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

David Henningsson david.henningsson at canonical.com
Tue Feb 28 19:11:15 CET 2012

On 02/28/2012 04:20 PM, Takashi Iwai wrote:
>> I'm talking about recording an internal mic in *stereo*, as I just wrote
>> below. Or don't you agree that is a valid and probably fairly common use
>> case?
> Well, when you record it in stereo, and play it back, then you hear
> the sound without problem.

That could definitely be questioned: depending on the distance between 
speakers when you're finally playing it back, you might lose bass 
frequencies [1]. (That said, I'm not sure how much bass these mics pick 
up anyway.)

> The problem happens only when you sum the
> left and right signals into mono.  Thus, as long as the stream is
> handled as stereo, it could be passed as is, although it's not
> optimal.

So the official recommendation is that summing left and right to make a 
mono signal, is to be considered an invalid operation?

David Henningsson, Canonical Ltd.

[1] Or possibly get distorted sound in different ways, not sure.

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