Here I am 
I spent several hours in the last few days testing the sync within DjayPro. I have to say I still feel like this part is still probably the weakest in DJayPro as in almost all the other areas I feel way better in DJay Pro than in other softwares. A lot of weird stuff happened while I was trying to test all the possible cases but in almost all of them I couldn’t find a deterministic way to reproduce it constantly.
While this is something that can be seen both as a good and a bad sign, as a software developer from my experience, this is happening most of the time when the code had several developments on top of a very old, usually not so well enginered, structure. This is the only part of DJay that gives me this feeling and, whether it’s true or not, I don’t want to offend anybody as I love DJay Pro, but I feel like Sync is not completely consistent or reliable.
Anyway, I based my analysis on this article How does sync work? | Algoriddim Support and this discussion Understanding Sync / Sync Master / Tempo Reset [Win / DVS] - #10 by Slak_Jaw and tried to do my best to test all the possible scenario.
I came to the conclusion that actually there is no way to avoid drifting using BPM Only Sync. There is no specific bad behavior I want to highlight but there are so many cases where it doesn’t work completely fine even tho I can’t report them.
One thing that I found very confusing, maybe fixing this can be enough already, is that sometime the tempo shown in the GUI is the same for both left and right deck, while you can see that are different. Maybe just improving the precision of the tempo shown can be considered a solution when the tempo of a track is changing. At least it will look more consistent. I’m talking about differences that should be considered relevant, I would not consider a 0.05 bpm difference something to be shown.
In any case I moved forward adjusting my Sync preferences to BPM and Beats and kept testing. Here I found something interesting. Most of the time this setting can be a solution as the beats are kept aligned. Even tho I don’t like this way of doing things it’s probably the best compromise, still I found an issue with the Master Tempo.
I’m talking about this scenario
SCENARIO 3: One Deck Playing
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By default, the actively playing Deck is the Master. So the Deck that is Playing through the master output and the audience can hear (ie. Channel Fader and Cross Fader Open).
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Pressing Play and the Sync Button on either Deck 1 or Deck 2 will Sync it to the one that was Playing first. For example, Deck 1 is playing through the main speakers and Deck 2 is paused with a new track. If you press Sync on Deck 1 or on Deck 2, Deck 2 will Sync to Deck 1 because it’s already playing and is considered the Master Deck.
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I believe the first Deck remains the Master Deck until you stop playback and load another track onto that Deck.
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In this case, the other Deck that is now actively Playing with the Channel Fader Open and Cross Fader side Open becomes the new Master Deck.
Sometime it would be good to decide which deck should be the Master Tempo as this would solve most of the issues I had but I wasn’t able to make it work.
I mapped a key for each deck to set the master tempo explicitly and pick whatever deck I wanted but it didn’t work.
The sequence is
- 1 Deck playing.
- Load a song in the other Deck.
- Sync.
- Pick the second Deck as the master tempo.
In this case the Master Deck is still the first one and there is now way I can decide to switch the master at will as DJay only changes the Master Deck with the channel fader.
Did I miss something? Am I doing wrong?
Please let me know
Best Francesco
