GB28181学习（十四）——语音广播与语音对讲

语音对讲 定义

用户端向设备通过视音频点播请求音频数据；用户端接收音频数据并通过特定的播放设备（如音响）播放；用户端向设备发送广播请求；设备解析广播成功后通过INVITE方法向用户请求音频数据；用户通过音频采集设备获取音频数据；用户将采集的音频数据发送至设备；

可以总结为：音频数据的双向传输。

抓包 发送INVITE请求（ mysipsdk—>设备） INVITE sip:xxx@192.168.0.111:5060 SIP/2.0 Via: SIP/2.0/UDP 192.168.0.107:5060;rport;branch=xxx Max-Forwards: 70 From: sip:xxx@192.168.0.107;tag=xxx To: sip:xxx@192.168.0.111 Contact: <sip:xxx@192.168.0.107:5060> Call-ID: xxx CSeq: 18467 INVITE Allow: SUBSCRIBE, NOTIFY, INVITE, ACK, BYE, CANCEL, UPDATE Supported: Subject: xxx:xx,xxx:xx Content-Type: application/sdp Content-Length: 169 v=0 o=xxx 0 0 IN IP4 192.168.0.107 <!--请求媒体流的操作类型:Talk--> s=Talk c=IN IP4 192.168.0.107 t=0 0 <!--媒体类型:音频(audio) 传输端口:38000 传输方式:UDP 负载类型:8(PCMA)--> m=audio 38000 RTP/AVP 8 a=sendrecv <!--负载类型:8(PCMA) 时钟频率:8000--> a=rtpmap:8 PCMA/8000 <!--"f=v/编码格式/分辨率/帧率/码率/码率大小a/编码格式/码率大小/采样率"--> f=v/a/1/8/1 y=0100000001 接收设备响应（设备—>mysipsdk） SIP/2.0 200 OK Call-ID: xxx Contact: <sip:xxx@192.168.0.111:5060> Content-Length: 270 Content-Type: application/sdp CSeq: 18467 INVITE From: <sip:xxx@192.168.0.107>;tag=xxx To: <sip:xxx@192.168.0.111>;tag=xxx User-Agent: SIP UAS V.2016.xxxx Via: SIP/2.0/UDP 192.168.0.107:5060;rport=5060;branch=xxx v=0 o=xxx 0 0 IN IP4 192.168.0.111 s=Talk i=VCam Talk Session c=IN IP4 192.168.0.111 t=0 0 m=audio 9712 RTP/AVP 8 a=recvonly a=rtpmap:8 PCMA/8000/1 m=audio 9712 RTP/AVP 8 a=sendonly a=rtpmap:8 PCMA/8000/1 y=0100000001 f=v/0/0/0/0/0a/0/0/0 发送ACK到设备（mysipsdk—>设备） ACK sip:xxx@192.168.0.111:5060 SIP/2.0 Via: SIP/2.0/UDP 192.168.0.107:5060;rport;branch=xxx Max-Forwards: 70 From: sip:xxx@192.168.0.107;tag=xxx To: sip:xxx@192.168.0.111;tag=xxx Call-ID: xxx CSeq: 18467 ACK Content-Length: 0 接收音频数据（设备—>mysipsdk）

代码 组装sdp static std::string CreateSDPForAudio(const GB28181MediaContext& mediaContext) { char str[500] = { 0 }; pj_ansi_snprintf(str, 500, "v=0\n" "o=%s 0 0 IN IP4 %s\n" "s=Talk\n" "c=IN IP4 %s\n" "t=0 0\n" "m=audio %d RTP/AVP 8\n" "a=sendrecv\n" "a=rtpmap:8 PCMA/8000\n" "f=v/a/1/8/1\n" "y=0100000001\n", mediaContext.GetDeviceId().c_str(), mediaContext.GetRecvAddress().c_str(), mediaContext.GetRecvAddress().c_str(), mediaContext.GetRecvPort() ); return str; } 音频数据接收与视频数据接收类似，根据sdp协商确定接收的音频格式； 语音广播 要求

流程

抓包 发送广播通知（mysipsdk—>设备） MESSAGE sip:xxx@192.168.0.111:5060 SIP/2.0 Via: SIP/2.0/UDP 192.168.0.107:5060;rport;branch=xxx Max-Forwards: 70 From: <sip:xxx@192.168.0.107>;tag=xxx To: <sip:xxx@xx> Contact: <sip:xxx@192.168.0.107:5060> Call-ID: xxx CSeq: 18467 MESSAGE Content-Type: Application/MANSCDP+xml Content-Length: 186 <?xml version="1.0" encoding="UTF-8"?> <Notify> <CmdType>Broadcast</CmdType> <SN>130</SN> <!--语音输入设备的设备编码--> <SourceID>xxx</SourceID> <!--语音输出设备的设备编码--> <TargetID>xxx</TargetID> </Notify> 广播通知响应（设备—>mysipsdk） SIP/2.0 200 OK Call-ID: xxx Content-Length: 0 CSeq: 18467 MESSAGE From: <sip:xxx@192.168.0.107>;tag=xxx To: <sip:xxx@xxx>;tag=xxx User-Agent: SIP UAS V.2016.xxxx Via: SIP/2.0/UDP 192.168.0.107:5060;rport=5060;branch=xxx 广播通知结果（设备—>mysipsdk） MESSAGE sip:xxx@192.168.0.107 SIP/2.0 Call-ID: xxx Content-Length: 180 Content-Type: Application/MANSCDP+xml CSeq: 2 MESSAGE From: <sip:xxx@192.168.0.111:5060>;tag=xxx Max-Forwards: 70 To: <sip:xxx@192.168.0.107> User-Agent: SIP UAS V.2016.xxxx Via: SIP/2.0/UDP 192.168.0.111:5060;rport;branch=xxx <?xml version="1.0" encoding="GB2312" standalone="yes" ?> <Response> <CmdType>Broadcast</CmdType> <SN>130</SN> <DeviceID>xxx</DeviceID> <Result>OK</Result> </Response> 广播通知结果响应（mysipsdk—>设备） SIP/2.0 200 OK Via: SIP/2.0/UDP 192.168.0.111:5060;rport=5060;received=192.168.0.111;branch=xxx Call-ID: xxx From: <sip:xxx@192.168.0.111>;tag=xxx To: <sip:xxx@192.168.0.107>;tag=xxx CSeq: 2 MESSAGE Content-Length: 0 广播请求（设备—>mysipsdk） INVITE sip:xxx@192.168.0.107:5060 SIP/2.0 Call-ID: xxx Contact: <sip:xxx@192.168.0.111:5060> Content-Length: 240 Content-Type: application/sdp CSeq: 1 INVITE Expires: 120 From: <sip:xxx@192.168.0.111:5060>;tag=xxx Max-Forwards: 70 Subject: xxx:xxx,xxx:xxx To: <sip:xxx@192.168.0.107:5060> User-Agent: SIP UAS V.2016.xxxx Via: SIP/2.0/UDP 192.168.0.111:5060;rport;branch=xxx v=0 o=xxx 0 0 IN IP4 192.168.0.111 s=Play i=VCam BroadCast Session c=IN IP4 192.168.0.111 t=0 0 m=audio 9712 RTP/AVP 8 96 a=recvonly a=rtpmap:8 PCMA/8000/1 a=rtpmap:96 PS/90000 y=0022371912 f=v/0/0/0/0/0a/1/8/1 广播请求响应（mysipsdk—>设备） SIP/2.0 200 OK From: <sip:xxx@192.168.0.107:5060>;tag=xxx To: <sip:xxx@192.168.0.111:5060>;tag=xxx Call-ID: xxx CSeq: 1 INVITE User-Agent: General SIP UAS V1.0 Via: SIP/2.0/UDP 192.168.0.111:5060;rport;branch=xxx Contact: <sip:xxx@192.168.0.107:5060> Content-Type: application/SDP Content-Length: 182 v=0 o=xxx 0 0 IN IP4 192.168.0.107 s=Play c=IN IP4 192.168.0.107 t=0 0 m=audio 40000 RTP/AVP 8 a=rtpmap:8 PCMA/8000 a=sendonly y=0022371912 广播请求响应ACK（设备—>mysipsdk） ACK sip:xxx@192.168.0.107:5060 SIP/2.0 Via: SIP/2.0/UDP 192.168.0.111:5060;rport;branch=xxx From: <sip:xxx@192.168.0.111:5060>;tag=xxx To: <sip:xxx@192.168.0.107:5060>;tag=xxx Call-ID: xxx CSeq: 1 ACK Contact: <sip:xxx@192.168.0.111:5060> Max-Forwards: 70 User-Agent: IP Camera Content-Length: 0 关闭广播（设备—>mysipsdk） BYE sip:xxx@xxx SIP/2.0 From: <sip:xxx@xxx>;tag=xxx To: <sip:xxx@xxx>;tag=xxx CSeq: 2 BYE Call-ID: xxx Via: SIP/2.0/UDP 192.168.0.111:5060;branch=xxx Max-Forwards: 70 Content-Length: 0 关闭广播响应（mysipsdk—>设备）