The Lion version of iShowU Classic contains a significant number of changes to previous versions. This section outlines the differences in functionality of iShowU Classic between previous versions of OS X (10.5, 10.6) and OS X Lion (10.7).
Video Codecs – Lions new capture system exposes only three codecs. They are JPEG, H.264 and ProRes. The 10.7.x version of iShowU Classic contains a modified interface that lets you choose from these three settings. All existing presets automatically migrate over to one of these three codecs.
Audio Codecs – Lions new capture system provides PCM and AAC compression. iShowU Classic lets you choose from three preset AAC modes, and one PCM mode. The three AAC modes represent low, medium and high quality compressed audio output. PCM lets you saved the audio uncompressed, and provides the highest quality at the expense of large file size.
“Show Mouse” always on – At present there is no way to turn off the mouse in a capture. This is a limitation of the Apple provided capture system in Lion. If and when Apple fix this issue (we have raised a bug report with them) we’ll re-enable the feature in iShowU Classic.
As mentioned above, there are only three codecs available in Lion. Here is our recommendation for their usage:
JPEG – This will provide the most fluid and least CPU intensive capture, at the expense of using considerably disk space.
H.264 – This provides the best compression, providing a recording that takes up the least disk space. Notice however that is uses considerably more CPU, which might result in lower frame rates or a jerky capture.
ProRes – Used as a professional intermediate format for editing. Typically if you know what ProRes is, then you know if you need it or not J. If you’re note sure – just choose JPEG with a quality of about 80%.
Note that in all cases (regardless of codec), the Lion capture system provides frames to iShowU Classic only if something changes on the screen. That means if you record (for example) a static desktop scene you’d be getting roughly 4 frames per second (from things like the clock in the menu bar updating, etc).
If you want to force the movie to have a fixed number of frames per second (e.g: you’re going to import into FCP for example), then you will need to reencode the movie at the end of recording. You can do this using any tool suitable for the purpose. Examples include QuickTimeX and Stomp.
If you notice that the CPU usage of iShowU Classic is higher in Lion than in previous OS X versions, you’re not going crazy. It is higher. In tests performed at SWB, we observed at least a twofold increased of CPU usage for similar capture parameters. Note that here we are talking about capture. The process of getting frames of video to compress. We are not considering video codec compression differences. Simply capture in isolation.
Does it matter?
Probably not. A case where you might notice it is if you were very close to 100% CPU performing recordings on Snow Leopard. In the switch to Lion, more CPU is taken up during capture of frames, meaning less is available for compression of those frames. You would notice it the most while compressing H.264. If you see stuttering or jerky captures using H.264 when using Lion, switch to JPEG and encode the movie into H.264 as a post processing step (you can do that in QTX or via Stomp).