I managed to get some more stable behavior after avoiding to use two accounts on my iMac. That sounds like a bug to me.
Then I got some feedback from another forum. It turns out that AVCHD footage rewrapped into .mov files (I am using ClipWrap to do that) are played back in Premiere using Adobe QT Server which is a 32 bit application and uses a single core [This BTW is not exactly correct, if at all, as all 4 cores of my i7 seem to be active. However, only one thread per core appears to be running, whereas .mts files seem to be processed with two threads per core]. Hence the stuttering. Indeed, if I preview the original .mts files in the media browser or in the timeline, everything plays back smoothly using all cores. That bad playback of .mov H.264 files is apparently a known bug... Yet another one.
The problem with .mts files is that they are not played by QT and neither are they by Adobe Bridge! So I cannot add metadata and organize my files using Bridge unless I convert them into .mov files. But then they are a pain in the butt to use in Premiere. Sounds like a 3rd bug to me (*)!
(*) it appears to be a problem introduced in CS 5 where Bridge is assuming the availability of tools provided with the rest of the suite which are not here, not being needed anymore...
Anybody at Adobe listening to this?
Message was edited by: uwxplorer
Workaround: rename the .mov files as .mpg. They are played correctly in both Bridge and PP (as good as the original MTS files in the latter case). The only problem is that now, you can't preview the files in the finder (which is a minor problem for me). You can however associate them with Mpeg Streamclip.
What are the full specs. of your iMac? The greater the detail, like CPU, GPU and I/O, the better.
Good luck, and sorry for the rough start.
iMac 21.5", 2.8 GHz i7, AMD Radeon HD 6770M 512 MB, 4GB RAM, 1TB SATA HD
I have 8 GB on its way, but the issues I have faced initially seem unrelated to those specs. Things have stabilized somewhat since reading a number of tutorials and blogs. I won't blame Adobe for providing a funky support of AVCHD when Apple itself doesn't provide any. By that I mean the ability to use mts file in PP but not being able to preview them in Bridge (Adobe) or the Finder (Apple).
The thing I don't quite understand is the .mov to .mpg renaming that seems to fix Bridge's AND PP's behavior, but I won't worry about it at this time. This is actually not completely true in the sense that Bridge still shows a black first frame preview (thumbnails are OK and playback works fine). Since I have seen that in tutorials I have watched and that did not seem to bother the speaker, I guess people have gotten use to quirks of that sort...