Documentation/FTL-Format.md

 ## Implemented Versions
-First the Header structure is written / read directly with no encoding, followed by the IndexHeader structure for version 2 or greater.
+First the Header structure is written / read directly with no encoding, followed by the IndexHeader structure for version 2 or greater. The structures below are for version 4.
 
 ```c++
 struct Header {
@@ -30,7 +30,7 @@ A stream packet locates a data packet within the overall context. It identifies
 ```c++
 struct Packet {
     ftl::codecs::codec_t codec;
-    ftl::codecs::definition_t definition;
+    ftl::codecs::definition_t definition;  // To be removed in version 5
     uint8_t frame_count;
     uint8_t bitrate;
     uint8_t flags;