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.

Quartz Composer.

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 want to see how I created the timer, and perhaps use it yourself, you can download the QC composition here. If you just want to see the pretty QT movie, download it here.

If you have an interesting approach to building a lecture timer, or a good app to use, add it to the comments.


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Cool timer

Thanks for this post, this makes me want to give QC a try (or maybe I should loathe you for potentially enticing me into interesting distractions!).

How did the speaker respond to that pressure? Did you display a giant timer on a separate screen, or did you just have it on a separate laptop? Does it work with Windows QT?


Re: Cool timer

We just had the timer running on a Mac mini on a small LCD screen facing the audience. Because the timer is full screen, you could see this everywhere in the hall.

There was one speaker that didn't seem to appreciate the timer, but the rest accepted it, and it did save us from the excessive talks of the two days. (I think it is very arrogant to take way too much time, either because you think your more important than others, or because you simply didn't prepare, but apparently many professors don't think this way.)

Don't know about Windows QT. Good question.


Drew McCormack