Adds a RFC 5285 header extension with a two bytes header to the end of the
RTP header. If there is already a RFC 5285 header extension with a two bytes
header, the new extension will be appended.
It will not work if there is already a header extension that does not follow
the mechanism described in RFC 5285 or if there is a header extension with
a one byte header as described in RFC 5285. In that case, use
gstrtp.rtpbuffer.RTPBuffer.addExtensionOnebyteHeader
Adds a RFC 5285 header extension with a two bytes header to the end of the RTP header. If there is already a RFC 5285 header extension with a two bytes header, the new extension will be appended. It will not work if there is already a header extension that does not follow the mechanism described in RFC 5285 or if there is a header extension with a one byte header as described in RFC 5285. In that case, use gstrtp.rtpbuffer.RTPBuffer.addExtensionOnebyteHeader