rtp_secure_media=true
--inbound: Accept the srongest supported offered crypto suite, MUST result in a negotiated crypto or aborts.
--outbound: offer all supported crypto suites, MUST result in a negotiated crypto or aborts.
rtp_secure_media=optional
--inbound: Accept the srongest supported offered crypto suite, fall back to no crypto if no valid ones accepted.
--outbound: offer all supported crypto suites, OPTIONAL result in a negotiated crypto falls back to no crypto.
rtp_secure_media=<suite1>,<suiteN>
--inbound: same behaviour as rtp_secure_media=true with smaller set of acceptable suites.
--outbound: offer supplied crypto suites, same behaviour as rtp_secure_media=true with smaller set of suites.
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