Traktor Beat Grid
Mixxx is an open source DJ tool designed for both professional and amateur DJs alike. Mixxx allows DJs to mix music live with a clean, simple interface. Futhermore, Mixxx has a number of key features to help DJs in the mix: Beat estimation, parallel visual displays, and support for various DJ hardware controllers. Yes, but I think 'Adjust beatgrid' works well 1 of 10 times. I don't blame Mixxx, every 'auto' feature has it's precision. But it took me to press button many times to make grid on kicks.
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).
Virtual Dj Beat Grid
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.
The problem here is that when one track is significantly out, in other words it's just not the start point thats wrong but the BPM across the whole track, I've been adjusting the beat grids manually.
The issue (and I mentioned this in an earlier post) is that the initial offset if wrong. When you try to align the track so that the vertical bar on the grid lines up with the actual beat it it's different to the default grid on all the other tracks. Serato generally positions the beat grid 2 minor clicks to the left of the actual beat.
I've now been leaving the default grids in place and mixing (albeit with the odd minor adjustment which is to be expected) and it works well. So my issue is, for example, where I accidentally delete the grid and I want to set it manually, if I line it up with the beat (the high point in the wave form) then it's out.
So, my solution, as I said before, would be to allow users to set a default offset for the first grid setting when doing the standard analysis.
Incidentally, I'm using a Mac... is anyone experiencing these issues using Windows?