3D Printing Demo at the HV Boy Scout CamporALL: Image Processing

More than five hours of stand-up comedy condensed into two minutes of frenzied video showing activity like this:

3D Printing Demo - HV Scout CamporALL 2014
3D Printing Demo – HV Scout CamporALL 2014

The Sony HDR-AS30V perched atop a tripod behind the table, where only one errant Scout bumped it, recording one image every 5 seconds. The non-adjustable focus seems biased for selfies, but the compression definitely produces softer images in subdued lighting conditions, so it’s hard to say.

Each NP-BX1 battery lasts about 2.5 hr in that mode and I brought all three, but simply forgot to install the third one. As a result, we don’t get to see the last 2+ hours… it was a long day.

The “image processing” behind the movie went a little something like this, modulo a few edits to elide my blundering around:

sudo mount /dev/sdb1 /mnt/backup
sudo mount -o uid=ed /dev/sdd1 /mnt/part
mkdir /mnt/backup/Video/2014-05-17
rsync -au /mnt/part/DCIM/100MSDCF/ /mnt/backup/Video/2014-05-17
rsync -au /mnt/part/DCIM/101MSDCF/ /mnt/backup/Video/2014-05-17
cd /tmp
mkdir Video
cd Video
sn=1 ; for f in /mnt/backup/Video/2014-05-17/*JPG ; do printf -v dn 'dsc%05d.jpg' "$(( sn++ ))" ; cp -a $f $dn ; done
mkdir Shrink
for f in *jpg ; do convert $f -resize 50% Shrink/$f ; done
cd Shrink/
avconv -r 30 -i dsc%05d.jpg -q 5 3DPrinting-q5.mp4
mv 3DPrinting-q5.mp4 "3D Printing Demo - HV Scout CamporALL 2104.mp4"

One could, of course, do all that in fewer steps, if one knew the answers ahead of time, which should may apply when I refer back to this post.

Using rsync -au to copy the files from the camera to the 2 TB backup drive neatly solves the problems that occur when the camera’s USB port abruptly disconnects itself during the copy: rsync can recover without losing or trashing any files. Alas, after the camera disconnects, it requires a power cycle to recover its wits.

The USB camera connection reads data at 6 MB/s. Removing the MicroSD card and jamming it in the card-reader slot on my monitor runs at 18 MB/s. Apart from the fact that the MicroSD card seems so flimsy, I wonder how long the spring-detent latch inside the camera will continue working. On the other paw, when the USB port finally breaks, it’ll take the GPS assist data path along with it.

Not shown: the rename 'y/A-Z/a-z/' *JPG that converts the original filenames to lowercase, which I did after the fact. Because blundering around, OK?

The 3964 original 1920×1080 images, hot from the camera, weigh in at 2.2 GB and the half-size video emerged at 118 MB. The default avconv quality setting produces surprisingly crappy results, so I used -q 5. Some after-the-fact fiddling showed that -qscale 5 produces the same file size with about the same apparent quality.

None of that matters, because Youtube set the maximum resolution to 480 and applied ruthless compression. Now I know better…

3 thoughts on “3D Printing Demo at the HV Boy Scout CamporALL: Image Processing

  1. I’m having similar fun with image processing/storing. Back east, I picked up a box of my late father’s slides in Airequipt magazines. The loose slides from his stash got discarded, but I have highlights from 1957 through 1970. 98% are Kodachrome II, and the archival nature of that film is no joke. The remaining 2% is Ektachrome, and while the 1967 stuff is more-or-less OK, one of the two batches from 1961 faded to red. (The other kept its blue bias–my father hated that, but needed the low light capability for a bunch of those shots.)

    The good news is that the third party software that drives my 2003 vintage scanner has a good color corrector. 6 bad slides, 4 really good fixes, one acceptable, and one (slightly overexposed) came out like something from the Op-art school in the late ’60s. This is VueScan, in the Win 7 “basic” version (Linux available, too.) It’s downloaded as “free” with watermarks, and you buy unlock codes for “basic” or “pro” to kill the watermarks and get the features. It sounds like I can sample the “pro” stuff with watermarks, but this is Good Enough. Later on, I’ll let the Gimp try to do better (my Linux boxes only have USB-1, way too slow for this scanner).

    I have about 3.5K of my own 35mm slides. Have to consider if it’s worth scanning. O, for a light table and a 10X loupe.

    1. Have to consider if it’s worth scanning

      Back when I scanned my collection, I realized that if I had to think about each slide, I’d never get it done. So I set the black and white points to span the range of the worst slides I could tolerate, then shoveled the entire lot through the scanner; the few that I really cared about, I re-scanned with more attention to detail.

      The scanned images look awful, but each contains all the (remaining) color from the original slide. They’re all ready for color correction in the unlikely event I want a specific slide, but I didn’t do anything special to the rest.

      For example, here’s the original slide and tweaked image of that water tank:

      Wood-plugged water tank - original slide vs. tweaked image

      Sturgeon’s Law definitely applies to my photos…

      1. Yeah, Sturgeon’s law is a best case for mine, too. I saved them as half-megabyte jpegs, though the ones that needed a fix were saved as 5MB TIFF files before filtering and resaving as jpeg.

        The scanner/software seems capable of a slide per minute, though it was slower getting them out of the Airequipt magazines and slide carriers (the department of redundancy department would be proud of them). Throw in a bit of annotation/puzzling out the notes/content, and it took 60-90 minutes for 36 slides. No such issues in mine–the notes are long gone, if they ever existed.

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