mrw wrote: 
> Possibly also the MSP firmware.
Agreed.  Although the msp430 firmware is available in the 'logitech
squeezeos github repo'
(https://github.com/Logitech/squeezeos/tree/public/7.8/poky/meta-squeezeos/packages/msp430/files),
the license in the recipe is Confidential.

mrw wrote: 
> Provides an ALSA control to switch on and off. This is used by
> Squeezeplay in the context of headphone jack activity to automatically
> disengage when headphones are plugged in, and engage (i.e. produce mono
> tweeter and woofer) when headphones are removed.

Perhaps providing 2 EQ curves, one for the bass crossover and another
"flat" for the headphone jack and switching between them in _setEndpoint
would be enough? You can create multiple alsa equals devices with
distinct settings.  Eventually even an applet to change the headphone
curve settings could be implemented.

mrw wrote: 
> Presumably well optimized code implementing equalization/crossover -
> would the alternatives provide adequate efficiency ?

So far, my only experience has been using alsaequals on a single arm
processor with fpu.  This would definitely need more research.

mrw wrote: 
> I've found those.
> By courtesy of the United States NSA, I used Ghidra nine or ten months
> ago to see what might be seen in the dsp plugin vis-à-vis the "bass drop
> out" issue[1]. On the way, I located the various filter co-efficients.
> 
> I have now matched these up to the relevant dsp "cook-book" algorithms
> (http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt) plus one other.
> Results agree to the penny, or, in two cases, to within a couple of
> quid[2].
> 
> [1] And found nothing that implicated the plugin.
> [2] Which, I suspect, may stem from the use of single floats instead of
> double floats when the firmware was prepared.

Amazing.  Knowing that you have the settings, makes researching
alsaequals performance on the radio a worthwhile next step.



Ralphy

*1*-Touch, *5*-Classics, *3*-Booms, *1*-UE Radio
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always appreciated.
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