OpenAL for iPhone does not support HRTF.
HRTF is the head related transform function used in three dimensional audio that models the shape of the head and ears. HRTF basically enables a low pass filter when the sound source is behind you making it sound as if... it were behind you.
In oalTouch (Apple's OpenAL demo source) the sound is the same when the source is either behind or in front of the listener. This seemed strange so I reported it as a bug to Apple (Problem ID: 6576577 in fact). I also noticed that the same problem exists on the Mac OSX Cocca native with the PIGE-OpenAL demo.
Got my answer today... "Engineering has determined this issue behaves as intended based on the following information: Please note that OpenAL doesn't support HRTF rendering."
This is disappointing. It means OpenAL only supports fading left to right and volume. It doesn't really take advantage of all the 3D positioning information. The phone certainly has the horsepower to do the computations for HRTF.
Labels: audio, HRTF, iphone developer, openAL
posted by JMathews at
11:26 PM
3 Comments:
This is really too bad. Has anyone tried building an HRTF library to extend OpenAL support on the mac or iPhone?
It's been almost a year...have there been any updates? Does anyone know of an HRTF library for the iPhone yet? Thanks!
I just have 1 quick question for you(the Master) and wondering if you have the answer or not....
I am making a very small iphone app using openAL. I record using AVrecorder, and when I play it back in OpenAL with this setting
alSourcef(source, AL_PITCH, 1.2f);
alSourcef(source, AL_GAIN, 1.0f);
The volume is very very low. The higher I set the pitch, the lower it sounds. I am wondering if there's a way to cheat this and push the max volume more than the limit within openAL.....
Looking forward to your magic!!!
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