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Action Camera Video Compression vs. License Plates

Having recently mounted a Cycliq Fly6 rear-facing camera (more about this later) on my Tour Easy’s seat, I had high hopes it might produce more legible images than the Sony HDR-AS30V helmet camera. Although these still images have been compressed a bit, that doesn’t affect the conclusions; the video files aren’t any more readable.

The Fly6 shows where the driver laid on the horn:

Rt 376 at Cedar Valley - 2015-05-22 13:34 - Seat - 1

Rt 376 at Cedar Valley – 2015-05-22 13:34 – Seat – 1

The next two come from the Sony HDR-AS30V helmet camera:

We couldn’t hear what the passenger said above the horn, but it didn’t sound friendly:

Rt 376 at Cedar Valley - 2015-05-22 13:34 - Helmet - 1

Rt 376 at Cedar Valley – 2015-05-22 13:34 – Helmet – 1

However, the driver gave us about as much clearance as can reasonably be expected with oncoming traffic:

Rt 376 at Cedar Valley - 2015-05-22 13:34 - Helmet - 2

Rt 376 at Cedar Valley – 2015-05-22 13:34 – Helmet – 2

Traffic generally hits the 40 mph = 60 ft/s speed limit on that curve and we’re rolling at 10 mph =  15 ft/s, so the relative motion might be upwards of 45 ft/s. The Fly6 runs at 30 frame/s = 1.5 ft and the AS30V at 60 frame/s = 0.75 ft. Although the exposure time is much shorter than the frame time, you can see plenty of motion blur in all the images.

The Fly 6 captures 1280×720 video @ 30 frame/s with variable bit rate compression, saving a separate file every 10 minutes on the dot. The files range from 300 MB to 600 MB, more or less.

The AS30V captures 1920×1080 @ 60 frame/s with constant bit rate compression, plopping a 4 GB file every 22 minutes and 43 seconds.

The Fly6 seems to preserve more image detail than the AS30V, but it’s probably a factor of the native resolution and compression method. The cameras provide absolutely no control over any image functions or settings; they do what they do and you get what you get.

The video compression algorithms seem overwhelmed by the number of pixels that change from frame to frame: asphalt and leaves generally have blocky compression artifacts, particularly in low light, and license plate text generally gets compressed into a blur.

When the camera remains stationary and the image doesn’t change, the compression artifacts largely disappear and the images become crisp and beautiful. Unfortunately, that’s not generally the situation while we’re riding.

I want to apply “low resolution OK here” masks to parts of the frame, leaving more bits for the critical parts. Perhaps applying thin tape to the top third of the frame would help?

Meanwhile, back on the road, nearly all drivers understand the rules and act accordingly; this was a rare occurrence.

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  1. #1 by Daniel B. Martin on 2015-05-26 - 11:55

    We couldn’t hear what the passenger said above the horn, but it didn’t sound friendly …
    When you can’t understand the shout, best to assume it is words of appreciation and encouragement.

    • #2 by Ed on 2015-05-26 - 13:44

      Aye… [sigh]

  2. #3 by Jason Doege on 2015-05-26 - 12:28

    One of my first experiences after moving to Arizona 30ish years ago was to visit Mandel’s Shooting Supplies in Old-Town Scottsdale. As I was walking up, a big, disreputable-looking biker rode up on his very noisy Harley, stopped and swung off. Strapped to his back was a sub-machine gun with a silencer. I actually asked him about it and he said that it kept the people in the cages very attentive and polite.

    • #4 by Ed on 2015-05-26 - 13:46

      Probably had the T-shirt, too: “Honk if you’ve never seen a gun fired from a moving motorcycle!”

      I suppose mastering a gas horn would be easier…

      • #5 by Red County Pete on 2015-05-26 - 21:06

        Slightly misquoting Robert Heinlein:

        “An armed society is a polite society.” Seems true here in backcountry Oregon. (And one of many reasons why I’d rather not visit Portland…)

        • #6 by Ed on 2015-05-27 - 08:03

          An annual bag limit of, say, two might suffice, although (as DD3 put it) you’d want to stay in the basement for the first six months…

          A bit more on RAH and guns may be helpful for newcomers.

  3. #7 by Kurt Higgins (@kurthiggins) on 2015-05-27 - 10:05

    I’ve been contemplating getting a Fly6 camera, but am disappointed to learn of its quality issues with motion. Would you consider it an asset in the realm of Protecting Myself from Aggressive or Inattentive Drivers? Or not worth it?

    • #8 by Ed on 2015-05-27 - 12:56

      It’s on the low side of marginal for license plates and seems somewhat soft-focused in general. If I didn’t see the same effect with the Sony AS30V’s fancy Zeiss Tessar glass lens (which surely has little to do with the original design), I’d blame it on the not-optically-flat plastic lens cover.

      For a synoptic record of What Just Went Down, it’s probably better than a helmet camera, as Really Bad Things generally come from behind. I think a vehicle description might count for at least as much as a plate number and is certainly better than the nothing you’d otherwise be able to report.

      With that in mind, I’d say even if the camera provides precious little protection, it should give your next of kin a way to shut down the whole conversation that starts “The motorist said the bicyclist swerved into traffic”. Whether that makes any difference remains up for debate, of course, as cyclists aren’t well protected by the law, either.

      • #9 by tantris on 2015-05-29 - 11:02

        I agree, a bike with a camera won’t help. But some propaganda that there are “camera-bikes” that report traffic violations would.
        Police never did much about bike thefts, but now they have “bait bikes” to catch bike thieves. (And most importantly stickers for your bike and local News coverage.)
        If some police department would be on board, “camera-bikes” -and News coverage about people getting caught, would change behaviour. Heck, one could even do it “educational”: have the ticket waived by attending a free safety training.

        • #10 by Ed on 2015-05-29 - 14:53

          I haven’t encountered the Sheriff’s Deputies patrolling the rail trail (on ATVs, for reasons) in quite some time; they used to be common sights.

          Expecting them to patrol the roads around here: dream on! [sigh]

  4. #11 by Koos van den Hout on 2015-05-31 - 10:15

    I’ve seen several helmet cam videos from UK cyclists who shout the license plate in a dangerous situation (when they can read it while saving their own lives) just to have it on record. Which in some cases does not improve the mood of the driver and the danger of their actions. You can’t win.

    • #12 by Ed on 2015-05-31 - 10:33

      I (try to) do that, too, when I have enough brain cells available; that was part of the motivation behind the absurd fake-fur tuft on the front of the helmet camera.

      In traffic, nobody can hear you scream…

    • #13 by Kurt Higgins (@kurthiggins) on 2015-06-03 - 11:00

      That’s a great tip. Thanks for mentioning it. Now to remember to do so in the heat of the moment…