问题
can any body please explain what is the RTCP Transmission Intreval ?
I read some material on internet at
http://www.ietf.org/rfc/rfc3550.txt but I think I should go for basic concepts,So please if anybody knows some sites to
learn this things .Please suggest.
回答1:
Not sure how much you understand about RTP in general, so I'll try to get a somewhat complete answer while keeping it simple:
RTP (not RTCP) is a protocol send media data, for example small fragments of audio, or small fragment of video. when you replay these fragments back to back you get audio/video. This can be used for streaming or for things like internet calls with or without video.
In RTCP the "C" stands for "Control" and is used in conjunction with RTP, usually mostly as a way to gather statistics (is all the audio video received at the other end for example). Using those statistics the sender and receiver can decide to use less bandwidth, for example by lowering video quality or image size. By sending RTCP data often enough, you can react to changing conditions in the communication quicker (maybe you are on a shared cable internet for example)
Now instead of doing a phone call between two people, imagine you are doing sneding your video to 1000 people for an online seminar. The amount of video data being sent from the presenter doesn't change regardless of how many people are viewing the presentation, so from an RTP point of view, it doesn't matter how many people are viewing it. On the other hand, if every viewer computer sends RCTP statistics back to the sender, the sender now has to deal with 1000 reports.
Now the RTCP traffic can make up a significant amount of the bandwidth being used at the sender's machine. the more viewers, the more of the total internet bandwidth is spent on those RTCP reports to the point that you could run out of bandwidth for the RTP audio/video data itself.
In practice you want to use no more than 5% of the bandwidth on RTCP, so that 95% of your connection is used for the "useful" audio/video RTP data. The way you control the RTCP traffic is by adjusting how often each party sends its RTCP statistics.the more participants, the less often the data is being sent to the aggrgate RTCP traffic stays below 5%
Hope this makes sense and that it is the level of explanation you wanted. The RFC you linked to explains how to calculate that interval between RTCP reports based on the type of communication and the number of participants.
来源：https://stackoverflow.com/questions/22033175/rtcp-transmission-intreval