on-connect and on-disconnect audio does not play, aplay is blocking

[photon-schiesser]

Hello,

Great project. I am trying to tinker with this to work for my needs.

One issue I have run into is that the service which streams the audio appears to block the alsa sink device from other sources. When I connect to the speaker, I get the following output:

Device connected. device=/org/bluez/hci0/dev_14_A3_64_58_DB_F9
Hiding adapter from all devices.
aplay: main:722: audio open error: Device or resource busy

Similarly on disconnect:

Device disconnected. device=/org/bluez/hci0/dev_14_A3_64_58_DB_F9
Showing adapter to all devices.
aplay: main:722: audio open error: Device or resource busy

But I can play audio just fine (except for the WiFi-caused underruns in issue #4 ).

Here is my /etc/bt_speaker/config.ini file:

[bt_speaker]
play_command = aplay -D plug0 -f cd -
connect_command = aplay -D plug0 /usr/share/sounds/freedesktop/stereo/service-login.wav
disconnect_command = aplay -D plug0 /usr/share/sounds/freedesktop/stereo/service-logout.wav

[bluez]
device_path = /org/bluez/hci0

[alsa]
mixer = PCM

Let me know what I can try.

[lukasjapan]

I think your sound card (plug0) does not have an integrated hardware mixer. That is why you can only use one sound stream at a time, preventing the login/logout sounds which are played after the bluetooth audio stream connects (to your soundcard).

I don't think a mixer function belongs in this repository, so your best bet is to setup a software mixer with alsa.

http://alsa.opensrc.org/Hardware_mixing,_software_mixing

Or you could try to use a full suite like pulseaudio or jack. But I only had trouble with those on the Pi, thats the reason I made this project.

[photon-schiesser]

Or you could try to use a full suite like pulseaudio or jack. But I only had trouble with those on the Pi, thats the reason I made this project.

And that's the reason I am using this project. I love simple and low-level over the black magic of pulseaudio.

I think software mixing is the ticket. Thanks for your help.

I would like to leave this open until I can post a solution or my findings. What do you think?

Just out of curiosity, do you think the lack of a hardware mixer is due to a driver issue, or the USB audio chip (PCM2704) simply lacks the functionality?

[lukasjapan]

A very quick research left me with even more questions but I get the impression that the mixing function is build in the driver (called mmap) rather than using real hardware mixing.

Anybody correct me if I am wrong.

ALSA seems to have settings for mmap in the config too. I think people will appreciate it if you can manage to post a working config.