PACKET_OVERHEAD

mumble_server_runtime_gateway::limits

Constant PACKET_OVERHEAD 

Source 
pub const PACKET_OVERHEAD: usize = _; // 32usize
Expand description

What the reference server adds to a voice payload to account for what the network actually carried.

REF: references/mumble/src/murmur/Server.cpp : processMsg bills 20 + 8 + 4 + payload - IP, UDP, crypt, data - against the bandwidth record.