Bike Commute, Pushing Codecs

Had a few ideas about ways to present multiple views of GPS data in a multimedia project, part of which involved videotaping my bicycle commute along the Ohlone Greenway from handlebar-eye-view, then speeding up the 27 minutes of footage to a more watchable five minutes. Mounted a camera with a very sturdy professional cam clamp left over from a long-ago project and set off. Hit a bunch of snags, and am not sure whether they might be show stoppers for the whole project. What I had hoped would capture a lovely ride turned into a struggle with the outer limits of the most advanced codec technology, and ended up looking like total dooky.

Problem #1: Because camera is rigidly attached, it picks up every little bump in the road. This mounting method is inherently shaky.

Problem #2: Because camera is on handlebars rather than on my head, the camera view doesn’t track my line of sight, which is very disconcerting for the viewer (or maybe just for me, since it doesn’t match my experience at all).

Problem #3: Video doesn’t account for a human’s peripheral vision, which accounts for so much of the experience not shown here. Again, disconcerting (makes it seem much more dangerous than it actually feels).

Problem #4: The natural side-to-side pumping action of bicycling adds to a seasick, high-motion effect not actually experienced by the rider.

Problem #5: Once the footage was speeded up, pauses at stop signs pass by in a blink, making it look like I ride with total disregard for both death and the law. Not so! Though I do do some rolling stops, I’m actually very careful at intersections, especially because the Ohlone Greenway cuts across streets a ways away from the “real” intersections, so most drivers aren’t in the headspace to be expecting cross-traffic (despite zebra stripes and big yellow warning signs). I wear an orange safety vest and treat those intersections with kid gloves.

Problem #6: Video codecs rely on data similarities between frames, and none of them perform well under high-motion conditions. What could have more motion than shaky footage played back at 5x? Thought I could convey a beautiful morning experience, but this looks completely pixelated and smeared-out, even though I used the usually gorgeous h.264 codec. Of course, YouTube also apply their own compression, but my local version doesn’t look much better than this one. The only version that came out looking passable was the version with no compression at all — and it’s 750 MBs.

The footage is also a bit over-exposed, but that’s operator error rather than endemic. Hope to have access before long to a helmet-mountable lipstick camera, which should help a lot with problems 1, 2, 3, and 4, but will do little for problems 5 and 6. Back to the drawing board.

Music is “High Water” by Bruce Lash – Bruce gave me permission to use his stuff in projects back when I was at Adamation, and he now offers a bunch of downloadable music free for personal use.

10 Replies to “Bike Commute, Pushing Codecs”

  1. Try motion JPEG as a codec. Each frame will be saved separately as a still image. This is obviously larger than codecs which do interframe compression, but still much smaller than uncompressed. Unfortunately that won’t help you publish high quality to the web through YouTube or any other Flash-based site.

  2. Nice effort! I think my favorite part, however, is watching you dodge around pedestrians on the greenway – even though there is a perfectly good Ped path 10 feet to the right! Drives me insane.

    This does make your morning commute look dreadful dangerous, which despite your cautious riding skills, supports my impression of riding in Berkeley.

    As far as issue #2: once time-compressed, following your head whipping back and forth as you check to the left and right may be even more disorienting than the handlebar cam. But at least the camera won’t be butt-height for the cyclist in front of you, which is hilarious.

  3. Drives me insane. Other insanity makers: People “waiting at the light” halfway into the crosswalk (I give them a piece of my mind), and peds walking towards oncoming traffic in the LEFT lane, totally oblivious.

    Check some of the New York bicycle messenger videos on YouTube to see some helmet-mounted video – it’s much smoother and much less disorienting – which is also due in part to it being real time rather than sped up. But watch those and see if you still think Berkeley riders ride dangerously :)

  4. Thanks for the tip Daniel. I’ll give Motion JPEG a shot. I think I may also change approaches and try editing down to 5 minutes, rather than speeding it up 5x. Although that will of course not match up with animated GPS tracks.

  5. Vincent – Heh, that’s pretty funny. I’m trying to figure out: In what universe is constructing a contraption like that easier or more effective than a helmet cam? The body is like the ultimate shock absorber, right? I mean, wow – cool device he’s got there, but seems SO unnecessary…

  6. That is true, and having such a device, i suppose would be cumbersome and heavy.

Leave a Reply

Your email address will not be published.