Ok, I'm pretty sure this is a pulseaudio issue now and I'm going to
close.
I reverted back to linux-firmware 1.176, and I had also used undervolt
[1] to help reduce thermal load on the Core i9 Dell XPS 15 which has
suffered from thermal shutdown under high load. I disabled undervolt
service from running and ensured everything was back to normal values -
the stuttering improved, but was still present.
I then focused on the difference between my Mi8 and my Ubuntu 18.10
installation. The Mi8 is running a LinesageOS ROM that supports
LDAC/Apt-X codecs. I noticed with the regular AD2P codec in Ubuntu that
I was getting some noise included in the Bluetooth audio encoding, and
it sounded much cleaner via the Mi8 connection. I then found pulseaudio-
modules-bt repo on github [2] that includes [3] a Ubuntu 18.04|18.10
repo that enabled LDAC/Apt-X codecs, LDAC is supported by the Sony
bluetooth speaker.
After installing and rebooting the machine, I confirmed that the codec
was correctly initialised in the a2dp sync:
berg@bxps:~$ pactl list sinks | grep -e bluez -e a2dp_codec
Name: bluez_sink.E0_37_BF_09_F9_8B.a2dp_sink
Driver: module-bluez5-device.c
Monitor Source: bluez_sink.E0_37_BF_09_F9_8B.a2dp_sink.monitor
bluetooth.a2dp_codec = "LDAC"
device.api = "bluez"
bluez.path = "/org/bluez/hci0/dev_E0_37_BF_09_F9_8B"
bluez.class = "0x240414"
bluez.alias = "bshg"
The sound is now perfect, and copying files across the network results
in no stuttering. I think this proves that the btcoex support is working
correctly and there is no issue specifically with the Qualcomm firmware.
I notice if I pair the bluetooth speaker and play back audio my network
throughput is limited to about 14-15 MB/s, when I turn of the speaker it
improves to 17-18 MB/s. So the module is correctly allowing bluetooth to
operate with priority.
Resuming the undervolt [1] service, I notice no stuttering as well with
the updated pulseaudio and pulseaudio-module-bt packages in [2].
I'm going to continue testing for a few days before closing this bug,
but I'm pretty sure I've gotten to the bottom of this one. Thanks
@kaihenfeng.
[1] https://github.com/georgewhewell/undervolt
[2] https://github.com/EHfive/pulseaudio-modules-bt
[3] https://github.com/EHfive/pulseaudio-modules-bt/wiki/Packages
** Summary changed:
- QCA6174 doesn't utilise btcoex - Ubuntu 18 Bluetooth Audio
Skip/Stutter/Delay WiFi bandwidth conflict Dell XPS 9570
+ Suspect QCA6174 btcoex | Ubuntu 18 Bluetooth Audio Skip/Stutter/Delay WiFi
bandwidth conflict Dell XPS 9570 [Pending PulseAudio testing]
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https://bugs.launchpad.net/bugs/1810636
Title:
Suspect QCA6174 btcoex | Ubuntu 18 Bluetooth Audio Skip/Stutter/Delay
WiFi bandwidth conflict Dell XPS 9570 [Pending PulseAudio testing]
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