I wanted to connect my Yamaha YDP-163B digital piano to Pianoteq, but had to go through a floor to make it work. Bluetooth MIDI to the rescue, I thought, and found the CME WIDI devices and bought an Uhost and Bud Pro, plus the USB-B OTG Cable Pack I.
The setup is easy, and overall it works as expected. The Uhost pairs automatically with the Bud Pro. It also pairs fine with my Linux computer, and I get Bluetooth-MIDI that way too.
Latency wise, I carefully measured this programmatically and found that the latency between the Uhost and Bud Pro is 7 ms, with a range of 3 to 11 ms. In other words the "3 ms" advertisement figure is the minimum and there will always be some jitter.
I also measured between the Uhost and my computer which has Bluetooth 5.2. The results are pretty much the same there: 6-8 ms on average, and the same jitter.
There is no way around these latency figures with Bluetooth versions before 6.2 because the minimum "connection interval" is 7.5 ms in the spec. Without any other factors, the average latency should have been half of that, so around 3.75 ms. But there is clearly some inherent latency in the Bluetooth processing that pushes the average up by around 4-5 milliseconds.
The newly released Bluetooth 6.2 spec allows reduction of this interval, so even lower latency will have to wait for that spec to make it into devices.
