A/B Roll editing is a hangover from the old videotape days when the two clips were separate tapes being played in two separate decks. It's not necessary to think in those terms anymore. Simply overlap the clips on the same track, then drop the desired transition on that overlap. Once you get used to it you'll wonder how anyone ever edited video before.

Thank you, Kelly and Ian, for your prompt replies. To this point, I've observed and understood what you've suggested through last night's experimentation. I did discover the opacity control and fiddled with it a bit, but it seems that tn only flat-lines --- the level remains constant for the duration of the clip. I thought that, perhaps, one could add node points and adjust the opacity ramp-style from start of clip to the end. And, in my case, it seems that I wouldn't want both clips on the same track.

Maybe it would be helpful if I tried to explain my project a little more clearly:

It's a musical performance, shot with two cameras -- a fixed wide shot and a mobile close-up camera. I want to to a "traditional" A/B roll, mapping in appropriate closeups. The two clips are exactly the same length, and I've placed them on different video tracks, so that I can select the areas of the close-up track that I wish to use.

I've tried splitting the two tracks at the same point and deleting the one I don't want to see -- effectively a jump cut. And I've tried moving the retained portion into the hole left by the deleted clip. That also works fine -- as a jump cut. But I'd like to use the occasional dissolve, and it appears to move the clips so that they overlap enough to do the transition. If it moves the video, I'm going to have trouble with a/v sync in subsequent clips, aren't I? And if it moves audio along with it, that's going to cause problems with sound, isn't it?

Do I need to trim clips rather than split? With the trimmer, should I lengthen the out-point of the first clip and in-point of the second by 1/2 the length of the transition, so that the net length of the transitioned clips equals the length of the two when they are adjacent, and played as a jump cut?

And, by the way -- is it possible to numerically set the transition length? (Looked, but couldn't find it...)

In the spirit of Murphy's Corollary: "By making something absolutely clear, someone will be confused"....

cbrillow, if ou've got your video on two tracks, cutting the upper track when you want it to jump to the lower, then you've got the hard work done.

No need to move your clips to create a dissolve, so you won't risk messing up the sync.

Simply extend the upper clip you want to dissolve from (or to) by dragging the end (being careful not to move the clip) so that it overlaps the clip in the track below and then setting opacity.

To set the opacity for a dissolve, drag the opacity line on your video clip from the upper corner of a clip so that it angles to zero at either the beginning or end of the clip (depending on whether you're dissolving in or out). The effect will be that, when the opacity is set to zero, your clip will be transparent and then, as the opacity angles up, your new clip will dissolve in.

You may have to fish around a bit at first, since you probably didn't even realize the opacity line was there but, once you do it, it should be pretty easy.

I've got a screenshot of what it looks like when you add a fade to the beginning of a clip. You can see it here: http://www.chienworks.com/media/dragfade.gif
Of course, the same thing works the other way 'round at the end of a clip. If you do these sorts of fades with the clip on the upper track, you will see a crossfade to the clip in the lower track.

I just did basically the same thing for my son. Taped a live performance with two cameras (Sony TRV350's), one stationary on a tripod and the other moving around. I put the tripod cameras video on the botton video track of Screenblast and the mobile cameras video on the middle video track. I sync'd the two up with the audio track. This leaves the top video track open for titles and special effects. Then I just watched (you just see the mobile video, you can adjust the opacity to see what is underneath) and deleted the stuff from the top track I didn't want. Use the S key to splt the track where you want it (always before where you want it to start and after where you want it to end) and the DEL key to delete the section you hace "split away". When you are finished you have a continous bottom track (tripod) and little bits and pieces of the top track. This leaves them in sync with the audio. Then go in a add fade ins and fade outs for all of the top level video clips. This works ok, but then I went in and split up the bottom video track (usually under a top video clip) at sefveral different places. You can then use PAN and SCAN on sections of the bottom track so it isn't so obvious you have a static camera on the bottom track. Breaking up the bottom track under the middle track kept me from having to line up END and BEGIN points in my bottom track. Overall, it worked fine for me, the main defect being my camera work with the mobile camera

For your helpful responses and suggestions.

I was aware of the opacity control, but couldn't seem to do anything with it other than adjust it as a straight line last night. But then, I was moving it vertically. After looking at the link that Chienworks so generously offered, looks like a horizontal drag is what does the trick.

This is fun stuff....

Great description, Tom. I can see that there are a couple of different ways to achieve the same results, and I'll probably wind up using some combination of the two.

BTW -- the similarity to your situation is striking -- my camera is also a TRV350. I saw in another post that you didn't know what the difference was between this and the TRV250. One huge difference is that you apparently can't use the 250 as an analog to DV pass-through device. (Which I think is a great way to do analog-to-digial conversions...)

One thing I have found with Screenblast, there are many ways to do things. I spend a lot of time just playing around, trying different video effects in combination, changing settings, colors, etc. I have actually come up with a neat little intro using basically straight lines and several effects overlaid on a simple video of a sunrise. I originally got Screenblast to do simple editing on home movies, played around with it for about a year, never really getting anything done, then it hit me, I sort of figured the program out. A lot of power hidden in there.