[pulseaudio-discuss] What-did-you-plugin-dialog

Alexander E. Patrakov patrakov at gmail.com
Tue Nov 26 23:37:05 PST 2013

David Henningsson wrote:

(sorry for hijacking the thread)

> The current logic hard codes the port names of headphones, headset and headphone mic.

I think there is one more functional requirement likely to appear in the 
future. Namely, at LCE 2013, we discussed a reimplementation of 
module-virtual-surround using IIR filters (that I still have to clean up 
before submission), and Tanu suggested that it should be activated by 
default for headphones, which, from my viewpoint, is reasonable. After 
that discussion, some complications appeared:

  * My desktop PC has a Gigabyte H87N-WIFI board that allows for 
headphones to be plugged into the front panel. However, the Streacom FC8 
Evo case does not have the headphone jack on the front panel at all, so 
I have to plug them into the rear jack. As a result, PulseAudio does not 
recognize them as headphones. So, for the purpose of filter application, 
some way needs to exist to hint PulseAudio here that the thing currently 
plugged into the green rear jack is, in fact, headphones, and not, say, 
desktop speakers. Or to say that this HDMI output, ultimately, leads to 
headphones. This may also be relevant for disabling the echo 
cancellation, as it is useless for headphones anyway.

  * I also have a set of filter coefficients that produce "virtual 
headphone" effect from 2.0 laptop speakers, which, combined with the 
above filter, allows for much better downmixing of 5.1 audio for such 
speakers. The caveat is: this currently works only for 13" laptops. 
Other laptop sizes need different coefficients. So, in the very unlikely 
case if I clean up the coefficient-generation program for submission and 
if someone generates more coefficients for me, then we might need a rich 
vocabulary for "stereo" speakers: traditional properly-placed stereo 
speakers, 17" laptop, 13" laptop, 32" TV on a stand, 47" wall-mounted 
TV, and so on. But, as I said, it is much more likely that I will not 
submit this at all due to lack of time - so please don't take this as 
something to consider immediately.

Alexander E. Patrakov

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