Webcam

Time Lapse Process

The time lapse movie is made each night from a collection of the days images.  The camera is set up to capture one image every 30 seconds.  Thirty seconds makes for a pretty smooth time-lapse although it set to 12 seconds during ice-out.

At the end of the day the camera is turned off and a script is run to process the images.  Each image is resized to 640x480 pixels, contrast is adjusted and the image is sharpened.  Finally, the script will rename each image and write to disk in order beginning with 000001.jpg, 000002.jpg... and so on.

Once this script is completed there will be about 3000 images ready to be made into the movie.  An open source program called ffmpeg is used to process the images and output a wmv formated file.  Wmv is Windows Media Video which is compatible with PC and Mac computers.

The ffmpeg command line looks like this: ffmpeg -y -r 30 -i %06d.jpg -b 1500k output.wmv  The size of the resulting video file is about 20 MB.  The frame rate is set to 30fps and the bitrate to 1500bps.  FFMPEG is available from  ffmpeg.mplayerhq.hu

The final step is to automatically write the video file to the server and this is done using an ftp script.