BT_蓝牙音乐协议分析

dupz11192023-11-03 14:04

协议架构

上面描述的就是整体的协议架构，我们针对蓝牙音乐的协议架构分析，其中涉及到了几个协议：

其中针对业务层的逻辑，涉及到了A2DP和AVRCP协议；

AVRCP

AVRCP全称：Audio/Video Remote Control Profile，即音频/视频远程控制配置文件。

AVRCP设计用于提供控制TV，Hi-Fi设备等的标准接口，此配置文件用于许可单个远程控制设备（或其他设备）控制所有用于可以接入的A/V设备。AVRCP定义了如何控制流媒体的特征。包括暂停、停止、启动重放、音量控制及其他类型的远程控制操作（其实和DLNA的指令控制类似）；

AVRCP是一种在蓝牙协议栈A2DP/AVRCP上实现的控制技术；

A2DP

A2DP全称：Advenced Audio Distribution Profile，即蓝牙音频传输模型协定；

A2DP规定了使用蓝牙异步传输信道方式，传输高质量音乐文件数据的协议堆栈软件和使用方法，基于该协议就能通过以蓝牙方式传输高品质的音乐。例如使用蓝牙耳机或蓝牙音响设备来收听音乐了；

针对上述的相关的协议，其实和蓝牙命令请求和响应有密切的关联；

Command & Event

Command

我们整理一下蓝牙音乐过程中涉及到的常见的一些Command；

Protocol JNI Command Desc
A2dpSink BluetoothA2dpSinkServiceJni classInitNative 初始化A2dpSink Native
A2dpSink BluetoothA2dpSinkServiceJni connectA2dpNative 用于连接A2dp
Sdp BluetoothSdpJni sdpCreateOppOpsRecordNative 创建服务记录列表
Sdp BluetoothSdpJni sdpSearchNative 搜索服务
Avrcp BluetoothAvrcpControllerJni getPlayerListNative 获取播放列表
Avrcp BluetoothAvrcpControllerJni sendPassThroughCommandNative 68：播放 70：暂停 75：下一首 76：上一首

Event

Event代表的就是上层业务层向下发送指令到底层返回的callback响应；

Protocol JNI Event Desc
A2dpSink BluetoothA2dpSinkServiceJni bta2dp_connection_state_callback 响应A2dp服务连接
Sdp BluetoothSdpJni sdp_search_callback 响应sdp服务搜索结果
A2dpSink BluetoothA2dpSinkServiceJni bta2dp_audio_config_callback A2dp audio配置变化回调
Avrcp BluetoothAvrcpControllerJni btavrcp_connection_state_callback Avrcp服务连接状态回调
Avrcp BluetoothAvrcpControllerJni btavrcp_get_rcfeatures_callback
Avrcp BluetoothAvrcpControllerJni btavrcp_play_status_changed_callback 当前播放状态变化信息回调
Avrcp BluetoothAvrcpControllerJni btavrcp_track_changed_callback TrackInfo信息变化回调
Avrcp BluetoothAvrcpControllerJni btavrcp_set_addressed_player_callback 设置address地址信息结果回调
Avrcp BluetoothAvrcpControllerJni btavrcp_uids_changed_callback uid变化回调
Avrcp BluetoothAvrcpControllerJni btavrcp_get_folder_items_callback 获取文件夹目录信息回调
Avrcp BluetoothAvrcpControllerJni btavrcp_playerapplicationsetting_callback 播放器设置结果回调
Avrcp BluetoothAvrcpControllerJni btavrcp_playerapplicationsetting_changed_callback 更换播放器结果回调
Avrcp BluetoothAvrcpControllerJni btavrcp_available_player_changed_callback 播放可行性变化回调
Avrcp BluetoothAvrcpControllerJni btavrcp_addressed_player_update_callback address信息变化回调
Avrcp BluetoothAvrcpControllerJni btavrcp_play_position_changed_callback 播放进度条信息回调
Avrcp BluetoothAvrcpControllerJni btavrcp_passthrough_response_callback 指令响应结果回调
A2dpSink BluetoothA2dpSinkServiceJni bta2dp_audio_state_callback A2dp audio状态变化结果回调

协议分析

我们按照蓝牙音乐的播放流程逐一分析涉及到的协议；

A2dpSink 连接

这个过程中涉及到的Command和Event为：

  • Command

    • connectA2dpNative

  • Event

    • bta2dp_connection_state_callback
    • bta2dp_audio_config_callback
connectA2dpNative
Operation
ruby 复制代码 
01-01 00:07:30.619  1713  2134 I BluetoothA2dpSinkServiceJni: connectA2dpNative: sBluetoothA2dpInterface: 0x77307fd3e8
01-01 00:07:30.619  1713  1713 D A2dpSinkStateMachine: Connection state 30:AA:E4:42:C7:DD: 0->1
01-01 00:07:30.619  1713  2134 I btif_av : sink_connect_src: Peer 30:aa:e4:42:c7:dd
01-01 00:07:30.619  1713  2134 D A2dpSinkStateMachine: Exit Disconnected: 1
01-01 00:07:30.619  1713  2134 D A2dpSinkStateMachine: Enter Pending: 1
01-01 00:07:30.619  1713  1794 I bt_btif_queue: queue_int_add: adding connection request: address=30:aa:e4:42:c7:dd UUID=110B busy=false
01-01 00:07:30.619  1713  1794 I bt_btif_queue: btif_queue_connect_next: executing connection request: address=30:aa:e4:42:c7:dd UUID=110B busy=false
01-01 00:07:30.619  1713  1794 I bt_btif : connect_int: peer_address=30:aa:e4:42:c7:dd uuid=0x110b
01-01 00:07:30.619  1713  1794 D bt_btif : BtifAvPeer *BtifAvSink::FindOrCreatePeer(const RawAddress &, tBTA_AV_HNDL): peer_address=30:aa:e4:42:c7:dd bta_handle=0x0
01-01 00:07:30.619  1713  1794 I btif_av : BtifAvPeer *BtifAvSink::FindOrCreatePeer(const RawAddress &, tBTA_AV_HNDL): Create peer: peer_address=30:aa:e4:42:c7:dd bta_handle=0x41 peer_id=0
01-01 00:07:30.619  1713  1794 D bt_btif : virtual void BtifAvStateMachine::StateIdle::OnEnter(): Peer 30:aa:e4:42:c7:dd
01-01 00:07:30.619  1713  1794 W bt_btif : btif_av_get_peer_sep: No active peer found
01-01 00:07:30.619  1713  1794 I bt_btif_a2dp: btif_a2dp_on_idle: ## ON A2DP IDLE ## peer_sep = 1
01-01 00:07:30.619  1713  1794 W bt_btif : btif_av_get_peer_sep: No active peer found
01-01 00:07:30.619  1713  1794 I bt_btif_a2dp_source: btif_a2dp_source_on_idle: state=STATE_OFF
01-01 00:07:30.619  1713  1794 D bt_btif : virtual bool BtifAvStateMachine::StateIdle::ProcessEvent(uint32_t, void *): Peer 30:aa:e4:42:c7:dd : event=BTIF_AV_CONNECT_REQ_EVT(0x19) flags=0x0(None) active_peer=false
01-01 00:07:30.619  1713  1794 I bt_bta_av: BTA_AvOpen: peer 30:aa:e4:42:c7:dd handle:0x41 use_rc=true sec_mask=0x12 uuid=0x110b
01-01 00:07:30.619  1294  1294 D BTDevConnectionPolicy: Received Intent for device: 30:AA:E4:42:C7:DD android.bluetooth.a2dp-sink.profile.action.CONNECTION_STATE_CHANGED
01-01 00:07:30.620  1294  1294 D GwmBTDevConnePolicy: Received Intent for device: 30:AA:E4:42:C7:DD android.bluetooth.a2dp-sink.profile.action.CONNECTION_STATE_CHANGED
01-01 00:07:30.620  1713  2064 I bt_btif : bta_sys_event: Event 0x1209
01-01 00:07:30.620  1713  2064 D bt_btif : bta_av_do_disc_a2dp: peer_addr: 30:aa:e4:42:c7:dd use_rc: 1 switch_res:0, oc:0
01-01 00:07:30.620  1713  2064 D bt_btm  : BTM_GetRole
01-01 00:07:30.620  1713  2064 D bt_btif : bta_av_do_disc_a2dp: ok_continue: 1 wait:0x0, q_tag: 0
01-01 00:07:30.620  1713  2064 D bt_btif : bta_av_save_addr: peer=30:aa:e4:42:c7:dd recfg_sup:1, suspend_sup:1
01-01 00:07:30.620  1294  1294 D BTDevConnectionPolicy: Received BluetoothA2dpSink.ACTION_CONNECTION_STATE_CHANGED currState = 1
01-01 00:07:30.620  1713  2064 I bt_bta_av: bta_av_save_addr: reset flags old_addr=00:00:00:00:00:00 new_addr=30:aa:e4:42:c7:dd
01-01 00:07:30.620  1294  1294 E GwmBTDevConnePolicy: notifyGWMConnectionStatus currentState = 1
01-01 00:07:30.620  1713  2064 D bt_bta_av: SetAvdtpVersion: AVDTP version for 30:aa:e4:42:c7:dd set to 0x103
01-01 00:07:30.620  1713  2064 D bt_btif : bta_dm_pm_cback: st(2), id(18), app(0)
01-01 00:07:30.620  1294  1294 D GwmBTDevConnePolicy: notifyGWMConnectionStatus() Ignoring state: 1
01-01 00:07:30.620  1713  2064 D bt_btif : bta_av_do_disc_a2dp: Initiate SDP discovery for peer 30:aa:e4:42:c7:dd : uuid_int=0x110b sdp_uuid=0x110a
01-01 00:07:30.620  1713  2064 I a2dp_api: A2DP_FindService: peer: 30:aa:e4:42:c7:dd UUID: 0x110a
01-01 00:07:30.620  1713  2064 I bt_sdp  : sdp_conn_originate: SDP - Originate started for peer 30:aa:e4:42:c7:dd
01-01 00:07:30.620  1713  2064 D bt_l2cap: l2cu_allocate_ccb: cid 0x0000
01-01 00:07:30.620  1713  2064 D bt_l2cap: l2cu_enqueue_ccb CID: 0x0043  priority: 2
01-01 00:07:30.620  1713  2064 D bt_l2cap: l2c_link_adjust_chnl_allocation
01-01 00:07:30.620  1713  2064 I bt_l2cap: CID:0x0041 FCR Mode:0 Priority:2 TxDataRate:1 RxDataRate:1 Quota:200
01-01 00:07:30.620  1713  2064 I bt_l2cap: CID:0x0043 FCR Mode:0 Priority:2 TxDataRate:1 RxDataRate:1 Quota:200
01-01 00:07:30.620  1713  2064 I bt_l2cap: L2CAP - LCID: 0x0043  st: CLOSED  evt: UPPER_LAYER_CONNECT_REQ
01-01 00:07:30.620  1713  2064 D bt_btm  : btm_sec_l2cap_access_req() is_originator:1, 0x3090e688, psm=0x0001
01-01 00:07:30.620  1713  2064 I bt_btm  : btm_find_or_alloc_dev
01-01 00:07:30.620  1713  2064 D bt_btm  : btm_sec_is_serv_level0: PSM: 0x0001 -> mode 4 level 0 service
01-01 00:07:30.620  1713  2064 D bt_l2cap: l2c_link_sec_comp2: status=17, p_ref_data=0x773090e688, BD_ADDR=30:aa:e4:42:c7:dd
01-01 00:07:30.620  1713  2064 I bt_l2cap: L2CAP - LCID: 0x0043  st: CLOSED  evt: SECURITY_COMPLETE
01-01 00:07:30.620  1713  2064 D bt_l2cap: TotalWin=6,Hndl=0x2,Quota=8,Unack=2,RRQuota=0,RRUnack=0
01-01 00:07:30.620  1713  2064 D bt_l2cap: RR scan pri=2, lcid=0x0041, q_cout=0
01-01 00:07:30.620  1713  2064 D bt_l2cap: RR scan pri=2, lcid=0x0043, q_cout=0
01-01 00:07:30.620  1713  2064 I bt_l2cap: L2CAP - L2CA_conn_req(psm: 0x0001) returned CID: 0x0043
01-01 00:07:30.620  1713  1794 D bt_btif : virtual void BtifAvStateMachine::StateIdle::OnExit(): Peer 30:aa:e4:42:c7:dd
01-01 00:07:30.620  1713  1794 D bt_btif : virtual void BtifAvStateMachine::StateOpening::OnEnter(): Peer 30:aa:e4:42:c7:dd
01-01 00:07:30.620  1713  1794 I btif_av : btif_report_connection_state: peer_address=30:aa:e4:42:c7:dd state=1
01-01 00:07:30.620  1713  1794 I BluetoothA2dpSinkServiceJni: bta2dp_connection_state_callback
..................
01-01 00:07:30.915  1713  1794 I BluetoothA2dpSinkServiceJni: bta2dp_audio_config_callback
01-01 00:07:31.103  1713  1794 I BluetoothA2dpSinkServiceJni: bta2dp_connection_state_callback

通过上述log，我们可以知道，当上层发送了connect A2dp指令之后，底层将该请求添加到了bt_btif_queue队列中了，然后等待该queue中执行的执行；

然后通过bta2dp_audio_config_callback和bta2dp_connection_state_callback接收到connect的结果反馈；

Protocol

connectA2dpNative 协议分析

yaml 复制代码 
Frame 283: 17 bytes on wire (136 bits), 17 bytes captured (136 bits)
    Encapsulation type: Bluetooth H4 with linux header (99)
    Arrival Time: Jan  1, 2020 00:07:30.685660000 CST
    [Time shift for this packet: 0.000000000 seconds]
    Epoch Time: 1577808450.685660000 seconds
    [Time delta from previous captured frame: 0.000557000 seconds]
    [Time delta from previous displayed frame: 0.000557000 seconds]
    [Time since reference or first frame: 8.423062000 seconds]
    Frame Number: 283
    Frame Length: 17 bytes (136 bits)
    Capture Length: 17 bytes (136 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    Point-to-Point Direction: Sent (0)
    [Protocols in frame: bluetooth:hci_h4:bthci_acl:btl2cap]
Bluetooth
    [Source: BarrotTe_50:67:20 (04:7f:0e:50:67:20)]
    [Destination: HuaweiDe_42:c7:dd (30:aa:e4:42:c7:dd)]
Bluetooth HCI H4
    [Direction: Sent (0x00)]
    HCI Packet Type: ACL Data (0x02)
Bluetooth HCI ACL Packet
    .... 0000 0000 0010 = Connection Handle: 0x002
    ..10 .... .... .... = PB Flag: First Automatically Flushable Packet (2)
    00.. .... .... .... = BC Flag: Point-To-Point (0)
    Data Total Length: 12
    Data
    [Connect in frame: 109]
    [Source BD_ADDR: BarrotTe_50:67:20 (04:7f:0e:50:67:20)]
    [Source Device Name: HAVAL_6720]
    [Source Role: Master (1)]
    [Destination BD_ADDR: HuaweiDe_42:c7:dd (30:aa:e4:42:c7:dd)]
    [Destination Device Name: dupz]
    [Destination Role: Slave (2)]
    [Last Role Change in Frame: 107]
    [Current Mode: Active Mode (0)]
    [Last Mode Change in Frame: 109]
Bluetooth L2CAP Protocol
    Length: 8
    CID: L2CAP Signaling Channel (0x0001)
    Command: Connection Request
        Command Code: Connection Request (0x02)
        Command Identifier: 0x0f
        Command Length: 4
        PSM: AVDTP (0x0019)
        Source CID: Dynamically Allocated Channel (0x0045)
    [Service: Audio Source (0x110a)]

首先我们先分析一下：

ruby 复制代码 
Bluetooth
    [Source: BarrotTe_50:67:20 (04:7f:0e:50:67:20)]
    [Destination: HuaweiDe_42:c7:dd (30:aa:e4:42:c7:dd)]
  • Source：代表了指令的发起方，即指令发送者，BarrotTe_50:67:20，代表了车机端，04:7f:0e:50:67:20为车机端的蓝牙地址；
  • Destination：代表了指令的接收方，HuaweiDe_42:c7:dd，代表了手机端，30:aa:e4:42:c7:dd为手机端的蓝牙地址；
css 复制代码 
Bluetooth HCI H4
    [Direction: Sent (0x00)]
    HCI Packet Type: ACL Data (0x02)
  • HCI H4：代表了UART的transport，这一块涉及到的是Transport层，用于实现Host和Controller的交互；

H4是UART传输中最简单的一个Transport，只是在HCI raw data的前面加一个type就行。

H4定义了5种类型的packet type：

HCI packet type HCI packet indicator Desc
HCI Command packet 0x01 由蓝牙协议栈发送给芯片的命令
HCI ACL Data packet 0x02 蓝牙协议栈跟蓝牙芯片双向交互的普通数据
HCI Synchronous Data packet 0x03 蓝牙芯片跟蓝牙协议栈双向交互的通话/语音识别等音频数据
HCI Event packet 0x04 由蓝牙芯片上报给蓝牙协议栈的事件
HCI ISO Data packet 0x05 LE audio用的数据包格式(这部分是在core 5.2才添加的)
  • Sent (0x00)：代表了发送，一共有两个类型的发送方式：一种是单独的包（00）；一种是连续的包（01 10 11）；
yaml 复制代码 
Bluetooth HCI ACL Packet
    .... 0000 0000 0010 = Connection Handle: 0x002
    ..10 .... .... .... = PB Flag: First Automatically Flushable Packet (2)
    00.. .... .... .... = BC Flag: Point-To-Point (0)
    Data Total Length: 12
    Data
    [Connect in frame: 109]
    [Source BD_ADDR: BarrotTe_50:67:20 (04:7f:0e:50:67:20)]
    [Source Device Name: HAVAL_6720]
    [Source Role: Master (1)]
    [Destination BD_ADDR: HuaweiDe_42:c7:dd (30:aa:e4:42:c7:dd)]
    [Destination Device Name: dupz]
    [Destination Role: Slave (2)]
    [Last Role Change in Frame: 107]
    [Current Mode: Active Mode (0)]
    [Last Mode Change in Frame: 109]

上面描述了BT Device Master和Slave的信息

  • Master

    • Source BD_ADDR：车机端蓝牙地址
    • Source Device Name：车机端蓝牙名称
    • Source Role：车机端角色

  • Slave

    • Destination BD_ADDR：手机端蓝牙地址
    • Destination Device Name：手机端蓝牙名称
    • Destination Role：手机端蓝牙角色
yaml 复制代码 
Bluetooth L2CAP Protocol
    Length: 8
    CID: L2CAP Signaling Channel (0x0001)
    Command: Connection Request
        Command Code: Connection Request (0x02)
        Command Identifier: 0x0f
        Command Length: 4
        PSM: AVDTP (0x0019)
        Source CID: Dynamically Allocated Channel (0x0045)
    [Service: Audio Source (0x110a)]
  • CID：Channel Identifiers，通道标识符，这里使用了Signaling Channel (0x0001)
  • Command Code：命令code
  • Command Identifier：命令标识符
  • PSM：代表给什么协议来建立l2cap连接，这里使用了AVDTP，对应了上述架构图中A2DP协议下关联了AVDTP协议；
  • Source CID：Source Channel Identifiers；
  • Service: Audio Source (0x110a)：表明了在该过程中需要启动的Service；

bta2dp_connection_state_callback

yaml 复制代码 
Frame 289: 21 bytes on wire (168 bits), 21 bytes captured (168 bits)
    Encapsulation type: Bluetooth H4 with linux header (99)
    Arrival Time: Jan  1, 2020 00:07:30.707200000 CST
    [Time shift for this packet: 0.000000000 seconds]
    Epoch Time: 1577808450.707200000 seconds
    [Time delta from previous captured frame: 0.000283000 seconds]
    [Time delta from previous displayed frame: 0.000283000 seconds]
    [Time since reference or first frame: 8.444602000 seconds]
    Frame Number: 289
    Frame Length: 21 bytes (168 bits)
    Capture Length: 21 bytes (168 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    Point-to-Point Direction: Received (1)
    [Protocols in frame: bluetooth:hci_h4:bthci_acl:btl2cap]
Bluetooth
    [Source: HuaweiDe_42:c7:dd (30:aa:e4:42:c7:dd)]
    [Destination: BarrotTe_50:67:20 (04:7f:0e:50:67:20)]
Bluetooth HCI H4
    [Direction: Rcvd (0x01)]
    HCI Packet Type: ACL Data (0x02)
Bluetooth HCI ACL Packet
    .... 0000 0000 0010 = Connection Handle: 0x002
    ..10 .... .... .... = PB Flag: First Automatically Flushable Packet (2)
    00.. .... .... .... = BC Flag: Point-To-Point (0)
    Data Total Length: 16
    Data
    [Connect in frame: 109]
    [Source BD_ADDR: HuaweiDe_42:c7:dd (30:aa:e4:42:c7:dd)]
    [Source Device Name: dupz]
    [Source Role: Slave (2)]
    [Destination BD_ADDR: BarrotTe_50:67:20 (04:7f:0e:50:67:20)]
    [Destination Device Name: HAVAL_6720]
    [Destination Role: Master (1)]
    [Last Role Change in Frame: 107]
    [Current Mode: Active Mode (0)]
    [Last Mode Change in Frame: 109]
Bluetooth L2CAP Protocol
    Length: 12
    CID: L2CAP Signaling Channel (0x0001)
    Command: Connection Response
        Command Code: Connection Response (0x03)
        Command Identifier: 0x0f
        Command Length: 8
        Destination CID: Dynamically Allocated Channel (0x004b)
        Source CID: Dynamically Allocated Channel (0x0045)
        Result: Successful (0x0000)
        Status: No further information available (0x0000)

在这个Response响应中，Result的值为：Successful，表示A2DPSinkService已经连接成功；

bta2dp_audio_config_callback

yaml 复制代码 
Frame 353: 25 bytes on wire (200 bits), 25 bytes captured (200 bits)
    Encapsulation type: Bluetooth H4 with linux header (99)
    Arrival Time: Jan  1, 2020 00:07:30.915044000 CST
    [Time shift for this packet: 0.000000000 seconds]
    Epoch Time: 1577808450.915044000 seconds
    [Time delta from previous captured frame: 0.000876000 seconds]
    [Time delta from previous displayed frame: 0.000876000 seconds]
    [Time since reference or first frame: 8.652446000 seconds]
    Frame Number: 353
    Frame Length: 25 bytes (200 bits)
    Capture Length: 25 bytes (200 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    Point-to-Point Direction: Sent (0)
    [Protocols in frame: bluetooth:hci_h4:bthci_acl:btl2cap:btavdtp]
Bluetooth
    [Source: BarrotTe_50:67:20 (04:7f:0e:50:67:20)]
    [Destination: HuaweiDe_42:c7:dd (30:aa:e4:42:c7:dd)]
Bluetooth HCI H4
    [Direction: Sent (0x00)]
    HCI Packet Type: ACL Data (0x02)
Bluetooth HCI ACL Packet
    .... 0000 0000 0010 = Connection Handle: 0x002
    ..10 .... .... .... = PB Flag: First Automatically Flushable Packet (2)
    00.. .... .... .... = BC Flag: Point-To-Point (0)
    Data Total Length: 20
    Data
    [Connect in frame: 109]
    [Source BD_ADDR: BarrotTe_50:67:20 (04:7f:0e:50:67:20)]
    [Source Device Name: HAVAL_6720]
    [Source Role: Master (1)]
    [Destination BD_ADDR: HuaweiDe_42:c7:dd (30:aa:e4:42:c7:dd)]
    [Destination Device Name: dupz]
    [Destination Role: Slave (2)]
    [Last Role Change in Frame: 107]
    [Current Mode: Active Mode (0)]
    [Last Mode Change in Frame: 109]
Bluetooth L2CAP Protocol
    Length: 16
    CID: Dynamically Allocated Channel (0x004b)
    [Connect in frame: 283]
    [Service: Audio Source (0x110a)]
    [PSM: AVDTP (0x0019)]
Bluetooth AVDTP Protocol
    Signal: SetConfiguration (Command)
        1000 .... = Transaction: 0x8
        .... 00.. = Packet Type: Single (0x0)
        .... ..00 = Message Type: Command (0x0)
        00.. .... = RFA: 0x0
        ..00 0011 = Signal: SetConfiguration (0x03)
    ACP SEID [2 - Audio Source]
        0000 10.. = ACP SEID: 2
        .... ..00 = RFA: 0x0
    INT SEID [2 - Audio Source]
        0000 10.. = INT SEID: 2
        .... ..00 = RFA: 0x0
    Capabilities
        Service: Media Transport
            Service Category: Media Transport (0x01)
            Length of Service Category: 0x00
        Service: Media Codec - Audio MPEG-2,4 AAC
            Service Category: Media Codec (0x07)
            Length of Service Category: 0x08
            0000 .... = Media Type: Audio (0x0)
            .... 0000 = RFA: 0x0
            Media Codec Audio Type: MPEG-2,4 AAC (0x02)
            1... .... = MPEG2 AAC LC: True
            .0.. .... = MPEG4 AAC LC: False
            ..0. .... = MPEG4 AAC LTP: False
            ...0 .... = MPEG4 AAC Scalable: False
            .... 0000 = RFA: 0x0
            0... .... = Sampling Frequency 8000 Hz: False
            .0.. .... = Sampling Frequency 11025 Hz: False
            ..0. .... = Sampling Frequency 12000 Hz: False
            ...0 .... = Sampling Frequency 16000 Hz: False
            .... 0... = Sampling Frequency 22050 Hz: False
            .... .0.. = Sampling Frequency 24000 Hz: False
            .... ..0. = Sampling Frequency 32000 Hz: False
            .... ...1 = Sampling Frequency 44100 Hz: True
            0... .... = Sampling Frequency 48000 Hz: False
            .0.. .... = Sampling Frequency 64000 Hz: False
            ..0. .... = Sampling Frequency 88200 Hz: False
            ...0 .... = Sampling Frequency 96000 Hz: False
            .... 0... = Channels 1: False
            .... .1.. = Channels 2: True
            .... ..00 = RFA: 0x0
            0... .... .... .... .... .... = VBR Supported: False
            .000 0010 1110 1110 0000 0000 = Bit Rate: 0x02ee00

在 Bluetooth AVDTP Protocol 协议块中的 Capabilities 中，描述了Audio Source的多个信息：

  • Service: Media Transport

  • Service: Media Codec

    • Media Type：Audio

    • Media Codec Audio Type：MPEG-2,4 AAC

    • Sampling rate：44100 Hz

    • Channel：CHANNEL_OUT_STEREO

    • Bit Rate（码率）：0x02ee00

    • 码率类型：

      • VBR：可变码率编码
      • CBR：恒定码率编码

AVRCP 连接

在Avrcp协议中涉及到了AVCTP协议；

AVCTP协议描述了蓝牙设备间Audio/Video的控制信号交换的格式和机制，他是一个总体的协议，具体的控制信息由其指定的协议（AVRCP）实现，AVCTP协议本身只指定控制Command和Response的总体的格式；

yaml 复制代码 
........................
Bluetooth
    [Source: BarrotTe_50:67:20 (04:7f:0e:50:67:20)]
    [Destination: HuaweiDe_42:c7:dd (30:aa:e4:42:c7:dd)]
Bluetooth HCI H4
    [Direction: Sent (0x00)]
    HCI Packet Type: ACL Data (0x02)
Bluetooth HCI ACL Packet
    .... 0000 0000 0010 = Connection Handle: 0x002
    ..10 .... .... .... = PB Flag: First Automatically Flushable Packet (2)
    00.. .... .... .... = BC Flag: Point-To-Point (0)
    Data Total Length: 12
    Data
    [Connect in frame: 109]
    [Source BD_ADDR: BarrotTe_50:67:20 (04:7f:0e:50:67:20)]
    [Source Device Name: HAVAL_6720]
    [Source Role: Master (1)]
    [Destination BD_ADDR: HuaweiDe_42:c7:dd (30:aa:e4:42:c7:dd)]
    [Destination Device Name: dupz]
    [Destination Role: Slave (2)]
    [Last Role Change in Frame: 107]
    [Current Mode: Active Mode (0)]
    [Last Mode Change in Frame: 109]
Bluetooth L2CAP Protocol
    Length: 8
    CID: L2CAP Signaling Channel (0x0001)
    Command: Connection Request
        Command Code: Connection Request (0x02)
        Command Identifier: 0x17
        Command Length: 4
        PSM: AVCTP-Control (0x0017)
        Source CID: Dynamically Allocated Channel (0x0048)
    [Service: A/V Remote Control Target (0x110c)]

上述为AVCTP-Control建立L2CAP连接的Command，对应H4的Sent (0x00)；

yaml 复制代码 
........................
Bluetooth
    [Source: HuaweiDe_42:c7:dd (30:aa:e4:42:c7:dd)]
    [Destination: BarrotTe_50:67:20 (04:7f:0e:50:67:20)]
Bluetooth HCI H4
    [Direction: Rcvd (0x01)]
    HCI Packet Type: ACL Data (0x02)
Bluetooth HCI ACL Packet
    .... 0000 0000 0010 = Connection Handle: 0x002
    ..10 .... .... .... = PB Flag: First Automatically Flushable Packet (2)
    00.. .... .... .... = BC Flag: Point-To-Point (0)
    Data Total Length: 16
    Data
    [Connect in frame: 109]
    [Source BD_ADDR: HuaweiDe_42:c7:dd (30:aa:e4:42:c7:dd)]
    [Source Device Name: dupz]
    [Source Role: Slave (2)]
    [Destination BD_ADDR: BarrotTe_50:67:20 (04:7f:0e:50:67:20)]
    [Destination Device Name: HAVAL_6720]
    [Destination Role: Master (1)]
    [Last Role Change in Frame: 107]
    [Current Mode: Active Mode (0)]
    [Last Mode Change in Frame: 109]
Bluetooth L2CAP Protocol
    Length: 12
    CID: L2CAP Signaling Channel (0x0001)
    Command: Connection Response
        Command Code: Connection Response (0x03)
        Command Identifier: 0x17
        Command Length: 8
        Destination CID: Dynamically Allocated Channel (0x005d)
        Source CID: Dynamically Allocated Channel (0x0048)
        Result: Successful (0x0000)
        Status: No further information available (0x0000)

上述为AVCTP-Control建立L2CAP连接的Response，Result为Successful，对应H4的Rcvd (0x01)，代表了接收；

音乐信息加载

这个过程中，包含了多种类型的信息，包括歌曲信息、音乐播放状态、音乐进度信息；

歌曲信息

歌曲信息对应了btavrcp_track_changed_callback回调；

yaml 复制代码 
........................
Bluetooth L2CAP Protocol
    Length: 123
    CID: Dynamically Allocated Channel (0x0048)
    [Connect in frame: 392]
    [Service: A/V Remote Control Target (0x110c)]
    [PSM: AVCTP-Control (0x0017)]
Bluetooth AVCTP Protocol
    1001 .... = Transaction: 0x9
    .... 00.. = Packet Type: Single (0x0)
    .... ..1. = C/R: Response (0x1)
    .... ...0 = IPID: Profile OK (0x0)
    Profile Identifier: A/V Remote Control (0x110e)
Bluetooth AVRCP Profile
    0000 .... = Reserved: 0x0
    .... 1100 = Ctype: Stable (0xc)
    0100 1... = Subunit Type: Panel (0x09)
    .... .000 = Subunit ID: 0x0
    Opcode: Vendor dependent (0x00)
    Company ID: 00:19:58 (Bluetooth SIG, Inc.)
    PDU ID: GetElementAttributes (0x20)
    0000 00.. = RFA: 0x00
    .... ..00 = Packet Type: Single (0x0)
    Parameter Length: 110
    Number of Attributes: 7
    Attribute Entries
        Attribute [                Title]: 忘了你忘了我
            Attribute ID: Title (0x00000001)
            Character Set: UTF-8 (106)
            Value Length: 18
            Value: 忘了你忘了我
        Attribute [               Artist]: 王杰
            Attribute ID: Artist (0x00000002)
            Character Set: UTF-8 (106)
            Value Length: 6
            Value: 王杰
        Attribute [                Album]: 忘了你‧忘了我
            Attribute ID: Album (0x00000003)
            Character Set: UTF-8 (106)
            Value Length: 21
            Value: 忘了你‧忘了我
        Attribute [         Media Number]: 1
            Attribute ID: Media Number (0x00000004)
            Character Set: UTF-8 (106)
            Value Length: 1
            Value: 1
        Attribute [Total Number of Media]: 1
            Attribute ID: Total Number of Media (0x00000005)
            Character Set: UTF-8 (106)
            Value Length: 1
            Value: 1
        Attribute [                Genre]: 
            Attribute ID: Genre (0x00000006)
            Character Set: UTF-8 (106)
            Value Length: 0
            Value: 
        Attribute [         Playing Time]: 279000
            Attribute ID: Playing Time (0x00000007)
            Character Set: UTF-8 (106)
            Value Length: 6
            Value: 279000
    [Response Time: 498/1000ms]
    [Command in frame: 502]

上述的TrackInfo信息中包含了音乐的Title、Artist、Album、Media Number、Number of Media、Genre、Playing Time信息；

音乐播放状态 & 音乐进度信息

这个过程中对应了Event中的btavrcp_play_status_changed_callback和btavrcp_play_position_changed_callback；

yaml 复制代码 
........................
Bluetooth L2CAP Protocol
    Length: 13
    CID: Dynamically Allocated Channel (0x005d)
    [Connect in frame: 392]
    [Service: A/V Remote Control Target (0x110c)]
    [PSM: AVCTP-Control (0x0017)]
Bluetooth AVCTP Protocol
    0001 .... = Transaction: 0x1
    .... 00.. = Packet Type: Single (0x0)
    .... ..0. = C/R: Command (0x0)
    .... ...0 = IPID: Profile OK (0x0)
    Profile Identifier: A/V Remote Control (0x110e)
Bluetooth AVRCP Profile
    0000 .... = Reserved: 0x0
    .... 0001 = Ctype: Status (0x1)
    0100 1... = Subunit Type: Panel (0x09)
    .... .000 = Subunit ID: 0x0
    Opcode: Vendor dependent (0x00)
    Company ID: 00:19:58 (Bluetooth SIG, Inc.)
    PDU ID: GetPlayStatus (0x30)
    0000 00.. = RFA: 0x00
    .... ..00 = Packet Type: Single (0x0)
    Parameter Length: 0
    [Response Time: 24/1000ms]
    [Response in frame: 685]
  • 这里涉及到了一个概念：PDU，Protocol Data Unit，L2CAP和底层交互用的数据包，PDU ID代表了数据包标识为GetPlayStatus；

上述为PDU ID对应的PDU Name以及Command Type；

  • C/R：代表了该数据帧的类型

    • 命令帧（0）
    • 响应帧（1）

  • IPID：在响应帧中表示无效的配置文件标识符（1），否则为0；在数据帧中为0；

  • Profile Identifier：表示根据所识别的Profile定义的规则对命令/响应帧进行编码

  • Company ID：蓝牙认证联盟的注册代码

对应的Response：

yaml 复制代码 
..............................
Bluetooth L2CAP Protocol
    Length: 22
    CID: Dynamically Allocated Channel (0x0048)
    [Connect in frame: 392]
    [Service: A/V Remote Control Target (0x110c)]
    [PSM: AVCTP-Control (0x0017)]
Bluetooth AVCTP Protocol
    0001 .... = Transaction: 0x1
    .... 00.. = Packet Type: Single (0x0)
    .... ..1. = C/R: Response (0x1)
    .... ...0 = IPID: Profile OK (0x0)
    Profile Identifier: A/V Remote Control (0x110e)
Bluetooth AVRCP Profile
    0000 .... = Reserved: 0x0
    .... 1100 = Ctype: Stable (0xc)
    0100 1... = Subunit Type: Panel (0x09)
    .... .000 = Subunit ID: 0x0
    Opcode: Vendor dependent (0x00)
    Company ID: 00:19:58 (Bluetooth SIG, Inc.)
    PDU ID: GetPlayStatus (0x30)
    0000 00.. = RFA: 0x00
    .... ..00 = Packet Type: Single (0x0)
    Parameter Length: 9
    Song Length: 279000
    Song Position: 1989
    Play Status: Playing (0x01)
    [Response Time: 24/1000ms]
    [Command in frame: 681]
  • C/R：响应（1），Response
  • Song Length：音乐时长
  • Song Position：position信息，可以通俗的理解为进度条信息
  • Play Status：播放状态
Play Status Value Desc
Stopped 0x00 停止
Playing 0x01 播放
Paused 0x02 暂停
Fwd Seek 0x03 下一首
Rev Seek 0x04 上一首
Reserved 0x05 - 0xfe 保留状态
Error 0xff 错误状态

Avrcp 指令

yaml 复制代码 
01-01 00:07:56.540  1713  2180 I BluetoothAvrcpControllerJni: sendPassThroughCommandNative: sBluetoothAvrcpInterface: 0x77307fd890
01-01 00:07:56.540  1713  2180 I BluetoothAvrcpControllerJni: key_code: xx, key_state: 0
01-01 00:07:56.540  1713  2180 I BluetoothAvrcpControllerJni: sendPassThroughCommandNative: sBluetoothAvrcpInterface: 0x77307fd890
01-01 00:07:56.540  1713  2180 I BluetoothAvrcpControllerJni: key_code: xx, key_state: 1
01-01 00:07:56.595  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_passthrough_response_callback: id: xx, pressed: 0
01-01 00:07:56.596  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_passthrough_response_callback: id: xx, pressed: 1

Avrcp指令下发过程中，涉及到了sendPassThroughCommandNative方法，其中通过key_code来确认控制指令，key_state来控制操作过程中需要响应的动作；

key_code
key_code value Desc
PASS_THRU_CMD_ID_PLAY 0x44 播放
PASS_THRU_CMD_ID_PAUSE 0x46 暂停
PASS_THRU_CMD_ID_FORWARD 0x4B 下一首
PASS_THRU_CMD_ID_BACKWARD 0x4C 上一首
PASS_THRU_CMD_ID_VOL_UP 0x41 音量调高
PASS_THRU_CMD_ID_VOL_DOWN 0x42 音量调低
PASS_THRU_CMD_ID_STOP 0x45 停止
key_state
Key State value Desc
KEY_STATE_PRESSED 0 按下
KEY_STATE_RELEASED 1 松开

每一个指令都对应了两个动作：按下和松开；

代码需要对这两种动作进行相应的指令发送和响应接收；

Playing
yaml 复制代码 
01-01 00:07:56.540  1713  2180 I BluetoothAvrcpControllerJni: sendPassThroughCommandNative: sBluetoothAvrcpInterface: 0x77307fd890
01-01 00:07:56.540  1713  2180 I BluetoothAvrcpControllerJni: key_code: 68, key_state: 0
01-01 00:07:56.540  1713  2180 I BluetoothAvrcpControllerJni: sendPassThroughCommandNative: sBluetoothAvrcpInterface: 0x77307fd890
01-01 00:07:56.540  1713  2180 I BluetoothAvrcpControllerJni: key_code: 68, key_state: 1
01-01 00:07:56.595  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_passthrough_response_callback: id: 68, pressed: 0
01-01 00:07:56.596  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_passthrough_response_callback: id: 68, pressed: 1
PRESSED 指令发送/响应
yaml 复制代码 
........................
Bluetooth HCI ACL Packet
    .... 0000 0000 0010 = Connection Handle: 0x002
    ..10 .... .... .... = PB Flag: First Automatically Flushable Packet (2)
    00.. .... .... .... = BC Flag: Point-To-Point (0)
    Data Total Length: 12
    Data
    [Connect in frame: 109]
    [Source BD_ADDR: BarrotTe_50:67:20 (04:7f:0e:50:67:20)]
    [Source Device Name: HAVAL_6720]
    [Source Role: Master (1)]
    [Destination BD_ADDR: HuaweiDe_42:c7:dd (30:aa:e4:42:c7:dd)]
    [Destination Device Name: dupz]
    [Destination Role: Slave (2)]
    [Last Role Change in Frame: 107]
    [Current Mode: Active Mode (0)]
    [Last Mode Change in Frame: 515]
Bluetooth L2CAP Protocol
    Length: 8
    CID: Dynamically Allocated Channel (0x005d)
    [Connect in frame: 392]
    [Service: A/V Remote Control Target (0x110c)]
    [PSM: AVCTP-Control (0x0017)]
Bluetooth AVCTP Protocol
    0000 .... = Transaction: 0x0
    .... 00.. = Packet Type: Single (0x0)
    .... ..0. = C/R: Command (0x0)
    .... ...0 = IPID: Profile OK (0x0)
    Profile Identifier: A/V Remote Control (0x110e)
Bluetooth AVRCP Profile
    0000 .... = Reserved: 0x0
    .... 0000 = Ctype: Control (0x0)
    0100 1... = Subunit Type: Panel (0x09)
    .... .000 = Subunit ID: 0x0
    Opcode: Pass Through (0x7c)
    0... .... = State: Pushed (0x0)
    .100 0100 = Operation ID: PLAY (0x44)
    Data Length: 0x00
    [Response Time: 54/200ms]
    [Response in frame: 556]
  • State：Pushed，对应了PRESSED动作；
  • Operation ID：PLAY，对应了上述的0x44指令，播放指令；
  • C/R：Command，代表了本次数据帧类型为指令类型；
yaml 复制代码 
..............................
Bluetooth L2CAP Protocol
    Length: 8
    CID: Dynamically Allocated Channel (0x0048)
    [Connect in frame: 392]
    [Service: A/V Remote Control Target (0x110c)]
    [PSM: AVCTP-Control (0x0017)]
Bluetooth AVCTP Protocol
    0000 .... = Transaction: 0x0
    .... 00.. = Packet Type: Single (0x0)
    .... ..1. = C/R: Response (0x1)
    .... ...0 = IPID: Profile OK (0x0)
    Profile Identifier: A/V Remote Control (0x110e)
Bluetooth AVRCP Profile
    0000 .... = Reserved: 0x0
    .... 1001 = Ctype: Accepted (0x9)
    0100 1... = Subunit Type: Panel (0x09)
    .... .000 = Subunit ID: 0x0
    Opcode: Pass Through (0x7c)
    0... .... = State: Pushed (0x0)
    .100 0100 = Operation ID: PLAY (0x44)
    Data Length: 0x00
    [Response Time: 54/200ms]
    [Command in frame: 552]
  • C/R：Response
  • Operation ID：PLAY (0x44)
RELEASED 指令发送/响应

RELEASED 动作指令和 PRESSED 类似；

Audio State Callback

play指令发送完成之后，等待底层响应，然后会上报Audio State Callback；

yaml 复制代码 
01-01 00:07:56.595  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_passthrough_response_callback: id: 68, pressed: 0
01-01 00:07:56.596  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_passthrough_response_callback: id: 68, pressed: 1
01-01 00:07:57.033  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_play_status_changed_callback
01-01 00:07:57.033  1713  1794 I BluetoothA2dpSinkServiceJni: bta2dp_audio_state_callback

这里涉及到了AVDTP信道通讯流程；

yaml 复制代码 
..............................
Bluetooth L2CAP Protocol
    Length: 3
    CID: Dynamically Allocated Channel (0x0045)
    [Connect in frame: 283]
    [Service: Audio Source (0x110a)]
    [PSM: AVDTP (0x0019)]
Bluetooth AVDTP Protocol
    Signal: Start (Command)
        0011 .... = Transaction: 0x3
        .... 00.. = Packet Type: Single (0x0)
        .... ..00 = Message Type: Command (0x0)
        00.. .... = RFA: 0x0
        ..00 0111 = Signal: Start (0x07)
    ACP SEID [2 - Audio Sink] item 1
        0000 10.. = ACP SEID: 2
        .... ..00 = RFA: 0x0

手机端接收来气车机端Start Play 指令；

  • RFA：保留给将来添加（Reserved for Future Additions）
  • ACP SEID：流端点 id = 2
yaml 复制代码 
..............................
Bluetooth L2CAP Protocol
    Length: 2
    CID: Dynamically Allocated Channel (0x004b)
    [Connect in frame: 283]
    [Service: Audio Source (0x110a)]
    [PSM: AVDTP (0x0019)]
Bluetooth AVDTP Protocol
    Signal: Start (ResponseAccept)
        0011 .... = Transaction: 0x3
        .... 00.. = Packet Type: Single (0x0)
        .... ..10 = Message Type: ResponseAccept (0x2)
        00.. .... = RFA: 0x0
        ..00 0111 = Signal: Start (0x07)
​
  • Packet Type：消息类型
Packet Type Value
Single Packet 0x0
Start Packet 0x1
Continue Packet 0x2
End Packet 0x3
  • Message type：方法类型
Message Type Value
Command 0x0
General Reject 0x1
Response Accept 0x2
Response Reject 0x3
  • Signal：信令标识符
Signal Identifier Value
Reserved 0x00
AVDTP_DISCOVER 0x01
AVDTP_GET_CAPABILITIES 0x02
AVDTP_SET_CONFIGURATION 0x03
AVDTP_GET_CONFIGURATION 0x04
AVDTP_RECONFIGURE 0x05
AVDTP_OPEN 0x06
AVDTP_START 0x07
AVDTP_CLOSE 0x08
AVDTP_SUSPEND 0x09
AVDTP_ABORT 0x0A
AVDTP_SECURITY_CONTROL 0x0B
AVDTP_GET_ALL_CAPABILITIES 0x0C
AVDTP_DELAYREPORT 0x0D

从这里开启了AudioTrack的工作，开启从手机端向车机端实时的传输音频数据；

所以这里就又涉及到了一种协议：RTP；

  • RTP：Real-time Transport Protocol，实时传输协议，RTP为Internet上端到端的实时传输提供时间信息和流同步，但并不保证服务质量，服务质量由RTCP来提供。

RTP是一种运行在传输层的协议，通常基于 UDP 协议，但也支持 TCP 协议；

yaml 复制代码 
..............................
Bluetooth L2CAP Protocol
    Length: 577
    CID: Dynamically Allocated Channel (0x0046)
    [Connect in frame: 361]
    [Service: Audio Source (0x110a)]
    [PSM: AVDTP (0x0019)]
Bluetooth A2DP Profile
    [ACP SEID: 2]
    [INT SEID: 2]
    [Codec: MPEG-2,4 AAC (0x02)]
    [Stream Start in Frame: 574]
    [Stream End in Frame: 4434]
    [Stream Number: 1]
Real-Time Transport Protocol
    [Stream setup by BT A2DP (frame 3662)]
        [Setup frame: 3662]
        [Setup Method: BT A2DP]
    10.. .... = Version: RFC 1889 Version (2)
    ..0. .... = Padding: False
    ...0 .... = Extension: False
    .... 0000 = Contributing source identifiers count: 0
    1... .... = Marker: True
    Payload type: Unknown (96)
    Sequence number: 2793
    [Extended sequence number: 68329]
    Timestamp: 2859008
    Synchronization Source identifier: 0x00000002 (2)
Data (565 bytes)
    Data: 47fc0000b090800300ffff2b211bd465ee094160c2244047...
    [Length: 565]
  • Version：RTP协议的版本号
  • Padding：填充标志，如果P=1，则在该报文的尾部填充一个或多个额外的八位组，它们不是有效载荷的一部分
  • Extension：扩展标志，占1位，如果X=1，则在RTP报头后跟有一个扩展报头
  • Contributing source identifiers count：CSRC计数器，占4位，指示CSRC 标识符的个数
  • Marker：标记，占1位，不同的有效载荷有不同的含义，对于视频，标记一帧的结束；对于音频，标记会话的开始
  • Payload type：有效载荷类型，占7位，用于说明RTP报文中有效载荷的类型，如GSM音频、JPEM图像等,在流媒体中大部分 是用来区分音频流和视频流的，这样便于客户端进行解析
  • Sequence number：序列号，占16位，发送方在每发送完一个RTP包后就将该域的值增加1，接收方可以由该域检测包的丢失及恢复包序列。序列号的初始值是随机的
  • Timestamp：时间戳，占32位，记录了该包中数据的第一个字节的采样时刻。它是去除抖动和实现同步不可缺少的
  • Synchronization Source identifier：SSRC，同步源标识符，占32位，同步源就是指RTP包流的来源。在同一个RTP会话中不能有两个相同的SSRC值。 该标识符是随机选取的 RFC1889推荐了MD5随机算法

RTP协议实时Audio数据流是连续、持续的，直到遇到Paused或Stopped指令；

Paused

暂停的操作流程基本上也是相同的；

yaml 复制代码 
01-01 00:09:15.042  1713  2180 I BluetoothAvrcpControllerJni: sendPassThroughCommandNative: sBluetoothAvrcpInterface: 0x77307fd890
01-01 00:09:15.042  1713  2180 I BluetoothAvrcpControllerJni: key_code: 70, key_state: 0
01-01 00:09:15.043  1713  2180 I BluetoothAvrcpControllerJni: sendPassThroughCommandNative: sBluetoothAvrcpInterface: 0x77307fd890
01-01 00:09:15.043  1713  2180 I BluetoothAvrcpControllerJni: key_code: 70, key_state: 1
01-01 00:09:15.226  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_passthrough_response_callback: id: 70, pressed: 0
01-01 00:09:15.227  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_passthrough_response_callback: id: 70, pressed: 1
01-01 00:09:16.387  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_play_status_changed_callback
01-01 00:09:16.402  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_play_status_changed_callback
01-01 00:09:18.346  1713  1794 I BluetoothA2dpSinkServiceJni: bta2dp_audio_state_callback

上层发送了Paused指令之后，底层会上报Audio State变化状态，然后上层根据 Audio State 来执行对应的处理逻辑；

yaml 复制代码 
..............................
Bluetooth L2CAP Protocol
    Length: 3
    CID: Dynamically Allocated Channel (0x0045)
    [Connect in frame: 283]
    [Service: Audio Source (0x110a)]
    [PSM: AVDTP (0x0019)]
Bluetooth AVDTP Protocol
    Signal: Start (Command)
        0101 .... = Transaction: 0x5
        .... 00.. = Packet Type: Single (0x0)
        .... ..00 = Message Type: Command (0x0)
        00.. .... = RFA: 0x0
        ..00 0111 = Signal: Start (0x07)
    ACP SEID [2 - Audio Sink] item 1
        0000 10.. = ACP SEID: 2
        .... ..00 = RFA: 0x0
yaml 复制代码 
..............................
Bluetooth L2CAP Protocol
    Length: 2
    CID: Dynamically Allocated Channel (0x004b)
    [Connect in frame: 283]
    [Service: Audio Source (0x110a)]
    [PSM: AVDTP (0x0019)]
Bluetooth AVDTP Protocol
    Signal: Start (ResponseAccept)
        0101 .... = Transaction: 0x5
        .... 00.. = Packet Type: Single (0x0)
        .... ..10 = Message Type: ResponseAccept (0x2)
        00.. .... = RFA: 0x0
        ..00 0111 = Signal: Start (0x07)

Playing和Paused不一致的地方在于：Transaction属性；

  • 0x3：
  • 0x5：
FORWARD & BACKWARD

对应的指令为PASS_THRU_CMD_ID_FORWARD和PASS_THRU_CMD_ID_BACKWARD；

Forward

yaml 复制代码 
01-01 00:08:31.791  1713  2180 I BluetoothAvrcpControllerJni: sendPassThroughCommandNative: sBluetoothAvrcpInterface: 0x77307fd890
01-01 00:08:31.791  1713  2180 I BluetoothAvrcpControllerJni: key_code: 75, key_state: 0
01-01 00:08:31.791  1713  2180 I BluetoothAvrcpControllerJni: sendPassThroughCommandNative: sBluetoothAvrcpInterface: 0x77307fd890
01-01 00:08:31.791  1713  2180 I BluetoothAvrcpControllerJni: key_code: 75, key_state: 1
01-01 00:08:31.826  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_play_status_changed_callback
01-01 00:08:31.826  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_play_position_changed_callback
01-01 00:08:31.870  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_passthrough_response_callback: id: 75, pressed: 0
01-01 00:08:31.891  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_passthrough_response_callback: id: 75, pressed: 1
01-01 00:08:32.347  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_track_changed_callback
01-01 00:08:32.427  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_track_changed_callback
01-01 00:08:32.826  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_play_status_changed_callback

Backward

yaml 复制代码 
01-01 00:09:02.573  1713  2180 I BluetoothAvrcpControllerJni: sendPassThroughCommandNative: sBluetoothAvrcpInterface: 0x77307fd890
01-01 00:09:02.573  1713  2180 I BluetoothAvrcpControllerJni: key_code: 76, key_state: 0
01-01 00:09:02.574  1713  2180 I BluetoothAvrcpControllerJni: sendPassThroughCommandNative: sBluetoothAvrcpInterface: 0x77307fd890
01-01 00:09:02.574  1713  2180 I BluetoothAvrcpControllerJni: key_code: 76, key_state: 1
01-01 00:09:02.626  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_passthrough_response_callback: id: 76, pressed: 0
01-01 00:09:02.626  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_passthrough_response_callback: id: 76, pressed: 1
01-01 00:09:02.852  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_track_changed_callback
01-01 00:09:02.906  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_track_changed_callback
01-01 00:09:03.346  1713  1794 I BluetoothAvrcpControllerJni: btavrcp_play_status_changed_callback

在该过程中，只涉及到了track_changed_callback和play_status_changed_callback的回调；

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