The following is a detailed analysis of replay files as used in Grand Theft Auto: San Andreas. Due to similar programming, this article may be partially applicable to replay files for Grand Theft Auto III and Grand Theft Auto: Vice City.
Description[]
Replays are the sequence of the scenes and actions recorded and stored in the replay.rep file. In GTA San Andreas, this file is located in the User Files directory.
Each .rep file consists of a header string and variable amount of 'scenes' (or 'frames'). A scene is a copy of important game information at given moment of time (actors, vehicles positions, weather, clothes, etc). Following one after another, the scenes create an illusion of a movie when played. The most of scenes contains a same set of blocks and ends with Block 8.
The .rep file itself consist of a header string which is simply the text GtaSA29 and up to 8 parts, size of each one is 100,000 bytes, depending on the replay length. So, the maximum size of a replay file is 800,008 bytes (including 8 bytes of the header string). If the replay length is that it does not match 100,000 bytes boundary being less, the rest of the file is filled with useless data (commonly the previous replay data).
Data blocks[]
Each block consists of a byte denoting its type and some data as described below. A number in a block name is the data type stored in the first byte of the block. Reading this byte, the game detects what block follows.
Block 0: End of file[]
This block denotes the end of replay data. It consists only of a data type. After this block the game stops reading the replay file.
OFFSET TYPE DESCRIPTION 0x00 byte data type (0x00) 0x01 (end)
Block 1: Vehicle1[]
size 52 bytes
Block 2: Vehicle2[]
size 56 bytes
Block 3: Player data[]
Common information about player ped.
OFFSET TYPE DESCRIPTION
0x00 byte data type (0x03)
0x01 byte index (handle?)
0x02 WORD modelID
0x04 byte ped type
0x05 byte[3] (align)
0x08 (end)
Block 4: Ped[]
size 52 bytes
Block 5: Camera[]
size 88 bytes
Block 6: Day time[]
This block contains information about current day time during a scene.
OFFSET TYPE DESCRIPTION 0x00 byte data type (0x06) 0x01 byte currentHour 0x02 byte currentMinute 0x03 byte (align) 0x04 end
Block 7: Weather[]
size 8 bytes
Block 8: End of scene[]
This block denotes the end of the current scene (frame). It consists only of a data type.
OFFSET TYPE DESCRIPTION 0x00 byte data type (0x00) 0x01 (end)
Block 9: Scene timing[]
This block contains value of the global game timer. The replay play length could be found by using this block.
OFFSET TYPE DESCRIPTION 0x00 byte data type (0x09) 0x01 byte[3] (align) 0x04 DWORD timer 0x08 (end)
Block 10: Unknown[]
size 28 bytes
Block 11: Unknown[]
size 20 bytes
Block 12: Unknown[]
size 16 bytes
Block 13: Unknown[]
size 4 bytes; same as Block 8?
Block 14: Unknown[]
size 4 bytes; same as Block 8?
Block 15: Unknown vehicle[]
size 56 bytes; same as Block 2?
Block 16: Unknown vehicle[]
size 56 bytes; same as Block 2?
Block 17: Unknown vehicle[]
size 60 bytes
Block 18: Unknown[]
size 76 bytes
Block 19: Clothes[]
This block contains information on the current clothes of the player. The block structure is identical to the one in the Player structure in a save file.
OFFSET TYPE DESCRIPTION 0x00 DWORD[10] modelCRCs 0x28 DWORD[18] textureCRCs 0x70 WORD Fat 0x72 WORD Muscle;
Tools[]
There is a template for 010 Editor, made by Seemann. It allows to edit different replay data: http://sannybuilder.com/dev/Replay.rar