On 2016-03-01 15:44, Tanu Kaskinen wrote:
On Tue, 2016-03-01 at 14:40 +0100, Klaus Jaensch wrote:
Am 01.03.2016 um 11:19 schrieb Tanu Kaskinen:
On Mon, 2016-02-29 at 17:33 +0100, Klaus Jaensch wrote:
I'm wondering why it is the default to mix the channels.
If there's a device with channel map "front-left,front-right", and a
capture stream appears that has channel map "mono", do you wish that
pulseaudio would by default take audio only from the left channel? Why
would that be more likely what the user wants, rather than taking audio
from all channels the device has, or only from the right channel?
Yes. If the user wants only the left channel he has no chance to do so.
(Without changing the configuration.)
You can't split the mixed channels later. The only way is to record
stereo and split the channels later.
If you want a mix of both channels it is always possible to record
stereo and mix it later.
Another problem with mixing is that the level meter of applications like
audacity show the amplitude of the mix. If you do not know that the
level meter shows only half of the dynamic range (-6dB) if only one
microphone is plugged to the left channel it is likely that you overmodulate
the recording.
And as far as I know it is the default on Windows and Mac OS X to record
only the left channel. I've checked this with some of our USB audio devices.
It could be also argued that if the recording application wants to pick
just one specific channel, it should set the stream channel map
accordingly. But after pondering this for a bit, I think I agree it
would probably good to map mono recording streams only to the first
channel (usually left) of the device by default.
But - now every mono recording of, e g, line in, will only record the
left channel instead of both.
Also, what about dual-channel internal laptop microphones with high
background noise? By not mixing the channels, won't your S/N ratio
decrease by 6 dB?
This sounds like fixing one problem but causing other problems.
--
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic
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