Change rtp max package size to 1200 (#930)

* Change rtp max package size to 1200

Author: qwu16

source/core/rtc_adapter/VideoSendAdapter.cc

@@ -21,6 +21,7 @@ namespace rtc_adapter {
 // To make it consistent with the webrtc library, we allow packets to be transmitted
 // in up to 2 times max video bitrate if the bandwidth estimate allows it.
 static const int TRANSMISSION_MAXBITRATE_MULTIPLIER = 2;
+static const int kMaxRtpPacketSize = 1200;
 
 static int getNextNaluPosition(uint8_t* buffer, int buffer_size, bool& is_aud_or_sei, int& sc_len)
 {
@@ -198,6 +199,8 @@ bool VideoSendAdapterImpl::init()
         m_rtpRtcp->SetMid(mid);
     }
 
+    m_rtpRtcp->SetMaxRtpPacketSize(kMaxRtpPacketSize);
+
     webrtc::RTPSenderVideo::Config video_config;
     m_playoutDelayOracle = std::make_unique<webrtc::PlayoutDelayOracle>();
     m_fieldTrialConfig = std::make_unique<webrtc::FieldTrialBasedConfig>();