Comment 4 for bug 1114643

We may not be able to do much for the general case of a song that has gone totally arrhythmic but we see lots of patterns of tempo-shifts in songs (breakdowns or dubstep-interludes are the most common I can think of).

I think if we can accurately detect cases like these we could do something reasonable with the master sync. For example, if we know there is a distinct tempo shift (i.e. before point X it is 100bpm and after it shifts to 110) then we can simply adjust decks that are following that track to match the new BPM.

If there is a breakdown or interlude, if the beat 'goes away' then we could look ahead to when it comes back and make sure that following decks are on-track to be in sync when the beat comes back.

Syncing phase alignment is already done locally -- i.e. we only look at the previous and next beats from both tracks. Syncing the tempo is done globally (looking at the global BPM) but we could switch to syncing that locally as well. For a fixed-tempo-assumption user this will have no effect as the local BPM is the same as the global.