Thursday 31 May 2012

"Video" Editing in Linux

Video editing is one of those domains for which there are some expensive options and several attempts at open source alternatives. Unfortunately, few efforts have even gotten past the first few months.

A couple months ago, I had to do some "video" editing. I put that in quotes because in fact, it was more of a slideshow. I had done something similar a few years ago in PowerPoint. After the pain of that experience, I was quite certain I didn't want to do it that way again. I looked for some alternatives, but pretty much knew what my list of prerequisites was:

  1. Background music and voiceover audio
  2. Easy positioning of audio clips (Possibly meaning multi-track editing)
  3. Good set of transitions
  4. HD output, if possible, since all my photos were high resolution already

Weighing the Options

I know there are dedicated slideshow tools out there, like Imagination, but I wasn't sure how to get points 1 and 2 taken care of. I was pretty much certain that I'd have to use a video editor of some sort. There are really only about three or four I'd expect to work.

I was originally thinking of OpenShot, but annoyingly, you can't drag multiple clips from the Project to the Timeline. This might seem like a small issue, but for a slideshow of a few hundred images, it becomes a bit tedious. That's one of the reasons I didn't like PowerPoint, since you had to create a slide per picture and then add it. Overall, OpenShot just seemed to be a bit too simplified to be usable. On the upside, it did seem to have a good selection of transition effects.

The next option was PiTiVi. A long time ago, when I had to settle for PowerPoint, I had looked at PiTiVi. It was really just not ready to use for much of anything then. Just loading files used to cause a caught-in-abrt-but-not-totally-fatal exception. Nowadays, it's become much more polished. The UI looks much nicer with a good layout of controls. Unfortunately, it's limited in the transition aspect. Basically, you've got crossfading and that's about it. With no transition wipes, that pretty much cut out PiTiVi, although I really do like the direction it's going.

A possible contender?

The final choice was Kdenlive. Kdenlive uses the same video processing toolkit as OpenShot (MLT), but has been around since before OpenShot and PiTiVi. I can't say whether this longer development time is the sole reason or not, but it's certainly turned out to be the best of the three at this time. It's obviously multi-track (points 1 and 2), there's a good selection of transitions (point 3), and it'll render almost whatever resolution you want (point 4).

Now, does editing real video have its issues? I can't exactly say, but for what I had to do, I found Kdenlive to be extremely stable. In the course of this project, I saw maybe two crashes. That's two crashes too many, but video editing seems to be a tricky art (likely due to there being too many video specs, with poor descriptions, and poorer implementations). Actually, I did have to insert two real video clips, and they didn't cause any trouble.

Kdenlive was certainly up to the task for this slideshow/video project. It was perhaps of a moderate size, a few hundred images, two video clips, a dozen music tracks, plus 15-20 audio voice clips, resulting in about 25 minutes of final video.

Alas, it's not quite perfect...

Let's not say that Kdenlive doesn't still have its rough edges. It did appear to use a large amount of RAM, but I think that's because the project was 1080p, and I wasn't using proxies. Randomly (but thankfully not too many times), an invisible spacer would insert itself on a track and shift all the subsequent clips. Eventually, I did find the Lock Track button, and then could shift the incorrect track back. Once, a clip became half-deleted, getting in the way of other clips, but staying immovable and un-deletable until I re-opened the file.

While there are many to choose from, there are twenty transitions that are just named numerically, meaning you have to pick a point in the middle of a transition, look at the result, and guess which direction it's going (it doesn't auto-preview the whole thing, for example). What would be really useful is a "base" transition set, with an editor to tweak a few settings. For example, if you had a expanding star, the editor could enable you to position that star over some important object instead of dead-centre.

The other transitions that were missing were some good 3D effects. I tried following these instructions to create a page curl effect, but ended up keying every frame of the overlay position just to make sure it looked good. For another effect, I used a rotate about Z to create a sort of full page flip, but the Z rotate doesn't seem to cause any perspective changes (the far end does not shrink in height and the near end does not grow in height). It didn't look too bad in the end, but it could have been easier to do.

Wrapping up

In the end, I managed to finish my project relatively easily with Kdenlive. OpenShot is really just not up there at this time, although it does have a nice set of 3D titles in Blender. PiTiVi is also moving along quite nicely, and if it wasn't for the lack of transitions, I might have used it. Kdenlive seems to be the best choice right now. But everything's under rapid development, so this might change any time soon.

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