Interesting Tech Projects
Photography
Astrophotography and CHDK
Jun 7th
CHDK is an alternative firmware for many Canon cameras, particularly point and shoot and I previously wrote about it here. One of the nice features is the ability to take continuous pictures for long periods, which makes taking photographs of the night sky possible with a low cost camera.
Here are my first experiments to see what is possible. I am fortunate to live in a place where the light pollution isn’t so bad and there are over 300 sunny days a year.
I set my Canon A480 up to take continuous 30 second exposures pointing roughly north, around 45 degrees above the horizon. I left it for about one and a half hours, during which time it took 155 pictures. I used ISO 80 and the auto focus set to infinity. More >
CHDK and Canon A480 Quick Start Guide
Jun 3rd
CHDK is an alternative firmware for some Canon cameras. It provides access to lots of cool features that are found only on high end SLR cameras, plus some features that are not found anywhere.
Why the Canon A480? Because refurbished cameras are available for $75 from Adorama with a one year warranty and only one version of firmware has been seen on them to date. This means that there is a very good chance the firmware in the A480 you receive will be compatible with CHDK.
This short guide shows how to quickly access some useful features. It is not intended to be exhaustive or replace the CHDK wiki or forums.
CHDK can be set to automatically load when the camera is turned on, however I don’t use that feature because I want to use an 8Gb SD memory card. Cards of 8Gb create complications when autoloading CHDK, but I want the extra space for long time lapse photography.
Download and extract the A480 “full” CHDK zip file from the CHDK website. Extract the files to the top level of your SD card and put the card into your camera. More >
You Tube, H.264, High Definition and FFmpeg
Jun 3rd
Recently I had the need to take a set of jpeg images and convert them into a high definition time lapse video, then upload to You Tube. Easier said than done…
To get the best quality I wanted to use H.264/MP4, which is also recommended by You Tube. I also wanted 1080P. The problem is that You Tube doesn’t seem to like B-frames in the file, and messes up the start of videos. So here is the solution I found.
Firstly I needed to upgrade my Debian server to Squeeze.
Next I compiled x264 and FFmpeg as described in How To Build FFmpeg on Debian Squeeze.
Finally I ran the following FFmpeg command line to generate a time lapse video at 24 frames per second (-r 24), using 1080P (-s hd1080) with no B-frames (-bf 0):
ffmpeg -r 24 -i %04d.jpg -s hd1080 -vcodec libx264 -vpre hq -bf 0 -crf 16 myfile.mp4
It’s important that the frame rate is specified before the input source in order to make FFmpeg apply the frame rate to the source. Note that trying to use qt-faststart causes You Tube to complain about the audio, even though there isn’t any audio.
