[openal] Attenuation Roll-Off problems (too silent)

Roland Plüss roland at rptd.ch
Sat May 21 07:55:24 EDT 2022

Actually I do not want any automatic gain modification on reverb effects 
since I use a form or auralization which already does such a room model. 
Doing it twice causes problems. What options do I all have to disable to 
make sure OpenAL does not apply any kind of gain modification on filter 
or effects?

Am 21.05.22 um 05:42 schrieb Chris Robinson:
> On Friday, May 20, 2022 2:14:00 PM PDT Roland Plüss wrote:
>> There is also something else I have troubles with which is connected
>> with this problem. To do distance sounds I have to manipulate the
>> attenuation calculation. To achieve this I tried disabling attenuation
>> on a per-sound basis by setting roll-off to 0 and setting the source
>> gain to my calculated attenuation. While this works for direct sound
>> path I get into troubles with EAX reverb gain. I simply can't figure out
>> if the EAX reverb gain is applied to the full volume source or to the
>> source with the source gain applied, hence which one is true?
>> 1) final reverb gain = source.gain * source.attenuation * reverb.gain
>> 2) final reverb gain = source.gain * reverb.gain
>> 3) final reverb gain = reverb.gain
>> The documentation does not state this. I would assume 1 to be true but
>> my experiments do not give me a usable answer.
> For reverb, it starts with source.gain * reverb.gain. There is additional
> attenuation applied based on the sound distance and the reverb properties,
> although it's not the same as the distance attenuation applied to the direct
> path. This extra attenuation is a statistical model to simulate the kind of
> room path attenuation found in real environments. There doesn't seem to be
> much public information about this statistical model, so as far as OpenAL Soft
> is concerned, its had to come up with its own thing which may still need more
> tweaking, but the latest version should be better than older versions, at
> least.
> There are source and reverb room rolloff properties which work like the
> source's direct path rolloff, but these are disabled by default (set to 0)
> since the statistical model is applied. You can disable that statistical model
> and use the room rolloff properties instead (set the auxiliary effect slot's
> AL_EFFECTSLOT_AUXILIARY_SEND_AUTO property to false, then set the source's
> want), but it's up to you to set them correctly.
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