8 ms·
It's easier than ever to de-censor videos
- mikelitoris 2y agoDoes this guy look like Eminem or what?
- JKCalhoun 2y agoYeah, that is pretty wild. I recall a co-worker doing something related(?) for a kind of fun tech demo some ten years or so ago. If I recall it was shooting video while passing a slightly ajar office door. His code reconstructed the full image of the office from the "traveling slit". I think about that all the time when I find myself in a public bathroom stall.... :-/
- Agree2468 2y agoLine scan cameras operate on this principle, and are still used in various ways to this days. I'm especially partial to the surreal photos generated by them at the end of cycling races https://finishlynx.com/photo-finish-trentin-sagan-tour-de-france/ https://finishlynx.com/photo-finish-trentin-sagan-tour-de-fr...
- JKCalhoun 2y agoI was not aware of those. Reminds me of slit-scan as well. And of course rolling shutters.
- whycome 2y agoSimilar to https://hackaday.com/2024/08/17/olympic-sprint-decided-by-40000-fps-photo-finish/ https://hackaday.com/2024/08/17/olympic-sprint-decided-by-40...
- hifikuno 2y agoI love line scan cameras. Wikipedia has an awesome photo of a tram taken with a line scan camera on the relevant wiki page[1]. I've just moved to a house with a train line track out front. I want to see if I can use a normal camera to emulate a line scan camera. I have tried with a few random YouTube videos I found [2]. I think the biggest issue I face is that there simply isn't the frame rate in most camera's to get a nicely detailed line scan effect. --- [1]: https://en.wikipedia.org/wiki/Line-scan_camera https://en.wikipedia.org/wiki/Line-scan_camera [2]: https://writing.leafs.quest/programming-fun/line-scanner https://writing.leafs.quest/programming-fun/line-scanner
- mkl 2y agoA normal frame rate is probably enough if you do it with groups of columns rather than a single column of pixels. That's what https://trains.jo-m.ch/ https://trains.jo-m.ch/ does with a Raspberry Pi camera, posted in https://news.ycombinator.com/item?id=35738987 https://news.ycombinator.com/item?id=35738987 with lots of questions and answers.
- hifikuno 1y agoOh wow that's neat! I honestly didn't think of using chunks instead of a single line and the result looks pretty good. I love the fact the top (or first?) comment is by dllu, and looking on their webpage I saw the tram photo from Wikipedia! It's cool to see the photographer talking about their work. I think about that tram photo so much.
- nkrisc 2y ago> I think about that all the time when I find myself in a public bathroom stall.... :-/ Walk past a closed bathroom stall fast enough and you can essentially do that with your own eyes. Or stand there and quickly shift your head side to side. Just don't do it on one that's occupied, that's not cool.
- donatj 2y ago"Sir, why do you keep running back and forth in the bathroom?"
- altruios 2y agoThe dither effect. Same as seeing through splayed fingers on a franticly oscillating hand.
- messe 2y ago> Walk past a closed bathroom stall fast enough and you can essentially do that with your own eyes Only in the US. The rest of the world has doors without a gap at the sides.
- freddie_mercury 2y agoDoors in Vietnam are exactly the same as in the US. You clearly haven't traveled much so you should refrain from sweeping generalisations.
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- MisterTea 2y ago> His code reconstructed the full image of the office from the "traveling slit". This method is commonly used in vision systems employing line scan cameras. They are useful in situations where the objects are moving, e.g. along conveyors.
- geerlingguy 2y agoEven today most cameras have some amount of rolling shutter—the readout on a high-megapixel sensor is too slow/can't hold the entire sensor in memory instantaneously, so you get a vertical shift to the lines as they're read from top to bottom. Global shutter sensors of similar resolution are usually a bit more expensive. With my old film cameras, at higher shutter speeds, instead of opening the entire frame, it would pass a slit of the front/rear shutter curtain over the film to just expose in a thousandth of a second or less time.
- rosswilson 2y agoThis reminds me of https://github.com/jo-m/trainbot https://github.com/jo-m/trainbot, a neat example of stitching together frames of passing trains to form a panorama. This frontend presents them nicely: https://trains.jo-m.ch https://trains.jo-m.ch
- stevage 2y agoSurprised I've never come across this idea before
- all2 2y agoFor a long time I've wanted to install one of these to pull graffiti off of trains. As art goes, graffiti is one of the last 'free' expressions where it is essentially truly anonymous and definitely not for money. Being free of those constraints, I think, frees the mind to truly create. And I'd love an archive somewhere of some of the truly awesome train art I've seen.
- jo-m 2y agohere you go... https://trains.jo-m.ch/#/trains/44010 https://trains.jo-m.ch/#/trains/44010
- quietbritishjim 2y agoSorry if you're already aware, but in case not: The weird huge gap around the edge of cubical doors in pubic toilets is specific to the US. (For those that don't know, it's literally 1 or 2 cm.) In Europe you just get a toilet door that shuts properly and there's no slit to reconstruct. I remember my first visit to a toilet in the plush US office of a finance company and thinking WTF are they doing with their toilet cubicle? I only found out later that it's common there.
- stevage 2y agoIt can be much more than 2cm. The US really hates people for some reason.
- fc417fc802 2y agoI believe it started as an anti-drug thing more than 50 years ago but somehow it became pervasive even in fairly high end settings where you would never expect such measures. Cargo cult bathroom construction IMO. Luckily things seem to be gradually changing.
- nkrisc 2y agoI am aware, and of course this works for any gap you might be walking past. Plenty of newer bathroom stalls here do not have a gap.
- nzach 2y agoAnd if you "reverse" this idea you can make a "holographic(?) display"[0]. [0] - https://www.youtube.com/watch?v=ric-95ig5oE https://www.youtube.com/watch?v=ric-95ig5oE
- brunosutic 2y agoI like this Jeff Geerling guy.
- ge96 2y agohe's like THE or was THE raspberry pi guy
- its-summertime 2y agoSpeaking of, the Lockpicking Lawyer's "Thank you" video https://www.youtube.com/watch?v=CwuEPREECXI https://www.youtube.com/watch?v=CwuEPREECXI always irked me a bit, yeah its blurred, but as can be seen, (and as was possible back then, and way before then too, recovering poor data from windowed input has been a thing for 50+ years (e.g. radio signals, scanning tools, etc), if you think about it, its a cheap way to shift costs from physical improvement to computational improvement, just have a shutter), and yet he didn't block the information out, only blurred it
- IshKebab 2y agoThat's a totally different scenario. You can't unblur that video.
- its-summertime 2y agoWhy not? Would you be willing to stake hypothetical customer data on your assumptions?
- IshKebab 2y agoBecause in real videos where blurring is done by physical processes there is too much additional noise and uncertainty in the blurring process. Unblurring is an extremely ill-posed problem so any noise or modelling errors get massively amplified. In only works in this case because there is essentially zero noise, and the correlation between source frames is an exact move. Yes I would stake hypothetical customer data on this.
- wodenokoto 2y agoTo save others a click: the video is a pile of customers packages with addresses ready to send. “It’s” are the Address lines, which are blurred instead of blacked or whited out, potentially revealing customers private information.
- formerly_proven 2y ago> Intuitively, blur might do better than pixelation... but that might just be my own monkey brain talking. I'd love to hear more in the comments if you've dealt with that kind of image processing in the past. A pixelization filter at least actively removes information from an image, a Gaussian blur or box blurs are straight up invertible by deconvolution and the only reason that doesn't work out of the box is because the blurring is done with low precision (e.g. directly on 8-bit sRGB) or quantized to a low precision format afterwards.
- deleted 2y ago[deleted]
- danjl 2y agoExactly. Do not use blur to hide information. Blurring simply "spreads out" the data, rather than removing it. Just search (you know, on Google, without an LLM) for "image unblur".
- kccqzy 2y agoEven if the precision is low, the deconvolution process you described is still good enough to reconstruct the original text in the majority of cases.
- AdmiralAsshat 2y agoMy Windows-98 approved method for redacting a screenshot: 1) Open screenshot in MS-Paint (can you even install MS-Paint anymore? Or is it Paint3D now?) 2) Select Color 1: Black 3) Select Color 2: Black 4) Use rectangular selection tool to select piece of text I want to censor. 5) Click the DEL key. The rectangle should now be solid black. 6) Save the screenshot. As far as I know, AI hasn't figured out a way to de-censor solid black yet.
- remram 2y agohttps://jspaint.app/ https://jspaint.app/ (https://github.com/1j01/jspaint https://github.com/1j01/jspaint)
- murdockq 2y agoWow glad to see there were other fans of MSPaint, can't believe I built my open source version with wxWidgets 16 years ago https://github.com/murdockq/OpenPaint https://github.com/murdockq/OpenPaint
- jebarker 2y agoThat's going to be a lot of work for a YouTube video though
- JimDabell 2y agoIt’s possible, depending upon the circumstances. If you are censoring a particular extract of text and it uses a proportional font, then only certain combinations of characters will fit in a given space. Most of those combinations will be gibberish, leaving few combinations – perhaps only one – that has both matching metrics and meaning.
- HPsquared 2y agoNot forgetting subpixel rendering.
- its-summertime 2y agoThere was a programming competition, can't remember which, similar to IOCCC but more about problematic software? where the redaction was reversible despite being pure black, due to the format chosen allowing for left over information in the image (vastly reduced quality but it was enough to allow text to be recovered!) [edit: see replies!] There was also the Android (and iOS?) truncation issue where parts of the original image were preserved if the edited image took up less space. [edit: also see replies!] Knowing some formats have such flaws (and I'm too lazy to learn which), I think the best option I think is to replace step 6 with "screenshot the redacted image", so in effect its a completely new image based on what the redacted image looks like, not on any potential intricacies of the format et al.
- Funes- 2y agoJapanese porn is being "decensored" with AI as we speak, in fact. It looks a tad uncanny, still, but finding a "decensored" clip in the wild was quite the thing for me a couple of weeks ago.
- internetter 2y agoThis is a completely different process — the AI is inferencing what goes there, it isn't actually using any information from the pixels so it wouldn't work in this case. Not to mention deeply and disturbingly unethical
- gjsman-1000 2y agoSo let me get this straight: Porn can be ethical - selling your nude features online can be ethical - doing the activities in porn consensually can be ethical - pleasuring yourself on other people doing so can be ethical - but using AI to infer nude features is "disturbingly unethical"?
- ziddoap 2y ago>but using AI to infer nude features is "disturbingly unethical"? If it is against the wishes of the people in the video, yes, yes it is. E: Never thought I'd see the day I'm downvoted for saying un-blurring porn of people who made porn under the assumption that it would be blurred (and may not have made that same decision without that context) is unethical, on HN of all places, but times are strange I guess.
- zoky 2y agoI also have a network share named “mercury” connected to my Mac, and that last example nearly made me shit myself.
- geerlingguy 2y agoHa! I name most of my shares after celestial bodies... Jupiter is the big 100 TB volume for all my archives. Mercury is an all-NVMe volume for speed, for my video editing mostly.
- zoky 2y agoHeh, mine is actually called mercury because I took to naming all of my homelab systems after Roman and Greek mythology, so the server was called “minerva” because of the knowledge it stores, and the share name was “mercury” because it was the messenger between myself and minerva… I swear I was going for something with this, LOL!
- deleted 2y ago[deleted]
- HPsquared 2y agoI wonder how much random noise (or other randomness) would have to be added to the pixelated version to make this method unusable.
- miki123211 2y agoIf you really want that blur effect so badly, you can just replace your content with something innocuous, and then blur that innocuous content. This is what you actually have to do with websites, e.g. when you want some content blurred when it's behind a paywall. If you leave the original text intact, people can just remove the CSS blur in dev tools. Some implementations get this slightly wrong, and leave the placeholder content visible to accessibility tools, which sometimes produces hilarious and confusing results if you rely on those.
- wlesieutre 2y ago> If I hadn't moved around my Finder window in the video, I don't think it would've worked. You might get a couple letters right, but it would be very low confidence. > Moving forward, if I do have sensitive data to hide, I'll place a pure-color mask over the area, instead of a blur or pixelation effect. Alternately - don't pixelate on a stationary grid when the window moves. If you want it to look nicer than a color box but without giving away all the extra info when data moves between pixels, pixelate it once and overlay with a static screenshot of that. For bonus points, you could automate scrambling the pixelation with fake-but-real-looking pixelation. Would be nice if video editing tools had that built in for censoring, knowing that pixelation doesn't work but people will keep thinking it does.
- geerlingguy 2y agoThat's another good way to do it. I wonder if it might be good for the blur/censor tools (like on YouTube's editor even) to do an average color match and then add in some random noise to the area that's selected... Would definitely save people from some hassle.
- wlesieutre 2y agoThe part that might take some work is matching the motion correctly, with a pixelated area or blacked out rectangle it doesn't matter if it's exactly sized or moving pixel perfectly with the window. I haven't done any video editing in 20 years, so maybe that's not very difficult today? That moving pixelation look is definitely cooler though. If you wanted to keep it without leaking data you could do the motion tracked screenshot step first (not pixelated, but text all replaced by lorem ipsum or similar) and then run the pixelation over top of that. If any of you nerds reading this are into video editing, please steal this idea and automate it.
- IshKebab 2y agoYeah this scenario is purposefully chosen specifically to make this attack possible. It's basically irrelevant in the real world.
- BoredPositron 2y agoBad blackout jobs are in the news since the 50s and every time an expert tells the same solution. If you want to censor something remove the information.
- nightpool 2y agoEasier said than done if you're using a proportional font though
- Calwestjobs 2y agoblack box is black box, or other more pleasing color.
- nightpool 2y agohttps://arxiv.org/pdf/2206.02285 https://arxiv.org/pdf/2206.02285 In this work we find that many current redactions of PDF text are insecure due to non-redacted character positioning information. In particular, subpixel-sized horizontal shifts in redacted and non-redacted characters can be recovered and used to effectively deredact first and last names. Information-theoretic attacks work on black boxes too
- deleted 2y ago[deleted]
- lynndotpy 2y ago> Years ago it would've required a supercomputer and a PhD to do this stuff This isn't actually true. You could do this 20 years ago on a consumer laptop, and you don't need the information you get for free from text moving under a filter either. What you need is the ability to reproduce the conditions the image was generated and pixelated/blurred under. If the pixel radius only encompasses, say, 4 characters, then you only need to search for those 4 characters first. And then you can proceed to the next few characters represented under the next pixelated block. You can think of pixelation as a bad hash which is very easy to find a preimage for. No motion necessary. No AI necessary. No machine learning necessary. The hard part is recreating the environment though, and AI just means you can skip having that effort and know-how.
- cogman10 2y agoIn fact, there was a famous de-censoring that happened because the censoring which happened was a simple "whirlpool" algorithm that was very easy to unwind. If media companies want to actually censor something, nothing does better than a simple black box.
- lynndotpy 2y agoAh yes, Mr. Swirl Face. This was pretty different though. The decensoring algorithm I'm describing is just a linear search. But pixelation is not an invertible transformation. Mr. Swirl Face just applied a swirl to his face, which is invertible (-ish, with some data lost), and could naively be reversed. (I am pretty sure someone on 4chan did it before the authorities did, but this might just be an Internet Legend).
- Modified3019 2y agoA long while ago, taking an image (typically porn), scrambling a portion of it, and having others try to figure out how to undo the scrambling was a game played on various chans.
- cjbgkagh 2y agoChristopher Paul Neil is a real person who went to jail.
- bob1029 2y agoIt would seem techniques like this have been used in domains like astronomy for a while. > The reconstruction of objects from blurry images has a wide range of applications, for instance in astronomy and biomedical imaging. Assuming that the blur is spatially invariant, image blur can be defined as a two-dimensional convolution between true image and a point spread function. Hence, the corresponding deblurring operation is formulated as an inverse problem called deconvolution. Often, not only the true image is unknown, but also the available information about the point spread function is insufficient resulting in an extremely underdetermined blind deconvolution problem. Considering multiple blurred images of the object to be reconstructed, leading to a multiframe blind deconvolution problem, reduces underdeterminedness. To further decrease the number of unknowns, we transfer the multiframe blind deconvolution problem to a compact version based upon [18] where only one point spread function has to be identified. https://www.mic.uni-luebeck.de/fileadmin/mic/publications/StudentProjects/MasterTheses/Masterthesis_HSchomburg.pdf https://www.mic.uni-luebeck.de/fileadmin/mic/publications/St... https://en.wikipedia.org/wiki/Blind_deconvolution https://en.wikipedia.org/wiki/Blind_deconvolution
- Havoc 2y agoThat was a cool vid. I recall interpol doing similar a couple years back to bust a dodgy kids image ring. That was a swirl though which I guess is mathematically easier
- vault 2y agoI noticed the link in Jeff's post to RX 10 Elements Noise Reduction. The audio in their YouTube presentation was not horrible at all though. Has anybody tried it with some real horrible recording? Like those from a blink mini camera in a room without furniture.
- geerlingguy 2y agoI have, I was going to go for a more extreme example but couldn't find one quickly on their channel. It's not perfect, by any means, but you can get intelligible speech from a pretty terrible recording at least. Adobe has their AI assist tool too, it works pretty well though I've found it can't isolate a speaker when there are a lot of other people talking nearby.
- draw_down 2y ago[dead]
- marcodiego 2y ago> For the second attempt, GIMP was used to get a better window selection algorithm with ffmpeg, and with a slight bit more data (more frames extracted), a perfectly legible result Take that adobe.
- mrlonglong 2y agoSo it's now possible to redub phrases such as melon farmers with the real swears?
- taf2 2y agoGiving the final image at 13 seconds to ChatGPT and I wonder if this is pretty close... https://x.com/taf2/status/1912260125278032228 https://x.com/taf2/status/1912260125278032228
- syntaxing 2y agoReminds me of the "swirl face". [1] https://matzjb.se/2015/07/26/deconstructing-swirl-face/ https://matzjb.se/2015/07/26/deconstructing-swirl-face/
- feverzsj 2y agoYou should try "AV-8500 Special" from 90s' Japan. [0] https://groups.google.com/g/alt.video.laserdisc/c/Ws6h9uiumFo https://groups.google.com/g/alt.video.laserdisc/c/Ws6h9uiumF... [1] https://x.com/nabetora164/status/1660981662006775809 https://x.com/nabetora164/status/1660981662006775809
- netsharc 2y agoI once thought the publishers of those videos would use a reversible algorithm, as malicious compliance... Or having the pixelated parts be a particular pattern, and then releasing an XOR video to get the original footage..
- HocusLocus 2y agoThe Bell Labs A-3 scrambler used real time band inversion and transposition and was 'snake oiled' into the commercial market, but under the pressure of WWII it fell quickly. It was bad enough it was self-clocked and a German engineer had helped design it. But even more embarrassing was, without having to reverse engineer the circuit, humans could train their ears to recognize individual speakers and even words. Today we take for granted the ability to conjure a complicated pseudorandom digital stream for keying, but in those days it was just "no can do". In WWII... SIGSALY was the first system secure by modern standards. Pairs of synchronized one-time phonographic records containing a sequence of tones seeded from a noise source.
- Calwestjobs 2y agosuperresolution is here for 20+years, even GPUs use that now... geerling is clickbait. maybe this youtube channel will be interesting https://www.youtube.com/@mikirubinstein https://www.youtube.com/@mikirubinstein so if we could do that 12 years ago, debluring/depixelating of video should be easy
- luk4 2y agoIt's worth noting that it could have dramatic consequences for some people. In France, public television raised the alarm a few years ago about the anonymization of voices and the blurring of faces of investigative sources. As a result, an anonymization policy has been implemented requiring that voices be replaced by an actor reading the text and that people be filmed from behind at the very least, or even replaced by an actor altogether. More problematic are the archives of past investigations, which put people like political dissidents and witnesses against organized crime or the mafia at high risk of suffering retaliation. To mitigate this risk, tens of videos have been taken down, and efforts have been made to contact those who may be affected. https://larevuedesmedias.ina.fr/urgence-france-televisions-inventer-le-floutage-de-demain https://larevuedesmedias.ina.fr/urgence-france-televisions-i... (in french)