基于Android P版本分析
通话过程协议分析
音源切换
音源播放有两个渠道：AG侧和HF侧；
我们在分析outgoing和incoming场景的时候，分析了AT指令流程的时候，在每一次通话中，都包含了 Established Audio Connection ，这个就是用来建立eSCO链路的；
而我们知道，通话的音频数据的传输是在eSCO链路上进行的，蓝牙多媒体的音频是在ACL链路上传输的；
建立了SCO链路通道就代表了通话语音切换到了车机端播放，否则断开SCO就代表了通话语音切换到了手机上进行播放；
HF侧播放
HF侧播放时，需要建立eSCO链路；
在数据包中涉及到了3 frame：frame-607、frame-608、frame-609；
yaml
Frame 607: 67 bytes on wire (536 bits), 67 bytes captured (536 bits)
Bluetooth
[Source: host]
[Destination: controller]
Bluetooth HCI H4
[Direction: Sent (0x00)]
HCI Packet Type: HCI Command (0x01)
Bluetooth HCI Command - Enhanced Accept Synchronous Connection Request
Command Opcode: Enhanced Accept Synchronous Connection Request (0x043e)
0000 01.. .... .... = Opcode Group Field: Link Control Commands (0x01)
.... ..00 0011 1110 = Opcode Command Field: Enhanced Accept Synchronous Connection Request (0x03e)
Parameter Total Length: 63
BD_ADDR: HuaweiDe_42:c7:dd (30:aa:e4:42:c7:dd)
Tx Bandwidth (bytes/s): 8000
Rx Bandwidth (bytes/s): 8000
Transmit Coding Format
Codec: mSBC (0x05)
Company ID: Ericsson Technology Licensing (0x0000)
Vendor Codec ID: 0x0000
Receive Coding Format
Codec: mSBC (0x05)
Company ID: Ericsson Technology Licensing (0x0000)
Vendor Codec ID: 0x0000
Transmit Codec Frame Size: 60
Receive Codec Frame Size: 60
Input Bandwidth: 32000
Output Bandwidth: 32000
Input Coding Format
Codec: Linear PCM (0x04)
Company ID: Ericsson Technology Licensing (0x0000)
Vendor Codec ID: 0x0000
Output Coding Format
Codec: Linear PCM (0x04)
Company ID: Ericsson Technology Licensing (0x0000)
Vendor Codec ID: 0x0000
Input Coded Data Size: 16
Output Coded Data Size: 16
Input PCM Data Format: 2's complement (0x02)
Output PCM Data Format: 2's complement (0x02)
Input PCM Sample Payload MSB Position: 0
Output PCM Sample Payload MSB Position: 0
Input Data Path: Vendor Specific
Output Data Path: Vendor Specific
Input Transport Unit Size: 0
Output Transport Unit Size: 0
Max. Latency (ms): 13
Packet Type: 0x0388, 3-EV5 may NOT be used, 2-EV5 may NOT be used, 3-EV3 may NOT be used, EV3 may be used
0000 00.. .... .... = Reserved: 0x00
.... ..1. .... .... = 3-EV5 may NOT be used: True
.... ...1 .... .... = 2-EV5 may NOT be used: True
.... .... 1... .... = 3-EV3 may NOT be used: True
.... .... .0.. .... = 2-EV3 may NOT be used: False
.... .... ..0. .... = EV5 may be used: False
.... .... ...0 .... = EV4 may be used: False
.... .... .... 1... = EV3 may be used: True
.... .... .... .0.. = HV3 may be used: False
.... .... .... ..0. = HV2 may be used: False
.... .... .... ...0 = HV1 may be used: False
Retransmission Effort: At least 1 retransmission, optimize for link quality (2)
[Pending in frame: 608]
[Command-Pending Delta: 0.915ms]
[Response in frame: 609]
[Command-Response Delta: 80.717ms]- HCI Packet Type：HCI Command
- Command Opcode：Enhanced Accept Synchronous Connection Request
yaml
Frame 608: 7 bytes on wire (56 bits), 7 bytes captured (56 bits)
Bluetooth
[Source: controller]
[Destination: host]
Bluetooth HCI H4
[Direction: Rcvd (0x01)]
HCI Packet Type: HCI Event (0x04)
Bluetooth HCI Event - Command Status
Event Code: Command Status (0x0f)
Parameter Total Length: 4
Status: Pending (0x00)
Number of Allowed Command Packets: 1
Command Opcode: Enhanced Accept Synchronous Connection Request (0x043e)
0000 01.. .... .... = Opcode Group Field: Link Control Commands (0x01)
.... ..00 0011 1110 = Opcode Command Field: Enhanced Accept Synchronous Connection Request (0x03e)
[Command in frame: 607]
[Response in frame: 609]
[Command-Pending Delta: 0.915ms]
[Pending-Response Delta: 79.802ms]frame-608为等待状态；
yaml
Frame 609: 20 bytes on wire (160 bits), 20 bytes captured (160 bits)
Bluetooth
[Source: controller]
[Destination: host]
Bluetooth HCI H4
[Direction: Rcvd (0x01)]
HCI Packet Type: HCI Event (0x04)
Bluetooth HCI Event - Synchronous Connection Complete
Event Code: Synchronous Connection Complete (0x2c)
Parameter Total Length: 17
Status: Success (0x00)
Connection Handle: 0x0004
BD_ADDR: HuaweiDe_42:c7:dd (30:aa:e4:42:c7:dd)
Link Type: eSCO connection (0x02)
Transmit Interval: 12 slots (7.5 msec)
Retransmit Window: 6 slots (3.75 msec)
Rx Packet Length: 60
Tx Packet Length: 60
Air Mode: Transparent Data (3)
[Command in frame: 607]
[Pending in frame: 608]
[Pending-Response Delta: 79.802ms]
[Command-Response Delta: 80.717ms]- Event Code：Synchronous Connection Complete (0x2c)
- Status：Success (0x00)
AG侧播放
在AG侧播放，本质上就是断开HF侧eSCO链路；
同样也是涉及到了3 frame数据；
yaml
Frame 620: 7 bytes on wire (56 bits), 7 bytes captured (56 bits)
Bluetooth
[Source: host]
[Destination: controller]
Bluetooth HCI H4
[Direction: Sent (0x00)]
HCI Packet Type: HCI Command (0x01)
Bluetooth HCI Command - Disconnect
Command Opcode: Disconnect (0x0406)
0000 01.. .... .... = Opcode Group Field: Link Control Commands (0x01)
.... ..00 0000 0110 = Opcode Command Field: Disconnect (0x006)
Parameter Total Length: 3
Connection Handle: 0x0004
Reason: Remote User Terminated Connection (0x13)
[Pending in frame: 621]
[Command-Pending Delta: 3.195ms]
[Response in frame: 622]
[Command-Response Delta: 13.029ms]- Command Opcode：Disconnect
- Reason：Remote User Terminated Connection (0x13)
yaml
Frame 621: 7 bytes on wire (56 bits), 7 bytes captured (56 bits)
Bluetooth
[Source: controller]
[Destination: host]
Bluetooth HCI H4
[Direction: Rcvd (0x01)]
HCI Packet Type: HCI Event (0x04)
Bluetooth HCI Event - Command Status
Event Code: Command Status (0x0f)
Parameter Total Length: 4
Status: Pending (0x00)
Number of Allowed Command Packets: 1
Command Opcode: Disconnect (0x0406)
0000 01.. .... .... = Opcode Group Field: Link Control Commands (0x01)
.... ..00 0000 0110 = Opcode Command Field: Disconnect (0x006)
[Command in frame: 620]
[Response in frame: 622]
[Command-Pending Delta: 3.195ms]
[Pending-Response Delta: 9.834ms]
yaml
Frame 622: 7 bytes on wire (56 bits), 7 bytes captured (56 bits)
Bluetooth
[Source: controller]
[Destination: host]
Bluetooth HCI H4
[Direction: Rcvd (0x01)]
HCI Packet Type: HCI Event (0x04)
Bluetooth HCI Event - Disconnect Complete
Event Code: Disconnect Complete (0x05)
Parameter Total Length: 4
Status: Success (0x00)
Connection Handle: 0x0004
Reason: Connection Terminated by Local Host (0x16)
[Command in frame: 620]
[Pending in frame: 621]
[Pending-Response Delta: 9.834ms]
[Command-Response Delta: 13.029ms]- Event Code：Disconnect Complete (0x05)
- Status：Success (0x00)
- Reason：Connection Terminated by Local Host (0x16)
总结
针对音源切换，每一个connection和disconnection都会对应上层的一个onAudioStateChanged，上层根据onAudioStateChanged回调的信息，执行对应的逻辑；