Age of Empires 2: The Conquerors — Savegame File Format Specification

Table of Contents

• Structure Definitions
• Ruby Parser
• References
• Actions
• FAQ

Structure Definitions

The structure definitions kind of follow the BinData Ruby Gem declarations. They should be as readable as pseudo code though. More information on BinData can be found here.

Synchronization

Tag	Description			Validated
	SYNCH

Messaging

Tag	Description			Validated
0x000001F4	GAMESTART
0xFFFFFFFF	CHAT			+

Gameplay Actions

Tag	Description			Validated
0x00	ATTACK			+
0x01	STOP			+
0x02	AI_PRIMARY			+
0x03	MOVE			+
0x0a	AI_MOVE
0x0b	RESIGN			+
0x10	WAYPOINT			+
0x12	STANCE			+
0x13	GUARD			+
0x14	FOLLOW			+
0x15	PATROL			+
0x17	FORMATION			+
0x1b	SAVE & EXIT
0x1f	AI_COORD			+
0x64	AI_TRAIN			+
0x65	TECH			+
0x66	BUILD			+
0x67	MULTIPURPOSE
0x69	WALL			+
0x6a	DELETE			+
0x6b	ATTACKGROUND			+
0x6c	TRIBUTE			+
0x6e	REPAIR			+
0x6f	UNGARRISON			+
0x72	GATE			+
0x73	FLARE			+
0x75	GARRISON			+
0x77	TRAIN			+
0x78	RALLY			+
0x7a	SELL			+
0x7b	BUY			+
0x7e	RELIC			+
0x7f	TOWNBELL			+
0x80	BACKTOWORK			+
0xFF	GAMESTATS	UP only

FAQ

1. What actions are not saved but only calculated on replay simulation?

   • Only actions that are actively taken by players are stored
   • Any other actions are either simulated during replay (map reveal) or determined by the random number generator (Gaia movement)
   • Pause is not saved, that is why chat messages that were sent during the pause are displayed nearly at once when replayed.

2. What actions are only saved for certain players, i.e., the owner of the recorded game?

   • Viewpoints (for lock view) are only saved for the owner of the recorded game, together with the sychronization info.

3. How does AoE2 create an .mgx file?

   • Singleplayer games are recorded by getting actions from the input buffer and writing them into the .mgx file.
   • During multiplayer games, actions are distributed to all players (even messages). The input buffer is transferred over the network to the other players.

4. Why are there so many zeros in the actions?

   • Most of the zeros are caused by memory alignment. Because networking and recording directly work on the input buffer, the data is aligned to 3the size of (menory) words (4 bytes). Example:

   struct example {
     uint8_t player_id;
     uint32_t unit_id;
   };

   Here the first variable player_id will take up 1 out of 4 bytes of the first word. The next variable, unit_id, doesn't fit into the first word anymore, so it will use a second word instead. The remaining 3 bytes in the first word remain uninitialized and therefore have zero values in them.

5. Why are they doing this weird memory stuff? It sounds stupid

   • Because it is fast. Data can be put to use directly and does not have to be parsed.

6. What are the various IDs used for?

   • Players have an ID and a number. This is necessary because of an undocumented cooperative mode in AoE2, where players can have the same player number.
   • Unit IDs reference a type of unit/building or object in the game files.
   • Object IDs reference a specific object during a game. Every building, unit or resource gets an ID. For new units, the IDs are incremented.