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EVTC File Format Overview

The EVTC file format is a binary format that stores structured data about combat encounters in Guild Wars 2. It is designed to be compact and efficient, enabling tools like arcdps (a combat logging plugin) to generate logs that can be parsed for performance analysis, such as by tools like Elite Insights. The file is divided into several sections:

  1. Header: Contains metadata about the file, such as the file identifier, version, and revision.
  2. Agents: Lists entities (players, NPCs, gadgets, etc.) involved in the encounter, including their attributes like profession, name, and team.
  3. Skills: Records skills used during the encounter, identified by a skill ID and name.
  4. Events: A sequence of combat events (e.g., damage, healing, buff applications) with detailed attributes like source, destination, and timestamps.

Each section uses fixed-size binary structures defined using Python's struct module, ensuring precise parsing of the binary data.

Header Structure

  • Format: <4s8sBHB (4-byte string, 8-byte string, unsigned byte, unsigned short, unsigned byte)
  • Fields:
    • magic (4 bytes): Must be b'EVTC' to identify a valid EVTC file.
    • version (8 bytes): Version string (e.g., b'EVTC20250525'), null-terminated.
    • instruction_set_id (1 byte): Likely indicates the architecture or instruction set.
    • revision (2 bytes): File format revision number.
    • padding (1 byte): Unused, aligns the header to 16 bytes.
  • Purpose: Validates the file and provides versioning information for compatibility.

Agent Structure

  • Format: <QIIHHHHHH64s4x (unsigned long long, unsigned int, unsigned int, 4 unsigned shorts, unsigned short, unsigned short, 64-byte string, 4-byte padding)
  • Size: 96 bytes (calculated by struct.calcsize(AGENT_STRUCT)).
  • Fields:
    • address (8 bytes): Unique identifier for the agent (e.g., memory address or instance ID).
    • profession (4 bytes): Profession ID (maps to PROFESSION_NAMES like Guardian, Warrior, etc.).
    • is_elite (4 bytes): Indicates elite specialization (0 for core profession, specific values for elite specs, or 4294967295 for non-player entities).
    • toughness, healing, condition, concentration (2 bytes each): Combat attributes (e.g., toughness, healing power).
    • hitbox_width, hitbox_height (2 bytes each): Physical dimensions of the agent (likely for collision detection).
    • name (64 bytes): Null-terminated string containing the agent’s name, account, or subgroup (e.g., CharacterName\x00AccountName\x00Subgroup for players).
    • padding (4 bytes): Aligns the structure.
  • Purpose: Describes all entities in the encounter, including players, NPCs, and objects.

Skill Structure

  • Format: <i64s (signed int, 64-byte string).
  • Size: 68 bytes.
  • Fields:
    • skill_id (4 bytes): Unique identifier for a skill.
    • name (64 bytes): Null-terminated string of the skill’s name.
  • Purpose: Catalogues skills used in the encounter for reference in event data.

Event Structure

  • Format: <qQQiiIIHHHHBBBBBBBBBBBBI (signed long long, 2 unsigned long longs, 2 signed ints, 2 unsigned ints, 4 unsigned shorts, 12 unsigned bytes, unsigned int).
  • Size: 48 bytes.
  • Fields:
    • time (8 bytes): Timestamp of the event (in milliseconds since encounter start).
    • src_agent, dst_agent (8 bytes each): Source and destination agent addresses.
    • value, buff_dmg (4 bytes each): Primary and buff-related damage/healing values.
    • overstack_value (4 bytes): Additional value for buff stacking mechanics.
    • skill_id (4 bytes): ID of the skill associated with the event.
    • src_instid, dst_instid (2 bytes each): Instance IDs for source and destination agents.
    • src_master_instid, dst_master_instid (2 bytes each): Master instance IDs (e.g., for pets or minions).
    • iff (1 byte): Indicates if the event involves friend (1), foe (2), or unknown (0).
    • buff (1 byte): Indicates if the event is a buff-related action (0 or 1).
    • result (1 byte): Outcome of the event (e.g., hit, miss, block).
    • is_activation, is_buffremove, is_ninety, is_fifty, is_moving, is_statechange, is_flanking, is_shields, is_offcycle (1 byte each): Flags for specific event conditions (e.g., activation, movement, flanking).
    • pad (4 bytes): Padding for alignment.
  • Purpose: Records individual actions (damage, healing, buff applications, state changes) with detailed context.