In settings, there is an option for Beat Sync Interval: 1 beat or 4 beats. Default goes for 4 beats.
Question is, I am a newbie in DJing so can someone shed some light over what is this option doing / how it works?
With Sync activated on both decks, it is actively syncing anyway, disregarding what setting I have on the above option. What is the consequence / change in switching to 1 beat sync vs 4 beat sync?
Assuming your grids are correct, it will work as you are experiencing.
But when you have a song with a 1 beat break for example, the grid after that break won’t be in step anymore (the songs’ ‘1’ will be on the grids’ ‘2’ from that point in time going further). Syncing from there won’t line up the next track correctly when you are defaulting to 4 beats.
Does that make sense?
Flipping this around, setting it on ‘1’ will allow you to start a track on a different beat.
This determines how your tracks are synced. In the image below, I scrolled the upper track one beat ahead. If I sync them both and press play on both of them at the same time, the behavior will be different depending on the setting. With an interval setting of 1, they will both play from the position they are at.
But with a setting of 4, they will line up on the yellow bars (those might be a bit hard to see, sorry in advance), making one of the two songs jump a little. The yellow bars mark the downbeat or the „1“ of a „1, 2, 3, 4“. Most non-classical music strictly follows this „1, 2, 3, 4“ throughout the whole song but as @Mister_Tuur mentions, some songs get creative and throw in an extra „1, 2“ or do other shenanigans. djay currently can’t handle this, so after this little extra, the yellow lines now don’t mark the „1“ but the „3“.
Also good to know is that there are a lot of songs where djay does not recognize the „1“ properly - this is a setting that I very often need to adjust.
Why are there two settings at all? As a DJ you always want to line up your „1“s because songs mixed together just sound better like this. The „4“ setting takes care of that (with the caveats mentioned above).