[alsa-devel] [RFC PATCH] Inverted internal mic
david.henningsson at canonical.com
Fri Jun 22 17:27:51 CEST 2012
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! :-)
> + * 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.
Thanks for looking at this long-standing problem :-)
David Henningsson, Canonical Ltd.
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