|
In order to make Netmeeting and QuickTime player
interoperable, we need to decide which audio and video codec we want to use. For the video
codec, Netmeeting has H.261 and H.263, while Quicktime player only allows H.263. There are
more audio codecs that are allowed on both Netmeeting and QuickTime player, f.g. gsm,
g711, uaw, alaw, etc. The OpenH323 project can allow video format transmitted between
players in H. 261 codec, while QuickTime player can only accept video format in the H.263
codec. We need to add H. 263 codec implementation into OpenH323 project. After we get
video data in H.263 codec, we have learned that real time data is transmitted from
QuickTime server to QuickTime player over the Internet through RTP/RTCP protocols. RTP
protocol will carry real time data and run RTP on top of UDP to make use of its
multiplexing and checksum services. Each RTP packet consists of a fixed RTP header, a
possible empty list of contributing sources, and the payload data. RTCP protocol monitors
the quality of service and coveys information about the participants in an on-going
session. By defining RTP and RTCP header, each packet real-time audio and video data is
able to send over RTP through UDP. |
|