linux - (Bluez) 如何获取蓝牙耳机按键输入？

Question

我有一个连接到 Linux 设备的蓝牙耳机。我想以编程方式接收播放/暂停/下一个/上一个/volUp/volDown 按钮按下。

经过一些研究，我发现我可以使用 dbus 与 Bluez 交互。我尝试使用此脚本注册 MediaPlayer https://github.com/bluez/bluez/blob/master/test/example-player但是当我检查 dbus 时，没有新的播放器，而且它似乎没有任何改变。

我也尝试过使用 Gatt 服务，但我在任何地方都找不到 org.bluez.GattService1。

获取输入的最佳方式是什么？我的 Bluez 有问题吗？

背景:我的目标是让音频输入和音频输出都通过蓝牙连接到 rpi。我确实设法做到了这一点，并在输出上播放了输入播放的声音。现在我也想转发输入。

Answer 1

我对此进行了一些调查并发现了一些东西，但没有得出完整的结论。我想我会在这里分享它，希望有人可以编辑/改进答案。

我已将蓝牙耳机连接到我的 Raspberry Pi，感兴趣的 DBus 接口(interface)似乎是 org.bluez.MediaControl1 和 org.bluez.MediaTransport1

(venv) pi@raspberrypi:~/stack_overflow $ busctl tree 'org.bluez'
└─/org
  └─/org/bluez
    ├─/org/bluez/hci0
    │ ├─/org/bluez/hci0/dev_74_5C_4B_F8_6D_95
    │ │ └─/org/bluez/hci0/dev_74_5C_4B_F8_6D_95/fd2
    └─/org/bluez/test

(venv) pi@raspberrypi:~/stack_overflow $ busctl introspect 'org.bluez' '/org/bluez/hci0/dev_74_5C_4B_F8_6D_95'
NAME                                TYPE      SIGNATURE RESULT/VALUE                             FLAGS
org.bluez.Device1                   interface -         -                                        -
.CancelPairing                      method    -         -                                        -
.Connect                            method    -         -                                        -
.ConnectProfile                     method    s         -                                        -
.Disconnect                         method    -         -                                        -
.DisconnectProfile                  method    s         -                                        -
.Pair                               method    -         -                                        -
.Adapter                            property  o         "/org/bluez/hci0"                        emits-change
.Address                            property  s         "74:5C:4B:F8:6D:95"                      emits-change
.AddressType                        property  s         "public"                                 emits-change
.AdvertisingData                    property  a{yv}     -                                        emits-change
.AdvertisingFlags                   property  ay        -                                        emits-change
.Alias                              property  s         "Jabra Move SE v1.0.0"                   emits-change writable
.Appearance                         property  q         -                                        emits-change
.Blocked                            property  b         false                                    emits-change writable
.Class                              property  u         2360324                                  emits-change
.Connected                          property  b         true                                     emits-change
.Icon                               property  s         "audio-card"                             emits-change
.LegacyPairing                      property  b         false                                    emits-change
.ManufacturerData                   property  a{qv}     -                                        emits-change
.Modalias                           property  s         -                                        emits-change
.Name                               property  s         "Jabra Move SE v1.0.0"                   emits-change
.Paired                             property  b         true                                     emits-change
.RSSI                               property  n         -                                        emits-change
.ServiceData                        property  a{sv}     -                                        emits-change
.ServicesResolved                   property  b         true                                     emits-change
.Trusted                            property  b         false                                    emits-change writable
.TxPower                            property  n         -                                        emits-change
.UUIDs                              property  as        5 "00001108-0000-1000-8000-00805f9b34fb… emits-change
org.bluez.MediaControl1             interface -         -                                        -
.FastForward                        method    -         -                                        deprecated
.Next                               method    -         -                                        deprecated
.Pause                              method    -         -                                        deprecated
.Play                               method    -         -                                        deprecated
.Previous                           method    -         -                                        deprecated
.Rewind                             method    -         -                                        deprecated
.Stop                               method    -         -                                        deprecated
.VolumeDown                         method    -         -                                        deprecated
.VolumeUp                           method    -         -                                        deprecated
.Connected                          property  b         true                                     emits-change
.Player                             property  o         -                                        emits-change
org.freedesktop.DBus.Introspectable interface -         -                                        -
.Introspect                         method    -         s                                        -
org.freedesktop.DBus.Properties     interface -         -                                        -
.Get                                method    ss        v                                        -
.GetAll                             method    s         a{sv}                                    -
.Set                                method    ssv       -                                        -
.PropertiesChanged                  signal    sa{sv}as  -                                        -

(venv) pi@raspberrypi:~/stack_overflow $ busctl introspect 'org.bluez' '/org/bluez/hci0/dev_74_5C_4B_F8_6D_95/fd2'
NAME                                TYPE      SIGNATURE RESULT/VALUE                            FLAGS
org.bluez.MediaTransport1           interface -         -                                       -
.Acquire                            method    -         hqq                                     -
.Release                            method    -         -                                       -
.TryAcquire                         method    -         hqq                                     -
.Codec                              property  y         0                                       emits-change
.Configuration                      property  ay        4 17 21 2 51                            emits-change
.Delay                              property  q         -                                       emits-change
.Device                             property  o         "/org/bluez/hci0/dev_74_5C_4B_F8_6D_95" emits-change
.State                              property  s         "idle"                                  emits-change
.UUID                               property  s         "0000110A-0000-1000-8000-00805F9B34FB"  emits-change
.Volume                             property  q         -                                       emits-change writ
org.freedesktop.DBus.Introspectable interface -         -                                       -
.Introspect                         method    -         s                                       -
org.freedesktop.DBus.Properties     interface -         -                                       -
.Get                                method    ss        v                                       -
.GetAll                             method    s         a{sv}                                   -
.Set                                method    ssv       -                                       -
.PropertiesChanged                  signal    sa{sv}as  -                                       -
lines 1-19/19 (END)

旁边的 org.bluez.MediaControl1 已弃用，org.bluez.MediaTransport1 记录在:https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/doc/media-api.txt#n587

org.bluez.MediaTransport1 有一个 volume 属性，但是当我尝试读取它时出现错误:

(venv) pi@raspberrypi:~/stack_overflow $ busctl get-property 'org.bluez' '/org/bluez/hci0/dev_74_5C_4B_F8_6D_95/fd2' 'org.bluez.MediaTransport1' Volume
No such property 'Volume'

但我可以很好地阅读其他属性:

(venv) pi@raspberrypi:~/stack_overflow $ busctl get-property 'org.bluez' '/org/bluez/hci0/dev_74_5C_4B_F8_6D_95/fd2' 'org.bluez.MediaTransport1' State
s "active"

在我检查接口(interface)时，我一直在使用这段代码将其保持在 Active 状态。

import os
from gi.repository import GLib
from pydbus import SystemBus
from time import sleep

dev_addr = '74:5C:4B:F8:6D:95'

bluez_service = 'org.bluez'
adapter_path = '/org/bluez/hci0'
device_path = f"{adapter_path}/dev_{dev_addr.replace(':', '_')}"

bus = SystemBus()
mngr = bus.get(bluez_service, '/')
adapter = bus.get(bluez_service, adapter_path)

def get_media_transport_path(dev_path):
    mng_objs = mngr.GetManagedObjects()
    for dev_objs in mng_objs:
        if dev_objs.startswith(dev_path):
            state = mng_objs[dev_objs].get('org.bluez.MediaTransport1', {}).get('State', False)
            print('State', state)
            if state:
                return dev_objs

mt_path = get_media_transport_path(device_path)
mt = bus.get(bluez_service, mt_path)
mt_data = mt.Acquire()
print('Acquire', mt_data)
print('GetAll', mt.GetAll('org.bluez.MediaTransport1'))
print('Transport Device', mt.Device)
print('Transport state', mt.State)

sleep(20)
mt.Release()
print('Transport State', mt.State)

我的下一个调查将围绕 Acquire 返回的文件描述符进行，但是我选择的 DBus 库有一个关于 fd 的 https://github.com/LEW21/pydbus/pull/86 的问题。