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No, however Kamailio can be configured to proxy media if needed. (See rtpproxy, iprtpproxy, and mediaproxy http://www.kamailio.org/w/features/)
Kamailio supports all codecs (even codecs that haven't been created yet).
Since Kamailio is a SIP proxy, it does not handle the media streams. Codecs are negotiated between the two endpoints.
Yes, Kamailio can be used for video calls. The two SIP phones must support video codecs/calling.