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Microscopes can see video on a laserdisc
- BobMcBob 8mo agoTech Tangents is one of the best retro channels on youtube but by retro I dont mean glorified nostalgia either. Shelby puts a lot of work into his videos and likes to showcase what awesome engineering went into some of the early tech that was practically magic. Love the channel and glad to see it on HN.
- smusamashah 8mo agoSo CAV (constant angular velocity) is an encoding format for laser disks. When something is written with CAV, it is basically analogue data and therefore repeating patterns can be recognized on the disk.
- jmkd 8mo agoNot simply repeating patterns, readable text from the credits as shown in the video.
- accrual 8mo agoHere's where the text comes into focus, pretty cool: https://youtu.be/qZuR-772cks?t=1540 https://youtu.be/qZuR-772cks?t=1540
- wtallis 8mo agoNo, CAV has nothing to do with encoding, and both analog and digital formats have used both CAV and CLV and hybrids of the two. The legible text seen in the microscope images happens because of the combination of LaserDisc recording a raw and uncompressed encoding of the analog video signal, the way that LaserDisc used CAV to store an integer number of frames per track so that the image data for corresponding on-screen locations of subsequent frames would be aligned at the same radial position on the disc, and the credits scrolling vertically at constant speed. If LaserDisc had used a digital encoding (especially a compressed encoding), the data on disc may still have had discernible patterns but the text would not necessarily have been legible. If it had used CAV but not stored a whole number of frames per track, then temporal and spatial locality on screen would not have corresponded so well to spatial locality on disc. And the vertically-scrolling credits are pretty much the only kind of content that can produce the recognizable and legible images on the disc surface. I think the fact that the aspect ratio of the text came out approximately right probably is a consequence of the scrolling speed of the credits being chosen to suit the vertical resolution of the video. If the text had appeared squished in the microscope, it would probably have been moving too fast on screen to be clearly legible.
- xattt 8mo agoIs the image seen via microscope basically a readout of the image on a spectroscope? Those can have near-legible images, but most of the time they are not.
- wtallis 8mo agoFor the images seen through the microscope, the horizontal axis is the same as the horizontal axis of the video. The vertical axis of what the microscope sees is the time axis of the video: it's essentially a slit camera view of a particular individual scan line position within the frame.
- Zafira 8mo agoSorta? The data being written to the disk is the same in CAV or CLV disks, but the player just needs to know how to spin the disk at the right speed so that the laser can read the pits/lands correctly. It is purely a detail about the speed that the disk is spun at so they can cram more data on it with CLV disks. What CAV LaserDiscs allow for, though, is to make it extremely obvious where scanlines and blanking intervals are in the video signal.
- VerifiedReports 8mo agoNo; it's strictly a reference to constant RPM or variable RPM. CAV discs contained one frame per rotation. While this meant you could only fit half an hour on one side of a disc, it did give you perfect slow-motion and freeze-frames. I worked in a video store and loved LaserDiscs. The Duran Duran video album was CAV, and the Pioneer LD-700 had such a fast transport mechanism and remote control that I could to DJ-style "scratching" with it.
- VorpalWay 8mo agoThe live stream of this had more interesting things as well, such as looking at the ink on mimeographs compared to inkjet printing. Long and rambly as live streams tend to be, but it is there if anyone cares. https://m.youtube.com/watch?v=zIsCswtkozI https://m.youtube.com/watch?v=zIsCswtkozI (mimeograph around 3:36:00 mark)
- amelius 8mo agoBut the opto mechanical parts of a laserdisc reader are way more interesting than a microscope.
- rustyhancock 8mo agoHere's a screen capture of the end credits visible on the disc the videos worth it but I do think sometimes you need to start with the money shot https://ibb.co/v4KK88fF https://ibb.co/v4KK88fF
- crazydoggers 8mo agoThis is from a CED not a laserdisc.
- iamtedd 8mo agoIf you watch the video, he looked at both.
- crazydoggers 8mo agoYes, but the end credits mentioned by the parent and the link to the image is the CED. That and the title of this post make it seem like this level of image clarity is from a LaserDisc which its not. I think it's worth being clear.
- jmkd 8mo agoWatch the video if you believe it's worth being clear. The credits are perfectly visible on both the LaserDisc AND the CED. Approx 22:00-24:00 is the laser disc and 25:00 onwards is the CED. Enjoy.
- jmkd 8mo agoWow. Downvoted for factual clarification and helpful citation. No idea what drives such people, but must logically assume deception and obfuscation.
- irl_zebra 8mo agoUgh, I'm pretty sure it's Big CED deceptively here to muddy the waters and obfuscate superior LaserDisc Technology. Perhaps flag the post so the moderators can see it and make sure we root Big CED out of these forums and out of our lives for good.
- ralferoo 8mo agoActually amazing being able to read the text like that, and on two different types of discs. Great video, was much better than I was expecting it to be from the title!
- csours 8mo agoNot nearly as cool, but I was able to show a colleague the letters in a raster image section of a pdf using xxd by varying the output width
- EvanAnderson 8mo agoI wrote a simple tool, when I was a kid, that dumped binaries into VGA mode 0x13 and allowed me to vary the width. Mode 0x13 is one byte per pixel so it was just a simple REP MOVSB to put data into the buffer (no worrying about bitplanes). It was so useful in reverse engineering software. Besides raster data, regular data structures often jump out.
- Retr0id 8mo agoFun fact, if you load a file with extension ".data" into GIMP there's a UI where you can set the pixel format and adjust the width/height with sliders
- userbinator 8mo agoPhotoshop does the same with the .raw extension.
- CamelCaseCondo 8mo agoI did the same thing to evaluate random number generators by drawing pixels with the count value. You see a pattern, line or clusters? Bad generator.
- sixothree 8mo agoI feel like everyone needs a peek inside a file in this manner at least once in their life. I just like to show people various file headers. Without you showing them, they might never see this kind of stuff.
- oofbey 8mo agoFun fact about laser discs. They are analogue not digital. CD’s store digital information with the presence or absence of pits. Fairly ancient but still fundamentally feels like a very old version of a thumb drive. Laser discs are not digital. They encode the analogue video signal’s value as the length of the pit. It is digitized in the time domain - sampled at some frequency, but the “vertical” signal value is stored entirely analogue. In terms of encoding it’s more similar to a VHS tape than a CD. Kinda crazy.
- a-dub 8mo agoyeah i remember learning this as a kid and being surprised. i originally thought laserdiscs were modern high tech, but then they turned out to actually be from the late 70s/early 80s with the primitive analog video encoding where red book audio cds of the mid to late 80s were actually digital.
- mh- 8mo agoI just learned this in my 40s and am surprised. Very cool.
- VerifiedReports 8mo agoBUT... Pioneer put AC-3 (Dolby Digital) surround on LaserDiscs before DVDs came out. So LaserDiscs were the first video medium to offer digital sound at home. And at that point, most players sold were combo players that could also play CDs. And there was one more disc format: CD Video. It was a CD-sized digital single that also had a LaserDisc section for the (analog) music video. I have a couple; one is Bon Jovi.
- throwaway85825 8mo agoWas CD video compressed? I thought it existed at the same time as DVD but cheaper.
- yourusername 8mo ago
- JohnnyLarue 8mo ago[dead]
- SV_BubbleTime 8mo agoVery cool but, I was hoping he was going to spin it and align with the camera’s refresh rate.
- system2 8mo agoThat would be cool with a variable motor and a 3d printed mount maybe.
- macshome 8mo ago[flagged]
- onnimonni 8mo agoI'm not that familiar with CED but the fact that we can see the images with microscopes is because these are analog discs? And that was because computing power back then was non-existent so they didn't use any kind of compression?
- throwaway27448 8mo agoThis is a distinction without meaning: all digital anything is analogue if you look closely enough > And that was because computing power back then was non-existent so they didn't use any kind of compression? Compression is not a medium-level detail. You can easily store compressed data on a laserdisc.
- system2 8mo agoNo, with digital, you need encoding. How can you even compare binary with embedded images.
- throwaway27448 8mo ago> How can you even compare binary with embedded images. How are the images encoded?
- brazzy 8mo agoIn ways that ensure that they are not visually recognizable on the physical medium afterwards, because the visual layout represents a whole lot of redundancy, and the job of compression is to remove redundancy. If the end result has any recognizable patterns, the compression is not doing its job well.
- system2 8mo agoIf you watch the video, you can see that the images are burnt to the medium and can be seen optically. With 1 and 0, you cannot do this. All you'd see would be random dots everywhere.
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- throwaway27448 8mo agoIs there a version that doesn't require watching a video please? This would be 10x faster and easier as a text blob
- nilslice 8mo agoyes, you must save it to a laserdisc, and then observe it though a highly magnified digital microscope looking for a specific frame.
- imtringued 8mo agoYou can ask your human to watch the video and write the text blob for you.
- comboy 8mo agoJust post it to social media to generate the text description for free (multiple humans in parallel work better)
- FrozenSynapse 8mo ago[flagged]
- bonoboTP 8mo agoIt's likely based on just the transcript, even if it describes visual things, it likely guesses those things from the transcript text only. Maybe it's better now, but that was how it did it recently. To be convinced that it "watches" the video, I would need to see evidence of it referring to facts that are strictly only possible to know from the video, but not guessable from the audio.
- ilija139 8mo agoYou can try it with your own recorded video. I record myself doing exercises and Gemini gives me really good feedback on my form.
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- throwaway85825 8mo ago[flagged]
- luzionlighting 8mo agoInteresting to see how optical technology has evolved. In lighting design we also deal a lot with how light interacts with surfaces, lenses and reflectors. Even small changes in optics can drastically change how light spreads or how uniform illumination appears in a space.
- Aardwolf 8mo agoNow I wonder if something similar is possible with the magnetic fields on VHS tape
- valleyer 8mo agoThoughts on that: (1) you'd need a way to visualize the magnetic fields, (2) the data is frequency modulated, (3) due to helical scan, the video field lines do not line up evenly one over the next as they did so nicely in the Laserdisc / CED (there'd be a skew). So I don't want to say it's impossible, but I think it would require a lot more creativity.
- grishka 8mo agoI thought about that recently while researching how VCRs work before attempting to fix one. I didn't even think about seeing the actual video signal, I was just curious what the diagonal lines and control pulses on the tape look like. There are many other things as well that would be interesting to look at (all kinds of tapes, all kinds of floppies, hard drive platters, magstripe cards), but unfortunately I don't think there exists a technology capable of visualizing magnetic fields with enough precision.
- anfractuosity 8mo agoI have a magneto optic sensor that can visualise the field lines of a magstripe when using a polarising microscope - https://www.youtube.com/watch?v=c8nM4Z-hkTw https://www.youtube.com/watch?v=c8nM4Z-hkTw I'm going to try a VHS under it, to see what I get.
- Aardwolf 8mo agoPlease do share if this succeeded :)
- deleted 8mo ago[deleted]
- geon 8mo agoAs I understand it, this only works with still images that scroll vertically. Each revolution is one frame, so if you compare the data paths next to each other, they don't make up an image but the same single line of several consecutive frames. Scrolling a still image makes the same line on the screen cover a different part of the image each frame, so you can sort of make out what the original image looked like. The end credits should show up as a single tall image, since the only limit to the height is the radius of the disc.
- sixothree 8mo agoGreat points. And it just so happens in this video that the scrolling was at a speed where everything was preserved and also not stretched. Too slow and it would be elongated vertically on the disc and too fast and it would be compressed and you'd miss information.
- harrall 8mo agoIf I’m not mistaken, it also doesn’t work with LaserDiscs… it works only with CEDs. The title is a bit misleading. LaserDiscs are digital but CEDs are analog. Very different technologies.
- NoMoreNicksLeft 8mo agoI was under the impression that laserdisc encoded the video signal in analog. Some (all?) audio tracks were digital/pcm, however.
- itisit 8mo agoLaserDiscs are not quite a digital medium. The video is an FM analog signal (composite). Digital PCM audio was introduced about half a decade into the format's life.
- IAmGraydon 8mo agoJust an aside - I love that he's using The Mind's Eye (https://www.imdb.com/title/tt0167285/ https://www.imdb.com/title/tt0167285/), which is a video that really captured my imagination when I was young (along with Beyond the Mind's Eye) and changed the course of my life as it got me into 3D animation at a young age.
- withinboredom 8mo ago1000 years from now, someone will discover these discs and wonder why we wrote text so small and so many times across the disk. They’ll say the rainbow is for artistic effect and the repetition for religious reasons. Some people will argue that it is for primitive digital technology and be called crazy people. Nobody will be allowed to study it except for those who go to the right schools or have the right connections.