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Lots of help on how to put up Jackd with lower latencies on Raspberry pi

published Mar 06, 2019 11:55   by admin ( last modified Mar 06, 2019 12:15 )

I got here:

https://lucidbeaming.com/blog/setting-up-a-raspberry-pi-3-to-run-zynaddsubfx-in-a-headless-configuration/

In a quick test this morning it seemed to make a difference although some of the adjustments had already been made. Jackd had already prioritized up things. The things I did that were new were the following:

1. Disable the internal audio card by commenting out the "dtparam=audio=on" :

sudo nano -w /boot/config.txt

...

# Enable audio (loads snd_bcm2835)
# dtparam=audio=on

2. DBus security policy (disclaimer: I have no idea what this one does in this context):

sudo nano -w /etc/dbus-1/system.conf

...
<!-- Only systemd, which runs as root, may report activation failures. -->
<policy user="root">
<allow send_destination="org.freedesktop.DBus"
    send_interface="org.freedesktop.systemd1.Activator"/>
</policy>
<policy user="pi">
    <allow own="org.freedesktop.ReserveDevice1.Audio0"/>
</policy>

3. Default configuration to use the USB card:

sudo nano -w /etc/asound.conf

pcm.!default {
 type hw card 0
 }
ctl.!default {
 type hw card 0
 }

4. Force the pi to always be alert, by telling it so on startup:

sudo nano -w /etc/rc.local
...
echo "performance" > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
echo "performance" > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor
echo "performance" > /sys/devices/system/cpu/cpu2/cpufreq/scaling_governor
echo "performance" > /sys/devices/system/cpu/cpu3/cpufreq/scaling_governor
...