[alsa-devel] [RFC PATCH] Inverted internal mic

Takashi Iwai tiwai at suse.de
Wed Jun 20 15:31:26 CEST 2012

At Tue, 19 Jun 2012 09:43:07 +0200,
David Henningsson wrote:
> On 06/19/2012 05:07 AM, Eliot Blennerhassett wrote:
> > David Henningsson<david.henningsson<at>  canonical.com>  writes:
> >> On 02/28/2012 02:22 PM, Takashi Iwai wrote:
> >>> At Tue, 28 Feb 2012 14:07:59 +0100,
> >>> David Henningsson wrote:
> >>> Is there a way we can
> >>>> know the corresponding processing coefficients to set for ALC268 and
> >>>> ALC272X as well?
> >>>
> >>> AFAIK, no, it was specific to the codec model.
> >>
> >> Ok, then we can only hope for Kailang to supply this information if
> >> possible. And if not possible we could attempt the workaround (when/if
> >> we agree on it...) for these devices as well?
> >
> > Greetings,
> >
> > Any chance that there has been any progress on this?
> > I have a machine with dmic and ALC272X (details below) that exhibits this
> > problem, and can test any proposed patch.
> We have a patch in for the Thinkpad U300s, but that one had a Conexant 
> codec.
> I haven't had time to start working on kernel patches for the Realtek 
> ones yet, but meanwhile, I'm tracking known machines here:
> https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/1002978

Looking at the codec, it's not so trivial to port the inverted switch
to Realtek.  In the input path of Realtek codecs, there is no
individual capture volume/switch but only a central ADC volume and a
MUX (or a mixer).

I can think of a new boolean switch or an enum to choose whether to
shut off the right channel of the input-mux and the loopback volume.
But it's feasible only if it make sense to PA.


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