Video Formats

[Blaise A. Darveaux]

When I import digital footage into iMovie from my digital movie camera the files are large. I then use these "Events" to make "Projects", and then, when the "Project" is done I make the final "Movie." The final movie is in either .m4v (MPEG-4) or .mov (Quicktime) formats and are much smaller then the files imported into iMovie from the camera.

I recently took our old home movie films (6,600 ft) to a service for digitization. I ordered a number of copies on DVD for my siblings, but, for myself, I wanted to get the digital files on a hard drive so I could add transitions, names, dates, etc. with iMovie. I sent along a 2 Terabyte drive for these files which I expected to be huge, like the ones I get from my camera. I paid a lot extra for the files on a hard drive. When I got the finished products back home (about 2 months later) there was only one 74 GB file in Quicktime format on the hard drive. I was able to import it into iMovie without a hitch.

My question is one of quality. Will importing a Quicktime movie, modifying it, then saving it as another movie degrade the quality similar to how the quality of a JPG photo degrades each time you re-save it? If so, would the quality change be noticeable to the average person? Remember, these are from old films with under exposures, over exposures, double exposures, and often, poor focus, so maybe I'm worrying about mole hills when I have mountains before me.

Thanks,

Blaise A. Darveaux

[ttl]

Re: Video Formats

Technically, every transformation will introduce degradation. You may be choosing to do resolution changes, the process of which is very good but imperfect. Also, each save involves data compression (as does the jpeg process you reference) which introduces data loss to the copy. That being said, the algorithms are very good and a couple of generations worth of saves is not likely to be a big deal, especially for home movies.

The safe thing to do is always to run a snippet through your production process from beginning to end and see what it looks like when you're done--if it looks good to you, it's good. If you're doing a lot of home movies, this won't add much extra work to do the test once.

[ttl]

Re: Video Formats

To clarify, iMovie isn't resaving every clip in its library every time you save a movie... the only video that's affected by a save is the actual new copy that's being generated in the save/share action.

[Blaise A. Darveaux]

Re: Video Formats

To clarify, iMovie isn't resaving every clip in its library every time you save a movie... the only video that's affected by a save is the actual new copy that's being generated in the save/share action.

Oh, yes, I do understand that. Only when you make a clip (or selection of clips) into a new "Movie" does it compress to MPEG-4 and incur a slight loss of data.

I guess what I was expecting to get was the "raw" digital files without compression rather then the compressed Quicktime movie.

Thanks for your responses, Tim.

--Blaise