The Packet Header contains a single key called "fields".
JSON key: fields
This defines the fields contained in the common message header of the protocol you want to decode.
"PacketHeader" : { "fields": [ { "name": "Timestamp", "type": "INT64_LE" }, { "name": "StreamID", "type": "INT8" }, { "name": "MsgBlockCount", "type": "INT8", "flags": ["msg_count"] }]The additional keys provided in the “fields“ key are described in section MessageHeader.