💾 Archived View for zaibatsu.circumlunar.space › ~solderpunk › phlog › story-of-a-roophlop.txt captured on 2023-01-29 at 16:00:53.
⬅️ Previous capture (2023-01-29)
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Story of a ROOPHLOP ------------------- This post is *about* my ROOPHLOCH 2022 efforts, but does not itself meet the criteria to *be* a ROOPHLOCH post. At this point, with just a bit over 24 hours left, with tonight already dark and cold and with family plans already made for Friday night, it seems increasingly less likely I'll make a post which does meet the criteria. I'm less than happy about that, believe you me, but at least this year it genuinely wasn't through a lack of trying. I was content to make my very first ROOPHLOCH post back in 2019 via the relatively unremarkable means of connecting an eeePC to a smartphone's wireless hotspot, but after that humble beginning I always intended to escalate my game, and from even early days I had a really clear plan: I was going to head out with the eeePC, write a post, and then use the `minimodem` to render said post into a .wav file encoded the file via audio frequency shift keying. This is exactly the technology that the earliest dial-up modems were based on. You play a sine wave at one frequency for "0" and at another frequency for "1", and you just sing your bits, one by one, in sequence, at a fixed rate, perhaps with some "stop bits" in there to help synchronise things. Then I'd use my phone to call my wife back at home, who would pick up and point her phone at my ThinkPad, which would be running its own copy of minimodem, set to listen, not to sing, in part of a script which would save what it heard to a text file and upload it to my phlog. The big appeal of this approach was, while I'd probably do it using an ordinary old phone call, the same basic approach would work exactly the same via walky-talky or amateur radio or any other means of remote sound transmission. But while coming up with the plan was easy, I had thus far failed to getting around to actually trying this in time to make a successful post via the method. Well, I started down the road to finally making this long-standing plan a reality, early last Saturday. After a small but irritating amount of yak-shaving related to the fact that minimodem, to my surprise, wants to use PulseAudio by default but PA wasn't set up on either of the machines that I was using, I quickly got to the point where this worked well and reliably with both laptops in the same room, even separated by a few meters of empty space. I used a low baud rate and a wide separation between the two frequencies, to make the whole thing more robust to noise, and because of that it worked despite street noise filtering in through the open windows, etc. Success! But as soon as I moved from transmitting a phlog post across a few meters of empty space, and tried to use exactly the same minimodem commands on both ends to transmit a phlog post from one end of our apartment to the other via a simple phone call, everything stopped working and I wasted the better part of the day trying to figure out why, to no avail, leaving me dejected and bitter. We tried putting the call on speakerphone, or not doing that, holding it close to the ThinkPad's microphone or far away from it (and same with holding the transmitting phone near or far from the eeePC's speakers), muting the receiving phone call to avoid feedback, and we tried giving up on the traditional telephone network proper and using a Signal voice call instead, and we tried every other sensible little change you can think of, and simply nothing worked. I dropped the baud rate down so low that sending a post as long as this one would take a literal hour, it didn't help. You can plainly hear with the unaided ear (and I confirmed it by visualising the ThinkPad's perspective using the `baudline` software) that one tone is reproduced by the receiving phone much more quietly than the other. The output sounds more like on-off amplitude shift keying than shift keying. I have no idea why, but it's clear that modern phones are in some sense too "smart" for this to just work - some kind of automatic gain control or noise reduction technology or something is distorting the audio badly and nothing gets through. I tried reducing the frequency shift to be very narrow, just 25 Hz, figuring that some kind of window-based frequency domain analysis which tried to figure what the signal bandwidth was and filter out anything outside it, but didn't operate fast enough to reconfigure its filters between the frequency shifts, probably wouldn't have windows so narrow that it would differentiate between tones so close together, but this had no effect at all. I don't know why, but accurately reproducing an audio signal consisting of nothing other than sine waves alternating between two fixed frequencies is apparently completely beyond the capabilities of a modern smartphone. I'm sure it's not impossible in principle, no doubt if I dedicated my ongoing energies to solving this problem I could discern the reason and come up with a work around. But truly, friends, life is short and time is precious and this is not an important problem. I'm old and tired and techno-jaded enough at this point (and self-aware enough to know it) that if I fought the long, hard battle and won, my lasting trophy wouldn't be joy and pride and a sense of achievement at the victory, but disdain and hatred over the fact that there was a battle to fight at all when this should have simply "just worked" like I'm sure it would have with an analog landline phone that I had to walk uphill in the snow to use. I declined to throw good time after bad and gave up, and I'm not ashamed of it. I'll have to think up something completely different for ROOPHLOCH 2023.