I am having a similar problem to what others mentioned. For those of us who just want to piece clips together and add effects, but know very little about codecs and what all this crap means to begin with, most responses mean pretty much nothing. So far, I still haven't seen an answer, but thank you, Tim Fenton, for at least offering a straightforward response. However, my videos are 320x240, so unless the software can't handle smaller sizes, that isn't the problem.
Here's my situation. I have never used iMovie HD before because I had no interest in it. However, I'm becoming more interested in video editing. I have a pile of public domain videos I downloaded from archive.org in mp4 format. I would like to use this to piece various clips together, add effects, music, and generally just do pointless stuff so I can find out if I even want to do something more serious.
These are all mp4 videos. They range in size from 2.6 MB to 500+MB. The 2.6 MB file takes 7 minutes to import into iMovieHD. An 8MB file takes 15 minutes. I don't even want to know how long the 24MB, much less the 500MB files are going to take.
None of these videos have been altered since I downloaded them. Since they are in mp4 format, I foolishly thought it would be a simple matter of adding the clips to iMovieHD and start editing, especially since I was led to believe that mp4 was a native format to Macs. However, if the software cannot handle it for some murky, codec-based reason, just tell me now and I will stop trying to do any video editing from now on.
If it requires me to buy/use more software and take extra steps to do what should be easily done in the software that's supposedly made for the purpose I want to use it for, tell me now so I can cease any attempts at video editing.
If it requires a new version of iMovie, then just tell me. While I don't understand why the version I have will be unable to function for the purposes intended, I would like to at least know why. If this version of iMovie cannot handle mp4, please just tell me. And if that's the case, why does all the documentation and help files say it can handle mp4s?
I don't know anything about codecs other than I first saw them a few years ago when they made playing videos near impossible without extra downloads and I gave up even watching videos on my computer because it was too much hassle.
Thank you.