Friday, December 30, 2011


Tuesday, December 20, 2011

Researchers Turn an Ordinary Canon 5D Into a Hyperspectral Camera

Hyperspectral imaging goes beyond what the human eye can see, collecting information from across the electromagnetic spectrum for use in analyzing a particular object or location (seeing if certain mineral deposits are present, for example). The specialized equipment doesn't run cheap, but researchers at the Vienna University of Technology have been able to turn an ordinary consumer DSLR camera into a full-fledged computed tomography image spectrometer.

Starting with a Canon EOS 5D, the team added a frankenlens made of PVC pipe and a diffraction gel combined with a 50mm, 14-40mm, and a +10 diopter macro lens. They were then able to mathematically reconstruct the full range of spectra from the data captured by the camera's imaging sensor, achieving performance comparable to that of commercial imagers: a resolution of 4.89nm in a hyperspectral configuration of 120 x 120 pixels. The downside is exposure time, with the DSLR requiring several seconds to capture the data, while tailor-made devices need mere milliseconds. The team admits that the current system is on the "low-end" of what is possible, but they already have their sights set on a direct-mount version, which will increase the aperture and lower the necessary exposure time — all while costing under $1,000.

via Technische Universtat Wien

Tuesday, December 6, 2011

Monday, December 5, 2011

Saturday, December 3, 2011

VP8 vs H.264

First, the conclusions for the lazy:
  • VP8 is very similar to H.264, but it does not have better quality, nor is it faster.
  • In the face of such striking similarities, the burden of proving VP8 being patent-free is still on Google.
  • The VP8 spec is not complete or final in any way, so it might take time to integerate this codec into hardware devices.
  • and lastly, having no hardware-accelerated support in existing smartphones/mobile-devices for decoding VP8 makes it very CPU and battery intensive.
One thing good about VP8: it does away with interlacing. Who needs it today, anyway? But VP8 lacks B-frames. What? B-frames can give 10-20% (or more) compression benefit for minimal speed cost.


Friday, December 2, 2011

How NOT to Upgrade Linux Mint from Katya to Lisa

The way to upgrade an Ubuntu-based distro (copied from a lucky person who got is working):
  1. Open a terminal and run 'sudo bash' to get a root terminal
  2. Using a text editor (as root), replace the contents of /etc/apt/sources.list with the following sources list:
    deb lisa main upstream import backport
    deb oneiric main restricted universe multiverse
    deb oneiric-updates main restricted universe multiverse
    deb oneiric-security main restricted universe multiverse
    deb oneiric partner
    deb oneiric free non-free
  3. Run 'apt-get update'
  4. Run 'apt-get dist-upgrade'
  5. Follow the instructions issued, don't worry about overwriting configuration files dpkg will keep a copy in the same directory with the string ".dpkg-old" appended to the filename
  6. Run 'apt-get upgrade'
  7. Reboot
Theoretically, the steps above should be sufficient for Ubuntu upgrading. But Linux Mint discourages in situ upgrades. The recommended way is to back up all personal files and reinstall with new ISO.

I should know. The steps above left me with a system that doesn't allow me to login. Arrgh! I'm beginning to like Fedora more and more already.

Thursday, December 1, 2011

ffmpeg sample use collection

Caveat: may not work in all cases

Very important, add "-threads 0" to every ffmpeg invocation to use all available cores.