[pulseaudio-discuss] Horribly choppy sound during bluetooth a2dp playback

[Georg Chini]

On 04.09.2017 00:23, Vladimir Lebedev wrote:
> Hi All,
>
> I'm trying to create bluetooth speaker from my nanopi neo plus 2 SBC 
> (running Ubuntu 16.04.3 LTS with Linux 4.11.2 provided by 
> FriendlyElec). (With some pain) I've managed to make all native linux 
> clients to use pulseaudio server on nanopi as network sink via 
> zeroconf. But I'm stuck with bluetooth - currently all my android 
> devices can seamlessly connect to pulseaudio server and are correctly 
> negotiated as a2dp devices but actual sound playback is horribly choppy.
>
> I've tried to play with priority and realtime settings, performed NTP 
> timesync on all devices involved(including android phones), disabled 
> WIFI on nanopi without any result. Also it looks like that distance 
> between bluetooth transmitter and reciever doesn't play any role - 
> skipping is constant. Or I'm hearing it as constant.
>
> My google-fu failed me so any help would be greatly appreciated! I've 
> already spent two days to no avail. I think that my next step if 
> posting here won't succeed will be digging pulseaudio source code and 
> a2dp spec and this idea hurts =/
>
> Thanks and Regards,
> Vladimir
>
>
> pulse at garble:~$ /usr/bin/dbus-run-session /usr/bin/pulseaudio -n 
> --daemonize=no --realtime=no --high-priority=no -L 
> "module-suspend-on-idle" -L "module-position-event-sounds" -L 
> "module-alsa-sink device=hw:1,0" -L "module-native-protocol-tcp 
> auth-ip-acl=127.0.0.1;192.168.1.0/24 <http://192.168.1.0/24> 
> auth-anonymous=1" -L "module-zeroconf-publish" -L 
> "module-bluetooth-policy" -L "module-bluetooth-discover" -vvvv

The neo pi is not very fast, so it may be difficult to get it working. 
Did you check the CPU load
while trying to listen to a2dp? What is the reason for --realtime=no and 
--high-priority=no?
I think this can only make things worse.

In your log I find the line:
> D: [pulseaudio] module-loopback.c: Loopback overall latency is 18.79 
> ms + 0.00 ms + 25.00 ms = 43.79 ms
Normally, module-loopback should run at 200ms latency. The small overall 
latency
may also be a reason for the choppy sound. Did you wait for a while to 
see if it gets
better after a few minutes?

Did you try recent git? From your log I guess you are using PA 8.0. That 
is rather old
and the loopback and bluetooth code have changed a lot since then.

Regards
              Georg
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