On Tue, May 05, 2009 at 09:17:52PM +0200, Jan Stary wrote: > On Apr 25 22:23:21, Jacob Meuser wrote: > > On Sat, Apr 25, 2009 at 01:15:33PM +0200, Jan Stary wrote: > > > Hi all, > > > > > > I am doing some trivial sound-recording on my Compaq Armada 110 laptop > > > (dmesg and mixerctl below). The sound device is > > > > > > auvia0 at pci0 dev 7 function 5 "VIA VT82C686 AC97" rev 0x20: irq 9 > > > audio0 at auvia0 > > > > for ac97 devices, the codec is also very important. although the > > AD1881A looks pretty standard. no jack sense or anything. > > > > > and it works without problems. > > > > > > Now, the laptop has an internal microphone - that tiny little hole > > > you have seen on some laptops. It records fine, set up as > > > > > > inputs.mic=255 > > > inputs.mic.mute=off > > > inputs.mic.preamp=on > > > inputs.mic.source=mic0 > > > record.source=mic > > > > > > The laptop also has an input for an external mike (the usual small jack, > > > just next to the headphones output). When you plug in an external mike, > > > the audio chip is smart enough to record from that one, and no longer > > > record from the internal mike. (I use Shure SM57 as the external mike, > > > which I believe is irrelevant.) Recording with the external mike plugged > > > in works fine too, EXCEPT the signal level from the external mike is > > > much weaker, and I wonder why. > > > > maybe there is a separate preamp on the internal mic pin? > > Well, both mikes do respond to setting > > inputs.mic.preamp=off/on > > so I suppose either each has its own preamp, > or there is just one mic preamp, pre-amping > the one mike (int/ext) that is currently in use.
yes, there is one preamp on the mic pin in the codec. but, there could be *external to the codec* preamp circuitry between the built-in mic and the codec. the codec's datasheet explains how to do this. > > > Can it be that the (one) audio input the laptop has is meant as an > > > "universal" audio input for both mic and line-in, expecting a much > > > stronger signal? > > > > maybe ... what does inputs.line* affect? > > nothing, in neither case (int/ext). > > > or record.source=line? > > silence; only record.source=mic records something. then probably it's just a mic input, and the line-in pin is unconnected. > > > For the internal mike, having > > > > > > inputs.mic.preamp=off/on > > > > > > makes a difference of recording just fine vs. recording a dog barking > > > two blocks away. With the external mike, it makes a difference of > > > barely audible recording vs. fine recording. With headphones on, > > > you can hear the signal strength drop when you plug in the external > > > mike. > > > > does changing inputs.mic.source have any effect? > > inputs.mic.source=mic0 is set by default and behaves as described. > inputs.mic.source=mic1 is accepted and results in silence being recorded. then there is probably jack sense circuitry (again, external to the codec), that switches which mic is connected to the mic pin on the codec. inputs.mic.source can be used for this purpose, if the vendor connects the mics to the two mic pins instead of handling it themselves. > inputs.mic.source=line or line0 or line1 says 'bad enum value'. well, yeah. they are not valid choices for any ac97 device. -- jake...@sdf.lonestar.org SDF Public Access UNIX System - http://sdf.lonestar.org
