问题
Im trying to figure out which is the maximum size of a RTP packet. I know that the minimum header size is 12 bytes, but i dont find anything about the payload.
It is possible that the maximum size of the RTP packet is the same as the UDP payload maximum size? I mean, that i have only a RTP packet with a huge payload. Is this possible and, in this case, there is any recommended size for the RTP packet for not doing this?
For example im encapsulating MP3 frames in RTP. Do I make an RTP frame with 1 MP3 frame, 2, or how many?
I hope you understand my question :)
回答1:
It is possible that the maximum size of the RTP packet is the same as the UDP payload maximum size?
The RTP standard does not set a maximum size so you're free to do this.
(Jumbo packets often have issues of their own with transport, but that's generally to do with the lower layer protocols playing up.)
It is possible that the maximum size of the RTP packet is the same as the UDP payload maximum size? I mean, that i have only a RTP packet with a huge payload. Is this possible and, in this case, there is any recommended size for the RTP packet for not doing this?
Yes, you could create a 1446 byte long payload and put it in a 12 byte RTP packet (1458 bytes) on a network with an MTU of 1500 bytes.
By the time you include an 8 byte UDP header + 20 byte IP header + 14 byte Ethernet header you've 42 bytes of overhead which takes you to 1500 bytes.
In practice if you're transporting this over the internet, this traffic is getting encapsulated or carried across varied transport layers, you'd probably want to keep it below 1400 bytes to be on the safe side.
For example im encapsulating MP3 frames in RTP. Do I make an RTP frame with 1 MP3 frame, 2, or how many?
RTP has a one-to-one mapping from one unique source to one RTP stream (Unless the streams are mixed/muxed together into one stream) so each of the MP3 sources would be put into their own RTP stream, each with it's own unique Synchronization Source Identifier (SSRC) to differentiate between each stream.
For more info on RTP there's the RFC 3550 itself, there's a great book by Colin Perkins called "RTP: Audio and Video for the Internet", I'vea fair bit on RTP on my blog and I've also created a Python library for creating RTP packets.
来源：https://stackoverflow.com/questions/58097580/rtp-packet-maximum-size