The More You Know

Extracting Music From GFC Files -(Portal: Still Alive)

If you had the delight of picking up Portal from Valve and beat it, you know all about cake, the lies, and the masterful end song. I found that upon beating it, I kept humming the song and wishing to know the words. Googling to find the song in any format I found the a YouTube link, awesome. That satiated my ears for a little bit, but I found that my MP3 player, desktop, and laptops were all missing the song while I worked. So, I set out to find how to obtain the song from the data files. Most games store songs as either WAV files or MP3 files and I figured there was a good chance that Valve did just that! I was right and it took a little working.

Digging into the directory structure you can find the following directory: \Steam\steamapps\*. This directory holds two very large files name “portal english.gcf” and “portal content.gcf”. It is a common practice for game makers to use a proprietary file format to store contiguous game data in a single file. This allows known pointer offsets in files to allow fast reading from disk. It also turns out that the file extension GFC is commonly for Grid Cache Files. Which is a common format for Steam released games. It also turns out there are many developer out there making programs capable of browsing these data caches without having to hack them yourself (you should, just for fun!). One that I found useful was GFCScrape.

Extraction Tutorial

1. Download GFCScrape & install (or any other GFC editor/browser)
2. Start GFCScrape
3. File => Open
4. Navigate to your Steam installation directory (e.g. C:\Program Files\Steam)
   
5. Open the directory “steamapps” (e.g. C:\Program Files\Steam\steamapps)
6. Open the file “portal content.gcf”
7. Within GFCScrape, navigate to: root\portal\sound\music\
   
8. Drag and drop the file “portal_still_alive.mp3” to your desktop or mp3 directory

Quick Links

Valve Wiki Article About GFCScrape

GCFScrape Home Page