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Transform Cellphones Into a CCTV Swarm

Posted by Zonk on Thu Nov 01, 2007 12:55 PM
from the now-how-to-interface-your-brain dept.
Security Communications Programming Technology IT
holy_calamity writes "Swiss researchers have developed java software that has bluetooth-capable camera phones form a distributed camera network. Each phone shares information on visual events with its neighbours and can work out the spatial position of phones around it (pdf). The software will become open source sometime next year, and the creators say it could be used to make a quick and dirty surveillance system. 'The phones currently use the average speed people walk to guess the distances between themselves, based on how long people take to move from one phone's view to another's. In testing, the system determined the distances between each phone with about 95% accuracy. They were placed 4 metres apart, making it accurate to about 20 centimetres. In future, recording the speed at which objects pass by would make more accurate judgments possible.'"
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Submission: Hack cellphones into a CCTV swarm by holy_calamity (872269)
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  • So... (Score:3, Funny)

    by Smordnys s'regrepsA (1160895) on Thursday November 01 2007, @01:02PM (#21199765) Journal
    ...now stalking my favorite celebrity can be a group event!
  • Does the fact that this will be an open-source application compensate for the fact that this introduces yet another method of surveillance into society?
    • It'll depend on how instrumental it is in bringing about Skynet. Personally, I think it'll be pretty useful for it, so it goes in the 'evil' bucket. (Despite how unutterably cool it is.)
    • And more importantly, pervasive surveillance. Just you wait until they make public displays of affection illegal.

    • Re:Open source surveillance (Score:4, Interesting)

      by jibster (223164) on Thursday November 01 2007, @01:24PM (#21200037)
      Maybe the glass is half full.

      Think of a peaceful protest group using, an admittedly far superior, form of this to camera swarm the police. The perpetrator of any action, a policeman clubbing an innocent citizen for instance, might question their actions if they knew they were surrounded by this swarm.
    • Clearly we all need to start wrapping tinfoil around our cell phones as well as our heads.
    • And, you can bet that AT&T will dip their grungy fingers into the code and obsequiously supply the alphabet soup names agencies with code to throw off the positioning far worse than GPS. They'll supply them with real-time image detection and distortion capabilities. Maybe even bluescreen/reboot the phone as a mild warning, or outright cripple the service. After all, the government HATES competition...

  • Holy privacy violations Batman! (Score:3, Funny)

    by edunbar93 (141167) on Thursday November 01 2007, @01:13PM (#21199913)
    it could be used to make a quick and dirty surveillance system

    Emphasis on "dirty". People take those things into their homes and leave them on their bedroom end-tables you know.

  • The real question at hand here. (Score:3, Informative)

    by blhack (921171) * on Thursday November 01 2007, @01:17PM (#21199963)
    But does it run skullbocks?

  • F&TF3: Tokyo Drift (Score:4, Interesting)

    by OctoberSky (888619) on Thursday November 01 2007, @01:20PM (#21199995)
    Is this basically the last drive sequence of F&TF3: Tokyo Drift?

    Where all the kids are viewing/filming the race down the mountain as it goes by?

    I thought that technology (well, that CGI) was rediculous but maybe it's not that far away?

    (NOTE: Give me Karma, I admitted to watching that movie, that's gotta count for something).

  • I predict (Score:5, Insightful)

    by Buelldozer (713671) <cliff@NOSpAm.gindulis.net> on Thursday November 01 2007, @01:21PM (#21200009)
    That the police are going to really dislike this.
      • Oh my.

        Bullet-time, swoop around come shots?

        Actually, in slow mo- people's bodies look disturbingly ripply.

  • concert-recording on the cheap (Score:5, Interesting)

    by smellsofbikes (890263) on Thursday November 01 2007, @01:24PM (#21200033) Journal
    I've spent some time designing and programming (but will never finish) something similar to this, just using cellphones' audio capabilities. Imagine getting twenty random people at a concert to call into a server and leave their cellphones running, recording the concert from twenty different points. From the overall stream, you should be able to derive an excellent, local-noise-removed bootleg, and from a bit of playing with signal intensities you should be able to figure out where the individual recorders were and do some nice sound balancing.

    We're all carrying these great little computers: we should start doing networked or collaborative stuff with them.
    • That seems really interesting but (Warning: non audio engineer question ahead) How would you deal with the distortion the audio goes through between transmission and general crappy quality input (ie microphones) on the phones themselves?

      I guess the little dinky mic may not be so different from a typical bootleg though...Still, neat idea. It makes sense that you could do that kind of manipulation, but I'd never really considered it (Signals *really* is not my forte)
      • Yeah, it'd be crap. My hope is that by using multiple microphones and relying on the fact that they're bad in different ways, you'd be able to derive a fair amount of quality. Obviously, information that none pick up is lost. But oversampling to partially compensate for poor signal/noise is done with a lot of other noisy signals.
        Signals isn't my forte either, by a long shot. It's just an idea I thought was interesting, so I started playing with using some dsp software mixers.
    • From the overall stream, you should be able to derive an excellent, local-noise-removed bootleg,

      Great idea. you are forgetting one small tidbit. Audio quality will suck because of 2 things you fail to consider. Microphone quality in cellphones is below dismal. Think lower than toy quality. Secondly the audio processing aspects of callphones is just as dismal. Unless you can get an open hardware platform to scab on decent microphones and decent audio circuits and encoders it will not sound any better th

      • Re:concert-recording on the cheap (Score:4, Interesting)

        by Jherek Carnelian (831679) on Thursday November 01 2007, @01:43PM (#21200273)

        This might be true with a 44- or 48kHz sampling rate, but "phone quality" 8kHz sampling will give you something that sounds worse than a cassette recorder stuck inside a coffee can.
        Not so fast there. If it is possible to algorithmically combine a handful of low-resolution (i.e. low sample rate) images of the same scene to get a high resolution version, it ought to be possible to algorithmically combine a handful of low-resolution recordings of the same audio to get a high resolution version.

        • Re: (Score:2, Informative)

          by Anonymous Coward

          If it is possible to [apples], it ought to be possible to [oranges].

          Sorry, but speaking as someone with a degree in electrical engineering who spent the better part of a decade studying this stuff, it just doesn't work like that. You can use padding tricks increase the [false] resolution of the spectrum you're dealing with, but you can't recover signal that you failed to record in the first place. See also: Nyquist-Shannon sampling theorem [wikipedia.org].

          For a simpler analogy, it's like using 16-bit registers to recor

          • Re: (Score:3, Informative)

            by matfud (464184)
            Yes that true, but only for one source. If you have multiple 8khz signals whose sample points are not synchronized then you can combine them to improve the overall frequency range obtainable. However this would increase the final achivable frequency in proportion to the log of the number of sampling devices (under ideal situations) so you would need a fair few sources (If I remeber correctly). Mobile phones would probably be quite far from this ideal as they
            a) would be physically seperated so you'd have to

            • Re: (Score:3, Insightful)

              by evanbd (210358)
              The problem with this approach is that audio ADCs have an analog antialiasing filter in front of them. It's not just that you can't see the high frequencies because you don't have enough samples; they're actually *removed* from the analog signal before it's digitized. If they weren't, you could recover them with enough microphones, but you'd also get weird aliasing artifacts. As it is, they're gone, never to return.
              • Well, that just sucks. So they've got, basically, a low-pass filter with a rolloff so that their sampler never sees anything above 8khz? Phoo.
                My oscilloscope dithers the clock rate so even though it's 350 MHz, it acts cleaner because it moves back and forth across a signal, to evade aliasing artifacts. My thought was that multiple data streams from different cellphones would act similarly, but if the data's shorted to ground before it ever sees the ADC's front end, well, just phoo.
                • Well, 4kHz, because that's the Nyquist frequency for 8kHz sample rate. Unfortuntaley, if you're intending to use the data without doing the dithering work, you need to get rid of the aliasing artifacts -- which, uncoincidentally, are the exact data that would allow the dithering to function.
                • My oscilloscope dithers the clock rate so even though it's 350 MHz, it acts cleaner because it moves back and forth across a signal, to evade aliasing artifacts.

                  Your oscilloscope uses random repetitive sampling to reconstruct repetitive waveforms which general audio is not. There is a trigger circuit which serves to align the sampling clock with the presumed start of the waveform so that new samples are placed into the correct place. This technique allows full reconstruction of a high bandwidth repetitive
                • If it's doing that, then there's a digital AA filter before the resampling for the same purpose as the analog AA filter. It would have the same effect.

          • You can use padding tricks increase the [false] resolution of the spectrum you're dealing with, but you can't recover signal that you failed to record in the first place.

            For a simpler analogy, it's like using 16-bit registers to record 32 bit integers. No matter how many 16 bit registers you use or how you combine them, you're not going to recover the upper 16 bits -- they're lost because you didn't record them.

            I'm not sure what you mean by "padding tricks" but I have to disagree and your analogy is what makes it clear. By using two 16-bit registers you can fully represent a 32-bit value.

            Similarly an 8KHz sampling rate means that a measurement is taken 8,000 times per second or once every 1.25 milliseconds. If you have two 8KHz recordings that are offset by exactly half of the sampling period (0.625 milliseconds) from each other then you can combine the two into a single recording with a sampling period of 0.62

            • I'm not sure what you mean by "padding tricks" but I have to disagree and your analogy is what makes it clear. By using two 16-bit registers you can fully represent a 32-bit value.

              Correct, but this is like storing the same (or very similar) 32-bit integer in two 16-bit registers (the same integer, put in both places). The top data is sliced off both of them.
              • Isn't that the whole point though of using multiple offset signals, so that one can obtain the data at some point in between the original waveform, thereby essentially doubling the effective sampling rate? What precisely is being sliced off the signals?

        • Re: (Score:2, Informative)

          by fenodyree (802102)
          That comparison is flawed.
          To use a car analogy: You can construct a complete working car from a junkyard provided that the cars in the junkyard have different problems and conversely different working parts.
          As the way multiple low resolution images of the same seen create a higher resolution is primarily based upon the (usually accurate) assumption that the images will be lit differently such that where information is lacking in one image, it _is_ in another, and vise versa.

          However, with the phones, the
  • It works in a lab but the real question is how well does this perform in the real world...
  • The Swiss team also found a unique characteristic of the network that it used to swarm around one of the nodes more often than not. Later they pinned it on the only hot blonde in the team.
  • A CCTV system from BT cellphones ? Why, oh why ? Because boffins have time and my money to lose ?
    Somebody please explain the use of such a... discovery ?

    Ah.

    Surveillance.
    I get it now. The T word is about to be spoken, again. Great. I'm looking forward to BT-holding surveillance militia roaming the streets.
  • Bluetooth is a big power draw as well as the camera. Also cell phone data costs alot as well.
  • Most people I know don't keep their cell phones in some snap-off carrier on their belt like a modern-geek pocket protector. They stay in pockets, where they can't see. And women keep them in purses. So only a few phones are actually going to be able to see without their owners holding them out on purpose.

    What's the point of this, again?
      • Becasue if there is something worth seeing, more people will take there cameras out of their pockets.

        You are also overlooking the fact that if Gollum had one, he would have know what was in Bilbo's pocketess

  • Can you see me now? (Score:3, Funny)

    by r_jensen11 (598210) on Thursday November 01 2007, @01:48PM (#21200335)
    Good!
  • I think soon, the last thing most of the public cameras need to see is a paintball or the business end of a spraycan. Just remember to wear a mask, hat and cloak while doing it- since you are going to be surveilled by multiple cameras as you take them out. For irony, I suggest a "V" mask.
    • There has got to be a Natalie Portman joke sitting somewhere in this comment.
    • Cameras in everybody's hand is a good thing. It levels the playing field.
      • Not if the government can monitor it and enforce arbitrary morality and political laws based on it.

        Only privacy protects that. Privacy comes with it's own risks and abuses but carries some ability to redress abuses.

        • If everyone does it, it minimizes abuse of power.

          In '1984' monitoring was bad because the people couldn't monitor the 'government', and if they could they had no recourse.

          In the US, people actually do have recourse, and in fact have protection that help them.
          Do people try to over ride those laws for there own agenda? From time to time, yes. Inevitably they get slapped down.
          We also have the advantage of being able to remove someone from office.

          Plus your appearance on a public area is not private information.
  • Correct me if I'm wrong, but doesn't CCTV mean "closed-circuit television"? As in, the camera is connected with a solid conductor to the display? If that's the case, then wouldn't a system that transmitted video over the air (at least, without displaying it locally first) be something other than CCTV?
    • Granted, it's been a while since I read Prey, but I recall nothing about cameras. Swarms, yes. Miniature, yes: nanoscale. But cameras? Hmm.

      Scary book nonetheless, though.
    • I can see this being advantageous for single system, but for people in general? This just reeks of being impractical.

      For one, no one I KNOW walks with their cameras out in front of them, so the cameras would have setup such a way such that there is a single camera dedicated to capture the event. How do you know a camera is going to capture an event in the first place? Seriously, phones are for talking, not being your peeping-tom from afar.

      It would be pretty easy to strap a cell phone to your vest, wou
    • "Seriously, phones are for talking, not being your peeping-tom from afar."

      Thanks for the thought, gramps.

      Seriously though, when something that does happen people want to record, there will be several people recording it. That is when it is useful.

      The bigger the event, the more people will be recording it. Most of the time, the bigger the event the more important it is.

    • I keep my cell phone in my back pocket
      Is that why so many Europeans keep losing their phones in the toilet?

    • So now someone could be watching all those cell phone cameras everybody is so afraid of. If the phones could somehow figure out where they're pointing and stitch the images together.. *shudder*
      No need for Google Street View?

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