Uncovering the Sounds of SkiFree

So I was looking into the disassembly of SkiFree (like you do), the classic skiing (pronounced she-ing) game for Windows 3.1 as part of the Microsoft Entertainment Pack #3. I noticed an odd string constant: “nosound”. The game checks for a command line parameter to turn off the sound, which is a very strange thing for a game with no sound effects or music to do!

I followed the disassembly to see where this option was being referenced, and to my surprise I found code to load sound effects, as well as trigger them at different points in the game. The only reason why the game appears to have no sound is that no WAV files were shipped in the EXE. So the obvious next step is, what happens if we edit some WAV files in? Will it play them as sound effects at the appropriate time?

Yes, in fact!

So I figured out which sounds meant what, by using a set of sounds that were just a robot voice saying “SOUND ONE” through “SOUND NINE”. I asked a musician friend to see if they could generate some appropriate sound effects. While I waiting for them to get back to me, I check the official site for information.

It turns out that back in 1993 the original creator of SkiFree (Chris Pirih) was working on a version 2.0 of the game, to add better physics, network play, sound effects, robot opponents, the works. Sadly they ran into difficulties with the physics implementation and then misplaced the source code, so that game was never completed.

However in 2005 they were able to locate a 1.03 version of the source, which is an intermediate step between the original 1.0 release and the planned 2.0 release. With this source they were able to build a 32bit version of the game, to allow it to run on modern systems (64bit windows is backwards compatible to 32bit programs, but not to 16bit programs like the original SkiFree). This version apparently included some of the improvements planned for 2.0, but no one had noticed the sound system for 12 years because it was effectively disabled by the lack of embedded sound effects. I was able to confirm this by partially disassembling the original 16bit 1.0 version, and found no trace of a sound system there.

I emailed Chris Pirih about my discovery, and to ask if they’d ever created sound effects to be used with SkiFree 2.0, and if they still had them. To my surprise, they emailed me back within a few hours, providing a full set of sound files for SkiFree!

They also included a header file which mapped the sound effect names to the resource numbers, to allow me insert them in the correct order. So I updated my earlier test with the new sounds, and created a new demo video of it in action.

The new sounds don’t play entirely properly, because SkiFree is using a very limited API to play back sounds. It only supports playing one sound effect at a time, so often sound effects will be cut off because another sound effect plays after it. The “argh” sound of the yeti is particularly cropped, because it’s a long sound that is cut off every time the yeti takes a step.

I’ve briefly looked into fixing this, but it’ll require switching to a different sound API, as SkiFree uses sndPlaySound, a very simple high-level API which can’t be used for any sort of sound effects that require mixing. That’s beyond the scope of my quick-hackery for today, it’ll probably require adding in an external wrapper DLL to manage the sound system. Hopefully that can be done without too much effort, I’ll have to see.

As for these sounds, I suspect some of them are placeholders that would have been replaced before SkiFree 2.0 was complete. It’s still neat to see them in action, even if they may not fit in perfectly.

If you’d like to try out this version of SkiFree with the sounds edited back in, you can download ski32sounds.zip. I’ve made no code changes in this version, just added the sound resources. This should work fine on both 32bit and 64bit windows systems.

One final thing to consider about sound in SkiFree: Even if the original version had been intended to have sound, it wouldn’t have been possible for two reasons:

1. The first version of Windows to include a sound API was the Windows 3.0 with Multimedia Extensions OEM-only release, which came out a month after SkiFree 1.0
2. There was no room on the disk. SkiFree 1.0 was released in an entertainment pack that included 7 games. Adding sound effects could have easily quadrupled the size of the game, requiring an extra disk or kicking another game out of the collection.