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Archive for June 3rd, 2015

Fly6 Video Compression: Blur to Sharpen?

So I stuck a snippet of ordinary “transparent” (it’s actually translucent) adhesive tape across the top of the Cycliq Fly6 camera lens:

Cycliq Fly6 Camera - blur tape

Cycliq Fly6 Camera – blur tape

That smoothly blurs the top third of the frame:

Fly6 - Tape-blurred frame

Fly6 – Tape-blurred frame

The motivation for using translucent tape: it should maintain roughly the same brightness and color balance across the whole image. Opaque tape would burn out the remaining image as the camera desperately tries to maintain an average gray level.

Fast-forwarding VLC with the video stopped forces it to display the inter-frame compression blocks spanning several seconds of video:

Fly6 - Forced compression artifacts

Fly6 – Forced compression artifacts

The upper third of the frame has big, simple blocks that pegged the files at a uniform 475 MB per ten minute file, somewhat lower than the un-blurred 500 to 700 MB. So the compression definitely isn’t working nearly as hard.

I hoped that simplifying the uninteresting part of the image would leave more bits for license plates and other interesting details, which might be the case. New York has two main licence plate color schemes (the obsolete high-contrast blue-on-white and the current low-contrast blue-on-orange “Empire Gold”) and both the Fly6 and the Sony AS30V cameras do much better with white plates in full sun.

Some samples at full size:

Fly6 - License Plates

Fly6 – License Plates

Those were chosen based on:

  • Similar range / angle: just over the center line
  • Same-size crop box: 350 x 197
  • Sun vs. shade

I think those are somewhat sharper than the plates from un-blurred frames, but it’s not like the camera suddenly woke up smarter and started paying attention to the important stuff.

Time for more riding, minus the tape…

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