新增配置项指定H264 rtp打包是否优先采用stap-a模式 (#2582)

H264 rtp打包模式是否采用stap-a模式(为了在老版本浏览器上兼容webrtc)还是采用Single NAL unit packet
per H.264 模式 有些老的rtsp设备不支持stap-a rtp，设置此配置为0可提高兼容性

src/Common/config.cpp

@@ -244,15 +244,15 @@ const string kVideoMtuSize = RTP_FIELD "videoMtuSize";
 const string kAudioMtuSize = RTP_FIELD "audioMtuSize";
 // rtp包最大长度限制，单位是KB
 const string kRtpMaxSize = RTP_FIELD "rtpMaxSize";
-
 const string kLowLatency = RTP_FIELD "lowLatency";
+const string kH264StapA = RTP_FIELD "h264_stap_a";
 
 static onceToken token([]() {
     mINI::Instance()[kVideoMtuSize] = 1400;
     mINI::Instance()[kAudioMtuSize] = 600;
     mINI::Instance()[kRtpMaxSize] = 10;
     mINI::Instance()[kLowLatency] = 0;
-
+    mINI::Instance()[kH264StapA] = 1;
 });
 } // namespace Rtp