[HN Gopher] The Hummingbird Clock: date videos by background mai... ___________________________________________________________________ The Hummingbird Clock: date videos by background mains hum Author : wodow Score : 382 points Date : 2022-10-09 13:49 UTC (9 hours ago) (HTM) web link (hummingbirdclock.info) (TXT) w3m dump (hummingbirdclock.info) | rajasimon wrote: | I bet there was a movie or a documentary around this if anyone | have the link please share it. | barbazoo wrote: | It's super shitty to just autoplay that sounds as soon as you | open the page. Firefox on Android. | chaosprint wrote: | Interesting topic. | | I tried to mimic that sound design using Glicol but winded up | getting something different. | | For those who are interested: | | 1. go to (https://glicol.org) | | 2. run the following code: | | // ---------------- | | o: sin ~freq >> mul 0.5; | | ~freq: sin 0.2 >> mul ~range >> add 50; | | ~range: sin 0.4 >> mul 1 >> add 2; | | // ---------------- | | 3. tweak the numbers to get different sound | manv1 wrote: | This is so fucking cool. | kzrdude wrote: | Just curious, are there any software hacks (not audio/video at | all) that use any aspect of mains hum for say info leakage? | (Could be impossible.) | GranPC wrote: | How does this auto-play sound without user interaction? | s0rce wrote: | It didn't for me on Chrome on OS X. I had to click one of the | links before the sound played. | kevingadd wrote: | Synthesized sound (AudioContext) works a bit differently from | playing videos/sound files in the web permissions model, for | whatever reason. IIRC Chrome and Firefox both treat various | forms of interaction as an OK to synthesize audio, so your | browser probably decided you had met that criteria. | | Chrome has a list of special websites that are given that | access automatically, though I doubt this website is on that | list... | GranPC wrote: | Very interesting. I'm using Firefox and it started playing | immediately when I switched to the tab. Thank you for the | details! | etaioinshrdlu wrote: | I have never heard mains hum as wobbly as on this site. It seems | exaggerated. | IshKebab wrote: | It's not real. It's obviously too high pitched. | rtanks wrote: | The sound is very aggravating. | ctxc wrote: | Exactly. Although it _is_ interesting, was not expecting auto- | play. | atoav wrote: | Time to get your own isolated grid huh? Maybe with solar and | inverters? | [deleted] | pugworthy wrote: | To what end? What do you want to obfuscate by doing this? | coldtea wrote: | https://www.aclu.org/news/national-security/you-may-have- | not.... | pugworthy wrote: | That's not really an answer beyond "Because FUD". | | FWIW, I've been an ACLU member for quite some time. | ris wrote: | Probably better to run a decoy signal (or two) in the | background with similar characteristics. | s0rce wrote: | You'd need to make sure there is no grid nearby. If you were | completely off-grid and away from power lines or anything then | you'd have no signal at the mains frequency. Certainly | possible. Probably easier to just use a filter to mask the | frequency component. | ratww wrote: | An on-line UPS like those used in datacenters or music studios | is probably enough. They basically have rectifiers and | inverters in them. | | Some of them have phase-locked loops to sync the output | frequency with the mains, but probably won't stray as far from | 50Hz (or 60Hz) as the mains themselves seem to do. If they do, | unplugging the mains and using the battery is probably enough | to get pure 50Hz back! | jsjohnst wrote: | > An on-line UPS like those used in datacenters or music | studios is probably enough. | | Only if you don't have mains power anywhere near the | recording device. You don't need to be plugged into mains | power to have it be present in a recording. | ratww wrote: | True! And that applies for every case. Even if you have | 100% isolated mains with solar or battery, you'll get 50hz | from neighbours (especially apartments) and power lines | close by. | | I remember having this issue when working in a recording | studio during college, even when we switched to battery and | turn the mains off, we'd still get hum in some guitars. | | Funny enough I was recently reading an interview with | producer Michael Beinhorn and he mentioned having some | "mystery EMF/RFI event" happening in New York around 1997, | coming from a specific block, and he had to relocate a | recording session to Los Angeles because of how strong it | was interfering with the guitar amps and other equipment | [1]. | | [1] | https://gearspace.com/board/interviews/1385579-interview- | mic... | jsjohnst wrote: | I really wish this story included which half block area | it was strongest. | ratww wrote: | That would be very interesting to know! Especially | considering the two studios he mentioned aren't exactly | close to each other: | | https://goo.gl/maps/MLw3twvRi9GumYeX8 | ok123456 wrote: | Filtering out 50Hz/60Hz noise as a band stop filter is a common | audio post processing step, precisely because it's noise from the | power system. | | I wouldn't be surprised if there were phones that automatically | applied this filter. | FPGAhacker wrote: | Your point still stands but the noise here is effectively a | higher frequency modulation of the base AC oscillation. | | In other words, the base oscillation of 50 or 60 Hz is not | stable, but instead varies a little above and a little below at | higher rates. | | The magnitude is significantly lower than the base mains | frequency. So possibly not audible above any other noise in the | recording, but present nonetheless. | ok123456 wrote: | These filters will take that into account since it never has | exactly been 50/60Hz. It's just the expected mean. | | Maybe it's present in subsequent harmonics (e.g., | 100/150/200Hz for 50Hz) as a systematic deviation from | additive white noise. But, this would be difficult in | practice to reliably isolate these signals via some form of | component analysis. | paulkrush wrote: | How far do I or can I transmit into the grid? How far do load | changes from my house transfer into the grid? Surely my neighbors | could detect 1us spikes not big enough to pop mains at say 800hz? | ratww wrote: | I remember consumer devices from the 80s that allowed | transmitting audio using mains. They were already outdated by | the time I saw them in the 2000s. | | Me and some friends tested them and tried transmitting to a | neighbours house (connected to the same electrical post) and | had no success at all. There was just too much noise, coming | from other houses. However with digital technology I'm sure you | can get a much better range. | mastax wrote: | Things like HomePlug GreenPHY are used for smart meters. (Also | electric car charging for some inexplicable reason) I don't | know how they're typically deployed but I'd think at least a | few miles? It wouldn't make much sense to use if you'd have to | have the receiver really close - just use wireless. | Shish2k wrote: | Using ethernet-over-powerlines within my house, different | circuits within the same building have trouble talking to each | other, so I wouldn't recommend that for cross-building | communications... | h2odragon wrote: | There were some small, low power AM radio stations that | "transmitted" via power grid in mountain towns in North | Carolina, a while back. I've been told that they had real | trouble getting through transformers and they were using the | main distribution lines and broadcast AM frequencies. That's | with decent levels of power applied. | | I expect the incidental signals your usage generates are going | to be hard to detect past your power meter and almost certainly | un-resolvable past the distribution step down transformer. | JohnJamesRambo wrote: | This is absolutely fascinating. | gugagore wrote: | What I don't understand is how much technique assumes of the | local oscillators on the recording device, which also vary. | jsjohnst wrote: | I don't see how this can be used to "authenticate" a video. If | I'm already editing the video anyway, could you filter the | original hum out and replace it with the correct frequency for | the time you wanted to fake? There's got to be a margin of error | anyway, so would seem very possible to fake unless I'm missing | something. | helsinkiandrew wrote: | Yes, in the same way you could leave fake fingerprints and DNA | at a crime scene. | | This was used in a court case in the UK where the defence | claimed the police had tampered with a recording - editing | together separate recordings into a single one to make their | case. An academic 'expert' analysed the recording and | corroborated the claimed recording times and the accused were | found guilty. | twawaaay wrote: | You could. The point is to disprove the validity of the video. | Correct signature is not a proof the video is valid but | incorrect one could be proof that it is not. | | In practice, most people who manufactured videos before very | recently were simply unaware of this possibility. I learned | about it many years ago but I still forgot about it and | probably would not try to do anything about it if I was | manufacturing a video. | mastax wrote: | Only if you know to do that. Nothing is ever 100%. | kadoban wrote: | You can use it as evidence either way, especially evidence that | something is _not_ genuine. It's not proof though. | braingenious wrote: | This is fascinating. Does anyone know if this phenomenon is | unique to Britain? I wonder if this could be replicated in other | countries. | LinuxBender wrote: | Interesting. What effect if any will my home being entirely on | off-grid inverter 100% of the time have on this? I use | Solar/Commercial/Generator -> DC Power Supplies / Charge | Controllers -> Inverter -> Non-Resistive loads. My inverters are | entirely isolated from commercial power. Can someone perhaps tell | the make/model of my inverter? | alexvoda wrote: | I guess it depends on how far you are from mains electricity | infrastructure. | spoonjim wrote: | Seems like you wouldn't need to actually record and store the | mains hum... you could just extract it from other videos with | known datestamps. | IshKebab wrote: | Definitely wouldn't work. You'd be matching two very noisy | signals instead of one clean and one noisy one (which already | requires a long time period to match), and it would be really | hard to get enough videos to cover all time and then why would | you bother when recording the hum directly is easier and | better? | beardyw wrote: | And then add it to your newly made black and white video tape. | Forgery 2022. | sbf501 wrote: | Except for the 10 other techniques we _don 't_ know about. | Did you know about this before the HN post (or original post | from 2021)? I sure didn't, which means there are other tricks | hiding out there. | coldtea wrote: | you might have not, but many did | beardyw wrote: | I didn't. | paulkrush wrote: | Fun fact: You can hear the harmonics of the grid and IP switching | if you open the site in two separate browser windows. | matja wrote: | Fun fact: The source contains: rand = (Math.floor(Math.random() | * 3) - 1); vco.frequency.value += rand * hum_delta; | zxcvgm wrote: | Tom Scott did a video about this topic in 2021: | https://www.youtube.com/watch?v=e0elNU0iOMY | Karellen wrote: | That's weird. | | I came here to check that someone had linked to that video, but | in my mind it feels a lot longer ago than Dec 2021. I feel like | that video should be 3 or 4 years old. | | It's doubly weird because that normally happens the other way | around, where I think something happened about a year ago, and | it was actually 3 or 4 years ago. Or I think something happened | 5 years ago, and it was actually 10-12. | Smoosh wrote: | People seem to be reporting anecdotally that the pandemic has | messed with their sense of time. I wonder if there are any | serious research projects underway to study this phenomenon. | curl-up wrote: | I would have said 3-4 years as well, and I would have been | certain beyond any doubt that it was more than 2 years. | Crazy. | ratww wrote: | I find it personally hard to date stuff that came out or that | I watched during the pandemic. To me it felt like I consumed | 4 or 5 years of content in the span of each year. My sense of | time is completely twisted. | djmips wrote: | Maybe you should submit the video to The Hummingbird Clock | and find out for sure! hehe | Aachen wrote: | In 2018, we went with school to the national forensics | institute where they (among other things) presented their | research on this. Not sure if it's also online somewhere; their | website is nfi.nl | helsinkiandrew wrote: | This 5 minute video from Tom Scott on YouTube is a good overview | without that annoying hum: | | https://www.youtube.com/watch?v=e0elNU0iOMY | sandworm101 wrote: | How many videos, outside fixed webcams, come from devices plugged | into the wall? I venture that 99.99% of videos where the | timestamp is questionable come from battery-powered devices. As | for mains hum, portable devices pick up so many hums from so many | sources that i doubt much useful mains hum is ever recorded. | nippoo wrote: | Mains hum is by far the most powerful source of electromagnetic | radiation in most indoor places. And the device doesn't have to | be connected to the mains to pick up EMI from it - turn up the | gain on any battery-powered preamp and you'll hear it. | lalopalota wrote: | If you follow the "How it works" link: | | > Digital recordings almost always have mains hum on them, | either because the device was plugged in to the mains or | because it inducts it off nearby cables, lights and | appliances in a room. | dev_tty01 wrote: | This is why guitars often use a humbucker pickup to cancel | the EMI from the mains. | | https://en.wikipedia.org/wiki/Humbucker | s0rce wrote: | You don't pick up the hum from being plugged into the mains. | Nearby equipment generates sound at the frequency (and | harmonics) which are picked up by the microphone. Various other | equipment is sensitive to the EMF. As others mentioned its | pervasive indoors and near power lines. | pugworthy wrote: | That clock graph is fantastic. | | I haven't let it run long enough to see if the minute and hour | hands do the same line, but if so what a great way to show | minute, hour, and day (24 hour clock) trends. | evan_ wrote: | This would be good to use for syncing clips from multiple cameras | in video editing packages | Phenomenit wrote: | I think this is useful in many ways, I hope one can get access | or build one. | anfractuosity wrote: | I'm surprised when it says "the exact same buzz can be heard at | the exact same moment nationwide from Land's End to John o' | Groats", I didn't realise it would be the same across the UK. | | I played a little with a transformer to take 230VAC -> 12VAC, and | then using a potentiometer to feed the waveform into a soundcard. | But I'm not sure the sample rate of the soundcard was high enough | to accurately measure the times between 0 crossings. | | Photo of the very messy setup - | https://www.anfractuosity.com/files/hum.jpg | sgtnoodle wrote: | Explicitly watching for zero crossing seems like a rather | limiting approach to quantifying a sine wave. Even then, at | 48Khz you should get 400 samples between zero crossings, so you | should do better than 0.5% accuracy. | | There's a lot of information held within the time series data | of an audio signal, and something like an FFT can tap into it. | For a 60Hz signal the Nyquist frequency is 120Hz, which is well | below any audio interface. It seems like accuracy of any | processing would be limited by a crystal oscillator somewhere | more than anything, and perhaps any unintentional signal | aliasing if there's no low pass filter before the audio | interface's ADC. | im3w1l wrote: | Well 60/50Hz isn't the only relevant frequency here. Lets say | you plug in ethernet-over-power (available off the shelf). | You'd need a very fast interface to notice that. | sgtnoodle wrote: | I can't imagine folks' ethernet-over-power signals are | propagating across the national power grid, and even if | they were, they aren't getting picked up in any audio | streams. | anfractuosity wrote: | That's a good point re. the crystal oscillator. | | Maybe I'm wrong re. the sample rate then, I found this paper | - http://www.forensic.to/ENF%20processed.pdf , where they | mentioned 8kHz as the sample rate. | | I think what I was thinking is commercial systems such as | https://synectic.co.uk/product/sd037-frequency-monitor-html/ | mention specs such as 'The frequency monitor units are | supplied pre-calibrated to an accuracy of +/-0.0001Hz' | sgtnoodle wrote: | I was mainly responding to the hobby experiment of | connecting a 12V transformer to an audio input on a | computer. | | Even then, it seems like 8Khz sampling would be plenty to | fingerprint a 60Hz signal. 8Khz sampling can capture | information up to 4Khz, per the Nyquist frequency. | | That frequency monitor spec sheet mentions 90ms response | and filtering, which would imply it averages information | across 5 periods. Also, because it's a purpose built | device, it's likely not periodically sampling the waveform | with an ADC, but rather has a dedicated zero-crossing | detection circuit that feeds into a capture input on a | digital timer with at least microsecond resolution. | quacksilver wrote: | This is widely known and allegedly used by law enforcement | forensics etc. | | I have often thought about building a SaaS service that strips or | adds the correct hum and harmonics to videos if you wanted to | plant some false evidence or make a good deepfake. If it failed | to make much cash I could put it on github for free. | | I have never quite found the time and openly doing that kind of | thing is probably likely to attract undesirable attention. | agilob wrote: | >If it failed to make much cash I could put it on github for | free. | | Silk road was closed in 2013 | alexeldeib wrote: | Markets are alive and well. Not as prolific, but not dead. | | Not really sure what your point is, though? They don't | typically have audio recordings so not sure I see the | relevance. | unvs wrote: | There's an artist called Oystein Wyller Odden that works with | mains hum. I find it pretty fascinating: | | _Kraftbalanse is a musical translation of the hum from the | mains; i. e. the frequency of the alternating current. The piece | is based on the fact that this frequency is not stable, it | fluctuates subtly around 50 Hz as a direct result of supply and | demand in the power market._ | | _The composition consists of a self-resonating piano that is | tuned to resonate on 50 hz and overtones of 50 hz (100 Hz, 150 | Hz, 200 Hz etc.) The piano is fitted with vibration-elements - | transducers - plugged directly into the electrical grid, causing | the resonance and timbre of the piano to change with the | fluctuations on the power market._ | | _The piano is accompanied by a string octet. The musicians are | equipped with voltmeters that measure the frequency of the | current in real time, as well as a score of instructions on how | to respond to changes in this frequency._ | | https://vimeo.com/370554138 | Waterluvian wrote: | I was expecting one of those music YouTubes where they take | some sample and process it so much that it doesn't really | matter what the sample even was. But I'm pleasantly shocked | (ha!) | | They really evoke the feeling of electricity. It reminded me of | the soundtrack to the Chernobyl miniseries. It's... powerful | and eerie and calmly, effortlessly, sluggishly intimidating. | huehehue wrote: | This is awesome. I've been kicking around the idea of a | notation/composition system that uses external forces | (temperature, moon phase, time, etc) as live input but prior | research is a bit hard to come by. | | Feeding signal into e.g. a guitar pedal is easy enough, but | mutating an entire orchestra in real time is a different beast. | If anyone knows of similar works I'd be grateful for links. | rzzzt wrote: | You can also hear it around 3:00 and towards the end, while the | artist talks about the work: https://youtu.be/I_BanULj8wk | mechanical_bear wrote: | Ugh. Login to watch. Hard no. Too bad, seems interesting. | sillysaurusx wrote: | Odd, I was able to watch it without logging in. (It is!) | Retr0id wrote: | I wonder if it's based on geolocation. I'm being forced to | log in, in the UK. I've noticed sites increasingly doing | this to UK audiences, despite the fact that, iiuc, the | draconian age-gate legislation hasn't actually landed yet. | taejavu wrote: | Umm, I simply ignored the "log in with Google" popup and | clicked play. Does that not work for you? | Retr0id wrote: | > Video is not rated. Log in to watch. | tgsovlerkhgsel wrote: | I was excited to possibly see this provided as an open source | tool or at least an automated service, but the site offers a form | to request dating, which looks like a manual process. That's not | really making it available to everyone. | IshKebab wrote: | Yeah it's kind of surprising that nobody has set up a properly | open one with downloadable history. This "fill in a form" one | is lame. | mike_hock wrote: | It's super fishy. Why should I trust them to process | potentially sensitive material? If you want to level the | playing field, just put the collected data out in the open so | anyone can download it and correlate any video they like with | it, no need to upload the video to Mr. Anonymous and hope he's | being truthful about his pure and noble intentions to support | human rights. | remram wrote: | How difficult would it be to defeat that completely or fake a | different date? If people can find subtle noise that fools | computer vision algorithms, can something similar not be applied | to this? | | A band-pass filter might be a little simplistic because it's | never 100% attenuated and the harmonics persist, so given a long | enough sample you would probably be able to correlate. But | perhaps more advanced techniques exist, if you know exactly what | the other party is looking for? | sholladay wrote: | Yet another reason that the world's electric grids should be | replaced with DC power. | | AC power was only a good idea when we didn't know how to make | good DC-to-DC voltage converters. | | https://www.electricaltechnology.org/2020/06/advantages-of-h... | KMnO4 wrote: | Or when we decided to live more than 100m away from the power | plant? DC doesn't travel well. | Aachen wrote: | Warning: site autoplays a loud (presumably 50Hz) buzz... | bumpty wrote: | According to http://hummingbirdclock.info/static/js/hum.js the | base frequency is 200 Hz, but has a gain of 4, which seems to | push it more into the higher harmonic range as the waveform is | clipped: // hum.js // toggle | html audio on/off // with cookie to maintain state | // and use html5 audio synthesis // ios html5 audio | must be triggered // call init_hum() after DOM loaded | // 0. create audio context // 1. create oscillator, | define // 2. connect oscillator to gain // 3. | create gain // 4. connect gain to output // 5. | start oscillator (on click) var audio; | var audio_context; var control; var vco, vca; | var hum_delta = 1; var hum_base = 200; var | hum_min = 100; var hum_max = 400; /* | init */ function init_hum() { | audio = get_cookie("audio"); console.log("audio = " | + audio); audio_context = get_audio_context(); | console.log("audio_context = " + audio_context); | control = get_control(); if (audio_context != | "false") { if (audio != "off") { | set_hum(); hum_on(); } | } else { set_cookie("audio", "off"); | } } function get_audio_context() { | var which_audio_context = window.AudioContext || // default | window.webkitAudioContext || // safari | false; this_audio_context = new | which_audio_context; return this_audio_context; | } function get_control() { var | this_control = document.getElementById("control"); | this_control.addEventListener("click", hum_on_off); | return this_control; } function | set_hum() { vco = audio_context.createOscillator(); | vco.type = 'sine'; vco.frequency.value = hum_base; | vca = audio_context.createGain(); vca.gain.value = | 4.0; vco.connect(vca); | vca.connect(audio_context.destination); } | /* on off */ function hum_on() { | set_hum(); vco.start(0); | control.innerHTML="×"; set_cookie("audio", | "on"); audio = get_cookie("audio"); | console.log("audio = " + audio); } | function hum_off() { vco.stop(0); | control.innerHTML="+"; set_cookie("audio", "off"); | audio = get_cookie("audio"); console.log("audio = " | + audio); cleanup(); } | function hum_on_off() { if (audio == "off") | hum_on(); else hum_off(); } | function cleanup() { vco.disconnect(0); } | /* cookies */ function set_cookie(cname, | cvalue) { document.cookie = cname + "=" + cvalue; | } function get_cookie(cname) { var | name = cname + "="; var ca = | document.cookie.split(';'); for(var i = 0; i | <ca.length; i++) { var c = ca[i]; | while (c.charAt(0)==' ') c = | c.substring(1); if (c.indexOf(name) == 0) | return c.substring(name.length,c.length); } | return ""; } function | check_cookie(cname) { if (getCookie(cname) != "") | return true; else return false; | } | | The audio spectrum analyzer on my phone (Spectroid) records it | most strongly around 1000 Hz. | jeffbee wrote: | At 50Hz it would be inaudible on most computers. | | https://szynalski.com/tone#50,v1 | tiborsaas wrote: | True, but cheating a bit with a triangle wave would solve | it thanks to the harmonics. ___________________________________________________________________ (page generated 2022-10-09 23:00 UTC)