| Awhile back a reader had commented that it appeared that iMovie 2 not only has new features but also support for dual processors. I didn't have a chance to test this before my G4/500 DP arrived, but just did - with some interesting discoveries.
I have iMovie 1 and 2 on the G4/500 DP and used the Tutorial file from iMovie 1 as a test.
I found that iMovie 2 did render the same movie in less than 1/2 the time of iMovie 1 on the same system using the Export movie "Medium Sized CDROM Movie" setting. One iMovie 1 performance drag is that I've found no way to disable the preview of the movie while it's exporting. In iMovie 2 there seems to be no way to enable this, so I can't test what effect this has on performance.
Despite the fact iMovie 2 doesn't preview during export, the fact it took less than half the time to export the movie made me dig a little deeper into the differences. I compared the output file sizes and found the iMovie 1 file was 11.1MB and the iMovie 2 file was 6.6MB. The size, FPS and audio settings were identical, so it had to be the compression codec. I should have noticed in the export dialog that iMovie 1 uses Sorensen by default for the Medium Movie export and iMovie 2 uses H263. Looking at the two movies side by side you can see the iMovie 1 Sorensen codec video is much sharper with better color fidelity.
Although it's still not a fair test since iMovie 1 previews the movie during export (but I did select lower quality previews to help a bit), I then ran a test with the same codec and settings using expert mode. (Sorensen codec, medium quality, 15FPS, keyframe every 5 frames, 600kb/sec data rate limit, 44KHz stereo audio, IMA 4:1 compression)
iMovie 1 vs 2 on G4/500 Dual CPU
(same codec and settings used)
- iMovie 1: 9 Min, 47 Sec.
- iMovie 2: 3 Min, 0 Sec.
Despite identical settings, the iMovie 1 file was 500KB larger (21.2MB vs 20.7MB). Using QT Pro's movie info option I saw that this was due to a slightly higher data rate on the iMovie 1 file.
I wish I could have disabled the preview during export in iMovie 1, or enabled it in iMovie 2, so that I'd have identical test conditions. Even if the 2nd CPU was 100% efficient, that can't explain the 3x+ faster performance in that test.
To determine if the 2nd G4 was really supported in iMovie 2, I ran the same export file test on my G4/500 single CPU system. This test clearly showed that iMovie 2 does not use the 2nd processor.
iMovie 2 Export - Dual vs Single G4/500
(same codec and settings used)
- G4/500 Single CPU: 2 Min, 53 Sec.
- G4/500 Dual CPUs: 3 Min, 0 Sec.
The G4/500 single CPU system has a slightly faster drive (7200 RPM WD vs 5400 RPM Maxtor) which may be the reason for the slightly faster times, and there may be some overhead with a 2nd CPU for apps that don't use it. The results however make it clear that iMovie 2 doesn't use the 2nd processor, although the much faster performance (and additional features) over iMovie 1 is a big plus.
For those that missed it, Hiram Wilson wrote an interesting iMovie article several months back that compared making movies with Film to iMovie titled 'iMovie - A Revolution Takes Hold
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