AirPods 4 A2DP silent on Jolla C2, Xperia 10 III after SFOS 5.0.0.72

Bug Reports
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1

REPRODUCIBILITY: Yes
OS VERSION: 5.0.0.78
HARDWARE: Jolla C2, Xperia 10 III
UI LANGUAGE: English
REGRESSION: Yes, Sailfish OS 5.0.0.72 → 5.0.0.78

DESCRIPTION:

Device: Jolla C2
Working version: 5.0.0.72
Broken version: 5.0.0.78, 5.1.0.11
Bluetooth device: AirPods 4

After upgrade, AirPods 4 pair and connect, but A2DP audio is silent.

PulseAudio shows the Bluetooth card and A2DP sink correctly. The active profile is a2dp_sink, the bluez_sink is created, and the sink goes RUNNING. Media playback and module-sine test streams attach to the Bluetooth sink. Sink and stream volumes are normal and unmuted, but no audio is heard.

autodetect_mtu=1 test did not help.

Gave it a shot and tried going to version 5.1.0.11, but it didn’t solve the problem either.

PRECONDITIONS:

SFOS version 5.0.0.77 and higher (for versions 5.0.0.73 and 5.0.0.76, I don’t have any details, but the last known working one was 5.0.0.72).

STEPS TO REPRODUCE:

  1. Pair AirPods with an SFOS phone

  2. Check that headphones connected

  3. Try to play any sound/ringtone/media

EXPECTED RESULT:

Should be abled to hear media.

ACTUAL RESULT:

No audio is heard.

MODIFICATIONS:

No additional repos or apps, just stock applications from sailfish store.

ADDITIONAL INFORMATION:

Additional observations:

  • Both the Jolla C2 and Xperia 10 III display identical behaviour.
  • AirPods Gen 2 worked on Sony Xperia 10 III up to Sailfish OS 5.0.0.73.
  • The switch from AirPods Gen 2 to AirPods 4 on Sony Xperia 10 III happened around the same time as the Sailfish OS upgrade to 5.0.0.76.
  • I cannot confirm or deny whether AirPods 4 worked on 5.0.0.76, as the SFOS upgrade from 5.0.0.76 to 5.0.0.77 occurred close together (within a span of 3 days)
  • Sailfish OS 5.0.0.78, and 5.1.0.11 also does not work with AirPods 4.
  • Reloading module-bluez5-device with autodetect_mtu=1 did not help.
  • HSP/HFP mode does not create a usable Bluetooth sink.
  • The issue appears to be below PulseAudio routing/volume, likely in Bluetooth A2DP transport, codec handling, or device adaptation.
  • Tested it with the Sony WH-H910N, and everything worked great without any issues

Happy to do some more thorough testing on the Jolla C2, whether it’s by going back to an older version or trying out new builds.