Source Relative [was Re: [Openal] How to vary the speed of sound]

[Daniel PEACOCK]

Hi Chris,

I've fixed the "Generic Software" device problems with Source Relative so
it is spec. compliant.   Each Source with AL_SOURCE_RELATIVE mode set to
AL_TRUE will be processed as if the Listener was positioned at 0,0,0, with
an Orientation of 0,0,-1, 0,1,0 and Velocity 0,0,0.    This fix will be
rolled into the new binary release - which will be made available soon.

Dan

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             Chris Robinson                                                
             <chris.kcat at gmail                                             
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             .com                                                  Subject 
                                       Re: [Openal] How to vary the speed  
                                       of sound                            
             05/18/2008 02:28                                              
             PM                                                            
                                                                           
                                                                           
                                                                           
                                                                           




On Sunday 18 May 2008 04:43:05 am wassim_belhadj at topnet.tn wrote:
> I would like to know how to vary the speed of sound using OpenAL.

The global speed of sound is defined by the attribute AL_SPEED_OF_SOUND:
alSpeedOfSound(343.3f);
speedofsound = alGetFloat(AL_SPEED_OF_SOUND);

Note that this only affects sounds playing with a doppler effect.

> For example, at a click on a button the sound is played with a  faster
> speed from the position where the action was made.

The speed of sound, however, doesn't sound like your problem here. This
makes
me think you either have a pitch set on the source, or velocities set on
the
source and/or listener (causing doppler to be applied). Or perhaps you
called
alBufferData with the incorrect frequency.

Note also that there are some issues if you're using AL_SOURCE_RELATIVE for

the sound. It seems some implementations don't make the velocity relative,
as
defined in the 1.1 spec (particularly, the old Windows version, and by
extension OpenAL Soft, and I think the SI). I can probably fix this for
OpenAL Soft, but I don't know about other implementations.
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