Hi Lennart,

Something interesting is that if I try to play audio and choice the Bluetooth device as the preferred sink, upon connection it sometimes works fine. Thus this could be a firmware bug in the device, it feels a little wonky though so without more concrete information it's hard to say at the moment.

Look forward to hear from you,
Edward.

Here is some random/interesting things I found in journalctl while trying to connect without audio playing and with audio play.

<-- snip -->

Nov 08 16:15:24 localhost.localdomain bluetoothd[1396]: Failed to disconnect device: Not Powered (0x0f)
Nov 08 16:15:41 localhost.localdomain rtkit-daemon[860]: Supervising 4 threads of 1 processes of 1 users.
Nov 08 16:15:41 localhost.localdomain rtkit-daemon[860]: Successfully made thread 2317 of process 1660 (/usr/bin/pulseaudio) owned by '1000' RT at priority 5.
Nov 08 16:15:41 localhost.localdomain rtkit-daemon[860]: Supervising 5 threads of 1 processes of 1 users.
Nov 08 16:16:11 localhost.localdomain bluetoothd[1396]: connect error: Connection timed out (110)
Nov 08 16:16:11 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 31
Nov 08 16:16:11 localhost.localdomain bluetoothd[1396]: Unable to get io data for Headset Voice gateway: getpeername: Transport endpoint is not connected (107)
Nov 08 16:16:11 localhost.localdomain bluetoothd[1396]: (bluetoothd:1396): GLib-CRITICAL **: Source ID 158 was not found when attempting to remove it
Nov 08 16:16:13 localhost.localdomain bluetoothd[1396]: (bluetoothd:1396): GLib-CRITICAL **: Source ID 209 was not found when attempting to remove it
Nov 08 16:16:14 localhost.localdomain bluetoothd[1396]: /org/bluez/hci0/dev_58_51_00_54_B9_9B/fd0: fd(34) ready
Nov 08 16:16:14 localhost.localdomain rtkit-daemon[860]: Supervising 4 threads of 1 processes of 1 users.
Nov 08 16:16:14 localhost.localdomain rtkit-daemon[860]: Successfully made thread 2323 of process 1660 (/usr/bin/pulseaudio) owned by '1000' RT at priority 5.
Nov 08 16:16:14 localhost.localdomain rtkit-daemon[860]: Supervising 5 threads of 1 processes of 1 users.
Nov 08 16:16:14 localhost.localdomain kernel: input: 58:51:00:54:B9:9B as /devices/virtual/input/input13
Nov 08 16:16:19 localhost.localdomain bluetoothd[1396]: Unknown seq type
Nov 08 16:16:27 localhost.localdomain bluetoothd[1396]: Unknown seq type
Nov 08 16:16:30 localhost.localdomain cupsd[1902]: PID 1903 (/usr/lib/cups/notifier/dbus) exited with no errors.
Nov 08 16:16:35 localhost.localdomain bluetoothd[1396]: Unknown seq type
Nov 08 16:17:27 localhost.localdomain dbus[843]: [system] Rejected send message, 10 matched rules; type="method_return", sender=":1.36" (uid=1000 pid=1660 comm="/usr/bin/pulseaudio --start --log-target=syslog ") interface="(unset)" member="(unset)" error name="(unset)" requested_reply="0" destination=":1.18" (uid=0 pid=1396 comm="/usr/libexec/bluetooth/bluetoothd ")

...

Nov 08 16:21:35 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 31
Nov 08 16:21:35 localhost.localdomain rtkit-daemon[860]: Supervising 4 threads of 1 processes of 1 users.
Nov 08 16:21:35 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Nov 08 16:21:35 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Nov 08 16:21:35 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Nov 08 16:21:35 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Nov 08 16:21:35 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Nov 08 16:21:35 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Nov 08 16:21:35 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 7936
Nov 08 16:21:35 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 48
Nov 08 16:21:35 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Nov 08 16:21:35 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Nov 08 16:21:35 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Nov 08 16:21:35 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Nov 08 16:21:35 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0

....

Nov 08 16:22:05 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Nov 08 16:22:05 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Nov 08 16:22:05 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Nov 08 16:22:05 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Nov 08 16:22:05 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Nov 08 16:22:05 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Nov 08 16:22:05 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Nov 08 16:22:05 localhost.localdomain kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Nov 08 16:22:05 localhost.localdomain bluetoothd[1396]: connect error: Connection timed out (110)
Nov 08 16:22:05 localhost.localdomain bluetoothd[1396]: Unable to get io data for Headset Voice gateway: getpeername: Transport endpoint is not connected (107)
Nov 08 16:22:08 localhost.localdomain bluetoothd[1396]: (bluetoothd:1396): GLib-CRITICAL **: Source ID 346 was not found when attempting to remove it
Nov 08 16:22:08 localhost.localdomain bluetoothd[1396]: /org/bluez/hci0/dev_58_51_00_54_B9_9B/fd1: fd(34) ready
Nov 08 16:22:08 localhost.localdomain rtkit-daemon[860]: Supervising 4 threads of 1 processes of 1 users.
Nov 08 16:22:08 localhost.localdomain rtkit-daemon[860]: Successfully made thread 2553 of process 1660 (/usr/bin/pulseaudio) owned by '1000' RT at priority 5.
Nov 08 16:22:08 localhost.localdomain rtkit-daemon[860]: Supervising 5 threads of 1 processes of 1 users.
Nov 08 16:22:08 localhost.localdomain kernel: input: 58:51:00:54:B9:9B as /devices/virtual/input/input14
Nov 08 16:22:14 localhost.localdomain bluetoothd[1396]: Unknown seq type
Nov 08 16:22:22 localhost.localdomain bluetoothd[1396]: Unknown seq type
Nov 08 16:22:30 localhost.localdomain bluetoothd[1396]: Unknown seq type
Nov 08 16:22:38 localhost.localdomain bluetoothd[1396]: Unknown seq type

<-- snip -->

My conjecture is that the device is going into some kind of power saving mode while a audio bitstream isn't being shoved into it possibly because we are missing a packet or something upon initial connection? I have no read the Bluetooth spec so this could be just rubbish? It certainly looks like some resource vanishes somewhere below the getpeername() syscall and perhaps Pulse continues on assuming its still there hence no audio?

But the the problem is definitely trigger if you don't play audio at the same time as trying to connect to the device. For example,

1.) connect to the device without playing audio
2.) then play audio after it says it is connected
3.) then run: $ pactl list sinks

you get a indication that everything 'seems' to be working fine yet no audio:

Sink #2
        State: RUNNING
        Name: bluez_sink.58_51_00_54_B9_9B
        Description: MD315
        Driver: module-bluez5-device.c
        Sample Specification: s16le 1ch 8000Hz
        Channel Map: mono
        Owner Module: 27
        Mute: no
        Volume: mono: 43691 /  67%
                balance 0.00
        Base Volume: 65536 / 100%
        Monitor Source: bluez_sink.58_51_00_54_B9_9B.monitor
        Latency: 0 usec, configured 128000 usec
        Flags: HARDWARE HW_VOLUME_CTRL LATENCY 
        Properties:
                bluetooth.protocol = "headset_head_unit"
                device.intended_roles = "phone"
                device.description = "MD315"
                device.string = "58:51:00:54:B9:9B"
                device.api = "bluez"
                device.class = "sound"
                device.bus = "bluetooth"
                device.form_factor = "headset"
                bluez.path = "/org/bluez/hci0/dev_58_51_00_54_B9_9B"
                bluez.class = "0x242404"
                bluez.alias = "MD315"
                device.icon_name = "audio-headset-bluetooth"
        Ports:
                headset-output: Headset (priority: 0)
        Active Port: headset-output
        Formats:
                pcm

Really weird eh..

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