5 ms·
Decimen Optical Transfer: fountain-coded QR file transfer
- elric 2mo agoNeat, 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?
- kooi 2mo agoAs 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.
- bigiain 2mo agoI had a Timex Data Watch over 30 years ago. https://en.wikipedia.org/wiki/Timex_Datalink 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.)
- atoav 2mo agoI have seen digital audio gear that solved firmware transfer like that. You basically go to a website on your phone and it flickers the screen and you hold it in front of a photosensitive bit of the device that needs to be updated for 20 seconds and done. If your firmware is small enough to fit that model, it isn't a bad variant. Beats downloading a file, transferring it to a USB drive, sticking that in,...
- krautsauer 2mo agoThat'd be a few 100 bytes at best… what firmware fits into that?
- account42 2mo ago100 bytes in 20 seconds would only be 40 bps. Surely you can do better than that even using only one bit symbols (off/on).
- krautsauer 2mo agoWith a flashing phone screen? 120Hz tops, right?
- _joel 2mo agoIf only they had a clean digital way of getting data into the system.
- ErroneousBosh 2mo agoYou 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.
- myself248 2mo agoOr SSTV! I recall a demo years ago where someone had SSTV running between a speaker at the focus of a small dish, across to the room to another small dish with a microphone...
- ErroneousBosh 2mo agoThere's a track on an Aphex Twin CD (yeah well it would be, eh?) called Bonus High Frequency Sounds that's an SSTV pic of him in his studio.
- krautsauer 2mo agoHave a look at minimodem. In short: yes, but it's slow and annoying.
- utopiah 2mo agoIndeed 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.
- elric 2mo agoOther cameras could presumably be snooping on the data transfer.
- inigyou 2mo agoThey could, you're right. Usability is important though. If you have to type in a bunch of hex digits before sending, it won't be used.
- utopiah 2mo agoRealistically speaking with another phone in front and imagining how close one has to be for it to work reliably (as it is not a 64x64 pixels image) I think it would be really hard not to notice. The same way you whisper to say something secret in a public space I would expect people who transfer something private in public would have the presence of mind not let other snoop on and react accordingly.
- bschwindHN 2mo agoEncryption is a toilet paper roll.
- pjc50 2mo ago> 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.
- throwaway260626 2mo agoBluetooth is a thing too and I think it is even faster than this qr code video transfer method. Of course still slower than Airdrop.
- inigyou 2mo agoActually it's the opposite - Airdrop is controlled by the vendor lock-in company that wants you to only buy its hardware.
- stronglikedan 2mo ago> by the online services company that wants you to use online services Do you mean the one that went to all the trouble to reverse engineer Airdrop so that people could access Apple's vendor-locked walled garden without the use of online services?
- orev 2mo agoLocalSend has been working great for me across different types of devices.
- deleted 2mo ago[deleted]
- kooi 2mo agoFountain codes are so lit
- felooboolooomba 2mo agoIs 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.
- legulere 2mo agoThe actual article explaining the use for fountain codes in this use case: https://divan.dev/posts/fountaincodes/ https://divan.dev/posts/fountaincodes/
- myself248 2mo agoOooooooooooo. 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.
- inigyou 2mo agoI bet they don't, because they didn't know about it or didn't think of it. I know GPS is a slow repeating stream (the ephemeris repeats every 30 seconds and the almanac every 12.5 minutes) but that probably came before fountain codes.
- cwmoore 2mo agoSpeculation about the past is probably unnecessary. Reed-Solomon/erasure codes have been in operations since the 1960s https://en.wikipedia.org/wiki/Reed%E2%80%93Solomon_error_correction https://en.wikipedia.org/wiki/Reed%E2%80%93Solomon_error_cor...
- inigyou 2mo agoAlthough a repetition of any high-rate erasure code can act similarly to a fountain code, they aren't classed as such.
- thisisauserid 2mo agoI visual reminder that perfect compression is indistinguishable from random noise.
- inigyou 2mo agoIt is. Though there's almost always some uncompressed header so you know how to decompress it.
- smalltorch 2mo agoNaturally 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.
- upofadown 2mo ago>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.
- inigyou 2mo agoApparently 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.