We are running Asterisk 16.3.0. In chan_sip.c/sip_rtp_read there is some code that I don’t understand. The is a case statement with: switch(ast_channel_fdno(ast). My question how do we know that case 0 is always RTP Audio or that case 2: is RTP Video? Is there a standard that lists out the fdno or is this just the way Asterisk assigns them? If this is how Asterisk assigns them can someone point me to the code that does that? Just trying to understand the flow of video packets through the codebase.