (Software compress raw mode data, save as PNG) even if it is slow to take pictures and drains battery.

Such devices don't exist. It was hard to convince camera makers to even offer raw saving as an option, and only really expensive cameras support it.
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Japa

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Re: The Generic Computer Advice Thread
« Reply #3648 on: May 07, 2018, 12:46:56 pm »

Fun fact! Most canon point and shoot cameras support third party firmware that can enable raw saving.

Reelya

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Re: The Generic Computer Advice Thread
« Reply #3649 on: May 07, 2018, 11:23:27 pm »

No, it does not. You need some kind of converter.

However, why do you want to do that? Converting to PNG does not magically recover the quality lost to JPG.

Of course not, but it stops further loss of quality.

"further loss of quality" for a JPG only makes sense if you edit the photo in an editing suite, make changes and save it again, and choose JPG deliberately. Storing, copying, and viewing JPG files doesn't change them at all. Converting to PNG just gives you a PNG that looks exactly like the JPG. So if you've got jpg photos then you can just leave them as JPGs and not worry about any loss of quality: the loss of quality was a one-time thing when the file was first created.

The only time they can get further degraded is if you open them in a photo-editing program, and save them again as a lossy format, especially if the format isn't exactly the same as the original JPG, or if you make changes such as applying filters to the whole image, or cropping it (since that usually throws the JPG blocks out of alignment). The rule of thumb here is to just leave your image files alone as whatever format they happen to be in, but remember to choose PNG for saving, when you edit pictures in a paint program. It makes literally zero difference if you convert them to PNG before editing.

~~~

Some of the new AI-based filters might help out in the near future. The premise is that they train the AI on millions of "sample" pairs of high-quality / low-quality versions of the same images, teaching it to repair the damage on the low-quality images so that they look as much like the high-quality images as possible.

You can then use the resultant neural network to clean up other images. However, the closer the training set resembles the data you wish to clean, the better. e.g. if you had low-quality JPGs of anime images, and wanted to upscale them while removing JPG compression artifacts, you'd want to get a huge number of high-quality anime images, downscale them, then convert to JPG, with as close to the same settings as possible as the images you wish to clean up. Then teach an NN to reverse that specific degradation for that specific class of images, and you'd have a custom filter which was really, really good at repairing images exactly like those ones.

EDIT the concept here is that if you teach an NN to upscale images of e.g. ... WWII planes, then it becomes really good at working out what WWII planes are meant to look like, so when you give it a new image of an unknown WWII plane, it fills in missing details intelligently, rather than just using a generic upscale filter. Sure, it will still upscale other types of things and might do passably ok, but it's going to be really good at the class of things it was trained on. In the future there might even be intelligent online filters that work out what something is, e.g. object and edge-detection, then apply specifically trained filters to subregions of the photo which hold those things. e.g. if there's a blurry plane and a blurry tree, it could apply different upscale filters to both regions of the photo, and do better than applying only one filter to the whole photograph.
« Last Edit: May 08, 2018, 12:29:20 am by Reelya »
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Maximum Spin

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Re: The Generic Computer Advice Thread
« Reply #3650 on: May 08, 2018, 01:52:56 am »

On the other hand, having an AI designed to upscale WWII planes run on a set of low-quality animu jpegs would be hilarious.
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scriver

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Re: The Generic Computer Advice Thread
« Reply #3651 on: May 08, 2018, 02:11:16 am »

Ah, I see. I was under the impression .jogs decrepited every time you copied them. How else would pics on the webs artifactify?
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wierd

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Re: The Generic Computer Advice Thread
« Reply #3652 on: May 08, 2018, 02:24:20 am »

JPEG has a configurable option at compression time to determine the quantization matrix. (EG, how much data to cut out using the quantizer). This is usually given the name "Quality".

When people make images for the web, they usually want to make the file size as tiny as possible, which means they crank the quantizer really hard (turn quality really low).  The result is really noticeable artifacts.

It is important to understand what an artifact is, and how it gets generated. JPEG looks for edges inside a fixed rectangle 'tile' of the image, then averages the pixels that do not meet edge threshold, and have similar color values. The issue, is that the average of one tile, and another, (especially with a very high quantization value) can be noticeably different.  This creates a rectangular artifact.

When the quantizer is not set on "Mangle! DEATH TO QUALITY!" settings, JPEG does not look that bad on natural images.  However, hosting companies dont want to pay for people downloading a 300kb jpeg on every visit. Instead, they want users to download 30kb jpeg on every visit. (Or smaller!!). So, they set the quantizer to MANGLE! and go on.

Most cameras (most..... ...) dont set the quantizer on MANGLE when they generate the jpeg from the CCD array's output. They still produce artifacts, just not really horrible ones. They only show up on post processing because the tile boundaries are what they are, and averages are averages. If you try to enhance edges, the edges between tiles will also be enhanced, for some algorithms. This makes JPEG undesirable for professional photography, and why professional cameras have the option to save as RAW.
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Reelya

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Re: The Generic Computer Advice Thread
« Reply #3653 on: May 08, 2018, 02:50:42 am »

Ah, I see. I was under the impression .jogs decrepited every time you copied them. How else would pics on the webs artifactify?

A normal copy is the same size and is digitally identical to the original, like copying any other type of file.

The degradation could happen if a site is storing all images in lossy formats, but then they decided to re-format the files with higher compression to reduce bandwidth costs. That would compound the problem: the new format is more lossy than the old one, but it's also not working from a clean version, but from another lossy version.

e.g. say the first filter lost 10% of detail, and the second filter lost 20% of detail (with linear reduction of file size). If you applied filter 1 to a raw image, you have 10% loss, and if you apply filter 2 to an image you have 20% loss. However, say you didn't store original images anywhere, to save space, then apply filter 2 to images that already used filter 1, then you're down to 72% detail, but the real kicker is that the file still takes up the same amount of space as one with only 20% detail loss created from the original file.

So, not storing original clean images actually backfires in terms of bandwidth, since if you always convert from 100% perfect copies you can compress the resultant images to smaller sizes for less perceptual loss of detail compared to trying to shrink an already-shrunk image.
« Last Edit: May 08, 2018, 02:59:00 am by Reelya »
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scourge728

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Re: The Generic Computer Advice Thread
« Reply #3654 on: May 12, 2018, 11:09:55 pm »

Can someone recommend me a good (free) defragmenter, preferably with a link to it's website, as I don't really know what to look for and REALLY don't want a virus

wierd

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Re: The Generic Computer Advice Thread
« Reply #3655 on: May 12, 2018, 11:12:40 pm »

Defraggler from Piriform. (It's from the same people as ccleaner and pals.)

https://www.ccleaner.com/defraggler
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IronTomato

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Re: The Generic Computer Advice Thread
« Reply #3657 on: May 16, 2018, 12:41:35 pm »

No, it does not. You need some kind of converter.

However, why do you want to do that? Converting to PNG does not magically recover the quality lost to JPG.

Of course not, but it stops further loss of quality.

"further loss of quality" for a JPG only makes sense if you edit the photo in an editing suite, make changes and save it again, and choose JPG deliberately. Storing, copying, and viewing JPG files doesn't change them at all. Converting to PNG just gives you a PNG that looks exactly like the JPG. So if you've got jpg photos then you can just leave them as JPGs and not worry about any loss of quality: the loss of quality was a one-time thing when the file was first created.

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heydude6

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Re: The Generic Computer Advice Thread
« Reply #3658 on: June 03, 2018, 04:45:23 pm »

If you guys frequent the wtf thread, you might remember this post:

My microsoft edge seems to have some sort of corruption issue. I knew it was wonky with pdfs, but this is the first time I used it normally and I got this:
Pretty creepy. Any idea how to fix?

Anyway, VLC media player and discord are starting to show the same kind of issue now. Can someone offer me a solution this time, rather than a joke please. This is pretty serious, I won't be able to play videos or game online with my friends now. Audio still works fine in VLC so I assume it's some sort of bug with the way windows is displaying images.
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Reelya

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Re: The Generic Computer Advice Thread
« Reply #3659 on: June 03, 2018, 04:54:10 pm »

If everything is doing it, your video card is broken. You can try removing the video card drivers and reinstalling them.

You can also try reducing or disabling hardware acceleration for video:
http://www.thewindowsclub.com/hardware-acceleration-windows-7

---

I also highly recommend mpv as a media player. It has customizable decoder and renderer settings so you can change hardware vs software decoding etc. It's worth a shot if nothing in VLC is working, since there are many more options here. You can use it raw or get it bundled with a front-end / library manager type deal (there are about 10 different projects to choose from, seek wikipedia). But I just use the vanilla version.

https://www.omgubuntu.co.uk/2017/02/swap-vlc-mpv-ubuntu
Main site:
https://mpv.io/
Windows build repo:
https://mpv.srsfckn.biz/

It's not an "installer" app, just extract it to a folder, right click on your video, then use Windows "open with" to find mpv.exe. however it does a shitload of things most players won't let you do. It's also incredibly good at not completely sucking if you need to run it on old hardware. (though they dropped XP support a while ago so if you need XP version ask me for the last compatible build).

e.g. I built an old machine for someone else, some high-end videos wouldn't play because they couldn't be decoded fast enough, so I put mpv on there, turned on decoder frame-skipping, plus renderer-frame-skipping, and a third option that occasionally resyncs the video by force, and then the videos would play and not fall out of sync. No fucking chance of VLC working correctly for something like that, which is the very reason I dumped VLC originally, for mplayer2 (precursor to mpv). mplayer2 just worked correctly, after setting a couple of options, for videos which were horrendously broken in VLC, no matter what I did.

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« Last Edit: June 04, 2018, 02:54:08 am by Reelya »
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