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Showing posts from August, 2011

Enabling External Screen

Another slow week ~ parenting, employment, school holidays and academia do not mix well. I have the hardware up and running how I want now. My initial build with the projector on the right and camera on the left had 2 problems. Firstly, as previously noted, its preferable to have the camera on the side of the users dominant hand since this will be used the most. Secondly...the PK301 has a small fan for cooling and having this on the right meant that the exhaust heat was blowing onto my neck and was hot enough to be very uncomfortable. So today I've switched things around, tied things off, added extra washers (oh, the technology!) for stability and, apart from the need for a more stable joint to hold the projector in a position so that it is level with the users view, I am reasonably satisfied with my budget implementation. Not $350...about £350 but then I could have bought a cheaper projector (and may well pick up a ShowWX for testing) and come under budget. I still need to add a...

Fixing "Corrupt JPEG data: n extraneous bytes before marker" error

http://www-personal.umd.umich.edu/~dennismv/corruptjpeg.html jdmarker.c lives in the OpenCV 3rdparty/libjpeg directory, edit out the appropriate line (search for "EXTRANEOUS"), make and install....happy days. Edit: Hmmmm actually the above doesn't work since OpenCV is linking the installed library rather than the 3rdParty version and I can't seem to convince CMake to use the local one...ahhh well one for another day since redirecting standard err to /dev/null works just as well.

Hardware Design

I finally took the plunge and did the epoxy wields on the prototype rig using some Bondloc titanium epoxy and it works really well, setting hard in just a few minutes and rock solid after 15. While the rig is incredibly primitive it does allow me to shoulder mount both the projector and camera and do so so that they are stable. I just need to make a final decision re placement (left vs right for camera/projector) ~ my initial take was to place the projector on the right so as to be in line with my dominant eye, but I think of more importance/potential is to have a better correlation between the forward facing camera and the dominant hand for pointing...which should also reduce occlusion of the projection. I'm slowly uncovering papers in this area and found another one today Designing a Miniature Wearable Visual Robot which details the design rationale behind a robotised wearable camera. Mayol et al (2002) use a 3D human model to examine different frames of reference and requirem...

Machine Learning & OpenCV

Slow progress. I've spent the last couple of days generally looking around at Neural Networks and OpenCVs machine learning code. My aim was to find some relatively simple to implement examples of NNs and form a basic impression of the applicability of the techniques to the task of skin and marker recognition in a video stream. Now I should point out that my understanding of most ML techniques and NNs is rudimentary at best and, at this point, that's fine since I am looking for practical techniques that can be employed at a rapid prototyping stage (hence the cost of experimenting with a proposed solution to a given problem should measure in the hours rather than days); so I am not going to go into too much depth on the AI part of things here. What I do need to do though is define the methodology and results of the experiments I've been running so far since a write-up at this stage will form a useful appendix to my thesis and demonstrate the design process and rationale b...

handwriting Recognition

More of a note post (I've been busy with work/children this week). I noted that one omission in the demonstrations of SixthSense was any form of text input. I want to address this by the provision of an "AirWriting" interface but had been struggling to find any form of decent hand-writting recognition software for Linux. However, Bret Comstock Waldow (now theres a name for the 21st Century!) has come to the rescue with ink2text and SHIP , which, as far as I can tell, runs the MS tablet hand-writing recognition DLLs under Wine and provides access to the routines via a service. Brilliant! I am getting quite excited at what may be possible by gluing these bits together! As a side note I also acquired a PS3eye and hacked it apart last night and was please to find support in Ubuntu 10.10 for it out of the box (so to speak). Colours seemed somewhat subdued in comparison to the c910 however the effects of the superior frame rate are obvious. Roll on weekend!

Markers

Playing with markers today yielded some interesting results ~ I'm using a rather brute force approach in opencv by using InRangeS against an HSV image, and have pulled the ranges via an app to obtain a sample of representative pixels. Quick and dirty, but I'm encouraged by the results. False positives are high and its not robust in terms of working across lighting conditions but in-part the problem is the choice of material for the markers (electrical masking tape) which suggests : CVFB-R5: Markers must be composed of a material which is minimally reflective. I need to define "minimally" with more precision obviously but I think the above would improve the detection in varied lighting conditions and possibly reduce false positives if I resample. And yes, I know this should have been obvious but I have to harken back to my comments about a lack of design rationale... I'd be reasonable confident that with a few improvements that this would roughly match the fu...