Off Topic: What about using tv screens to transmit data?


#1

I saw a video on YouTube where a bitcoin enthusiast showed how to send bitcoin through a tv screen using a smartphone’s scanner. The smartphone was held up to the screen and scanned a QR bar code to make the transaction, which was just a transmission of data onto the phone. Of course, the Bitcoin model relies partially on an existing internet connection to confirm the transaction but if the transmission is one way an internet connection would not be required.

I realize not every part of the world has televisions but couldn’t existing global channels transmit such data right now right through the screen to tablets and smartphones by scrolling different QR barcodes across the screen?

Not sure if this is applicable to Outernet (television channels can be highly regulated in authoritarian nations) but we were discussing mesh networks in another thread and the problems associated with them and long distance data transmission and it just dawned upon me the existing infrastructure for video transmission of data is already there, at least one way transmission…

All a startup would have to do is set up a tv channel with global distribution or rent time on one and broadcast data barcodes that could be scanned for their data by smartphones held up to the screen.


#2

it’s probably cheaper to use the phone/tablet’s microphone to pick up data encoded as audio. TV channel uses more bandwidth, and is therefore more expensive to broadcast (we’re using an audio channel right now).


#3

yea, I kind of figured this idea would just fall back to radio. Still I imagine it’s only a matter of time existing tv channels realize they can do this.

It wouldn’t top Lantern’s portability and off-grid self-reliance anyway. Not to mention it will be free to receive data through Outernet.


#4

I’m not a very maths person, but if I understand correctly, you can shove around 2900 bytes in a single QR code, which means you can do around 23Mbps if you can scan the codes at one per second rate. Is it just me or QR data can actually transmit a lot more than average DSL?

EDIT: Yeah, I added a couple of extra 0s… It’s 23Kbps… still pretty decent.


#5

No worries. Compared to me, you’re a math person. Even today I still don’t quite understand the significance of all the numbers when buying a computer. I just go with “larger numbers are better” and leave it at that.


#8

What if the data was encoded and rebroadcast via fm… smartphone devices with an app could decode and save the files as they were broadcast.


#9

Certainly possible

http://www.onebeep.org/about.htm


#10

are they still operating this? I found their facebook page but it hasn’t updated recently.

EDIT: see this video https://www.youtube.com/watch?v=ztvm8urrND4


#11

Yeah looks like it’s closed now, but the idea seems sound.

Someone could hire a shortwave antenna and broadcast data over PSK31 I could then just plug in my phone overnight to my £6 Shortwave radio when I wake up in the morning I have a bunch of news and weather content availabile to me.

This could cover the world from a single broadcast station.

Voice of America are still doing it: http://voaradiogram.net/


#12

this is very interesting. thanks for sharing it. i think i can give my old shortwave radio to a new life :smile:


#13

Yesterday I made a little tries with the VOAradiograms.


First not a received sound stream, but with recorded/compressed samples.
The setup was very simple, but need 2 computers:

  • On the first (A) I download/play a sample sound file: from youtube or from soundcloud archive.
    This machine is connected with a simple sound cabel to the second one: from the A machine,s sound card out to the B machine,s sound card mic input.
  • On the second machine (B) I have an installed fldigi sw. It need some config stepps, but I dont find all the necessery stepps. It need at least to choose the frequency and the OpMode. In the samples, I used it was MSK32.
    It need to note, this recorded sound files were compressed with mp3, this isnot the best format to play with this transmission method. The 32 different sound samples appeares in the sound file in random way, and the compressed methods ignores some of it.
    But for tries it is a good practice:
    You can see, there are three different “material” were transmitted: with the choosed modulation format mainly some simple text
    Sometimes it chnages the mode, and transmit (low quality) picture files, appeared in a small different window.
    and finally, sometimes at the end of the trasmission will insert a simple graphic characters, appeared from the waterfall… identified the VOA station.
    The result:
    with the recorded youtube samples, you can watch the original decode process, and the results on the A machine display. On B machine, I made some tunnings during the decode process, but I dont able to reach the similar decode quality: sometimes I was able to read some meaningfull texts. Maybe the decreased decode quality because the mp3 compression?
    If I able to get a short wave receiver, I will try this with a direct radio transmission.
    By the way:
    the fldigi able to code the text, prepared for trasmission, and produce the coded sound stream, for a radio transmission. Maybe, if somebody have a 27 MHz, CB band transmitter, we can try to organize a real data transmission too, in a “radio range”. (Another experiment: generate sound samples on the A machine with fldigi, and transmit it with the sound cabel, and decode it… transmit it with old phone line ?)
    t.janos