Hi! I am implementing audio sink on my desktop linux (as a first step; second step is linux embedded). My application uses Qt 5.15, and also bluez-qt library from KDE project. I am using bluez 5.55 On my laptop I have organized registering of endpoint to accept sbc audio from my android smartphone. When I receive BluezQt::MediaTransport::stateChanged signal with state = BluezQt::MediaTransport::State::Pending, I call transport->acquire(). In reply I get file descriptor 33, mtu read 672, mtu write 1008. But then, when I start new thread that reads from this file descriptor, I get errno 9 (returned length being -1) all the time (on each for(;;) loop iteration). On smartphones's side everything looks good - it streams audio over bluetooth (in youtube application) and I can change bluetooth volume. I found out that bluetooth documentation is scarce. The only detailed document I found besides *-api.txt files is https://www.lightofdawn.org/blog/?viewDetailed=00032 but it talks about bluez 4 Could you please give me advice on where to look to fix this problem? This is the log from bluetoothd -d: Jun 23 10:52:52 debian-e330 bluetoothd[629]: Endpoint registered: sender=:1.170 path=/MediaEndpoint/Sink/Sbc Jun 23 10:52:52 debian-e330 bluetoothd[629]: src/adapter.c:dev_class_changed_callback() Class: 0x14010c Jun 23 10:52:53 debian-e330 bluetoothd[629]: src/adapter.c:device_found_callback() hci0 addr 60:AB:67:17:74:03, rssi -79 flags 0x0000 eir_len 170 Jun 23 10:52:53 debian-e330 bluetoothd[629]: src/device.c:device_set_legacy() legacy 0 Jun 23 10:52:53 debian-e330 bluetoothd[629]: src/device.c:device_set_rssi_with_delta() rssi -79 Jun 23 10:52:57 debian-e330 bluetoothd[629]: src/adapter.c:discovering_callback() hci0 type 7 discovering 0 method 1 Jun 23 10:52:57 debian-e330 bluetoothd[629]: src/adapter.c:trigger_start_discovery() Jun 23 10:52:57 debian-e330 bluetoothd[629]: src/adapter.c:cancel_passive_scanning() Jun 23 10:52:57 debian-e330 bluetoothd[629]: src/adapter.c:start_discovery_timeout() Jun 23 10:52:57 debian-e330 bluetoothd[629]: src/adapter.c:start_discovery_timeout() adapter->current_discovery_filter == 1 Jun 23 10:52:57 debian-e330 bluetoothd[629]: src/adapter.c:start_discovery_timeout() sending MGMT_OP_START_SERVICE_DISCOVERY 127, 7, 0 Jun 23 10:52:57 debian-e330 bluetoothd[629]: src/adapter.c:start_discovery_complete() status 0x00 Jun 23 10:52:57 debian-e330 bluetoothd[629]: src/adapter.c:discovering_callback() hci0 type 7 discovering 1 method 1 Jun 23 10:53:02 debian-e330 bluetoothd[629]: src/adapter.c:connected_callback() hci0 device 60:AB:67:17:74:03 connected eir_len 12 Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/a2dp.c:confirm_cb() AVDTP: incoming connect from 60:AB:67:17:74:03 Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/source.c:source_set_state() State changed /org/bluez/hci0/dev_60_AB_67_17_74_03: SOURCE_STATE_DISCONNECTED -> SOURCE_STATE_CONNECTING Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_connect_cb() AVDTP: connected signaling channel to 60:AB:67:17:74:03 Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_connect_cb() AVDTP imtu=672, omtu=672 Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_register_remote_sep() seid 1 type 0 media 0 delay_reporting true Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/a2dp.c:register_remote_sep() Found remote SEP: /org/bluez/hci0/dev_60_AB_67_17_74_03/sep1 Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_ref() 0x560dcaedf8a0: ref=1 Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:set_disconnect_timer() timeout 1 Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:session_cb() Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_parse_cmd() Received DISCOVER_CMD Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:session_cb() Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_parse_cmd() Received GET_ALL_CAPABILITIES_CMD Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/a2dp.c:endpoint_getcap_ind() Sink 0x560dcaeb1050: Get_Capability_Ind Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:session_cb() Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_parse_cmd() Received SET_CONFIGURATION_CMD Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:caps_to_list() Invalid capability data in getcap resp Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/a2dp.c:endpoint_setconf_ind() Sink 0x560dcaeb1050: Set_Configuration_Ind Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_ref() 0x560dcaedf8a0: ref=2 Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_unref() 0x560dcaedf8a0: ref=1 Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/a2dp.c:setup_ref() 0x560dcaec4cc0: ref=1 Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/a2dp.c:setup_ref() 0x560dcaec4cc0: ref=2 Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/media.c:media_endpoint_async_call() Calling SetConfiguration: name = :1.170 path = /MediaEndpoint/Sink/Sbc Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_ref() 0x560dcaedf8a0: ref=2 Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_sep_set_state() stream state changed: IDLE -> CONFIGURED Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/a2dp.c:setup_unref() 0x560dcaec4cc0: ref=1 Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/a2dp.c:setup_unref() 0x560dcaec4cc0: ref=0 Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/a2dp.c:setup_free() 0x560dcaec4cc0 Jun 23 10:53:03 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_unref() 0x560dcaedf8a0: ref=1 Jun 23 10:53:05 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:session_cb() Jun 23 10:53:05 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_parse_cmd() Received OPEN_CMD Jun 23 10:53:05 debian-e330 bluetoothd[629]: profiles/audio/a2dp.c:open_ind() Sink 0x560dcaeb1050: Open_Ind Jun 23 10:53:05 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_ref() 0x560dcaedf8a0: ref=2 Jun 23 10:53:05 debian-e330 bluetoothd[629]: profiles/audio/a2dp.c:setup_ref() 0x560dcaec4cc0: ref=1 Jun 23 10:53:05 debian-e330 bluetoothd[629]: profiles/audio/a2dp.c:confirm_cb() AVDTP: incoming connect from 60:AB:67:17:74:03 Jun 23 10:53:05 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_sep_set_state() stream state changed: CONFIGURED -> OPEN Jun 23 10:53:05 debian-e330 bluetoothd[629]: src/service.c:change_state() 0x560dcaebb5a0: device 60:AB:67:17:74:03 profile a2dp-source state changed: disconnected -> connected (0) Jun 23 10:53:05 debian-e330 bluetoothd[629]: plugins/policy.c:service_cb() Added a2dp-source reconnect 1 Jun 23 10:53:05 debian-e330 bluetoothd[629]: profiles/audio/source.c:source_set_state() State changed /org/bluez/hci0/dev_60_AB_67_17_74_03: SOURCE_STATE_CONNECTING -> SOURCE_STATE_CONNECTED Jun 23 10:53:05 debian-e330 bluetoothd[629]: profiles/audio/transport.c:transport_update_playing() /org/bluez/hci0/dev_60_AB_67_17_74_03/fd1 State=TRANSPORT_STATE_IDLE Playing=0 Jun 23 10:53:05 debian-e330 bluetoothd[629]: profiles/audio/a2dp.c:setup_unref() 0x560dcaec4cc0: ref=0 Jun 23 10:53:05 debian-e330 bluetoothd[629]: profiles/audio/a2dp.c:setup_free() 0x560dcaec4cc0 Jun 23 10:53:05 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_unref() 0x560dcaedf8a0: ref=1 Jun 23 10:53:07 debian-e330 bluetoothd[629]: src/adapter.c:stop_discovery() sender :1.170 Jun 23 10:53:07 debian-e330 bluetoothd[629]: src/adapter.c:discovering_callback() hci0 type 7 discovering 0 method 1 Jun 23 10:53:07 debian-e330 bluetoothd[629]: src/adapter.c:trigger_start_discovery() Jun 23 10:53:07 debian-e330 bluetoothd[629]: src/adapter.c:cancel_passive_scanning() Jun 23 10:53:07 debian-e330 bluetoothd[629]: src/adapter.c:stop_discovery_complete() status 0x00 Jun 23 10:53:07 debian-e330 bluetoothd[629]: src/adapter.c:discovery_remove() owner :1.170 Jun 23 10:53:07 debian-e330 bluetoothd[629]: src/device.c:device_set_rssi_with_delta() rssi 0 Jun 23 10:53:07 debian-e330 bluetoothd[629]: src/adapter.c:trigger_passive_scanning() Jun 23 10:53:08 debian-e330 bluetoothd[629]: plugins/policy.c:policy_connect() /org/bluez/hci0/dev_60_AB_67_17_74_03 profile audio-avrcp-target Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/avrcp.c:avrcp_connect() path /org/bluez/hci0/dev_60_AB_67_17_74_03 Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/avctp.c:avctp_set_state() AVCTP Connecting Jun 23 10:53:08 debian-e330 bluetoothd[629]: src/service.c:change_state() 0x560dcaeba730: device 60:AB:67:17:74:03 profile audio-avrcp-target state changed: disconnected -> connecting (0) Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/avctp.c:avctp_connect_cb() AVCTP: connected to 60:AB:67:17:74:03 Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/avctp.c:init_uinput() AVRCP: uinput initialized for Mi A3 Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/avrcp.c:controller_init() 0x560dcaeae780 version 0x0103 Jun 23 10:53:08 debian-e330 bluetoothd[629]: src/service.c:change_state() 0x560dcaeba730: device 60:AB:67:17:74:03 profile audio-avrcp-target state changed: connecting -> connected (0) Jun 23 10:53:08 debian-e330 bluetoothd[629]: src/device.c:device_profile_connected() audio-avrcp-target Success (0) Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_controller_create() /org/bluez/hci0/dev_60_AB_67_17_74_03/player0 Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/avrcp.c:target_init() 0x560dcaee0d00 version 0x0103 Jun 23 10:53:08 debian-e330 bluetoothd[629]: src/service.c:change_state() 0x560dcaea88d0: device 60:AB:67:17:74:03 profile avrcp-controller state changed: disconnected -> connected (0) Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/avctp.c:avctp_set_state() AVCTP Connected Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/avrcp.c:handle_vendordep_pdu() AVRCP PDU 0x31, company 0x001958 len 0x0005 Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/avrcp.c:handle_vendordep_pdu() AVRCP PDU parameters length don't match Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_setting() Repeat: off Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_setting() Shuffle: off Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_position() 0 Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_status() stopped Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_playlist_item() 0 Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_metadata() Title: CIAO, 2020! Полная версия Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_metadata() Artist: Вечерний Ургант Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_metadata() Album: Вечерний Ургант Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_metadata() TrackNumber: 0 Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_metadata() NumberOfTracks: 0 Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_metadata() Genre: Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_metadata() Duration: 3184000 Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_duration() 3184000 Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_position() 0 Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_status() stopped Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_duration() 3184000 Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_position() 0 Jun 23 10:53:08 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_status() stopped Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:session_cb() Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_parse_cmd() Received START_CMD Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/a2dp.c:start_ind() Sink 0x560dcaeb1050: Start_Ind Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_ref() 0x560dcaedf8a0: ref=2 Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_sep_set_state() stream state changed: OPEN -> STREAMING Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/source.c:source_set_state() State changed /org/bluez/hci0/dev_60_AB_67_17_74_03: SOURCE_STATE_CONNECTED -> SOURCE_STATE_PLAYING Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/transport.c:transport_update_playing() /org/bluez/hci0/dev_60_AB_67_17_74_03/fd1 State=TRANSPORT_STATE_IDLE Playing=1 Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/transport.c:transport_set_state() State changed /org/bluez/hci0/dev_60_AB_67_17_74_03/fd1: TRANSPORT_STATE_IDLE -> TRANSPORT_STATE_PENDING Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/transport.c:media_owner_create() Owner created: sender=:1.170 Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_ref() 0x560dcaedf8a0: ref=3 Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/a2dp.c:a2dp_sep_lock() SEP 0x560dcaeb1050 locked Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_ref() 0x560dcaedf8a0: ref=4 Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/a2dp.c:setup_ref() 0x560dcaed05b0: ref=1 Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_unref() 0x560dcaedf8a0: ref=3 Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/transport.c:media_request_create() Request created: method=Acquire id=3 Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/transport.c:media_owner_add() Owner :1.170 Request Acquire Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/transport.c:media_transport_set_owner() Transport /org/bluez/hci0/dev_60_AB_67_17_74_03/fd1 Owner :1.170 Jun 23 10:53:09 debian-e330 bluetoothd[629]: /org/bluez/hci0/dev_60_AB_67_17_74_03/fd1: fd(37) ready Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/transport.c:media_owner_remove() Owner :1.170 Request Acquire Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/transport.c:transport_set_state() State changed /org/bluez/hci0/dev_60_AB_67_17_74_03/fd1: TRANSPORT_STATE_PENDING -> TRANSPORT_STATE_ACTIVE Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/a2dp.c:setup_unref() 0x560dcaed05b0: ref=0 Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/a2dp.c:setup_free() 0x560dcaed05b0 Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/avdtp.c:avdtp_unref() 0x560dcaedf8a0: ref=2 Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_status() playing Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_duration() 3184000 Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_position() 0 Jun 23 10:53:09 debian-e330 bluetoothd[629]: profiles/audio/player.c:media_player_set_status() playing ================= And this is the output of my application, Mi A3 is my smartphone. Change "org.bluez.Device1" QMap(("RSSI", QVariant(short, -79))) Change "org.bluez.Device1" QMap(("Connected", QVariant(bool, true))) isInSet false isConnected true CONNECTED configurationSet "/org/bluez/hci0/dev_60_AB_67_17_74_03/fd1" Change "org.bluez.Device1" QMap() Change "org.bluez.Adapter1" QMap(("Discovering", QVariant(bool, false))) Change "org.bluez.MediaControl1" QMap(("Connected", QVariant(bool, true))("Player", QVariant(QDBusObjectPath, ))) MediaTransportPrivate::onPropertiesChanged key "State" QVariant(QString, "pending") Transport state: BluezQt::MediaTransport::State::Pending "Mi A3" Transport state: BluezQt::MediaTransport::State::Pending "Mi A3" fd: 33 mtu read: 672 mtu write: 1008 fd reply err 0 fd reply mtu read write 672 1008 fd reply fd 33 MediaTransportPrivate::onPropertiesChanged key "State" QVariant(QString, "active") Transport state: BluezQt::MediaTransport::State::Active "Mi A3" Transport state: BluezQt::MediaTransport::State::Active "Mi A3" BluetoothAudioRead len errno -1 9 I use read() call: uint8_t payload[2 * 512]; ssize_t len = read(bluetooth_fd, payload, sizeof(payload)); qDebug()<<"BluetoothAudioRead len errno"<<len<<errno; I also tried using recvmsg() the way it is done in pulseaudio, but result is the same.
