Producing Audio for Halo

Putting it All Together

The scariest part of producing a game of this size is during the final stage,when everything seems to come together at the same time and each element is screaming for attention. Throughout the process we were dependent upon programmers, hardware people, artists, writers, and designers to get their part done enough so that we could add the sound, dialog and music. For months it seemed as though nothing was quite ready and then all of a sudden everything was ready at once.

While the testers were banging on the game, we were attempting to do what I call the "Final Mix". Those of you who come from the traditional linear mediums understand the importance of the final mix stage, and yet in game production this is something that is rarely budgeted for in terms of time. Part of the reason is that there really is no final mix in a product that must mix itself in real-time every time it's played by a new person. We used this time to re-record, re-mix, change volumes, tweak the DSP, adjust weighting of permutations, dynamically compress soundfiles, and a myriad of other tasks that affects the subtle balance of the overall sound design of a game. This is also the time when the user interface and splash screen finally comes on-line. If not handled correctly, this is an area where sound and music can really be butchered. I prefer a consistent audio experience where sound or music isn't abruptly cut off when the user makes a menu choice, where there can be a sense of elegance and continuity between the opening movie, interface, and loading screen. I try to experience the game as though I'm a first time user or a veteran returning for my 200th time, and make sure the audio flows like movie audio.

What Works
Many things work well in Halo's audio, but the thing I'm most pleased with is the Dolby 5.1 Surround working in real-time. I wasn't sure until near the end that this was an attainable goal. The music and ambient sound is made up of stereo files and never get positioned within the game geometry. However, I figured that in the same way stereo sound fills up your car's four speakers, we could do the same with our stereo files. We simply took the stereo signal and sent 50% of it to the rears, and also to the LFO. The listener gets the sense of being in the middle of the ambient space and music, and therefore the sound of marines yelling or an explosion happening behind you is not jarring in anyway. Sounds that are spacialized will move when the camera moves, but the music and ambient remain constant. The other area I'm most pleased with is the random combat dialog of the marines. This is something that ended up being greater than the sum of its parts. It can be improved upon, but is still one of the elements that exceeded my expectations.

What Could Be Better
Not everything that could or should make sound does. Some sounds that should respond dynamically don't. Not every character in the game has a unique voice. The overall mix could have been improved. Ambient sounds should attenuate according to distance not time. Fake string samples should have been replaced with live players. Basically, we could have used another 6 months of development time, but I'll probably always feel that way about each project.

In terms of surround sound, the main problem we encountered involved giving up control of speaker sends to the audio engine based on camera position. In order to get a character's lips to sync to the soundfile, and to take advantage of the room DSP, we had to attach the soundtag to the character model that was speaking. This caused the sound to emanate from whatever speaker is appropriate based on the character's position in relation to the camera. Consequently, a speech that is coming from the front speakers can suddenly jump to the rears simply because of a close up shot of a character who is supposedly listening. This happens a few times in Halo and is annoying. We'll fix it in the next project.

Conclusion

Interactive entertainment is in direct competition with all forms of entertainment. As game developers we are vying for the public's time as well as their dollars. Time spent playing games means less time for watching television, listening to music or going to the movies. More and more people are building home theater systems, and consoles like the Xbox and Playstation2 also allow for viewing DVD's and listening to CD's. All these entertainment choices are taking place in the same location. This means that audio production on games is not being judged just against other games but against all the audio that can be heard from that system. My goal is to not just meet the standards set by the other mediums, but exceed them - to hear someone say "Wow, that CD sounded great and that DVD soundtrack was amazing, but the audio from that game blew them both away!"