MPEGs and iMovie

I'm trying to save some deteriorating VHS tapes of music videos from oblivion by converting them to DVDs, using a borrowed computer and DV camera. So far it seems to be workable: the 90 minute test DVD-R we burned looks no worse than the original VHS tape (though I think the black level might be a little too high.)

I would like to end up with two things:

  • A stack of DVD-Rs with videos on them, one video per chapter;
  • A directory full of videos, one video per file, in some good resolution yet reasonably portable format (which I think means MPEG-2, not Quicktime/Sorensen.)

iMovie basically works, but it's got more bugs than the insect wing of the Smithsonian. Did they test it at all? It does stuff like: you have three icons, and icon 1 is selected. You drag icon 3 to the trash. Icon 1 gets thrown away. Really fundamental idiocy like that. But, once you figure out where the land mines are, it's not too hard to do simple things with it.

Here's where I use LJ as tech support, since I suspect that a bunch of you reading this list know about such things...

So, as far as I can tell, the process goes like this:

  • The camera digitizes the baseband NTSC input, and outputs DV, which is uncompressed digital video;
  • iMovie captures that DV to disk, inconveniently splitting it up into 10 minute chunks (due to Mac file size limits); this takes about 26G per 2 hour tape;

  • Then exporting from iMovie to iDVD does... something... that takes a very long time. Is it encoding lossless DV to lossy Quicktime?

  • Then, after setting up the iDVD project (editing menus, etc.) iDVD does... something else... that takes a long, long time. Converting Quicktime to MPEG-2? This results in a 4G disk image.

  • Then actually writing the disk takes 3 minutes per minute of video. At least that part I can understand.

I'm confused about where encoding is happening. From where the delays are, it really feels like video is being encoded twice. In this process, is video being decoded, modified, and then reencoded, losing quality along the way? Is there some way to have iMovie create the files in a way that is already what iDVD expects, so that iDVD won't re-encode it?

So, the obvious way to do all this is:

  • Use iMovie to divide the clips between videos, and also put a chapter marker at each such division. (About 1/3rd of the videos will span two clips, since iMovie divided them every 10 minutes, and there's no way to re-join two clips.)
  • Save each video to a file using "Export" from iMovie;

  • Write the disk using iDVD.

This is insanely tedious, of course, especially since every one of these steps involves a lot of waiting for the computer. But it occurs to me that maybe things could be sped up by combining steps -- for example, if I write out a bunch of files from iMovie in the format that DVDs want (which is MPEG-2, right?) then can I just import those files into iDVD without it wanting to re-encode them again?

Seems to me that once I've got a directory full of MPEG-2 files, I ought to be able to do something analagous to "cdrecord *.mpg" and have it spit out a DVD-R with one chapter per file. Or is that just hopelessly naïve?

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sucks to be a crab

Crab vs. Pipe

"This is a video taken in 6000 feet of water. An undersea robot is sawing a 3mm wide slit (1/10th of an inch... remember that width) in a pipeline. The pressure inside the pipeline is 0 psig, while the pressure outside is 2700 psi, or 1.3 tons per square inch. Then a crab comes along...."

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dnalounge update

DNA update. Actually three, if you haven't checked on your own lately.