[openal] stereo separation issue with a stereo source
chris.kcat at gmail.com
Thu Feb 5 23:09:15 EST 2015
On 02/05/2015 01:32 PM, Lubomir I. Ivanov wrote:
> after staring at alSource.c for a while and finding this thread:
> apparently each multichannel source has to set AL_DIRECT_CHANNELS_SOFT
> for the virtualization to not happen (where a slight downmix is the
You generally want to avoid using that. With headphones/HRTF, for
instance, a stereo buffer with direct channels will not sound great
unless the sound was authored specifically for them. The reason to use
direct channels is to play stereo sounds that have already had a
binaural filter applied.
Out of curiosity, what speaker setup do you have? Normal stereo output
should not have any bleed over with stereo buffers. There should only be
some bleed over with HRTF (which is by design, and you don't want to
prevent normally), or surround sound (although each channel is properly
localized to +30/-30 degrees, where the speakers would be in such setups
If you're using stereo speakers, check that they're not configured or
detected as headphones by OpenAL Soft.
> ^ also i think this appears to be partially true - there is no way to
> control the stereo field of a stereo source, say a 0-100% (where 0% is
> a mono downmix) on the fly via a alSourcei() call. is that correct?
There is the AL_EXT_STEREO_ANGLES extension
OpenAL Soft doesn't currently support it since the angles are supposed
to default to +30/-30 degrees, and the lib fudges with the angles with
stereo output to avoid bleed over (placing them at +90/-90 degrees with
non-HRTF stereo output to align with the speakers). It definitely won't
work with direct channels, since you can't map input channels directly
to output channels and still pan each input channel.
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