I've spent a while studying the snoop/syslogs and Bluez source, and I believe I've narrowed down the issue.
* From the Headset-Initiated snoop, we can see where the headset connected the ACL (23:54:47 UTC), followed shortly by connecting HFP (successfully). * Very soon after the headset connected HFP, the PC/bluez initiated an AVDTP connection, a bid to connect A2DP -- this is unfriendly behaviour, since the general convention is: whomever created the ACL gets to create the profiles. Or at least is given enough time to connect them, before the other end starts its own attempt. The result of this behaviour is that the headset, probably getting ready to connect A2DP itself, now gets confused by this incoming PC connection, its firmware apparently not strong or flexible enough to handle this A2DP crossover scenario, manifesting as follows: That AVDTP channel (for A2DP signalling) does get established, but then strange behaviour is seen while setting up the media-channel -- the headset takes 3s to respond to the AVDTP_DISCOVER command. These 3s end up being costly because... * The PC creates a SCO connection to the headset around this time -- I believe this is because the PC must route my current audio stream somewhere, and since A2DP media isn't setup yet after all this time, it (PulseAudio?) will settle for HFP/SCO. (Even this SCO connection takes 5s to complete, headset still not out of the woods.) -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to bluez in Ubuntu. https://bugs.launchpad.net/bugs/1941977 Title: PC streams music over low-quality HFP/SCO connection, instead of A2DP/AVDTP Status in bluez package in Ubuntu: New Bug description: This issue was first discovered when I got this headset 2 years back: https://www.amazon.co.uk/gp/product/B01C2QCPYI. STEPS * Enable Bluetooth on the PC * Have music or some video playing on the PC * Power on the (already-paired) headset. It automatically connects to the PC. EXPECTED RESULT The PC's audio should now be streamed to the headset, over high-quality A2DP ACTUAL RESULT The PC's audio gets streamed over the low-quality HFP/SCO connection instead. Stopping and resuming the stream changes nothing. I have to manually open Blueman and right-click on the device and select "High-quality A2DP profile", for it to switch to the expected high-quality A2DP transport. HCI snoop logs and verbose bluetoothd-syslogs taken in both headset- initiated and PC-initiated connections are attached. ProblemType: Bug DistroRelease: Ubuntu 20.04 Package: bluez 5.53-0ubuntu3.3 [modified: lib/systemd/system/bluetooth.service] ProcVersionSignature: Ubuntu 5.4.0-74.83-generic 5.4.114 Uname: Linux 5.4.0-74-generic x86_64 ApportVersion: 2.20.11-0ubuntu27.18 Architecture: amd64 CasperMD5CheckResult: skip CurrentDesktop: ubuntu:GNOME Date: Sun Aug 29 03:49:08 2021 InstallationDate: Installed on 2019-06-08 (812 days ago) InstallationMedia: Ubuntu 19.04 "Disco Dingo" - Release amd64 (20190416) InterestingModules: rfcomm bnep btusb bluetooth MachineType: Dell Inc. XPS 13 9380 ProcEnviron: LANGUAGE=en_GB:en PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=en_GB.UTF-8 SHELL=/bin/bash ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-5.4.0-74-generic root=UUID=93dae559-0f0d-4e36-9318-ee7154840a9f ro resume=UUID=01c18f00-e0eb-4891-9bf1-3110416d9b39 quiet splash mem_sleep_default=deep vt.handoff=7 SourcePackage: bluez UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 12/14/2020 dmi.bios.vendor: Dell Inc. dmi.bios.version: 1.12.1 dmi.board.name: 0KTW76 dmi.board.vendor: Dell Inc. dmi.board.version: A00 dmi.chassis.type: 10 dmi.chassis.vendor: Dell Inc. dmi.modalias: dmi:bvnDellInc.:bvr1.12.1:bd12/14/2020:svnDellInc.:pnXPS139380:pvr:rvnDellInc.:rn0KTW76:rvrA00:cvnDellInc.:ct10:cvr: dmi.product.family: XPS dmi.product.name: XPS 13 9380 dmi.product.sku: 08AF dmi.sys.vendor: Dell Inc. hciconfig: hci0: Type: Primary Bus: USB BD Address: 9C:B6:D0:99:1D:20 ACL MTU: 1024:8 SCO MTU: 50:8 UP RUNNING PSCAN RX bytes:3313120 acl:776 sco:26275 events:305102 errors:0 TX bytes:255208317 acl:298108 sco:22053 commands:6779 errors:0 mtime.conffile..etc.bluetooth.main.conf: 2020-04-27T23:21:52.866445 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/bluez/+bug/1941977/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
