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

Roland Plüss roland at rptd.ch
Sat May 21 08:12:59 EDT 2022

This does not seem to work. I tested with reverb gain of 0.02 once with 
source gain 10, 100 and 1000 but the final reverb gain is unchanged. 
This leads me to conclude reverb gain is not linked with source gain. Is 
this wrong?

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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