At Mon, 16 Mar 2009 18:30:00 +0100, Andreas Mohr wrote:
Hi,
On Mon, Mar 16, 2009 at 06:15:39PM +0100, Takashi Iwai wrote:
At Mon, 16 Mar 2009 18:00:15 +0100, Andreas Mohr wrote:
Hi,
On Mon, Mar 16, 2009 at 05:19:38PM +0100, Takashi Iwai wrote:
At Mon, 16 Mar 2009 17:06:35 +0100, 私 wrote:
> What are "sliders"?
Umm, volume level controls.
Yes but there are many of such :)
More exactly, from the driver perspective, there are no volume controls but only there are control elements with integer values. Do you mean "Capture Volume" control or which one?
Hmm, ok, this needs to be more precise: In gamix (codec "HDA Intel : Realtek ALC268"), the Capture Volume control.
Yeah, that's more understandable :)
BTW, does "Capture Volume" influence on the recording level even for the built-in mic, right? I'm asking this because the digital mic on STAC/IDT codecs isn't controlled via "Capture Volume" control that is bound to an ADC widget. (That's why "Digital Capture Volume" control exists. It's a value used by alsa-lib softvol plugin for "default" PCM.)
Yes, Capture Volume does influence i-Mic level. The Digital Capture control, however, doesn't influence level. As doesn't the Mic Boost Capture control (probably about e-Mic only?).
The "Digital Capture Volume" has effect only when "default" PCM is used. If you record via "hw" or "plughw", it's unused.
And, is the behavior consistent regardless of the value high, i.e. the key is only whether the values for both channels are identical?
BTW, what if you record with the following definition? Put the below to ~/.asoundrc
pcm.imix { type plug slave.pcm "hw" ttable.0.0 0.5 ttable.0.1 -0.5 }
and record like
% aplay -Dimix -c1 foo.wav
Does NOT exhibit the "equal sliders == no sound" bug (apart from this sliders are acting normally, i.e. slider low == no sound), despite being a "plug" type definition (this is what you wanted to discern, right? ;).
Interesting. This implies that one channel is inverted indeed.
Oh, you mean "inverted" as in "_hardware_ channel which provides opposite sample values as compared to the other channel"?
Right. My guess is that the hardware provides left (or right) channel is multiplied by -1 (yep "inverted" is no correct word choice).
As default the alsa-lib plugin downmixes a stereo stream to a mono stream simply by left/2 + right/2. The above changes the routing policy as left/2 - right/2.
That exactly matches my current stream of thought (while reading "one channel is inverted" above).
So we need to pass some information to change this kind of thing...
That's something specific to ALC268 codec setup, right? ("ALC268 digital mic == left plus right channel, but inverted setup"?)
No. It's specific to the digital-mic side.
Takashi