[pulseaudio-discuss] Pulseaudio BlueZ sink is running but not producing audio sound

[Tanu Kaskinen]

On Thu, 2014-07-17 at 22:08 +0000, Kaster, Kevin W wrote:
> Hi,
> 
> I'm having problems with a Pulseaudio BlueZ sink, and I don't know how
> to debug it further. My BlueZ sink appears to be running but it is not
> passing any audio to the BT headphones.
> 
> Background:
> I am using BlueZ 5.19, Pulseaudio 5.0, DBus 1.8.4, ALSA lib 1.0.26.
> I am basically building a new distribution using Yocto based on Poky.
> So I have to pull all the pieces in myself, and I may have missed
> something or built in with the wrong switches.
> I am running everything as root (this is a deeply embedded system),
> including pulseaudio. I have seen the message about not running as
> root, but I also saw a note that running as --system doesn't support
> dynamic loading, and I didn't know if that applied to Bluetooth
> detection or not. So I'm open to changing this if someone can tell me
> the correct thing to do. But regular audio to the Pulseaudio ALSA sink
> works fine so I don't think that is the problem.

The correct thing to do is to use --system.

Dynamic module loading does apply to bluetooth. It applies to alsa too,
but only if you plug in new devices during runtime.

Pulseaudio will print a warning, for security reasons, if you run it in
system mode without also disabling module loading. I don't think those
security reasons apply in your situation, or if they do, running as root
to avoid that warning is not any more secure.

So, if you get this warning:

    Running in system mode, but --disallow-module-loading not set!

then that's good, because it means that bluetooth won't be prevented
from working.

> I have a basic /etc/asound.conf file which just specifies that the
> default ALSA PCM and CTL use the pulse plugin.
> 
> Problem:
> When playing audio to the BlueZ sink, it looks like it is running
> properly, is not muted, has 100% volumes, and I can see the latency
> bouncing around at reasonable numbers. The Pulseaudio messages in the
> system log say it is streaming audio over A2DP. hcidump says ACL
> packets are being transmitted. But no audio comes out of the sink.
> 
> What could be wrong?

Broken headset?

> How can I debug this further?

Some ideas:

Record from the bluetooth sink monitor to check whether the audio is
muted at that point:

    parecord --device=bluez_sink.00_02_3C_43_4A_09.monitor > test.wav

If it's muted, then the problem is somewhere before the bluetooth sink.
If it's not muted, maybe you can investigate the data that hcidump
produces. Is it silence? I don't know how hard it is to interpret that
data, though. You could also try another headset to see if the problem
is specific to the headset.

-- 
Tanu