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- Hacker News
- Fountain codes are so litby kooi
- I visual reminder that perfect compression is indistinguishable from random noise.
- It is. Though there's almost always some uncompressed header so you know how to decompress it.by inigyou
- Naturally the first thing to test should be how far of a link can you create with LOS.
Radio's get intercepted, this is a cheap laser link.
by smalltorch - Apparently if you combine LT with a Reed-Solomon pre-coding stage, then it's a raptor code, which is better because it has a cooler name.by inigyou
- Is there a way to negotiate ongoing FPS? I was sending at 60 but only receiving at 40. When I changed TX to 30 the speed went though the roof! I better call a builder.
Otherwise ridiculously cool project. May author's pillow always be cool on both sides.
- >Neither mode is encrypted: whatever is on the sending screen is readable by any camera pointed at it.
Something like this would be good for transferring the public key(s) associated with some cryptographic messaging identity. This would allow that to happen entirely offline. The optical nature of the transfer would prevent a potential MITM. The idea that an identity is being transferred would be fairly easy to impart to the user.
So the lack of encryption would be a feature and not a bug. This would enable later encryption which could then use any medium for the transfer in a completely secure way.
by upofadown - The actual article explaining the use for fountain codes in this use case: https://divan.dev/posts/fountaincodes/by legulere
- > The receiver can start receiving blocks from any point, receive blocks in any order, with any erasure probability – fountain codes will work as soon as you received K+ different blocks.
Thats just cool.
by smalltorch - Oooooooooooo.
I bet that's how satellite radios get their firmware updates and stuff.
Actually I bet it's how they get almost everything aside from the audio streams themselves. Metadata. Channel art. Subscription info. Traffic data. Weather maps. Receiver firmware... The satellite is a textbook-perfect fountain, and the receiver may tune in at any time during the stream, and may miss any random number of packets, but fairly quickly it has what it needs.
I believe the various categories of metadata are sent at different rates according to how promptly a newly-awakened receiver should be able to update itself, so what's actually on the air is an interleaved collection of fountain streams, yeah? Hmm.
by myself248 - Neat, finally an easy way of transferring files between devices that doesn't rely on online services -- no clue why we didn't solve that ages ago.
Adding encryption shouldn't be hard, as long as you can communicate the keys out of band.
Could probably achieve the same result using audio instead of video, but maybe that would be too annoying?
by elric - Encryption is a toilet paper roll.by bschwindHN
- Have a look at minimodem. In short: yes, but it's slow and annoying.by krautsauer
- As someone who has implemented acoustic modems (underwater comms)... yes, yes very annoying. It's like a demonic dolphin.
Bringing it into the ultra sonic band would help.
by kooi - Indeed encryption should not be hard yet which situation do you have in mind where simply pulling away the emitting phone would not be enough? AFAIK the normal scenario is two persons in the same physical space so I am not sure what encryption would add.by utopiah
- You can do PSK31 across a room with just audio, but it is a kind of annoying noise after a while.
It's interesting that you learn to recognise patterns in the burbling tones after a while. "CQ CQ CQ" is very distinctive and after a while you can hear your own callsign in it. I guess it's not that different to very fast Morse.
- > between devices that doesn't rely on online services -- no clue why we didn't solve that ages ago
Airdrop is a thing, but remember that Android phones are controlled by the online services company that wants you to use online services.
by pjc50 - I had a Timex Data Watch over 30 years ago.
https://en.wikipedia.org/wiki/Timex_Datalink
It'd transfer phone numbers and calendar entries to the watch by blinking the screen of your computer. Kinda a 1 pixel version of this.
(I wonder where that ended up? From memory I threw it in a drawer when I finished the Windows 95 project I'd been working on, and switched to Mac. There was no Mac software to talk to it.)
by bigiain