3D Audio With Rapture3D
Rapture3D is all about 3D sound. With the march of 3D film and television, immersive virtual reality and gaming, it's about time for a real step forward in the quality of spatial audio. And we think we've achieved that.
Once upon a time, there was mono. Spatially, this was nice and simple - sounds just came from your speaker.
Later on, the "stereo" that we know so well came along. Largely developed by Alan Blumlein, this encodes a simple sound stage into two channels of audio, typically by varying the relative level of sounds in two speakers.
More recently, 5.1 and 7.1 "surround sound" systems have appeared, in the cinema and then the home. These put speakers around the audience and work typically in much the same way, varying the level of sounds in the two closest speakers.
So, What Now?
Firstly, height. We live in a 3D world - sounds come from above and below as well as the front, back and sides, both directly and indirectly. 5.1 and 7.1 systems don't manage this, which isn't that realistic. Okay, they beat stereo, but we can do better.
And also, there's been a lot of research done into how sounds behave in space. It turns out that just varying the level of sound in two speakers is not the best way to produce a realistic soundfield.
The Mathematical "Heavy Lifting"
Rapture3D uses a mathematical framework known as "Higher Order Ambisonics" (HOA) to drive your speakers. The maths is hard, but we worry about all that - and the results are worth it! HOA can work better and better as you add more speakers and, like its close relative "Wavefield Synthesis", can generate essentially correct soundfields over a wide area. Unlike Wavefield however, it doesn't insist on huge numbers of speakers. Instead, Rapture3D does the best it can and blends in more robust techniques where there isn't enough detail, or a large enough number of speakers, for more "holographic" approaches.
We think we have a superb HOA decoder in Rapture3D. We're using a range of new techniques, including handling of irregular speaker layouts and new psychoacoustic cues. If you're mathematically inclined, you might be interested in some Technical Notes.
Rapture3D also has support for surround stereo, HCTC crosstalk cancelled stereo, and 3D over stereo headphones, using five different "HRTFs" to help you find one that matches your head shape.
What Does This All Mean?
This means that Rapture3D can:
- Make better use of your existing multichannel speaker layout to produce a more realistic and immersive soundfield.
- Handle 3D speaker layouts and place sounds above and below, as well as to the front, back and sides.
- Use "irregular" speaker layouts - tell the software where your speakers are and Rapture3D will work out the best way to use them ("advanced" edition only).
- Drive headphones, stereo and surround stereo systems.