On 14/10/18 19:11, Ben Gonzales wrote:
Hi.
First post.
I have compiled Bluez 5.50 on a R-Pi for a synth using Fluidsynth.
Project page here:
https://gonzos.net/projects/pi-synth/
I'm using a Yamaha UD-BT01 MIDI-over-BTLE (MOB) peripheral to send
MIDI commands to the synth. Before the MOB functionality was
implemented I was using BluePy to send/receive the MIDI. The new
ability to create a MIDI port is excellent, but I find the latency
higher than I would like. It is certainly higher than with BluePy (no
measurements yet - just my subjective appraisal).
My question is: are there techniques for minimising latency over BTLE?
Ben
Further information:
I have set up a test rig on my RPi so I can measure the time difference
between the trigger (the air pressure pulse) on my wind controller and
the arrival of the MIDI command at the OS MIDI port. The sensor
by-passes the wind controller and connects directly to the RPi.
My wind controller is an Akai EWI-USB, the BTLE peripheral is a Yamaha
UD-BT01, and I did 20 tests of each of the following scenarios measuring
time difference in msec:
A) With the EWI wired to the USB port
Average: 34 , Max: 41.568 , Min: 30.496 , No.: 20
B) with the EWI connected via the Bluez 5.50 BTLE connection
Average: 76 , Max: 112.246 , Min: 35.877 , No.: 20
C) with the EWI connected via an "optimised" Bluez 5.50 BTLE connection
Average: 53 , Max: 61.032 , Min: 45.739 , No.: 20
"Optimising" the BTLE connection is done by running:
sudo hcitool lecup --handle $HANDLE --min 6 --max 7 --latency 0
--timeout 500
So, the optimised BTLE connection is 20ms slower than the wired one, and
the unoptimised BTLE connection is really bad at 40ms slower than the
wired one.
Any suggestions?
Ben
