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。
具体如下图
我们先来看看会话初始协议：
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
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。