Comparing iMovieHD vs. iMovie08

Question

I loaded iMovieHD today and noticed that encodings are so much more faster with HD than 08. So I started trying to figure out why. I noticed that a 2 minute clip imported is HUGE in the project where as in 08 it is about actual size(regardless of importing from camera or card). This HD project was over a 1gb in size.
I ended up creating the same size 720P AIC movie file in each version. It took 4 minutes in HD vs 16-18 in '08. The file output sizes was 538mb(HD) to 747mb('08). I compared by viewing in Quicktime at the same timecode. I can tell considerable differences where the larger 747mb('08) was sharper and more vivid. I attribute this to more databits in the file.
The source file was 4 clips from a Sanyo HD camera captured a 1920x1080 at 30P. The import was close to 8 minutes in HD and almost 4 in '08.
My question is, short of the editing functions that HD provides does the HD version compare with 08 in quality? I guess I am a little nitpicky about this even though HD seems so much faster. Maybe it is personal preference but I thought I would ask others what they thought about the two.
Thanks in advance.
--Mickey

Answer 1

I'm only guessing but in your particular case the difference may come from how each app treat 'still camera movies'.
I'm assuming Sanyo's HD clips are from Xacti HD1000, and although it is more like a camcorder than a still cam it does not fall into traditional camcorder category. Camcorders usually generate certain closed file types - DV, HDV, AVCHD and iMovie 08 either import them natively (DV) or convert to AIC movies (HDV,AVCHD). But when it comes to h264 or mpeg4 movies out of other cameras iPhoto store them as still cam movie and iMovie does not perform any conversion on them. Sanyo's h264 mp4 files are still considered this 'still cam movie' even at 1920x1080 res, and iMovie08 has difficulty performing in all realtime.
iMovieHD, on the other hand, converts everything to work with the project type. It does not support multi format / multi resolution mix up like iMovie08, and if you choose 1080i or 720p project setting it converts all source movies to AIC codec unless your source movie happens to match the target format. Thus file size becomes much larger but lighter on CPU to perform editing function.
As for 720p export, the file size difference is probably from the export setting if both movies are identical in length. Perhaps iMovie 08 uses a bit higher bitrate. Better quality attributes to higher bitrate, and also to the fact that iMovie08 did only one conversion (h264 -> 720p AIC) where as iMovieHD did it twice (h264->1080i AIC -> 720p), thus more generation loss in quality.
Personally I think iMovie should treat HD res h264 like the ones out of camcorder and convert them to AIC to maintain realtime operation, which is why it converts AVCHD - another HD res h264 movies - to AIC.