Videos: .bk2

Editing and Replacing videos in CyberPunk 2077 with RAD Video Tools

This wiki page is about the .bk2 file format used in the game, and how to edit them.

TL;DR

The .bk2 file format is used in many games including Cyberpunk 2077. It stands for Bink 2 By Rad Tools and needs to be used to extract and recompress the video that you want to replace.

Converting to back to .bk2 requires a byte offset for the video to appear in the game.

Prerequisites

• WolvenKit (obviously)

• RAD Video Tools (available here)

• Video Editor of Choice

Selecting A Video File

Searching in the asset browser for .bk2 files will get you every video in the game. For this tutorial we will be using the boxing video (q001_boxinggame.bk2)

Visit Viktor's RipperDoc, the boxing video consistently plays on his screen for easy testing.

Add q001_boxinggame.bk2 to your project

Locating Video File on Your Computer

Click: Open In Windows Explorer

Give it a Play

Converting to MP4 file format

1. Open RAD Video Editor and browse to: \source\archive\base\movies\fluff

2. Select File

3. Convert

Note: you can batch convert files in both directions by selecting multiple files.

Output Options

1. Convert

2. Defaults to MP4, keep it.

Video Specifications:

Length: Should match the converted .mp4

Export: MP4

Size: 480p

FPS: 15fps is the game speed, 30fps is possible, but not recommended.

You must export to Bink 2.

Byte Offset Requirement

For reasons unknown, CyberPunk requires the 4th byte of your .bk2 file to to be changed to: 6A

Once your bk2 file has been created, you will need to edit the file with a hex editor.

HxD is a good windows solution that is free.

hxd byte offset

Change the 4th byte to 6A and save to: source\archive\base\movies\fluff

Install Your Mod

Since the working directory is Archive, there is no need to import.

Resources:

YouTube Video for more on RAD Tools.

Discord community.

Python Script: Automate byte offset all .bk2 files

This will automatically change the byte offset in all your .bk2 files at once in the working directory and subdirs.

import os
import glob

def modify_fourth_byte(file_path):
    """
    Opens a file in read/write binary mode and overwrites 
    the 4th byte (index 3) with 0x6A.
    """
    try:
        # Print the filename as processing begins
        print(f"Working on: '{file_path}'...", end=" ", flush=True)

        # Check file size before opening
        file_size = os.path.getsize(file_path)
        
        if file_size < 4:
            print(f"\nSkipping: File is only {file_size} bytes (needs at least 4).")
            return

        with open(file_path, "r+b") as f:
            # Navigate to 4th byte (index 3) and overwrite
            f.seek(3)
            f.write(bytes([0x6A]))
            
        print("Done (4th byte set to 0x6A).")
        
    except PermissionError:
        print(f"\nError: Permission denied for '{file_path}'.")
    except Exception as e:
        print(f"\nAn unexpected error occurred with '{file_path}': {e}")

def main():
    # Use recursive glob pattern to find files in all subdirectories
    # '**/*.bk2' tells glob to look in current and all sub-folders
    bk2_files = glob.glob("**/*.bk2", recursive=True)

    if not bk2_files:
        print("No .bk2 files found in the current directory or subdirectories.")
        return

    print(f"Found {len(bk2_files)} file(s) across all directories. Starting processing...")

    for file_path in bk2_files:
        modify_fourth_byte(file_path)

    print("-" * 30)
    print("Batch processing complete.")

if __name__ == "__main__":
    main()

Authors note: Thank you to Dark Fortune Teller on Discord for doing the hard work finding about the Byte offset