如何在Android平台GB28181接入终端实现语音广播和语音对讲

技术背景

在之前的blog，我们以Android平台国标接入终端为例，分别介绍了一些常规的功能，比如REGISTER、CATALOG、INVITE、Keepalive、SUBSCRIBE、NOTIFY等常规操作，今天主要介绍下语音广播和语音对讲这部分。

GB28181平台广播和对讲这块，重要性不言而喻，没有广播的接入终端，数据只是单向流入，加入后，指挥中心和终端之间的联系更紧密，实时双向沟通更方便，适用的行业范围也更广泛。

相关SPEC解读

关于语音广播和对讲，感兴趣的开发者可直接参阅GBT 28181-2016.pdf相关技术规范里面的9.12章节，以下是部分精选介绍：

命令交互流程

命令描述流程

a) 1:SIP服务器向语音流接收者发送语音广播通知消息,消息中通过 To头域标明作为目的地址的语音流接收者ID,消息采用 Message方法携带。

举例说明：

MESSAGE sip:34020000001380000001@192.168.2.212:12070 SIP/2.0
Via: SIP/2.0/UDP 192.168.2.154:15060;rport;branch=z9hG4bK311226558
From: <sip:34020000002000000001@3402000000>;tag=280226558
To: <sip:34020000001380000001@192.168.2.212:12070>
Call-ID: 172226558
CSeq: 207 MESSAGE
Content-Type: Application/MANSCDP+xml
Max-Forwards: 70
Content-Length: 206<?xml version="1.0" encoding="GB2312"?>
<Notify><CmdType>Broadcast</CmdType><SN>461226558</SN><SourceID>34020000002000000001</SourceID><TargetID>34020000001380000001</TargetID>
</Notify>

b) 2:语音流接收者收到语音广播通知消息后,向SIP服务器发送200OK 响应。

SIP/2.0 200 OK
CSeq: 207 MESSAGE
Call-ID: 172226558
From: <sip:34020000002000000001@3402000000>;tag=280226558
To: <sip:34020000001380000001@192.168.2.212:12070>
Via: SIP/2.0/UDP 192.168.2.154:15060;rport=15060;branch=z9hG4bK311226558;received=192.168.2.154
Content-Length: 0

c) 3:语音流接收者向SIP服务器发送语音广播应答消息,消息中通过 To头域标明作为目的地址的SIP服务器ID,消息采用 Message方法携带。

MESSAGE sip:34020000002000000001@3402000000 SIP/2.0
Call-ID: 0fc1f2c83c28898a29e146d7ef581908@192.168.2.212
CSeq: 337044229 MESSAGE
From: <sip:34020000001380000001@3402000000>;tag=93882333
To: <sip:34020000002000000001@3402000000>
Via: SIP/2.0/UDP 192.168.2.212:12070;rport;branch=z9hG4bK-363733-79fd88c45667975e5ebaf18f84b91a8e
Max-Forwards: 70
User-Agent: NT GB28181 User Agent V1.2(daniusdk.com)
Content-Type: Application/MANSCDP+xml
Content-Length: 180<?xml version="1.0" encoding="GB2312"?>
<Response>
<CmdType>Broadcast</CmdType>
<SN>461226558</SN>
<DeviceID>34020000001380000001</DeviceID>
<Result>OK</Result>
</Response>

d) 4:SIP服务器收到语音广播应答消息后,向语音流接收者发送200OK 响应。

SIP/2.0 200 OK
Via: SIP/2.0/UDP 192.168.2.212:12070;rport=12070;received=192.168.2.212;branch=z9hG4bK-363733-79fd88c45667975e5ebaf18f84b91a8e
From: <sip:34020000001380000001@3402000000>;tag=93882333
To: <sip:34020000002000000001@3402000000>;tag=355226593
CSeq: 337044229 MESSAGE
Call-ID: 0fc1f2c83c28898a29e146d7ef581908@192.168.2.212
Content-Length: 0

e) 5:语音流接收者向SIP服务器发送Invite消息,消息中通过 To头域标明作为目的地址的语音流发送者ID,消息头域中携带Subject字段,表明请求的语音流发送者ID、发送方媒体流序列号、语音流接收者ID、接收方媒体流序列号等参数,SDP消息体中s字段为“Play”代表实时点播,m 字段中媒体参数标识为“audio”表示请求语音媒体流。

INVITE sip:34020000002000000001@3402000000 SIP/2.0
Call-ID: 2b4f0f0512aa1a49ffc645618d0e8bae@192.168.2.212
CSeq: 44264 INVITE
From: <sip:34020000001380000001@3402000000>;tag=32ecf22a
To: <sip:34020000002000000001@3402000000>
Via: SIP/2.0/UDP 192.168.2.212:12070;rport;branch=z9hG4bK-363733-15283c8a0ea0a1e9dbf295ce2359dbe7
Max-Forwards: 70
Contact: <sip:34020000001380000001@192.168.2.212:12070>
Subject: 34020000002000000001:0200006727,34020000001380000001:0
User-Agent: NT GB28181 User Agent V1.2(daniusdk.com)
Content-Type: APPLICATION/SDP
Content-Length: 221v=0
o=34020000002000000001 0 0 IN IP4 192.168.2.212
s=Play
c=IN IP4 192.168.2.212
t=0 0
m=audio 25002 TCP/RTP/AVP 8
a=setup:active
a=connection:new
a=recvonly
a=rtpmap:8 PCMA/8000
y=0200006727
f=v/a/1/8/1

f) 6:SIP服务器收到Invite请求后,通过三方呼叫控制建立媒体服务器和语音流发送者之间的媒体连接。向媒体服务器发送Invite消息,此消息不携带SDP消息体。

g) 7:媒体服务器收到SIP服务器的Invite请求后,回复200OK 响应,携带SDP消息体,消息体中描述了媒体服务器接收媒体流的IP、端口、媒体格式等内容。

h) 8:SIP服务器收到媒体服务器返回的200OK 响应后,向语音流发送者发送Invite请求,消息中通过 To头域标明作为目的地址的语音流发送者ID,消息头域中携带 Subject字段,表明请求的语音流发送者ID、发送方媒体流序列号、语音流接收者ID、接收方媒体流序列号等参数, 请求中携带消息7中媒体服务器回复的200OK 响应消息体,s字段为“Play”代表实时点播, m 字段中媒体参数标识为“audio”表示请求语音媒体流,增加y字段描述SSRC值,f字段描述媒体参数。

SIP/2.0 200 OK
Via: SIP/2.0/UDP 192.168.2.212:12070;rport=12070;received=192.168.2.212;branch=z9hG4bK-363733-15283c8a0ea0a1e9dbf295ce2359dbe7
From: <sip:34020000001380000001@3402000000>;tag=32ecf22a
To: <sip:34020000002000000001@3402000000>;tag=954226632
CSeq: 44264 INVITE
Call-ID: 2b4f0f0512aa1a49ffc645618d0e8bae@192.168.2.212
Contact: <sip:34020000002000000001@192.168.2.154:15060>
Content-Length: 222
Content-Type: APPLICATION/SDPv=0
o=34020000002000000001 0 0 IN IP4 192.168.2.154
s=Play
c=IN IP4 192.168.2.154
t=0 0
m=audio 30005 TCP/RTP/AVP 8
a=sendonly
a=rtpmap:8 PCMA/8000
a=setup:passive
a=connection:new
y=0200006727
f=v/a/1/8/1

i) 9:语音流发送者收到SIP服务器的Invite请求后,回复200OK 响应,携带SDP消息体,消息体中描述了媒体流发送者发送媒体流的IP、端口、媒体格式、SSRC 字段等内容,s字段为 “Play”代表实时点播,m 字段中媒体参数标识为“audio”表示请求语音媒体流。

j) 10:SIP服务器收到语音流发送者返回的200OK 响应后,向媒体服务器发送 ACK 请求,请求中携带消息9中语音流发送者回复的200OK 响应消息体,完成与媒体服务器的Invite会话建立过程。

k) 11:SIP服务器收到语音流发送者返回的200OK 响应后,向语音流发送者发送 ACK 请求,请求中不携带消息体,完成与语音流发送者的Invite会话建立过程。

l) 12:完成三方呼叫控制后,SIP服务器通过 B2BUA 代理方式建立语音流接收者和媒体服务器之间的媒体连接。在消息5中增加SSRC值,转发给媒体服务器。

m)13:媒体服务器收到Invite请求,回复200OK 响应,携带SDP消息体,消息体中描述了媒体服务器发送媒体流的IP、端口、媒体格式、SSRC值等内容,s字段为“Play”代表实时点播,m 字段中媒体参数标识为“audio”表示请求语音媒体流。

n) 14:SIP服务器将消息13转发给语音流接收者。

o) 15:语音流接收者收到200OK 响应后,回复 ACK 消息,完成与SIP服务器的Invite会话建立过程。

p) 16:SIP服务器将消息15转发给媒体服务器,完成与媒体服务器的Invite会话建立过程。

q) 17:SIP服务器向语音流接收者发送 BYE消息,断开消息5、14、15建立的Invite会话。

r) 18:语音流接收者收到 BYE消息后回复200OK 响应,会话断开。

s) 19:SIP服务器向媒体服务器发送 BYE 消息,断开消息 12、13、16 建立的同媒体服务器的 Invite会话。

t) 20:媒体服务器收到 BYE消息后回复200OK 响应,会话断开。

u) 21:SIP服务器向媒体服务器发送 BYE消息,断开消息6、7、10建立的同媒体服务器的Invite 会话。

v) 22:媒体服务器收到 BYE消息后回复200OK 响应,会话断开。

w)23:SIP服务器向语音流发送者发送 BYE 消息,断开消息8、9、11建立的同语音流发送者的 Invite会话。

x) 24:语音流发送者收到 BYE消息后回复200OK 响应,会话断开。

注：语音广播通知消息除上述流程中通过SIP服务器发出外,也可由语音流发送者发出,消息中通过 To头域标明作为目的地址的语音流接收者ID,经SIP服务器中转后发往语音流接收者;语音流接收者处理后发送应答消息,消息中通过 To头域标明作为目的地址的语音流发送者ID,经SIP服务器中转后回复给语音流发送者。后续呼叫流程与上述流程相同。

语音对讲

语音对讲功能实现中心用户与前端用户之间的一对一语音对讲功能。语音对讲功能由下述两个独立的流程组合实现:

a) 通过9.2的实时视音频点播功能,中心用户获得前端设备的实时视音频媒体流;

b) 通过9.12的语音广播功能,中心用户向前端对讲设备发送实时音频媒体流,语音流的封装格式见 C.2.4音频流的 RTP封装定义。

C.2.4 音频流的 RTP封装

语音比特流宜采用标准的 RTP协议进行打包，这里只摘录G.711A律的：

在一个 RTP包中,音频载荷数据应为整数个音频编码帧,且时间长度在20ms~180ms之间。

音频载荷数据的 RTP封装参数如下:

a) G.711的主要参数 G.711A律语音编码 RTP包的负载类型(PayloadType)的参数规定如下(见IETFRFC3551— 2003中的表4): 1）负载类型(PT):8; 2) 编码名称(encodingname):PCMA; 3) 时钟频率(clockrate):8kHz; 4) 通道数:1; 5) SDP描述中“m”字段的“media”项:audio。

技术实现

语音广播接收这块，由于有之前的RTMP和RTSP播放器积累，直接在player端做相应扩展即可，当收到广播后，GB28181语音广播按钮使能。

相关调用代码：

class ButtonGB28181AudioBroadcastListener implements OnClickListener {public void onClick(View v) {if (gb_broadcast_source_id_ != null && gb_broadcast_target_id_ != null) {if (gb28181_agent_ != null ) {if (gb28181_agent_.byeAudioBroadcast(gb_broadcast_source_id_, gb_broadcast_target_id_) ) {gb_broadcast_source_id_ = null;gb_broadcast_target_id_ = null;btnGB28181AudioBroadcast.setText("GB28181语音广播");btnGB28181AudioBroadcast.setEnabled(false);}}}stopAudioPlayer();destoryRTPReceiver();}}

@Override
public void ntsOnNotifyBroadcastCommand(String fromUserName, String fromUserNameAtDomain, String sn, String sourceID, String targetID) {handler_.postDelayed(new Runnable() {@Overridepublic void run() {Log.i(TAG, "ntsOnNotifyBroadcastCommand, fromUserName:"+ from_user_name_ + ", fromUserNameAtDomain:"+ from_user_name_at_domain_+ ", SN:" + sn_ + ", sourceID:" + source_id_ + ", targetID:" + target_id_);if (gb28181_agent_ != null ) {gb28181_agent_.respondBroadcastCommand(from_user_name_, from_user_name_at_domain_,sn_,source_id_, target_id_, true);btnGB28181AudioBroadcast.setText("收到GB28181语音广播通知");}}private String from_user_name_;private String from_user_name_at_domain_;private String sn_;private String source_id_;private String target_id_;public Runnable set(String from_user_name, String from_user_name_at_domain, String sn, String source_id, String target_id) {this.from_user_name_ = from_user_name;this.from_user_name_at_domain_ = from_user_name_at_domain;this.sn_ = sn;this.source_id_ = source_id;this.target_id_ = target_id;return this;}}.set(fromUserName, fromUserNameAtDomain, sn, sourceID, targetID),0);
}@Override
public void ntsOnAudioBroadcast(String commandFromUserName, String commandFromUserNameAtDomain, String sourceID, String targetID) {handler_.postDelayed(new Runnable() {@Overridepublic void run() {Log.i(TAG, "ntsOnAudioBroadcastPlay, fromFromUserName:" + command_from_user_name_+ " FromUserNameAtDomain:" + command_from_user_name_at_domain_+ " sourceID:" + source_id_ + ", targetID:" + target_id_);stopAudioPlayer();destoryRTPReceiver();if (gb28181_agent_ != null ) {String local_ip_addr = IPAddrUtils.getIpAddress(context_);boolean is_tcp = true; // 考虑到跨网段, 默认用TCP传输rtp包rtp_receiver_handle_ = lib_player_.CreateRTPReceiver(0);if (rtp_receiver_handle_ != 0 ) {lib_player_.SetRTPReceiverTransportProtocol(rtp_receiver_handle_, is_tcp?1:0);lib_player_.SetRTPReceiverIPAddressType(rtp_receiver_handle_, 0);if (0 == lib_player_.CreateRTPReceiverSession(rtp_receiver_handle_, 0) ) {int local_port = lib_player_.GetRTPReceiverLocalPort(rtp_receiver_handle_);boolean ret = gb28181_agent_.inviteAudioBroadcast(command_from_user_name_,command_from_user_name_at_domain_,source_id_, target_id_, "IP4", local_ip_addr, local_port, is_tcp?"TCP/RTP/AVP":"RTP/AVP");if (!ret ) {destoryRTPReceiver();btnGB28181AudioBroadcast.setText("GB28181语音广播");}else {btnGB28181AudioBroadcast.setText("GB28181语音广播呼叫中");}} else {destoryRTPReceiver();btnGB28181AudioBroadcast.setText("GB28181语音广播");}}}}private String command_from_user_name_;private String command_from_user_name_at_domain_;private String source_id_;private String target_id_;public Runnable set(String command_from_user_name, String command_from_user_name_at_domain, String source_id, String target_id) {this.command_from_user_name_ = command_from_user_name;this.command_from_user_name_at_domain_ = command_from_user_name_at_domain;this.source_id_ = source_id;this.target_id_ = target_id;return this;}}.set(commandFromUserName, commandFromUserNameAtDomain, sourceID, targetID),0);
}@Override
public void ntsOnInviteAudioBroadcastException(String sourceID, String targetID, String errorInfo) {handler_.postDelayed(new Runnable() {@Overridepublic void run() {Log.i(TAG, "ntsOnInviteAudioBroadcastException, sourceID:" + source_id_ + ", targetID:" + target_id_);destoryRTPReceiver();btnGB28181AudioBroadcast.setText("GB28181语音广播");}private String source_id_;private String target_id_;public Runnable set(String source_id, String target_id) {this.source_id_ = source_id;this.target_id_ = target_id;return this;}}.set(sourceID, targetID),0);
}@Override
public void ntsOnInviteAudioBroadcastTimeout(String sourceID, String targetID) {handler_.postDelayed(new Runnable() {@Overridepublic void run() {Log.i(TAG, "ntsOnInviteAudioBroadcastTimeout, sourceID:" + source_id_ + ", targetID:" + target_id_);destoryRTPReceiver();btnGB28181AudioBroadcast.setText("GB28181语音广播");}private String source_id_;private String target_id_;public Runnable set(String source_id, String target_id) {this.source_id_ = source_id;this.target_id_ = target_id;return this;}}.set(sourceID, targetID),0);
}
@Override
public void ntsOnInviteAudioBroadcastResponse(String sourceID, String targetID, int statusCode, PlaySessionDescription sessionDescription) {handler_.postDelayed(new Runnable() {@Overridepublic void run() {Log.i(TAG, "ntsOnInviteAudioBroadcastResponse, statusCode:" + status_code_ +" sourceID:" + source_id_ + ", targetID:" + target_id_);boolean is_need_destory_rtp = true;if (gb28181_agent_ != null ) {boolean is_need_bye = 200==status_code_;if (200 == status_code_ && session_description_ != null && rtp_receiver_handle_ != 0 ) {MediaSessionDescription audio_des = session_description_.getAudioDescription();SDPRtpMapAttribute audio_attr = null;if (audio_des != null && audio_des.getRtpMapAttributes() != null && !audio_des.getRtpMapAttributes().isEmpty() )audio_attr = audio_des.getRtpMapAttributes().get(0);if ( audio_des != null && audio_attr != null ) {lib_player_.SetRTPReceiverSSRC(rtp_receiver_handle_, audio_des.getSSRC());lib_player_.SetRTPReceiverPayloadType(rtp_receiver_handle_, audio_attr.getPayloadType(),audio_attr.getEncodingName(), 2, audio_attr.getClockRate());lib_player_.SetRTPReceiverRemoteAddress(rtp_receiver_handle_, audio_des.getAddress(), audio_des.getPort());lib_player_.InitRTPReceiver(rtp_receiver_handle_);if (startAudioPlay()) {is_need_bye = false;is_need_destory_rtp = false;gb_broadcast_source_id_ = source_id_;gb_broadcast_target_id_ = target_id_;btnGB28181AudioBroadcast.setText("终止GB28181语音广播");btnGB28181AudioBroadcast.setEnabled(true);}}} else {btnGB28181AudioBroadcast.setText("GB28181语音广播");}if (is_need_bye)gb28181_agent_.byeAudioBroadcast(source_id_, target_id_);}if (is_need_destory_rtp)destoryRTPReceiver();}private String source_id_;private String target_id_;private int status_code_;private PlaySessionDescription session_description_;public Runnable set(String source_id, String target_id, int status_code, PlaySessionDescription session_description) {this.source_id_ = source_id;this.target_id_ = target_id;this.status_code_ = status_code;this.session_description_ = session_description;return this;}}.set(sourceID, targetID, statusCode, sessionDescription),0);
}@Override
public void ntsOnByeAudioBroadcast(String sourceID, String targetID) {handler_.postDelayed(new Runnable() {@Overridepublic void run() {Log.i(TAG, "ntsOnByeAudioBroadcast sourceID:" + source_id_ + " targetID:" + target_id_);gb_broadcast_source_id_ = null;gb_broadcast_target_id_ = null;btnGB28181AudioBroadcast.setText("GB28181语音广播");btnGB28181AudioBroadcast.setEnabled(false);stopAudioPlayer();destoryRTPReceiver();}private String source_id_;private String target_id_;public Runnable set(String source_id, String target_id) {this.source_id_ = source_id;this.target_id_ = target_id;return this;}}.set(sourceID, targetID),0);
}@Override
public void ntsOnTerminateAudioBroadcast(String sourceID, String targetID) {handler_.postDelayed(new Runnable() {@Overridepublic void run() {Log.i(TAG, "ntsOnTerminateAudioBroadcast sourceID:" + source_id_ + " targetID:" + target_id_);gb_broadcast_source_id_ = null;gb_broadcast_target_id_ = null;btnGB28181AudioBroadcast.setText("GB28181语音广播");btnGB28181AudioBroadcast.setEnabled(false);stopAudioPlayer();destoryRTPReceiver();}private String source_id_;private String target_id_;public Runnable set(String source_id, String target_id) {this.source_id_ = source_id;this.target_id_ = target_id;return this;}}.set(sourceID, targetID),0);
}