Unlocking the Code: A Guide to Reverse Engineering Game Text Files
Have you ever played a fan-translated version of a game and wondered how it was made? The process of extracting, translating, and re-inserting text into a game is a fascinating intersection of linguistics and software engineering known as ROM hacking. It’s a complex journey that involves peeling back the layers of a game’s code to manipulate its core components.
This deep dive explores the fundamental steps and common challenges involved in editing the text of a video game, using a classic Nintendo DS adventure game as a case study.
The Initial Investigation: Peeking Inside the Cartridge
The first step in any game modification project is reconnaissance. Digital game files, like a Nintendo DS .nds file, are essentially containers holding all the game’s assets—graphics, sound, logic, and, most importantly for our purposes, text. The initial goal is to sift through the game’s file system to locate the script files.
Often, these files have telling names. In many cases, you might find a file named something like script.dat or text.bin. These large, data-packed files are prime candidates for containing the game’s entire dialogue and narrative content. Once a likely file is identified, the real work of decoding its contents begins.
Cracking the Code: Character Encoding and Control Tags
Opening a game’s script file in a standard text editor rarely reveals clean, readable dialogue. Instead, you’re likely to see a mix of legible words and gibberish. This is because the text is stored using a specific character encoding and is interspersed with non-textual commands.
Character Encoding: For games developed in Japan, the text is commonly stored in Shift-JIS encoding. A hex editor or a specialized text editor capable of interpreting different encodings is essential to view the characters correctly. Without the right encoding, the Japanese text would be completely unreadable.
Control Codes: Game scripts are more than just words; they contain instructions for the game engine. These instructions, or control codes, dictate how the text is displayed. You might find tags like
[para]to signify a paragraph break,[clr]to clear the screen, or[name:Haruhi]to display a character’s name above the dialogue box.
Identifying and understanding these control codes is crucial. Any new or edited text must preserve these codes for the game to function correctly. Accidentally deleting a screen-clearing tag or a character name command could cause visual glitches or even crash the game entirely.
The Pointer Problem: The Hidden Structure of Game Scripts
Once you can read the text and understand the control codes, you might think you can simply edit the dialogue and save the file. However, this is where most aspiring ROM hackers hit a major roadblock: the pointer table.
A pointer table is essentially the game’s table of contents for its script file. It’s a list of memory addresses (pointers) that tells the game engine exactly where to find the beginning of each specific line of dialogue. For example, the pointer for line #1 might point to memory address 0x1000, while the pointer for line #2 points to 0x1050, and so on.
Here’s the problem: if you change the length of a line of text, you break every subsequent pointer. If you shorten a sentence, you create a gap of empty data. If you lengthen it, you overwrite the beginning of the next line. In either case, the original pointer table becomes useless, and the game will start pulling the wrong data, leading to garbled text and crashes.
Engineering a Solution: Automating the Editing Process
Manually recalculating hundreds or thousands of pointers after every text edit is impractical and prone to error. The professional solution is to develop a custom tool or script to manage the process. Such a tool typically performs three key functions:
Extraction: The tool reads the original pointer table and uses it to locate and extract every string of text into a simple, editable format (like a plain text file). This separates the dialogue from the game’s complex file structure.
Re-insertion: After the text has been edited or translated, the tool takes the modified text and prepares it to be placed back into the ROM.
Rebuilding the Pointer Table: This is the most critical step. The tool rebuilds the script file with the new text and then calculates a brand new pointer table from scratch. It goes through the new data, notes the starting address of each line, and writes those new values into the table.
With an automated tool, the pointer problem is solved. The game is given a fresh, accurate “table of contents” that perfectly matches the newly inserted script, ensuring everything displays as intended.
Beyond Text: The Possibilities of Game Modding
This process of investigation, decoding, and tool creation is the foundation of ROM hacking. By understanding how a game organizes its data, you can modify far more than just dialogue. The same principles can be applied to swapping character models, changing background music, or even altering game logic. It’s a testament to the ingenuity and dedication of fan communities who work to preserve, translate, and create new experiences from the games they love.
Source: https://www.linuxlinks.com/serial-loops-editing-suite-suzumiya-haruhi-no-chokuretsu/
