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原始链接: https://news.ycombinator.com/item?id=43120582

这些思想集合涵盖了各种主题：由于透支和α融合而在移动设备上的高斯夹心构成了挑战，诸如基于网格的摄影测量法（Google Map，bing Maps）和Google Earth Earth VR等替代方案。然后，讨论转向了逐步的城市发展，表明变化的速度受到控制，将新结构限制在当地建筑物密度高的百分比。这旨在避免突然的密度尖峰，例如郊区的摩天大楼和促进有机邻里进化。辩论了城市密度的好处，包括较短的旅行距离，更有效的公用事业以及增加城市以外的绿色空间的机会。但是，承认大众运输系统的局限性，呼吁清除过时的分区以减轻压力。最后，讨论涉及欧洲数字地面电视（DVB-T），强调了有条件的访问模块（CAM）用于付费电视频道，智能卡以解锁内容和信号加密标准。

（评论） 2025-02-25

（评论） 2024-08-12

（评论） 2024-09-12

（评论） 2024-09-21

原文

As a child of the 90s, I see this as one of those rare, genuine examples of the “museum in cyberspace” imagined by the futurists of the day. Thank you for keeping the dream alive!

Decades ago a radio technician friend of mine took me up the elevator in the west leg to the top platform, to enjoy the fantastic view of the city. As the caption at the base of the west leg elevator entrance says, it was quite small and cramped indeed, and it definitely was disconcerting when it changed orientation passing through the waist of the tower!

Wow! I'd love to read a more in-depth blog post describing how to create one of these myself, and maybe even contribute my own splats to a collaborative library for iconic landmarks. I could see interactive splats being added to Wikipedia for popular locations.

San Francisco is just so beautiful. There's a serenity to it that I can't quite put my finger on. The way the fog waterfalls over the hills when you take the train in from the south... the view from Sutro. The gum tree trove near the tower.

This captured that serenity.

This is great! Back in 2009 or so, I took dozens of high-resolution photos with my digital camera from the observation spot at Sutro Tower (towards the city, not the tower), and combined the images together in Microsoft Photosynth [0] to create an astoundingly high resolution point cloud of the city. I started with lots of zoomed-out photos, then took an overlapping grid of photos at various zoom levels. I wish Photosynth was still around; I'd love to look at the result again.

[0] https://en.wikipedia.org/wiki/Photosynth

Fantastic work. This is one of the best gaussian splats I've experienced. Especially in regards to the distant objects and sky. I was surprised at how many more details I could perceive in the VR mode. I couldn't spot the "easter egg" until I switched over.

Ten television stations, three FM radio stations, and 20 wireless and mobile communications users (i.e. law enforcement agencies, taxi cabs, school buses, wireless internet, etc.) rely on Sutro Tower antennas to transmit signals over the air to the entire Bay Area.

For some reason it never occurred to me that Sutro was still a live radio tower - it’s such an SF landmark that I think I just assumed it was decommissioned or something.

Amazing.

I tried it on my MQ3 last night and it was the first thing like that which was photorealistic, but it badly overloaded the MQ3, so it was the closest experience to Sword Art Online I've had yet in VR. (The sky was transparent and my room showed through!) I should have been sitting when I started it but since the frame rate was low and the horizon improperly oriented I could have fallen transitioning to the couch if I hadn't steeled myself to rely 100% on proprioception.

Contrasted to the way too lo-fi Inside the Scaniverse and the bland but cringe Horizon Worlds it's a hit. I gotta try it again in tethered mode.

I had the privilege of spending about 30 minutes at level 6 in May of 2023. It was as spectacular as you might imagine. I would say that if you have even the slightest fear of heights the whole experience would be a nightmare.

I work in broadcast TV in San Francisco and am very good friends with one of the engineers who is responsible for the care and maintenance of some of the facilities up there. We talked about him taking me up there for ten years before we finally got around to it. :-)

It's really cool, but I can't shake off an "uncanny valley" feeling, with all of the small quirks in the geometry. What I think I'd be interested in is a post-processing step where this splat is automatically converted to a 3d model that approximates each component, only falling back to the point cloud if there's no simple shape that fits the observation at a particular location.

This is close to the idea of convex splatting (recent paper) in which convex shapes are used to approximate these real 3d objects as they are better suited than gaussians

This brings a meta quest 3s to its knees. It's almost so bad you can't quit it, and the video lags 15 seconds, which is very disorienting to be immersed in (it can make you fall down). Shame, since it looks gorgeous.

The Quest's Snapdragon GPU, like most mobile GPUs, uses a tiled rendering [1] architecture.

The basic technique for rendering gaussian splats is kryptonite for this architecture, essentially implementing every worse practice for rendering on a mobile GPU:

* Tons of overdraw (overlapping splats)

* Tons of alpha blending

* Millions of splats in the distance generate a lot of tiny triangles resolving to a single pixel

* Long thin splats in the foreground generate triangles that cover multiple tiles

These are all the ingredients you need to bring a mobile GPU to its knees! Any desktop GPU (including most laptops) will be far less sensitive to these issues, even if it's not very powerful. It's a fundamental issue of architecture rather than one of raw FLOPs.

[1] https://en.wikipedia.org/wiki/Tiled_rendering

The quest is underpowered (it's basically a midrange Android phone you wear.) More efficient coding or a simpler model would help. Inside the Scaniverse does something similar with a high framerate but the models are simple and don't look very good.

I had to power cycle mine to get out, but boy was the view great despite the motion sickness.

Not only does it look amazing, it renders super fast even on an iGPU. Feels like magic. A couple of questions: Why do objects flicker when moving the camera? And why do surfaces get translucent when close up?

This is very cool. I feel like the technique used (gaussian splatting) gives it a more realistic appearance from certain viewpoints. It almost felt like my monitor turned into a window in the sky looking out over the city for a moment. The illusion falls apart once once drifts too far from the nominal viewing area, but until then, it looks even better than something like Google Earth which renders actual polygons for everything.

This is fantastic.

I've been trying to build something myself for biological and heritage captures. Could you elaborate at all on the JS decoder method used or resources that ended up enabling you to make it?

I've been playing with Playcanvas React for the past week, would your method integrate with their platform?

I'm assuming you started working on this before their React release, or was Web Components chosen for a specific reason?

I'm trying to make something that can take in real-time data and also handle some XR/AR if possible as well, but I am pretty ignorant beyond html/css/js.

This is awesome. Have been enamored with Sutro Tower since I moved here a few years back. Love that you can see what the different antennas are for as well.

Beautiful, the visuals combined with the music gave me quite a nostalgic feeling for the city where I once worked daily but haven't visited in years.

Great video if you like watching videos from the front of BART which is pretty boring tbf. Much better videos of locos travelling through the alps

How feasible would it be to generate high-quality guassian splats of everywhere, starting with big cities, like Google Maps street view and 3D view?

Then you can make video games and interactive experiences in real-world locations. I doubt the collision handling is there, but you can at least start with something like Microsoft Flight Simulator with low-flying drones.

It would also be great for training AI to generate realistic-looking scenarios. Besides playing and working (ex: VR) in real places, you can in very-realistic liminal spaces. (And it's training on public areas, so less ethical issues.)

the collision handling part is actually not that hard to back into from the splat data. i think HQ splats of everywhere is something we'll start seeing in the next decade! we haven't quite solved scaling issues, LoD, and streaming for splats but the early work is promising

Could you direct me to resources about collisions and splat data?

I have an extreme interest in deriving measurements from splat data of vegetation, as it tends to reconstruct thin planes like leaves far better than other traditional SfM techniques.

I think it would help to be able to move up and down (ex. space and shift keys) without changing the camera angle. This seems a better solution, to me, than existing pan with 3rd mouse button.

I'm biased bc I worked with the team while there, but I believe Snap's acquisition of PlayCanvas was one of their most underrated. Incredible technology.

What blows me away is that R/C drones can operate that close to those antennas. Frequency differences don't tend to matter much once you go past 100,000 watts.

This is really cool, nice work!

Something I’ve been looking for for a while is an interactive view of SF from above - I think it’d be cool to experience the verticality of SF and see how all the different hills relate to each other (and gmaps/earth just isn't cutting it).

this is actually pretty good for around the panhandle, but if anyone is aware of something like that for the whole city please let me know!

This does not work at all on Android Chrome. The about dialog flies in super slowly, continually re-layouting the text, and there's no "small cube" and no way to dismiss the about dialog either.

The background looks tantalising but maybe a little more testing is needed... (e.g. for the most common browser/OS in the world).

Wow surprising, do you have any console errors? I tested extensively in Android chrome. To dismiss the modal you can tap in the margin.

I'm not sure how to see console errors on mobile (without the remote dev tools anyway).

I tried again today and it's still really slow but I do get the controls this time so I was able to use it. Very neat!

This is on a Pixel 8, Chrome 113.

Worked for me on a 2.5 year old OnePlus Nord 2T, both in Chrome and Firefox. Not a high frame rate, but perfectly usable, even on this pretty old mid-range phone.

What is the limiting factor for level of detail here? Is it the source data (too low res camera/too far away), the processing, or getting it rendered in real-time in browser? Is this the full detail, or is this somehow downsampled/compressed version for the web?

The background music seamlessly blended with the chorus of Nina Nesbitt's song 'On The Run,' which was playing when I opened the site. I genuinely didn't realize there was any background music at all.

Very beautiful and nostalgic, so well done.

I used to live nearby and my favorite “urban” hike was going up Glen Canyon, up and down the two Twin Peaks, loop through Sutro Forest and then go back to downtown walking down 17th. Loved those weekend walks.

Ha yes love that loop, so strange to see someone else tying it all together! Not quite as good but when I lived in the sunset — grand view to golden heights along the ridgeline then down to Laguna Honda trails and up to twin peaks and out sutro forest to Parnassus.

it so nearly runs on a Quest 3. The next gen of mobile XR chipsets (or maybe even the current gen with less thermal throttling) are going to be able to handle these kinds of scenes with a bit more optimization.

Can anyone give some numbers for a more intuitive understanding of the advantages from GS? How large would the file/content be if it is in mesh? Can we get similar rendering FPS?

That looks rad.

One bit of feedback: don't move the camera if someone clicks one of the circles, that is super disorienting. There is also a bug that if a drag to move the camera happens to end on a circle, the popup opens.

I wasn't expecting to be able to see through the lattice structure. Amazing amount of detail.

Naively, it seems to me that the many needle-like artifacts further away from the tower could be filtered out?

The wife got me a Sutro Tower shirt one year for Christmas. This was when OTA digital television rolled out. When the rest of San Jose seemed to be taking down their TV aerials or letting them fall apart I was nerding out: purchasing a new one and mast sections from Rat Shack to set up one on our house.

Scanning the spectrum to pull in KQED, etc. The first Austin City Limits I saw in HD blew my mind.

I think all but one TV station came to the South Bay by way of Sutro. Quite a reach.

The help text mentions a "little cube" that would enable AR mode, but I can see no cube.

Touch controls are very weird and don't rotate the view as expected.

Does anything like this exist for just flying around cities (not SF, anywhere) in general? Would love to experience what a drone sees even if it's in a limited area.

More conventional mesh-based photogrammetry options include:

- https://maps.google.com (satellite view)

- https://earth.google.com (also in browser, possibly better camera controls for what you want)

- Bing Maps (3D flyover mode, more stale data in my experience)

- Apple Maps satellite view (only on macOS/iOS)

- Google Earth VR[1] (requires a Windows PC and a VR headset that can connect to it)

- Microsoft Flight Sim 2020/2024 (requires a beefy Windows PC, uses Bing Maps plus a lot of other enhancements and rendering goodness. Most lifelike "feels like I'm there" but not true to earth)

I'm not aware of splat-based city photogrammetry aside from one-offs like this but I'd love to learn if there's any such projects!

[1] https://store.steampowered.com/app/348250/Google_Earth_VR/

Fun fact: NBC does not broadcast from Sutro tower, but San Bruno…

Which means effectively zero over-the-air reception in parts of the Mission. Lesson learned during a Super Bowl party the 2010s.

Completely unrelated, but aerial views of San Francisco blow my mind with how under-zoned the city is.

One of the most desirable places on earth to live and it's on a small peninsula. Yet it's a sea of single-family homes as far as the eye can see.

The distance between Sutro Tower and the "Downtown" SF is less than the distance between the Brooklyn Bridge and Central Park. But could you imagine if that space was filled with 2-3 story townhomes?

My criticism is aimed at the glacial and mostly mishandled infrastructure projects. That is one of the big reasons for zoning changes taking so long.

I hope the US gets its act together and learns from exemplar infrastructure projects around the world.

> One of the most desirable places on earth to live and it's on a small peninsula. Yet it's a sea of single-family homes as far as the eye can see.

Ever wondered if it’s desirable BECAUSE it’s not a dense urban jungle?

SF is kind of neither though. If you spend any time in the city, it definitely feels overstuffed. The houses may be cute and small but they are stuffed with roommates. The city is stuck in nostalgia and ignoring that it's bursting at the seams. It's like wearing clothes that are too small and pretending you are still skinny.

Kinda makes you wish there was a massive earthquake while everyone was safely tucked away at a Beyonce concert in an earthquake-proof stadium.

No. It is the good weather capital of the country.

Mild winters, mild summers.

Not too much rain.

No serious threat from tornadoes or hurricanes.

That’s a very big draw and it wouldn’t go away by making more dense housing, even if the rest of the peninsula was developed like Manhattan.

And it lives on a series of incredibly active fault lines. During my undergrad I had multiple geology profs adamantly mention that when not if aspect of this, and on time-scales of 100s of years, not 1000s. YRMV.

My friends in the geological sciences have told me there will be a big earthquake, but it will be capped at around magnitude 8.0; the faults here are not capable of a 9.0. Buildings in SF have been constructed or retrofit for modern earthquake safety by law.

An 8.0 would still cause massive devastation. Even if structures mostly survive there is the threat of fire and tsunami. This antenna tower looks like it is likely to survive though.

And it should be, given that they built the CBD on landfill which has the specific instructions of “do not shake”, since a seemingly solid foundation turns to liquid during an earthquake

The buildings should go somewhere else, on bedrock

Well, I desired and moved to SF exactly because it's the closest thing to a dense urban jungle that I could find in California. I even dream of moving to a denser part of the city one day, once I can reasonably afford it, but those parts are so in demand to be pricier.

sidentoe: If you wanna live out a super dense dream/experience on the cheap, go spend 6 months in Seoul, I lived in Manhattan for 10+ years and still found Seoul pretty intense.

There's a difference between urban jungle and (say) nice 5 story European city buildings.

Londons problem for example is that they tried to be clever and cheap at the same time in the 60s and now we're stuck with it.

This is why incrementalism is always the best method of development.

Spread out the pain so everyone only suffers a little. Spread out the development across different architectural eras. Spread out density to the point where you have diminishing returns.

The city shouldn't be changed overnight, but the city should be allowed to change an a consistent rate that slowly accelerates. A good example is to allow each building to only double the square footage of the median building within, say, a quarter-mile radius of the property being redeveloped. This means that SFH's can only become duplexes until duplexes are the norm. After that, quad-plexes can be built, and then when that's normal, you start building large, eight-unit, european-style flats.

This allows different areas to grow at different rates, while allowing density to remain generally uniform across neighborhoods. This incentivizes people who very much want low density to have a reasonably, predictably low-density neighborhood to invest in, while giving up the ghost when a piece of land is just to valuable to reasonably keep low density.

It would work, and would work quickly in areas where lots of development is needed.

Unless I'm misunderstanding, this solves for the problem in which someone wants to put a skyscraper in the middle of suburbia. In other words, based on the assumption that developers will always want to build bigger, but the locals don't want that.

Interesting to imagine what this city would look like. If it spread out evenly, you'd get a strange "bowl", with the original SFHs in the center, and high-rises on the periphery.

I guess in reality you wouldn't have such even growth; high rises would still potentially want to clump together for business districts, etc.

As buildings get torn down, you could do the recalculation; each new building can be x% above or below the local building density "slope". So over time, even the SFH areas could grow upwards, just at a slow pace.

There are various ways to do it, but I genuinely think uniform is better. Low density residential likely prefers, and naturally supports, low density retail.

> A good example is to allow each building to only double the square footage of the median building within, say, a quarter-mile radius of the property being redeveloped. This means that SFH's can only become duplexes until duplexes are the norm.

No, it doesn't; existing SFHs can, and have when allowed to, become duplexes, triplexes, and sometimes even quadruplexes without changing square footage at all, with doubling, you can go even further. All it takes is remodeling so that each subdivided unit meets minimum habitability standards (separate access, its own restroom, whatever other facilities are mininally required.)

> This is a general argument assuming units being arbitrary.

Well, no, it doesn't assume units are arbitrary, it assumes units are fixed square footage, which they are not. Under most regulatory schemes, there is a practical minimum size or a habitable unit, but a pre-existing area zoned for detached single-family units exclusively is unlikely to be comprised of single-family units that happen to also be the minimum square footage for a habitable unit.

The same concept, at a minimum, would need to be extended to units. This is what I mean by assuming it’s arbitrary. It’s just redundant to say that, yes, obviously you need an incremental increase in units, sqft’s, footprint, vertical footprint, etc.

It is easy to argue that Manhattan is far more livable than San Francisco due to the layout and highly convenient zoning, even before taking the obvious transportation advantages into account. San Francisco's advantage is the climate and beautiful natural setting.

Considering the advances in seismic technology made over the past fifty years, it is a shame that much faster upgrades to the real estate have not been encouraged.

You're assuming some linear/symmetric relationship, by trying to relate an inverted sign! The more direct question is, are there dense urban jungles that are desirable? A good way to measure that might be comparing where wealthy people live, with the assumption that desire and price are related, locally. Do they live more inner-city, or do they live more in the suburbs at the outskirts?

Could it be not desirable because of single-family homes, but rather because all lucrative and high paying jobs are located here? And it's proximity to the Valley? Also there is much more events and gatherings happen than in the Valley.

Maybe you're right, but we'll never know. It would be great if they allowed some sections to develop so we can test it out. To me it is a desirable location because of the companies, not the lifestyle.

Haha, no, it’s desirable because of geography and things to do. This is proven by the fact that large numbers of people are moving into expensive Mission Bay housing which has no single family homes by it.

I would not say that dense city living is not without its downsides. But if people need to work in these cities, they may as well get to live closer. And if you are already living in an apartment, it's not that much different to live in a 6 story apartment building vs a 4 story one.

> There would be 3-4X the people, yet still the same amount of roads, services, and public utilities.

That's the point! Per capita, it should be cheaper to live in cities because infrastructure goes so much further. And if you are arguing for better mass transit, you will have to build many, many more miles if you also want to encourage people to sprawl.

Although I think the strongest case for allowing cities to get dense is it allows greenbelts and less dense areas closer to the city. You can build a big dense city UP and make it easier for people to get out and enjoy nature and farms and etc. Or you can build a city OUT and then it's just desolate city for hours around.

Is it cheaper because the infrastructure is going farther, or because every individual is getting less and less of an overburdened commons?

If you build out instead and everyone gets the SFH white-picket-fence life, the escape to nature is suddenly less important. Even if it's more expensive to connect, in the process we develop ample capacity in the commons.

Maybe it's just not possible with so much cost focus and so many competing incentives in the West. And no superseding body who can make it happen like China.

Converting 4-story to 6-story isn't really what I see pitched either, it's generally rezoning SFH/2/4-plex to 6-story+ with subsidies, which is really a huge remaking of neighborhoods.

> Is it cheaper because the infrastructure is going farther

Yes, that's exactly it!

> or because every individual is getting less and less of an overburdened commons?

No, it's not that at all. Why would common services be overburdened? Everyone still gets their water, sewage, electricity, internet, etc., but it's far cheaper to provide per-person.

And with the density you get to build public transit, so people aren't burdened by having to necessarily own a car.

>Why would common services be overburdened?

Water restrictions? Fatbergs? Brownouts? Congestion? Traffic? Breathing room? Not to mention increasing demand on any inelastic local supply will drive up prices. To my initial point, the upscaling of utilities and infrastructure is often magically handwaved alongside the up-zoning demands. There are real negatives to cramming more and more people into one place!

Fatbergs and brownouts point to underinvestment in utilities (budget problems / many historic, undemolishable buildings)

You need to keep less $ invested in infrastructure per person if everyone lives on top of one another in a condo.

If everyone lives in a white picket fence SFH then you have to build miles of extra roads, pipes, cables. Every trip for every bus, truck, and car is a bit further.

There's a lot to be said for both rural and city life but cities can be much cheaper if there's unrestrained development.

The only reason why suburbia is possible is because it is _heavily_ subsidized.

If you had to pay the real bill for road maintenance alone suburbs would no longer be viable.

So the suburbs take from the commons and don't give back in your example.

Dystopia usually conjures up a neon bright towers of an overwhelming big city. I've been to Atlanta too and I quite liked it. Low density, lots of green space, decent public transit (MARTA). Lots of interesting neighborhood variability.

It is currently being force "low-densified" by restrictions. If those restrictions and force were removed, it would densify itself due to market demands. It would be much, much less forced than the current paradigm.

I enjoy both low and high density living.

The argument in favour of density is that if you increase density, then you also decrease the average distance that people have to travel until they get somewhere interesting, like a job or a shop.

Vehicle-delivered utilities like garbage collection, package deliveries, and mass transit get more efficient, and the same goes for tunnel-delivered utilities like fiber internet and water.

San Francisco is economically one of the world's most impactful cities; it'd be good for all of us if there was more of it. You get all sorts of interesting multiplier effects when you put lots of a certain kind of person in one place.

- all the theater kids in one town: LA

- all the bankers: NYC, London

- all the computer people: SF

Granted there are economic efficiencies. But I'm not convinced the fully expanded multipliers from one Super SF with 4X the density - turning it into somewhere like Manila - would be better across all metrics (economic and human) than fostering four easily interconnected mini-SFs.

Mass transit isnt a silver bullet either. Here in Brisbane, they standardized around a narrow gauge designed to pull cart loads of timber down mountains. They duplicate it where they can, but effectively its a city of technical debt. Theres a maximum size of train we are already at, and a maximum number of trains per minute we can sustain.

So we have a decent mass transit system but its not far from peak capacity, and most of what the government has been doing is hacking around that. Trammish busses, cross river rail etc.

So we need to attack the issue from the other side too. We have a weirdly non dense central region, largely due to single issue anti development voters, who dont want apartment buildings right where they should be (on top of mass transit hubs). Instead the inner suburbs are littered with 1950s character homes, battleaxed once for massive profit.

We can take significant load off of a system close to a decade from collapse by simply removing outdated zoning.

And the way the council here operates, utilities and road upgrades necessitated by development are borne by the property developer. So there's really near zero cost in approaching things this way. And they have also used priority approvals, where if a certain amount of floor space of a development is earmarked for light commercial, they can cut a few years off approval time. So theres absolutely no reason not to, as the big residential buildings grow, they grow their own services and utilities.

Public schools are closing due to lack of enrollment. Transit agencies are cutting back from low ridership and lack of fare revenue. If housing costs were low enough for more people to move in affordably it could be a boon for the city.

Why wouldn’t you slash the budgets when enrollment is decreasing? And when you expect a 15% decrease in enrollment over the next 10 years?

Have you actually checked on those Chinese cities to see how they’re doing? Many are literal vacant ghost towns because it turns out people don’t want to live in the middle of nowhere.

Broadcast television is amazing, and I'm so sad it's dying out. OK, maybe we don't need to tune in at 6 to watch the latest episode of "Friends" anymore, but for any kind of live events - news, sport, politics, having high-definition video you can pull right out of the air without having to worry about paying for data, latency, or bandwidth limitations, is amazing.

For certain applications the internet can never compete with "broadcast".

? Is over-the-air TV broadcast not encrypted and compressed to oblivion in the US? Cause it definitely is here, and you're expected to pay for a decoder card, except for a small handful of channels.

It’s not encrypted but compression and reliability of the signal is a mixed bag. It’s not encrypted because congress mandated it as a condition for privatizing the analog bandwidth (ie there’s a carve out for public digital and broadcasters have to broadcast publicly accessible signal just like they had to on analog)

Not really a power move but public broadcast will probably disappear at some point in a boiling the frog kind of way, but it’s definitely being starved and killed by corporate interests.

Are OTA channels subscription based where you are (where)? Or the "decoder card" is just some middleware crap you buy once? Our OTA TV has always been ad-supported, they just moved the same channels to digital though in larger markets there are now quite a few new low-overhead licensed syndicated content options, presumably due to the cheaper cost of air slots.

It's a subscription, billed monthly, with a minimum one year contract period. To the best I can tell, the service provider is in a completely monopolistic position too (is the only digital OTA (analog has been banned, and OTA is more commonly referred to here as terrestrial) television broadcaster in the country and is privately owned), so yeah, good fun all around.

I looked into it a bit deeper inspired by this thread, and it seems to be an explicit feature of the European digital TV broadcast system standard (DVB-T) [0], commonly used not just here in Europe, but also elsewhere around the world apparently [1].

The formal name for the "decoder card" I recalled is apparently CAM [2], which communicates with the TV using the DVB-CI protocol(?) [3], and uses the form factor of the old PCMCIA cards. I also see that the algorithm used is the CSA [4], and even more curiously I see mentions of DES [5] in the article for the encryption (with further mentions that AES is a new addition to the standard that is presently underadopted).

The only vendor-specific bit to this, because there is a bit that is vendor-specific, seems to be the key exchange algorithm used, although the articles are unclear to me about this. Interesting subject for sure. Here where I live, the Conax system [6] is in use supposedly. To be clear, they're not the service provider and have nothing to do with them (to the best I can tell).

Addendum:

Apparently I misinterpreted how it works a bit. So the Conditional-Access Module is plugged into the TV, so far so good, but that on its own is not going to achieve anything. The actual unlock comes from a smart card bundled with the CAM, and you're to put that into the CAM. As you can tell, we've only ever watched the free channels :)

[0] Digital Video Broadcasting - Terrestrial, https://en.wikipedia.org/wiki/DVB-T

[1] https://en.wikipedia.org/wiki/File:Digital_terrestrial_telev...

[2] Conditional-Access Module, https://en.wikipedia.org/wiki/Conditional-access_module

[3] Digital Video Broadcasting - Common Interface, https://en.wikipedia.org/wiki/Common_Interface

[4] Common Scrambling Algorithm, https://en.wikipedia.org/wiki/Common_Scrambling_Algorithm

[5] Data Encryption Standard, https://en.wikipedia.org/wiki/Data_Encryption_Standard

[6] https://en.wikipedia.org/wiki/Conax

Most every OTA channel here in Spain (at least in Valencia) is 1080i, with a few being 720i, but there's two 4K test channels, one SDR and one HDR. Not sure of the bitrate, but the SDR one looks stunning on my TV (which "supports" HDR but looks horrible in HDR mode). They usually just play loops of B roll of various Spanish things, festivals, random clips of theatre productions and things like that. It's pretty neat!

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