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<concept id="GUID-7D1E2DBD-004B-5047-BDA5-21CD55D0A95C" xml:lang="en"><title>Securing
RTP with SRTP</title><shortdesc>This topic explains how to use callbacks to secure RTP communications. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<p>If you have registered preprocessing and postprocessing callbacks, the
RTP stack calls them when sending or receiving RTP data. Therefore, your application
can implement Secure RTP by adding encryption and authentication steps after
reception and before sending. </p>
<p>Your callback class must derive from MPrePostProcessingCallback and implement
its four methods. Call the <xref href="GUID-97FC8566-E4AD-3881-8669-134798A88779.dita"><apiname>SetPrePostProcessingRegisterCallback(</apiname></xref> method
to register your callbacks. After registration, the callback behaviour is
as follows: </p>
<ul>
<li id="GUID-EC65A889-9113-5095-9E15-42C91E76327B"><p>The RTP stack calls
the appropriate preprocessing callback, <xref href="GUID-97FC8566-E4AD-3881-8669-134798A88779.dita"><apiname>PreRtpProcessing()</apiname></xref> or <xref href="GUID-97FC8566-E4AD-3881-8669-134798A88779.dita"><apiname>PreRtcpProcessing()</apiname></xref>, after data is received
from the socket and before processing RTP headers. </p> </li>
<li id="GUID-B78CDB23-D742-5B70-9F61-0712873EE3B3"><p>The RTP stack calls
the appropriate postprocessing callback, <xref href="GUID-97FC8566-E4AD-3881-8669-134798A88779.dita"><apiname>PostRtpProcessing()</apiname></xref> or <xref href="GUID-97FC8566-E4AD-3881-8669-134798A88779.dita"><apiname>PostRtcpProcessing()</apiname></xref> , after completing an
RTP or RTCP packet and before sending it to the socket. </p> </li>
</ul>
</conbody><related-links>
<link href="GUID-993629CB-17B4-5E87-8DE1-06A4AC473FDD.dita"><linktext>RTP Overview</linktext>
</link>
</related-links></concept>