An audio spectrogram is shown in the middle of the image, with intensity plots shown both above and below the spectrogram. A vertical yellow line runs through all three graphs.

Determining Location By Listening For Airplanes

November 9, 2026 by Aaron Beckendorf 30 Comments

Beyond what people deliberately disclose, there’s a surprising amount of information hidden in everyday messages, especially photos and videos. Even when people try to hide the location or time at which something was recorded, small details make these surprisingly difficult to obscure. One of the more well-known techniques correlates mains-frequency hum with power grid frequency variations. In a similar vein, [colsto] recently developed a powerful technique for precisely geolocating videos using the Doppler curves generated by passing aircraft.

Since aircraft are often audible for miles in all directions, they’re particularly likely to be inadvertently picked up in a video. The aircraft may not be discernible to the human ear, but the sound it makes can still show up in a spectrogram. To turn this data into a location, the pattern of Doppler curves needs to be correlated to an aircraft’s flight path. This is easy enough using public ADS-B records, which provide a timestamped history of each aircraft’s location, altitude, speed, and heading.

Having more than one Doppler curve in the recording simplifies the location process significantly: it’s possible to simply search for points at which Doppler curves would have been heard with the correct interval between them. It’s also important to exclude locations at which more Doppler curves would have been heard than were actually recorded – without this filter, most locations are around airports.

This eliminates most candidate areas, but it still leaves too many to manually check. The shape of the Doppler curve also provides a clue, though. The height of the curve is determined by the airplane’s speed, and the length by its distance. From an aircraft’s flight path, it’s possible to reconstruct the Doppler curve which would have been heard at any point around its flight path. These reconstructions can then be matched against the real curve to find the exact location. In a test, even a single Doppler curve was enough to locate a video without the help of any other clues.

This is just the latest in a long series of unexpected ways in which we’ve seen secrets shared, whether the secret in question is the location of a military base or the position of radar emitters.

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Stunning Volumetric 3D Display Goes For A Spin

November 5, 2026 by Donald Papp 15 Comments

[AncientJames] gives us a detailed look at Vortex, one of his impressive volumetric displays made with two back-to-back LED panels that spin at high speed with a Raspberry Pi 4 driving it all. Vortex generates a true 3D image hanging in space that one can move around, and look at from different angles independent of anything else. The software for Vortex is up on GitHub which includes a simulator as well as CAD models for the 3D-printed parts.

The images move, but can also be viewed from any angle.

Accomplishing what Vortex does requires precisely matching the images rendered on the panels to the physical rotation. If there’s a mismatch, the displayed 3D image will drift, or appear distorted. There’s also the physical matter of ensuring the spinning elements are balanced and stable while spinning at high speeds, a nontrivial undertaking that involved more than a little trial and error.

The amazing build quality and attention to detail really shines through, not just with the design but with smart use of off-the-shelf items like a large plastic globe for the display cover. [AncientJames] uses what looks like a plastic globe shade meant for a lighting fixture, and designs a clever fixture that attaches to a small rotary tool with a cutting wheel. With that, he can carefully and precisely cut away the unneeded section. Here’s a link to him doing so (at the 15:17 mark) in the video; sometimes it’s worth making a one-off gadget if it helps get a job done right.

[AncientJames] has made many volumetric displays in the past, and they’re each a little different. Check out one that spins a perforated drum around LED panels to create a lightfield display, instead of spinning the panels themselves.

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Watch VCF Southwest In Retrotastic SGI-Edited Footage

October 24, 2026 by Tyler August 1 Comment

There’s just something about backing way, way off the cutting edge to rediscover the simpler joys of yesteryear. We’ve got a contest about to wrap up along those lines, and there are festivals celebrating all things retro in the world of computers and electronics the world over. Vintage Computer Festival (VCF) Southwest happened back in the summer, but [Wave Design] just posted a gloriously retro retrospective, complete with the full 1990s video-editing workflow, completed on an SGI O2.

The footage was recorded on a 1990s vintage DV camera, and read using a somewhat-newer Sony tapedeck that we sadly have to admit also counts as retro in these late days. That gets piped into a vintage SGI O2 workstation that would have had us drooling back in the day, whose only concession to modernity is the inclusion of an NVMe SSD through a collection of adapters we can only call a hack. This may be burying the lede deep, but it turns out there is now an NVMe driver for IRIX 6.5. Using a modern SSD saves [Wave] from dealing with the literal stack of external drives video editing called for back in the day, so we can’t hardly blame him.

After the hardware walk-through, [Wave]’s video gets into the software, which is surprisingly modern. The footage he creates is decidedly not. It looks exactly like it was broadcast in 1996, perhaps following an episode of ReBoot — which conveniently enough, also used SGI workstations in its production, though with a decidedly rarer type of digital video tape.

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The World’s Smallest TV Console Plays DOOM

October 8, 2026 by Jenny List 15 Comments

We’ve seen plenty of game console projects here, many of them that seek to produce a miniature game console. But this one from [RayTriangle] may break a new barrier entirely — it fits an entire TV game console that plays DOOM, including the battery, into a TV antenna plug.

There’s a type of antenna plug with screw terminals, originally intended for matching 300 ohm balanced feeder to 75 ohm co-ax. It provides a tiny project box if you look at it that way, and it’s in here that the console sits. It’s an ESP32-S3 that talks to a controller via Bluetooth, and he’s gone into some detail on how the RF for the TV is made. Some clever tricks such as a look-up table for the phase shifted chroma waveforms for each color allow the creation of a good quality composite signal through a resistor-ladder DAC, and this is modulated in a surprisingly old-fashioned way onto a carrier provided by the ESP’s clock generator.

The result as can be seen in the video below is a bit noisy, but we think that might be fixable with a little filter magic. It’s designed for PAL TVs with a VHF tuner, but we’re guessing some ingenuity could be brought into play to make it happen for UHF or NTSC. The hardware meanwhile is put on two boards either side of the battery, with a flexible PCB joining the two.

It’s true that gaming though an analogue RF input to a TV is probably less common in 2026, but we applaud the ingenuity in getting this into such a small space. For some reason it reminds us of the world’s smallest MIDI synthesizer.

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Solve Your TTL Video Woes With An RP2350

October 7, 2026 by Jenny List 7 Comments

Before HDMI and DVI there was VGA, and before that? TTL RGB, in which instead of analogue voltages, the connector carried TTL logic voltages. TTL monitors used to be ten a penny because nobody wanted them in the VGA era, but the decades have not been kind to the TTL video aficionado. Stuck with a TTL card and no compatible monitor? Never fear, for [Charlysan] has your back with a TTL-to-DVI converter using an RP2350. The PIOs are used to sample the TTL input to a framebuffer, and the rest of the 2350 does the DVI magic using PicoDVI.

It requires a bit of level shifting hardware, which at minimum can be a set of resistors, and it targets the Waveshare RP2350-PiZero which comes with a handy ready-made HDMI socket. There’s a USB serial terminal to manage the thing, for which there’s even a TK GUI script.

This is the type of project which may never be center stage, yet performs such a vital function that it becomes indispensable. It’s not the first such project we’ve seen, a previous one did the same for VGA.

Electromechanical TV Goes 3D With This Light-field Display

September 29, 2026 by Tyler August 3 Comments

A mechanical TV — the kind that makes an image with a Nipkow disk and a single lamp with some help from persistence of vision — is easy enough to wrap your head around. Moving that technique into the third dimension, though? That’s a bit of a head scratcher. Luckily for us [AncientJames] provides a simple visual explanation for how the magic happens.

Instead of a disk doing a raster scan of the display, he’s using a rapidly-spinning drum with holes in it. In place of a single lamp, he’s got an array of LED matrix displays, each 32 pixels by 64 pixels in resolution. The trick is splitting the model up into a light field, so each hole projects its own image of the object at the proper angle.

In this demo there are three matrix displays, though that does limit the viewing angle as they’re arranged as one half of a hexagonal prism — you’d need more screens to get a full 360. The effective resolution through the drum is only about 100 pixels by 48 pixels per eye, but that’s still enough to play DOOM with.

This isn’t the first time this particular [Ancient] has got DOOM going on a volumetric display, and based on previous results, it probably won’t be the last time either. This implementation, which keeps the displays stationary and does not require a pricey laser projector, looks the most accessible to us, as long as you watch your fingers.

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The RP2350 Does 1080p

September 21, 2026 by Jenny List 16 Comments

Coaxing a DVI signal out of a microcontroller to drive a DVI or HDMI screen has been possible for a while now, but limitations in what the devices can do has, in turn, placed a limit on the resolution that can be delivered. Now [Aaron Gayle] has broken through a barrier by generating 1080p video from an RP2350. The previous best from Raspberry Pi Pico-class microcontrollers was 720p, which an RP2040 could deliver. The 2350 is faster and has faster peripherals, but even then, to reach this resolution he had to overclock it to 372 MHz. For all the impressive achievement, there’s still a limitation. Lacking space for a framebuffer, he generates scanline by scanline, a technique we associate more with 8-bit computers from the 1980s.

The 1080p video code is part of a package called TVtop, a board game in which the game board is displayed on the TV and whose players interact from their phones via Wi-Fi. For that reason, there’s an ESP32 in the project too, though it has nothing to do with the video hack.

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