The “B-Reel” option is a carry over from the linear tape to tape edit days. It teels you that two shots that are to joined by a transition are both on the same reel of tape. Obviously, when editing from tape, it can’t playback from two different spots on the tape at the same time. The solution was to dub one of the shots(or the entire source tape) over to a “B” reel that would play back on another machine which enabled you to transition from one shot to the other shot. A little later on, machines were developed that would do “Pre-read” edits where the outgoing shot would playback from the master record machine, thru your switcher where you would mix the incoming scene from a source tape and then record it back on the master deck. Basically the record machine was capable of playback and record at the same time. The master record machine had two sets of heads that were avtive at the same time basically making it do the duties of both a source machine and a recoed machine.It was a huge time saver. The only problem was that the process was destructive. You only got one chance to “Hit the reds” and get it right the first time. If you messed it up, you would have to go back and rebuild the previous scene on the master tape. It sounds a bit complicated but it worked very well in practice once you got used to the process.
If you are trying to generate an EDL to take into a tape to tape online room, you will need either the B-reel list or the Pre-read list for the editor. If it’s going into another non linear system, don’t worry about it. Just turn that feature off and you will be good to go when you generate the EDL.
Tom