[alsa-devel] [RFC PATCH] Inverted internal mic
david.henningsson at canonical.com
Fri Jun 22 19:33:06 CEST 2012
On 06/22/2012 05:37 PM, Takashi Iwai wrote:
> At Fri, 22 Jun 2012 17:27:51 +0200,
> David Henningsson wrote:
>> On 06/22/2012 02:46 PM, Takashi Iwai wrote:
>>> + * Inverted digital-mic handling
>>> + *
>>> + * First off, it's a bit tricky. The "Inverted Internal Mic Capture Switch"
>>> + * gives the additional mute only to the right channel of the digital mic
>>> + * capture stream. This is a workaround for avoiding the almost silence
>>> + * by summing the stereo stereo stream from some (known to be ForteMedia)
>> Stereo stereo? It's "stereo" in stereo! :-)
> Yeah, quad channels. Fixed now.
>>> + * digital mic unit.
>>> + *
>>> + * The logic is to call alc_inv_dmic_sync() after each action (possibly)
>>> + * modifying ADC amp. When the mute flag is set, it mutes the R-channel
>>> + * without caching so that the cache can still keep the original value.
>>> + * The cached value is then restored when the flag is set off or any other
>>> + * than d-mic is used as the current input source.
>> Ok, I get it now.
>> There is a slight drawback with this (IMO a bit hacky) patch, and that
>> is that you can get a short signal spike on the right channel when you
>> turn "Capture Switch" on while "Inverted Capture" is off. Hopefully it
>> is not a practical problem.
> Right, I fully admit it's hacky :)
> A good thing by this is, however, that it doesn't touch other parts
> too intrusively but just wraps over it.
>> Thanks for looking at this long-standing problem :-)
> I'm going to commit it once after hearing the test with a real machine
> from Eliot.
I'm adding the machines I know of in the patch attached (please commit
together with your patch).
For users running Ubuntu 12.04 (I think Eliot does), I have also made a
dkms package for easy testing of these two patches, and I also asked
existing bug reporters to test it.
David Henningsson, Canonical Ltd.
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