技术回顾
在本文开头，我们先一起回顾下GB/T28181联网系统通信协议结构：
联网系统在进行视音频传输及控制时应建立两个传输通道：会话通道和媒体流通道。
- 会话通道用于在设备之间建立会话并传输系统控制命令；
- 媒体流通道用于传输视音频数据，经过压缩编码的视音频流采用流媒体协议 RTP/RTCP传输。
具体如下图
我们先来看看会话初始协议：
- 安全注册、实时视音频点播、历史视音频的回放等应用的会话控制采用IETF RFC 3261规定的 Register、Invite等请求和响应方法实现；
- 历史视音频回放控制采用SIP扩展协议IETF RFC 2976规定的INFO方法实现；
- 前端设备控制、信息查询、报警事件通知和分发等应用的会话控制采用 SIP扩展协议IETF RFC 3428规定的Message方法实现；
- SIP消息应支持基于UDP和 TCP的传输；
- 互联的系统平台及设备不应向对方的SIP端口发送应用无关消息，避免应用无关消息占用系统平台及设备的SIP消息处理资源。
接下来是会话描述协议
联网系统有关设备之间会话建立过程的会话协商和媒体协商应采用IETF RFC 4566协议描述，主要内容包括会话描述、媒体信息描述、时间信息描述。
会话协商和媒体协商信息应采用SIP消息的消息体携带传输。
控制描述协议
联网系统有关前端设备控制、报警信息、设备目录信息等控制命令应采用监控报警联网系统控制描述协议(MANSCDP)描述。
联网系统控制命令应采用SIP消息Message的消息体携带传输。
媒体回放控制协议
历史视音频的回放控制命令应采用监控报警联网系统实时流协议(MANSRTSP),实现设备在端到端之间对视音频流的正常播放、快速、暂停、停止、随机拖动播放等远程控制。
历史媒体的回放控制命令采用SIP消息Info的消息体携带传输。
由于我们主要侧重于GB/T 28181音视频实时数据接入，这块未做实现，有相关需求的开发者，参考对应的spec章节即可。
媒体传输和媒体编解码协议
- 媒体流在联网系统IP网络上传输时应支持 RTP传输，媒体流发送源端应支持控制媒体流发送峰值功能；
- RTP的负载应采用如下两种格式之一：基于 PS封装的视音频数据或视音频基本流数据；
- 媒体流的传输应采用IETF RFC 3550规定的 RTP协议，提供实时数据传输中的时间戳信息及各数据流的同步；应采用IETFRFC3550规定的RTCP协议，为按序传输数据包提供可靠保证，提供流量控制和拥塞控制。
技术实现
下面以Android平台GB/T 28181设备接入实现为例，大概介绍下相关的参数配置和设计细节：
先说参数配置，除了常规的链接sip server基础配置外，我们根据规范要求，添加了注册有效期、心跳间隔、心跳间隔失败次数、信令传输协议等配置：
/*** GB28181 相关参数，可以修改相关参数后测试 ***/ GBSIPAgent gb28181_agent_ = null; private int gb28181_sip_local_port_ = 12070; private String gb28181_sip_server_id_ = "34020000002000000001"; private String gb28181_sip_domain_ = "3402000000"; private String gb28181_sip_server_addr_ = "192.168.0.105"; private int gb28181_sip_server_port_ = 15060; private String gb28181_sip_user_agent_filed_ = "NT GB28181 User Agent V1.2"; private String gb28181_sip_username_ = "31011500991320000069"; private String gb28181_sip_password_ = "12345678"; private int gb28181_reg_expired_ = 3600; // 注册有效期时间最小3600秒 private int gb28181_heartbeat_interval_ = 20; // 心跳间隔GB28181默认是60, 目前调整到20秒 private int gb28181_heartbeat_count_ = 3; // 心跳间隔3次失败，表示和服务器断开了 private int gb28181_sip_trans_protocol_ = 0; // 0表示信令用UDP传输, 1表示信令用TCP传输 private long gb28181_rtp_sender_handle_ = 0; private int gb28181_rtp_payload_type_ = 96; private long player_handle_ = 0; private long rtp_receiver_handle_ = 0; private AtomicLong last_received_audio_data_time_ = new AtomicLong(0); /*** GB28181 相关参数，可以修改相关参数后测试 ***/
为了测试方便，我们在界面加了个启动/停止GB28181的按钮：
/* * Github: https://github.com/daniulive/SmarterStreaming */ class ButtonGB28181AgentListener implements OnClickListener { public void onClick(View v) { stopAudioPlayer(); destoryRTPReceiver(); gb_broadcast_source_id_ = null; gb_broadcast_target_id_ = null; btnGB28181AudioBroadcast.setText("GB28181语音广播"); btnGB28181AudioBroadcast.setEnabled(false); stopGB28181Stream(); destoryRTPSender(); if (null == gb28181_agent_ ) { if( !initGB28181Agent() ) return; } if (gb28181_agent_.isRunning()) { gb28181_agent_.terminateAllPlays(true);// 目前测试下来,发送BYE之后,有些服务器会立即发送INVITE,是否发送BYE根据实际情况看 gb28181_agent_.stop(); btnGB28181Agent.setText("启动GB28181"); } else { if ( gb28181_agent_.start() ) { btnGB28181Agent.setText("停止GB28181"); } } } }
其中，initGB2818Agent()主要是基础参数设置，对应的实现如下：
private boolean initGB28181Agent() { if ( gb28181_agent_ != null ) return true; getLocation(context_); String local_ip_addr = IPAddrUtils.getIpAddress(context_); Log.i(TAG, "initGB28181Agent local ip addr: " + local_ip_addr); if ( local_ip_addr == null || local_ip_addr.isEmpty() ) { Log.e(TAG, "initGB28181Agent local ip is empty"); return false; } gb28181_agent_ = GBSIPAgentFactory.getInstance().create(); if ( gb28181_agent_ == null ) { Log.e(TAG, "initGB28181Agent create agent failed"); return false; } gb28181_agent_.addListener(this); // 必填信息 gb28181_agent_.setLocalAddressInfo(local_ip_addr, gb28181_sip_local_port_); gb28181_agent_.setServerParameter(gb28181_sip_server_addr_, gb28181_sip_server_port_, gb28181_sip_server_id_, gb28181_sip_domain_); gb28181_agent_.setUserInfo(gb28181_sip_username_, gb28181_sip_password_); // 可选参数 gb28181_agent_.setUserAgent(gb28181_sip_user_agent_filed_); gb28181_agent_.setTransportProtocol(gb28181_sip_trans_protocol_==0?"UDP":"TCP"); // GB28181配置 gb28181_agent_.config(gb28181_reg_expired_, gb28181_heartbeat_interval_, gb28181_heartbeat_count_); com.gb28181.ntsignalling.Device gb_device = new com.gb28181.ntsignalling.Device("34020000001380000001", "安卓测试设备", Build.MANUFACTURER, Build.MODEL, "宇宙","火星1","火星", true); if (mLongitude != null && mLatitude != null) { com.gb28181.ntsignalling.DevicePosition device_pos = new com.gb28181.ntsignalling.DevicePosition(); device_pos.setTime(mLocationTime); device_pos.setLongitude(mLongitude); device_pos.setLatitude(mLatitude); gb_device.setPosition(device_pos); gb_device.setSupportMobilePosition(true); // 设置支持移动位置上报 } gb28181_agent_.addDevice(gb_device); if (!gb28181_agent_.initialize()) { gb28181_agent_ = null; Log.e(TAG, "initGB28181Agent gb28181_agent_.initialize failed."); return false; } return true; }
参数设定后，开始发送Regiter到平台端，Android设备端，针对Register的处理如下：
@Override public void ntsRegisterOK(String dateString) { Log.i(TAG, "ntsRegisterOK Date: " + (dateString!= null? dateString : "")); } @Override public void ntsRegisterTimeout() { Log.e(TAG, "ntsRegisterTimeout"); } @Override public void ntsRegisterTransportError(String errorInfo) { Log.e(TAG, "ntsRegisterTransportError error:" + (errorInfo != null?errorInfo :"")); }
Catalog不再赘述，我们看看Inite处理：
@Override public void ntsOnInvitePlay(String deviceId, PlaySessionDescription session_des) { handler_.postDelayed(new Runnable() { @Override public void run() { MediaSessionDescription video_des = session_des_.getVideoDescription(); SDPRtpMapAttribute ps_rtpmap_attr = video_des.getPSRtpMapAttribute(); Log.i(TAG,"ntsInviteReceived, device_id:" +device_id_+", is_tcp:" + video_des.isRTPOverTCP() + " rtp_port:" + video_des.getPort() + " ssrc:" + video_des.getSSRC() + " address_type:" + video_des.getAddressType() + " address:" + video_des.getAddress()); // 可以先给信令服务器发送临时振铃响应 //sip_stack_android.respondPlayInvite(180, device_id_); long rtp_sender_handle = libPublisher.CreateRTPSender(0); if ( rtp_sender_handle == 0 ) { gb28181_agent_.respondPlayInvite(488, device_id_); Log.i(TAG, "ntsInviteReceived CreateRTPSender failed, response 488, device_id:" + device_id_); return; } gb28181_rtp_payload_type_ = ps_rtpmap_attr.getPayloadType(); libPublisher.SetRTPSenderTransportProtocol(rtp_sender_handle, video_des.isRTPOverUDP()?0:1); libPublisher.SetRTPSenderIPAddressType(rtp_sender_handle, video_des.isIPv4()?0:1); libPublisher.SetRTPSenderLocalPort(rtp_sender_handle, 0); libPublisher.SetRTPSenderSSRC(rtp_sender_handle, video_des.getSSRC()); libPublisher.SetRTPSenderSocketSendBuffer(rtp_sender_handle, 2*1024*1024); // 设置到2M libPublisher.SetRTPSenderClockRate(rtp_sender_handle, ps_rtpmap_attr.getClockRate()); libPublisher.SetRTPSenderDestination(rtp_sender_handle, video_des.getAddress(), video_des.getPort()); if ( libPublisher.InitRTPSender(rtp_sender_handle) != 0 ) { gb28181_agent_.respondPlayInvite(488, device_id_); libPublisher.DestoryRTPSender(rtp_sender_handle); return; } int local_port = libPublisher.GetRTPSenderLocalPort(rtp_sender_handle); if (local_port == 0) { gb28181_agent_.respondPlayInvite(488, device_id_); libPublisher.DestoryRTPSender(rtp_sender_handle); return; } Log.i(TAG,"get local_port:" + local_port); String local_ip_addr = IPAddrUtils.getIpAddress(context_); gb28181_agent_.respondPlayInviteOK(device_id_,local_ip_addr, local_port); gb28181_rtp_sender_handle_ = rtp_sender_handle; } private String device_id_; private PlaySessionDescription session_des_; public Runnable set(String device_id, PlaySessionDescription session_des) { this.device_id_ = device_id; this.session_des_ = session_des; return this; } }.set(deviceId, session_des),0); }
Ack后，开始发送打包后的ps数据：
@Override public void ntsOnAckPlay(String deviceId) { handler_.postDelayed(new Runnable() { @Override public void run() { Log.i(TAG,"ntsOnACKPlay, device_id:" +device_id_); if (!isRecording && !isRTSPPublisherRunning && !isPushingRtmp) { InitAndSetConfig(); } libPublisher.SetGB28181RTPSender(publisherHandle, gb28181_rtp_sender_handle_, gb28181_rtp_payload_type_); int startRet = libPublisher.StartGB28181MediaStream(publisherHandle); if (startRet != 0) { if (!isRecording && !isRTSPPublisherRunning && !isPushingRtmp ) { if (publisherHandle != 0) { libPublisher.SmartPublisherClose(publisherHandle); publisherHandle = 0; } } destoryRTPSender(); Log.e(TAG, "Failed to start GB28181 service.."); return; } if (!isRecording && !isRTSPPublisherRunning && !isPushingRtmp) { if (pushType == 0 || pushType == 1) { CheckInitAudioRecorder(); //enable pure video publisher.. } } startLayerPostThread(); isGB28181StreamRunning = true; } private String device_id_; public Runnable set(String device_id) { this.device_id_ = device_id; return this; } }.set(deviceId),0); }
再看看位置订阅处理：
@Override public void ntsOnDevicePositionRequest(String deviceId, int interval) { handler_.postDelayed(new Runnable() { @Override public void run() { getLocation(context_); Log.v(TAG, "ntsOnDevicePositionRequest, deviceId:" + this.device_id_ + ", Longitude:" + mLongitude + ", Latitude:" + mLatitude + ", Time:" + mLocationTime); if (mLongitude != null && mLatitude != null) { com.gb28181.ntsignalling.DevicePosition device_pos = new com.gb28181.ntsignalling.DevicePosition(); device_pos.setTime(mLocationTime); device_pos.setLongitude(mLongitude); device_pos.setLatitude(mLatitude); if (gb28181_agent_ != null ) { gb28181_agent_.updateDevicePosition(device_id_, device_pos); } } } private String device_id_; private int interval_; public Runnable set(String device_id, int interval) { this.device_id_ = device_id; this.interval_ = interval; return this; } }.set(deviceId, interval),0); }
语音广播和语音对讲处理：
@Override public void ntsOnNotifyBroadcastCommand(String fromUserName, String fromUserNameAtDomain, String sn, String sourceID, String targetID) { handler_.postDelayed(new Runnable() { @Override public 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() { @Override public 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); }
Bye处理如下：
@Override public void ntsOnByePlay(String deviceId) { handler_.postDelayed(new Runnable() { @Override public void run() { Log.i(TAG, "ntsOnByePlay, stop GB28181 media stream, deviceId=" + device_id_); stopGB28181Stream(); destoryRTPSender(); } private String device_id_; public Runnable set(String device_id) { this.device_id_ = device_id; return this; } }.set(deviceId),0); }
考虑到篇幅有限，上面仅展示基础的处理，如各种异常情况处理等，可单独沟通我，获取相关demo。
总的来说，GB/T 28181接入，资料相对全面，但是好多都是基于demo的验证，经不住推敲，如果要产品化，开发者还需要很长的路要走。
