What Worked, What Didn t, and the Future of Both


What Worked, What Didn't, and the Future of Both

The Good

Some of the most memorable audio experiences playing Halo came about because of a lot of hard work and a little luck. The Marine dialog, for instance, was a huge outpouring of effort in terms of scripting, recording, editing, and implementing. We did not, however, have any idea that it would work as well as it did until we got very close to shipping. The combination of great AI coding by Chris Butcher, an extensive script (153 AI categories), some top-notch improvisation in the studio by our cadre of actors, and a basic premise that each category should have as many unique permutations as possible (5,600 permutations in all) led to a tapestry of Marine dialog that is constantly changing and a great source of enjoyment.

There were also a lot of other things that worked really well, including Dolby 5.1, the performance of the reverbs, Doppler, 3D positioning, and our dynamic music system. We were developing content for the game at the same time that the hardware was being developed for the Xbox. Because of this, some of these features were not a sure thing until late in the summer of 2001, mere months before shipping. The Xbox audio team did a great job delivering what they promised, making it a great platform on which to develop.

The Not So Good

There were some things that did not work so well that we will fix for future games. Reverb morphing is something we had to hack in the Bungie audio engine to prevent hearing the borders of reverb areas pop, but it does not work perfectly in all cases. The HRTF function and some 3D positioning were too heavy-handed during cinematics, and we are looking at ways to disable or limit it in future titles. In a film, character voices do not swing around to the rear speakers because the camera angle changes. In Halo, there are actually a few spots (the bridge in the first level, for instance) where the camera position is so close to a character's face that the audio engine thinks the sound source is behind the player. Looking at a close-up of the Captain's eyes but hearing his voice coming from behind you is disconcerting. In Halo, everything but the music and ambiences were stored at 22.05 kHz ADPCM compressed and result in quite a bit of artifacting, depending on the source. It is most noticeable in the speech. In future titles, we will be moving to 44.1 kHz for all of our content, which will alleviate most artifacting.

The initial music we produced included some fine playing by members of the Chicago Symphony and Chicago Lyric Opera Orchestra. Due to time constraints, we were forced to use sampled instruments for the bulk of the production done during 2001. While there are quite a few good samples out there, they are not a replacement for live musicians. For future titles, we will build time into our schedule to record live musicians where appropriate.

Another time constraint issue was facial animation. We only had the ability to open or close a character's mouth in reaction to the amplitude of the speech sample. For future games, we will be adapting a more robust facial animation system, which will make the characters appear much more realistic when they are speaking.

There were several content areas in which we were constrained to mono sound effects, such as first-person animations and all 3D positional audio. Some 3D positional audio, such as the jeep engine, should be stereo. There is work being done both at Bungie and throughout Microsoft that will allow for stereo sound effects to be 3D positioned and will bring more life to sounds such as vehicles and weapons.

Occlusion is another area we would like to refine. Our engine did not allow for movable objects, such as doors, to occlude. For upcoming games, we will be working to make sure that anything that should occlude will occlude.

Our use of DSP was limited and is an area that has a lot of potential. We will be working with our programming team to allow us full use of real-time EQ, LFO, and plug-ins such as limiters. We will also be looking at the use of better data compression for high-quality, low-memory audio in certain areas of the game.

Creating content for a game is merely half the battle. Implementing that content in collaboration with a strong programming team is absolutely essential, and in closing we would like to thank Jason Jones and the Bungie programming team for giving us the tools and support necessary to help make Halo a great-sounding game.




DirectX 9 Audio Exposed(c) Interactive Audio Development
DirectX 9 Audio Exposed: Interactive Audio Development
ISBN: 1556222882
EAN: 2147483647
Year: 2006
Pages: 170

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