[Openal] Binaural recording + virtual 3D sound source + CMSS-3D

Wed Oct 14 14:57:29 PDT 2009

Hi Dan ,

I am using a XFi Platinum, or sometimes an Audigy 2 for testing.
Please tell me that one of these two can play an OpenAL application with HRTF [On] for mono source, without upmixing stereo source.
I really thought that upmix and downmix was only for nonOpenAL sound files.
I thought that stereo buffer in OpenAL application was not spatialized at all, but it is still 3D virtualized if I understood well.

Could you explain me how the sound card (XFi for example) will spatialize an OpenAL application when CMSS-3D is [off] ?

If both features (HRTF for mono buffer, upmix of stereo buffers) are linked in CMSS-3D function, maybe could you give me a trick in the OpenAL code ?

Thank you,

Francois

HITlabNZ

-----Original Message-----
From: Daniel PEACOCK [mailto:dpeacock at creativelabs.com]
Sent: Thu 10/15/2009 3:44 AM
To: Francois Montignies
Cc: openal at opensource.creative.com
Subject: Re: [Openal] Binaural recording + virtual 3D sound source + CMSS-3D

Hi Francois,

Which soundcard are you using?

>> When I enable Headphones CMSS-3D it adds a processing artifact on
>> my binaural recordings. I think it might be a cross-feed algorythm.

>> Is there a way to keep my original binaural track (that means left
>> channel to left ear, right channel to right ear) and add a 3D source
>> with CMMSS-3D "On" ?

The "CMSS-3D" feature includes upmix technology and enables high-quality 3D Audio virtualization.
Depending upon the soundcard you are using it may or may not be possible to separate these two
features unfortunately.

>> What would be the result if I turn off CMSS-3D and only select "headphones" reproduction, do I
lose the HRTF for the virtual 3D speaker ?

I believe the answer depends on the soundcard you are using.

Dan
Creative Labs (UK) Ltd.

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             Francois Montignies                                                                    
             <francois.montignies at canter                                                            
             bury.ac.nz>                                                                         To 
             Sent by:                            openal at opensource.creative.com                     
             openal-bounces at opensource.c                                                         cc 
             reative.com                                                                            
                                                                                            Subject 
                                                 [Openal] Binaural recording + virtual 3D sound     
             10/12/2009 05:07 AM                 source + CMSS-3D                                   

Hi,

I would be really happy if someone could tell me if it is possible to deal with binaural recordings
as background sound environments.
I work for a research project in which we only use headphones reproduction. Binaural recording is
therefore a solution to have a realistic sound environment. We would like to add a virtual speaker
with 3D coordinates that we can vary.

In my OpenAL source code I have :
- a stereo buffer for the binaural source (no spatialization with OpenAL)
- a mono buffer for the virtual source (3D definition with OpenAL)

Problem is :
When I enable Headphones CMSS-3D it adds a processing artifact on my binaural recordings. I think it
might be a cross-feed algorythm.

Two questions :

- Is there a way to keep my original binaural track (that means left channel to left ear, right
channel to right ear) and add a 3D source with CMMSS-3D "On" ?
- What would be the result if I turn off CMSS-3D and only select "headphones" reproduction, do I
lose the HRTF for the virtual 3D speaker ?

Thanks for any help,

Francois,

HITlabNZ

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