Proto definition.

protocols/proto.md

@@ -0,0 +1,27 @@
+# Protobuf protocol
+
+This protocol was created by adsb-tools. This specification is official.
+
+## Format
+
+[Protocol buffer](https://developers.google.com/protocol-buffers/docs/overview) encoding.
+Proto definition is [here](https://github.com/flamingcowtv/adsb-tools/blob/master/proto/adsb.proto).
+Stream is a series of Adsb records with length encoded in a prefix (protobuf isn't self
+delimiting). The prefix is structured such that an entire stream is a valid AdsbStream
+record.
+
+First frame must always be an AdsbHeader; frames can otherwise appear in any order, including
+additional headers.
+
+## Prefix
+* `0x0a`: in protobuf encoding, field #1, type 2 (length-encoded bytes); (1 << 3) | 2
+* Length of packet not including prefix, encoded as a [base 128 varint](https://developers.google.com/protocol-buffers/docs/encoding#varints)
+  
+## Packet
+See [definition file](https://github.com/flamingcowtv/adsb-tools/blob/master/proto/adsb.proto)
+for details.
+
+## Tips
+
+To decode a stream file:
+`$ protoc-c --proto_path=adsb-tools/proto --decode=AdsbStream adsb-tools/proto/adsb.proto < streamfile`