I’ve put up a build (beta, 2.3.1) of iShowU HD/HD Pro that includes support for Retina displays.

With the release of the recent MacBook Pro machines, we had a number of users reporting that iShowU HD wasn’t working. The symptom being that there would be no preview, and when you tried to record, you’d get nothing at all, and the recording indicator in the menu bar would remain orange.

The problem was one of resolution independence. It turns out that under Lion, a HiDPI system (e.g: one of those super fancy completely non-upgradable MacBook Pro’s :) would report a resolution of 1440×900. Yet the underlying capture system was returning textures at 2880×1800. Well, if that doesn’t break a fundamental assumption of HD, I don’t know what does!

What this could have meant was that for Retina displays, a capture of say 800×600 would produce a movie of size 1600×1200. That’s because even though you asked for 800×600, the screen is in HiDPI mode and produces images exactly twice the size.

So, after some head scratching and playing around, I think I’ve come up with an acceptable solution. Here’s what happens as of 2.3.1:

• HD actually works, for a start :)
• Captures remain the same in concept. e.g: Capture a 800×600 area to a movie.
• Using the example above – if we were to capture 800×600 into a movie of the same size, we’d expect an output of the same size. i.e: 800×600. This is true for a retina display as well as of 2.3.1.
• If you want to capture the additional pixels, you need only scale up the movie by 2x on the output side. So, keep the capture at 800×600, but make the movie 2x the capture size (you can do that via a scaling menu option on the gear button of the output segment in the toolbar).

Make sense? Hope so!
The summary is this: HD works much the same (on Retina machines), but if you want you get capture more detail by ‘scaling up’ the output.