3DsoundSurge: Sensaura - The Technology


	Mikael Hagén - takes a look at 3D audio technology from Sensaura

Please support 3DsoundSurge by visiting our sponsors

drivers.gif (6840 bytes)

The Sensaura Technology - Mikael Hagén Last revised on:2/5/ 99

For the latest info and news including a much more detailed technical overview check out our new Sensaura page

Watching the past few months battle between Creative and Aureal, where the weapons have been press releases, lawsuits and, I almost forgot, soundcards, would make you think that these are the only companies with a 3D audio technology.

Not so, there exists other companies that have developed 3D sound technology and one of them is Sensaura who developed the Sensaura 3D audio technology. Sensaura (the audio technology not the company) has over its 10-year history evolved from only being used by the music industry to now also being used for 3D audio gaming.

Sensuara isn't a small player either since ESS, Yamaha and Cirrus Logic/Crystal Semiconductor, who according to Mercury Research currently supply about 70% of the PC audio chip market, have all licensed the Sensaura 3D technology. A lot of those chips will of course end up in PCs never used for gaming and market share can change fast and there is no guarantee that all ESS, Yamaha and Cirrus chips will use 3D technology. Having said that, its still an impressive win by Sensaura and clearly shows that they will be an important player in the 3D audio market.

So why did they choose Sensaura? Cheap, sounds great, has a cool name or maybe it was Sensaura's great marketing. Whatever the reason, you may end up listening to Sensaura by your own choice or just by accident, it may come bundled with your next PC, so it's time to know what your ears may experience.

After some digging around on the Sensaura site and a few e-mails we found out as much as we could except for actually listening to a soundcard using Sensaura, which we will soon do in the form of Yamaha's Waveforce 192 Digital.

Sensaura uses HRTF and Cross-talk Cancellation

Sensaura uses HRTF for headphones and HRTF with cross-talk cancellation for 2 speakers, just like Aureal and many other companies.

Sensaura also got an innovative 4 speaker solution called Sensaura MultiDrive which Sensaura believe (and our Simon confirmed) sounds much better than simple volume panning schemes (as on the SB Live with current drivers). It is also an improvement over the hybrid HRTF/panning solution used by Aureal since it uses HRTF for both front and rear speakers. ESS already announced a chip, Canyon 3D, that will use MultiDrive. They will not only take advantage of MultiDrive for basic 3D sound but also offer an improvement for their reverb engine used in games that support EAX. We should be able to review the Canyon3D chip soon.

DS3D, A3D emulation and EAX

Sensaura supports DS3D like everyone else and supports A3D 1.X just like Creative, by converting A3D calls to DS3D calls. However, unlike the Live, Sensaura claims cards using their technology will work well with both Sin and Decent: Freespace.

When it comes to the number of 3D streams, current drivers report 5 channels for the Maestro 2, 8 for the Maestro 2E, 8 for the Yamaha YMF724 and 32 for ESS Canyon3D chip, which so far are the only chips using the Sensaura 3D technology. Sensaura offers a mode where as many channels as possible are done in hardware and the rest in software. On a fast CPU it wouldn't tax the CPU much according to Sensaura since their 3D code is much more efficient than what MS uses in DS3D.

Currently, the drivers for the cards that use the Maestro or Yamaha chips don't support this mode but if ESS or Yamaha wanted to they could. I hope they will include this mode later since many new games seems to need more 3D streams than 8 and it's better to take a small CPU hit than to use just stereo sound for the other streams.

Sensaura includes a voice manager with their DS3D drivers which can be used by the developer to choose the most important sound sources to use 3D sound while the rest will use stereo. This will of course help reduce the limitation of only 8 3D streams. Research also shows that humans can't locate more than about 6 sound sources well, so 8 3D streams should in theory be enough, but unfortunately, even with a voice manager is it not easy for the developers to choose the right ones. In new games like Unreal support for 16 3D streams sounds much better than cards which only support 8.

Sensaura supports EAX and released EAX drivers for the Yamaha WaveForce recently and there should be EAX drivers available for the Maestro 2E later. In our upcoming review of the Yamaha WaveForce card we will tell you how they compares with the Live and the performance but we asked if they would do the reverb processing with a DSP like Creative's Live! or like Aureal with the Vortex2, which will "handle EAX style reverb by doing the computationally intensive tasks of sample rate conversion and mixing in hardware, and the memory intensive task of running the reverb filters and delay lines on the host (using main memory and the host CPU)."

Peter Clare provides the answer:

Whether EAX is done on the host or on the soundcard DSP will depend on the particular sound chip. Sensaura is licensed to different manufacturers, each of which has one or more sound chips. This creates a wide variety of hardware platforms for Sensaura. Some of these chips have little or no DSP, others contain very powerful DSP cores. So, where possible we will do as much processing on the DSP, but if we can't in a particular case then it will be done on the host.

As you mention, the main limiting factor for reverb is not so much DSP performance as available memory - and for most sound card hardware that we work with on-chip or on-board memory is a precious resource. So, for the most part, reverb delay lines will be host based.

So if the CPU does the reverb what will the performance hit be?

We're currently seeing 5% for EAX on a Pentium 200MMX, so 2% on a PII 300 sounds about right.

That seems to be right on target with Aureal's estimates (1-3% on a PII 300). Sensaura's reverb engine now used for EAX is already ready for the upcoming I3DL2 standard. They will of course need to change the interface to it so there will be new drivers but there should not be much extra work. The most important addition in I3DL2 compared to EAX is the support for occlusion and obstructions so we asked how they would support it and Peter Clare answered:

Basically, we do occlusion/obstruction with a low pass filter with a variable cut-off point. Whether we do it on the host or DSP see answer above.

MacroFX

Sensaura will later this year also (probably this quarter) introduce something new they call MacroFX. Current implementations of HRTF aren't good at placing sound within 1 meter of the listener, especially when using loudspeakers, MacroFX will fix this.

MacroFX provides 6 zones, where zone 0 (far distance) and zone 1 (distant mode) will work just like DS3D distant model (see my DS3D article for more details about DS3D's distance model). The other 4 zones are Near Field, in the right ear, in the left ear and inside the head. Sensaura claims that this will allow the game developers to offer special 3D sound effects like whispering in the ear, wind noises (very useful when you're skiing, running, cycling etc), headphone simulation (e.g. air-traffic) and ultra-close fly-by (useful for bullets, rockets, insects etc).

For game developers to take advantage of these features they only need to make sure they position the sound close enough. In many cases they already do that today and Sensaura is working with developers to make sure that future games will take even better advantage of MacroFX by using near positioned sounds, such as whispering in the ear, more often.

MacroFX will be offered with new drivers for the Maestro 2E and Yamaha's WaveForce and whatever chips Cirrus Logic/Crystal Semiconductor will license the Sensaura 3D technology for.

ZoomFX

Sensaura will later introduce ZoomFX which will remove another limitation with the 3D sound used in games today. Peter Clare explains the problem and their solution

DS3D models all sounds as point sources. This is fine for big objects at far distances (e.g. a train). But, as that train gets closer in reality it is no longer a point source. The DS3D model still treats it as a point source and so it lacks realism (i.e. we hear it as a tiny train rather than a great big one rumbling by). ZoomFX solves this problem and also brings in the notion of a large object like the train actually being a collection of different sound sources (e.g. noise of wheels, noise of engine, etc.).

There is currently no information provided in DS3D about the size of the sound sources so Sensaura needs to create an extension and get developer support for it so it will probably take some time before we see any game supporting ZoomFX. If it works well I'm sure that the developers will think it's worth the rather limited effort of specifying the size of the sound sources.

Will all soundcards using Sensaura sound alike?

The chips that currently use Sensaura 3D sound technology are Yamaha's 724 chip, which Yamaha uses in their WaveForce soundcards and sell to other companies, and ESS' Maestro 2 and 2E chips, which are used on many soundcards (e.g. Videologic's Sonic Storm Pro) and in a lot of notebooks.

Will it matter then which of these sound cards you choose when they will all use Sensaura? Peter Clare again responds:

We use identical algorithms and filter libraries on the various chips from Yamaha, ESS Technology and Cirrus Logic/Crystal Semiconductor. The only difference is in performance (i.e. host CPU hit) which depends on how much work we can offload to DSP (see above). Other differences outside our control (e.g. quality/type of CODEC used) may affect SNR and distortion figures.

Conclusion

The Sensaura 3D audio technology on paper seems to be competitive and even set to introduce a few new features this year. What we've heard of Sensaura in form of the Yamaha's WaveForce indicate Sensaura isn't just good on paper but is a highly competitive 3D audio technology. The support for only 8 3D streams with current cards using the Sensaura bothers me though, but hopefully new drivers will remove that limitation and the new Canyon3D chips with support for 32 3D sound streams should be an excellent chip. For some initial impressions of Sensaura you should read Mark's Motorhead review where one of the tested soundcards were Yamaha's WaveForce. A full review of the Yamaha card should happen the next few weeks and a review of the Canyon3D chips should follow soon after. Hopefully drivers for MacroFX will be available when we test the Canyon3D chip. We will also test the new ZoomFX technology when it is available. For initial impression on MacroFX and Multidrive, you should read about Simon's visit to Sensaura.

If you have any comments, questions or see any errors in the article contact Mikael@3dsoundsurge.com. For information from Sensaura you can contact Farhaan Mirza.

Have comments or questions on this feature?
Why not post them in our forum?