I found myself wondering which of these codecs (as listed in iShowU) would be best for a screencast:
I tried searching Google — for specific codecs, at first, followed by more general searches for opinions on codec suitability for a screencast. But I couldn't even find descriptions of the codecs' strengths and weaknesses.
Clearly, there is a void here to fill.
First, the list of output files:
And now the screenshots of each set of output movies. Some pages have a “winner”; think of each codec page as a qualifying round. Codecs qualify based on image quality. The overall winners (for quality and size) will be decided in the final round.
With the exception of PNG, Cinepak, and Sorenson 2, all of the codecs that I tried were set at High, Medium, and Low quality (I consider these to be the three main quality settings). The reasons for the exceptions are:
Also, I did Animation at the other two quality settings in addition to the main three, since the main three looked so good. (I found out later that it's RLE. That's why.)
All the codec settings were configured as follows, when each setting was available:
There was no audio track.
Finally, my source video was a recording made with iShowU in demo mode. What I did in the recording:
Two seconds separated each step.
Important distinction: I did not attempt to re-record the video in iShowU with each combination of codec and quality. (I started out that way, but quickly realized the logistical and methodological folly of that.) Instead, I recorded the source video using the “Apple None” compressor (i.e. uncompressed), then used QTAmateur to convert the video for each permutation.
One thing I noticed after I originally put this up is that all the screenshots show a strange stretching effect on the very right edge of the frame. I first noticed this on Intermediate, and thought then that it was characteristic to that codec; I looked further, though, and saw that it is actually in all the screenshots, even of the original uncompressed movie. And when I looked at the original movie, I saw that the same artifact is in the movie itself.
So it is a bug in iShowU, not in any of the codecs.