adsb-tools/proto/adsb.proto

message AdsbHeader {
	// Always "aDsB"
	required string magic = 1;

	// Unique identifier for this server implementation
	// Recommended: "https://url/of/source#version"
	required string server_version = 2;

	// Unique identifier for this server instance
	// UUID recommended
	// 36 character limit
	required string server_id = 3;

	// MHz of the clock used in subsequent mlat_timestamp fields
	required fixed32 mlat_timestamp_mhz = 4;

	// Maximum value of subsequent mlat_timestamp fields, at which point values are expected to wrap
	required fixed64 mlat_timestamp_max = 5;

	// Maximum value of subsequent rssi fields
	required fixed32 rssi_max = 6;
}

message AdsbPacket {
	// Unique value for the source that recorded this packet
	// UUID recommended
	// 36 character limit
	required string source_id = 1;

	// Number of routing hops since source, when carried by protocols with a hop count.
	required uint32 hops = 2;

	// Value of the MLAT counter when this packet arrived at the recorder
	// Range [0, mlat_timestamp_max]
	// Units of 1 / (mlat_timestamp_mhz * 10^6) Hz
	optional fixed64 mlat_timestamp = 3;

	// RSSI of the received packet at the recorder
	// Range [0, rssi_max]
	// Units unspecified
	optional fixed32 rssi = 4;

	// Binary packet payload.
	// Length:
	//   mode_ac: 2 bytes
	//   mode_s_short: 7 bytes
	//   mode_s_long: 14 bytes
	required bytes payload = 5;
}

message Adsb {
	// Each message must contain exactly one; zero is invalid.
	// The first record of a stream must be a header.
	// Subsequent records may be in any order, including additional headers.
	oneof record {
		AdsbHeader header = 1;
		AdsbPacket mode_ac = 2;
		AdsbPacket mode_s_short = 3;
		AdsbPacket mode_s_long = 4;
	}
}

// adsbus proto serialization takes advantage of the fact that an AdsbStream
// with many messages and many AdsbStreams each with a single message encode
// identically.
message AdsbStream {
	repeated Adsb msg = 1;
}