Hi Jörn,

On 03 Jun 2016, at 15:27, Jörn Nettingsmeier 
<netti...@stackingdwarves.net<mailto:netti...@stackingdwarves.net>> wrote:

Note however that while the quality of first-order to binaural is quite good 
because the listener is by definition always in the sweet spot, first-order 
over speakers can be difficult for multiple listeners when they're far outside 
the center.


This is by no means meant to provoke, but I have never managed to hear a 
convincing B-format to binaural rendering, or to produce one myself. Could you 
possibly share some info on the decoding approach that you used that results in 
a good example?

In my experience, no matter how much tweaking in the decoding, there is severe 
localization blur, due to the large inherent spreading of directional sounds, 
and low envelopment due to the wrong (high) coherence in the binaural signals 
with reverberant sound, compared to the actual binaural coherence. And there is 
also serious colouration, with a loss of high-frequencies, that seems 
direction-dependent. The fact that everything is on the ideal sweet spot under 
free-field conditions doesn’t seem to improve much, it actually seems to do 
more harm (I believe that a small amount of natural added decorrelation from a 
room and tiny misalignments from speakers etc. seem to improve binaural 
coherence and the perceptual quality somewhat of loudspeaker B-format 
reproduction).

Listening to a binaural rendering from a real B-format recording is not so bad, 
there is no reference for comparison, but for VR the difference I’ve heard 
between using directly HRTFs and B-format rendering is huge. And as many of 
these applications rely on sharp directional rendering with accurate 
localization of multiple sound events, traditional B-format decoding seems 
unsuitable to me. The performance improves somewhat with 2nd-order rendering, 
and significantly with 3rd and 4th-order rendering. Also it improves 
dramatically using plain B-format with a well-implemented parametric active 
decoder, such as HARPEX or DirAC.
So my guidelines for VR till now have been,
a) if bandwidth is not an issue go for HOA rendering (at least 3rd-order),
b) if it is an issue, like the streaming application of the OP, stream B-format 
and use an active decoder at the client side.

But I’d like to hear many opinions on this too, and any counter examples!

Regards,
Archontis Politis

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