Meter Adaptation is a feature in Bidule that allows audio loops and MIDI sequences, and time lines of different meters (aka time signatures) to stay in synch with each other. Why is that useful, and why do we care? Well probably because (one of us) has listened to too much prog rock in his youth, and (he) didn't want Bidule to follow the same 4/4-only looping mentality that is the standard in all the other hosts at the moment.
It's a pain to start a track (or section) in 6/8, 7/8 or 7/4 and be limited by the choice of audio/MIDI loops we can use in it. With Meter Adaptation, synched bidules will try their best to fit "on the fly" to the bidule they are slaved to. But as you are going to see some compromises need to be made. At the moment only the Bidule Step Sequencer and the revamped Audio File Looper supports adaptation, more will follow, like the MIDI loop player and other surprises.
Say we have a basic one 4/4 bar audio loop of exactly 4 beats, and we want to synchronize it to timelines of different meters.
This is the easy case, both the loop and the timeline are at the same Meter. Move along.
This is getting interesting, the timeline is running at 5/4 so the loop player has to compensate by adding a 1 beat-long silence at the end of its 4 beat run. Why doesn't it repeat the first or last beat of the slaved loop instead of silence? Well it might work for this example, but what if you slaved a 4/4 bar to a 12/4 master? what do you copy now? We went for the easiest method to understand. (we might add another adaptation method later on)
Timeline at 3/4, so the loop player truncates its last beat and restarts over. If your slaved loop is more than 4 beats long (say 8 beats -> 2 bars), then the first 3 beats of the first mesure will be played, followed by the first 3 beats of the second mesure and so forth.
NB: All permutations of meters are possible, these were just an example.