Describe Media Stream Message

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See the Technical Overview

Media Stream Message (MSmsg)
The Media Stream message is formed from the SRT media stream (data) packets with some
elements of the SRT header used for the cryptography. An SRT header already carries a 32-bit
packet sequence number that is used for the cipher‘s counter (ctr), with 2 bits taken from the
header‘s message number (which is thereby reduced to 27 bits) for the encryption key
(odd/even) indicator. Note that the message number field is used when messages larger than
the MTU are send, which is not the case for TS/SRT so the reduction to 27 bits is without
consequence.