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

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 :-)