Creating a Lecture Timer with Quartz Composer
I recently helped organize the DFT2007 conference in Amsterdam, a meeting of around 400 Theoretical Chemists gathering to discuss Density Functional Theory. One of my tasks was to make sure speakers could connect their laptops to the beamer, and to ensure that they didn’t wildly exceed their time limit. For the latter, I resolved to use a lecture timer in the form of a full screen countdown on a Mac display.
Because I wanted the timer to look professional, I thought about using Quartz Composer (QC). QC is one of the best kept secrets on Mac OS X; you can use it to create 3D compositions by joining up the inputs and outputs of the built-in patches. This type of interface is commonly found in 3D visualization software like OpenDX, and is not dissimilar to how Automator works: you build up a data pipeline by connecting together components to render a time-dependent composition, such as the RSS screensaver on Mac OS X, which is created with QC.
When I was finished, I exported the composition to several QuickTime movies, and during the conference, I simply played the movie of the appropriate length for each speaker. You may be thinking that exporting a lecture-length movie would lead to a very large file, but that is the neat thing about the integration of QC and QT: the QT movie only stores the QC composition, and renders it on the fly, so the total size of the movie is on the order of kilobytes, not mega or giga bytes.
I had no experience with QC before starting, but it didn’t take long to come up with the lecture timer composition. It’s certainly not the most sophisticated QC composition ever created, but it does the job, and looks quite acceptable. The timer counts down in minutes: it starts out green, and when there are 5 minutes remaining, it turns yellow, and eventually red when time is up.
When the conference began, I only had the timer visible to the lecturer, but half way through the conference — having exceeded our time constraints a few times — we decided to make the timer clearly visible to everyone, to pressure the lecturers to stay on time. This change in approach allowed us to keep to the schedule for the last few days.
If you have an interesting approach to building a lecture timer, or a good app to use, add it to the comments.