ARI. LPCM. What is slin16 from external media server

Hello. I am sending data from an external media server via ARI. I use slin16 encoding (LPCM16). My program connects to an external media server. It accepts a packet of 652 bytes. Do I understand correctly that a packet consists of 12 bytes of overhead data and 640 bytes of raw data?

The media encapsulation desired.
With the first release of this capability, only rtp is supported as an encapsulation and that is the default if not supplied. Others may be supported in the future.
The rtp encapsulation will produce packets with a standard rtp header.

https://wiki.asterisk.org/wiki/display/AST/External+Media+and+ARI

https://tools.ietf.org/html/rfc3550

Thanks! I understand a lot more now about it.