[pulseaudio-discuss] On scaling the HRIR in module-virtual-surround-sink

Tanu Kaskinen tanu.kaskinen at linux.intel.com
Tue Mar 11 06:00:31 PDT 2014

On Sun, 2014-03-09 at 00:57 +0600, Alexander E. Patrakov wrote:
> Hello.
> [Do not blindly apply patches from this e-mail! They mutually exclusive, 
> and I don't have a firm opinion which one of them is correct.]
> Today I tried to improve the existing module-virtual-surround-sink (but 
> the same issue also affects the IIR-based rewrite that is still sitting 
> on my laptop). The problem is: the current normalization code does not 
> do what it is designed to do. The module clips on some testcases. Let me 
> copy-paste the problematic code for easy discussion.


> Thoughts?

My thoughts:

The scaling should be put in its own function with a comment that
explains why the scaling is done, a high level description of how the
scaling algorithm works, and a note that it's unclear whether the
algorithm actually makes sense. Something like this could be included
too: "This algorithm doesn't pretend to be perfect, it's just something
that appears to work (not too quiet, no audible clipping) on the
material that it has been tested on. If you find a real-world example
where this algorithm results in audible clipping, please write a patch
that adjusts the scaling factor constants or improves the algorithm (or
if you can't write a patch, at least report the problem to the
PulseAudio mailing list or bug tracker)."

So, I think the criteria for patches should be: does it fix audible
clipping in real-world material without making the audio too quiet?


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