The Lion version of iShowU HD contains a significant number of changes to previous versions. This section outlines the differences in functionality of iShowU HD 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 HD 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 HD 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.
Low CPU mode - It was not possible to migrate the Low CPU mode implementation over to Lion. As a result it is no longer present in the Lion build of the software, and the UI has been updated to reflect this.
“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 HD.
Recovery Mode – Due to the way the capture system works in Lion, we have had to disable recovery mode. While there is technically a way to checkpoint media so that something is written to disk, experiments have shown that the checkpointing process significantly degrades capture performance for a few seconds and also messes up the timing of video (and these experiments were performed on a reasonably fast 4-Core i7 machine). This then results in a video that appears to lag every 60s (we checkpoint every 60s) and that also more often than not lags and then speeds up at the same time.
As with the ‘Show Mouse’ option, if the underlying capture system improves, we may include this feature in the Lion build of iShowU HD in the future.
Important 10.7 and 10.7.1 note
The .0 and .1 releases of Lion have some pretty severe performance problems capturing from a secondary display. You can read more about it here, but for now the workaround is to capture using the primary display. This is the display that has the Dock on it (unless you've a vertical dual screen setup - in which case open System Preferences and check to see which display has the thin menu bar at the top of it... that's your 'main' display).
This issue is resolved with 10.7.2.
As mentioned above, there are only three codecs available in Lion. Here is our recommendation for their usage:
JPEG – This is a "fast" encoder. It will provide the most fluid capture and use the least CPU resource. This is at the expense of using considerable disk space. JPEG is an excellent choice if a) you're machine can't keep up with H.264 (see note below), or b) you want to minimize CPU usagge during recording. The only downside to JPEG is the size of the files it creates, and that it often requires recompression into H.264 after recording is complete.
H.264 – This provides the best compression, providing a recording that takes up the least disk space. However is considerably more CPU intensive, which might result in lower frame rates or a jerky capture. If this is the case, switch to using JPEG.
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. 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 HD 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 can do one of two things. Either:
Disable the ‘variable frame duration’ option. If this option is disabled, iShowU HD will automatically reencode the movie at the end of recording. This will force the movie to have fixed frame durations.
Right click the movie after recording and choose ‘Reencode (fix frame durations)’. This is exactly the same process, and can be performed on any recording made after installing build 1256 on 18th Sept 2011.
If you notice that the CPU usage of iShowU HD 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.
In some cases, particularly with Core2Duo machines, we observed that capture + compression would cause fans to come on much sooner than with our faster OpenGL capture tech that we had under 10.6.8. Unfortauntely, there's little we can do about this. Sorry. The capture + compression engine under Lion is built by Apple - and there's nothing we can do (other than submit bug reports - which we've already done) to effect a change. I wish the situation was different (believe me - I really didn't want to use it - but we didn't have a choice - Apple disabled our previous method of capture entirely).
Aside from additional noise (see above note), "it depends". 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).