Wednesday, 14 April 2010

Gallopers assembly timelapse sequence

As soon as I had decided to become a Bressingham Volunteer ideas started racing through my mind.  One of those was to produce a timelapse video when the Gallopers were being assembled following their winter overhaul.

How it was done

I had hoped that I could be present during the assembly process, but a call back in February to get and outline schedule revealed that it would take around two weeks to build, weather dependent. This was due to the parts being stored across the site - if everything was on a trailer then it could be built in a day or two. Work commitments ruled this out for me, so my fall-back position was to capture frames from the webcam at set intervals and sequence the stills into a video.

I set-up a script running on a Linux server that would direct the webcam at the Gallopers (there are three different views available), wait five seconds (to allow the camera time to move if needed), capture and save the current frame to a file using the date and time as the filename and then wait twenty seconds before repeating. In all I captured around 42,000 frames over a period of thirteen days.

The next step was to discard the frames taken early in the morning before anyone arrived and in the evening after everyone had gone home. Amongst the remaining 20,000 frames were a small number of the locomotive sheds, the Nursery Line platform and blurred images where the camera was mid-pan after being repositioned by other web viewers. These all had to be weeded out and it took a good few hours to assess every single image.

Fly on the camera housing

Bright sun reveals surface scratches and internal reflections which the autofocus locked on to
At this point I used a piece of Windows software called PhotoLapse to create an AVI file for each day's activity. This allowed me to see what the webcam had captured throughout the day and highlighted a few more bad frames where the sun was at a particular angle and the camera had focused on the camera housing instead. On one particular frame a fly had landed on the housing and was captured.

What was apparent when keeping an eye on the webcam from my desk was that the morning sun really washed out the contrast and it wasn't until later in the day that things improved. Sadly I couldn't move the webcam or tell the staff to only work in the afternoon when the light was better. The captured frames are also only 320 x 240 pixels, so I apologise in advance for the quality, but it was all that I could work with this time round.

Once I had produced AVI files for each day, I imported them into iMovie (Apple Mac) so that I could edit them together and add titles, credits and a soundtrack. Although iMovie is a great piece of software I found that my ideas were stretching its capabilities, so I went out and bought a copy of Final Cut Express and spent quite a few hours learning another piece of software. The moving footage and audio was captured on a subsequent visit when running under steam as the first few days were on electric which just isn't the same. You can watch the video embedded below, or a larger version on YouTube. Enjoy.

The soundtrack to the assembly is Silver by Moby and is used with permission.

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