[openal] Loading of HRTF file fails

Chris Robinson chris.kcat at gmail.com
Wed Feb 19 03:56:12 EST 2014

On 02/18/2014 11:49 PM, Dennis Franken wrote:
> Ah thank you, it worked! My mistake was to include quotation marks,
> since the hrtf tutorial on bitoutsidethebox had those. I've tried the
> resample option on one mhr file and it seems to work great too! This is
> truly amazing news for VR developers for the oculus rift, where
> headtracking and a slight "tilt of the head" improves the value of hrtf
> audio tremendously.

Sweet. :)

> Sorry but now I have to bother you with a few more questions:
> I haven't found any license or copyright info on the source site of
> those hrtf sample data, are they free to use?
> http://recherche.ircam.fr/equipes/salles/listen/

According to the info pages, 
and the others, the copyright is "Public".

> Does OpenAL-Soft support convolution filters?
> I checked out Web Audio and it's amazing what they do with those in the
> demos. In your browser! :o You simply "download" a recorded effect
> instead of using a proprietary algorithm.

OpenAL Soft implements HRTF using convolution, although there isn't 
currently a way for applications to specify a custom filter. The EFX 
extension does provide general reverb effects and low-pass filters, though.

> As I've hinted before, I'd love to help make a config utility to test
> different hrtf and make setup easier. I've noticed that when you shut
> down OpenAL and start it again, it reloads the hrtf and I think the
> config too.

Once OpenAL Soft loads the config (which typically happens when you 
first open a device or enumerate all devices), it won't reload it again 
in that process. The only way it can is if you unload and reload the 
library from the process, but there's no reliable way to do that (aside 
from the fact that OpenAL Soft will pin itself on Windows, since certain 
backends exhibit problems if the lib is unloaded and reloaded, there's 
no reliable way to ensure the OS will actually unload the lib).

The best way to handle this, probably, is to have the actual test launch 
as a separate process from the configuration UI, so a user doesn't have 
to restart the configuration app to test new settings.

Aside from that, a configuration app that lets you easily select and 
test different available HRTFs would be quite nice.

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