[Openal] Filter

[Andy Patrick]

Hi Luis, thanks, yes I am reassigning the filter to the source after
modifying it, however it still doesn't seem to change the sound very
much.
 
And I'm still wondering why a filter (for which I would expect to change
cutoff and slope) instead has fixed cutoff and slope, and only allows
you to change "gain" and "gainHF" and it's not clear what that is
expected to do.
 
Thanks
 
Andy
 
________________________________

From: Luis [mailto:h.k.1981 at gmail.com] 
Sent: 10 October 2007 06:12
To: Andy Patrick; openal at opensource.creative.com
Subject: Re: [Openal] Filter



	Hi Andy.
	Just checking, are you reassigning the filter to the source
after modifying its parameters? You must do this or the new parameters
won't affect the source at all.
	
	Hope that helps
	
	
	On 10/4/07, Andy Patrick <Andy.Patrick at rebellion-derby.com>
wrote: 

		Hello all,
		 
		We're looking at playing around with the per-voice
filter in the Effects Extension, in preparation for occlusion etc. We'd
also like to change the filter over distance using a method that offers
more control than the in-built distance filter in OpenAL, which I seem
to remember reading about but can't now find a reference to!
		 
		I understand that the low pass filter cut-off (-3dB
point) is fixed at 4KHz, and the slope is fixed at -6dB/octave. What I
don't understand is how the available parameters - AL_LOWPASS_GAIN and
AL_LOWPASS_GAINHF - relate to that. I assumed that GAIN would modify the
gain to the left of the cut-off point, and GAINHF would modify the gain
to the right of the cut-off point. However, my attempts at varying
GAINHF from 0 to 1 by distance doesn't seem to change the sound very
much, and based on this assumption setting both GAIN and GAINHF to 0
would silence the sound, which it doesn't.
		 
		Could someone please explain what the intent of these
settings is, and briefly suggest how I might be able to implement the
effects I'm after? I'm using OpenAL 1.1 on the Windows platform,
primarily.
		 
		Many thanks
		 
		Andy P

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	-- 
	Luis 

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