Using with rekordbox
You can sync BPM to rekordbox using Ableton link.
Ableton Link does work properly with rekordbox!!!
Testing with rekordbox V7.0.8 – rekordbox does not update the BPM as you move the tempo slider for a playing track, it looks like they’ve implemented it with the intention of rekordbox only following the BPM of another source (Ableton presumably). Rekordbox decks will follow the set BPM value, which you can manually change the value of using + and – buttons, but thats it. This limitation makes it pretty pointless currently it seems if you’re wanting to sync to a DJ just playing tracks as normal with rekordbox.
This is also true of the beat sync info sent via Ableton link. Running a test with a looping track and a beat responsive effect in Beyond receiving the Ableton Link stream, the Beyond effect does not respond to the live beat of the playing rekordbox track, it is fixed at the BPM that is sent (and wrong if rekordbox Tempo is changed).
Rekordbox
Prefereces > Controller > Others > Ableton Link
You will get a button named ‘LINK’ on the top toolbar, press it and rekordbox will stream ableton link via Ethernet.
QuickShow & Beyond
How to Sync Lasers to Music in QuickShow with Ableton Link & Pango Beats
You can use Ableton Link as a BPM In source (right click the BPM button), if rekordbox is on the same network it will automatically pick up its stream and sync to it.