According to the AltBeacon Docs :
m is the sequence of matching bytes for this type of beacon for parsing (exactly one is required)
s - ServiceUuid for this type of beacon for parsing (optional, only for Gat beacons)
i - identifier (at least one required, multiple allowed)
p - power calibration field (only one required)
d - data field (optional, somewhat allowed)
x is an optional layout. Indicates that the layout is secondary to the primary layout with the same sequence of matching bytes (or ServiceUuid). additional layouts do not require power fields or identifiers and create Beacon objects without identifiers.
Example parsing line for AltBeacon:
"m: 2-3 = BEAC, I: 4-19, I: 20-21, I: 22-23, pp: 24-24, d: 25-25"
This means that the type of beacon signal will be decoded when an advertisement is found with 0xbeac in bytes 2-3, and the three-part identifier will be taken out from bytes 4-19, bytes 20-21 and bytes 22-23, respectively. The signed power calibration value will be pulled from byte 24, and the data field will be pulled from byte 25.
here is a list of some beacon layouts
ALTBEACON m:2-3=beac,i:4-19,i:20-21,i:22-23,p:24-24,d:25-25 EDDYSTONE TLM x,s:0-1=feaa,m:2-2=20,d:3-3,d:4-5,d:6-7,d:8-11,d:12-15 EDDYSTONE UID s:0-1=feaa,m:2-2=00,p:3-3:-41,i:4-13,i:14-19 EDDYSTONE URL s:0-1=feaa,m:2-2=10,p:3-3:-41,i:4-20v IBEACON m:2-3=0215,i:4-19,i:20-21,i:22-23,p:24-24