On Fri, 2013-11-29 at 21:56 +0100, Oleksij Rempel wrote: > Am 29.11.2013 17:22, schrieb Tanu Kaskinen: > > On Fri, 2013-11-22 at 18:34 +0100, Oleksij Rempel wrote: > >> Am 22.11.2013 17:48, schrieb Tanu Kaskinen: > >>> On Thu, 2013-11-21 at 16:42 +0100, Oleksij Rempel wrote: > >>>> Hello all, > >>>> > >>>> i posted this email to ALSA, but probably PA devs have some ideas too. > >>>> > >>>> ====================================================================== > >>>> Hello Takashi, > >>>> > >>>> what is acceptable noise level for mic boost? > >>>> My laptop has three levels of mic boost (+36dB). Level 3 is useless > >>>> since noise level will be about 0db. With level 1 i get -12dB noise, so > >>>> there is almost 12dB room for data... but it is not enough for normal > >>>> speech, which is about 20dB. > >>>> > >>>> Are there any ALSA guide for HW designers, which will say some thing > >>>> like acceptable levels are 90-20dB? > >>>> There are some Skype and Microsoft prescriptions for certification. > >>>> For example M$ prescribe 18dB or more for speech to noise ration for > >>>> build in mics. It sound like good number to start. > >>>> > >>>> In my case, i need to remove mic boost completely to guarantee minimum > >>>> 18dB SpNR. Suddenly i didn't found correct way to do it. > >>>> I will be thankful for some tip. > >>>> > >>>> ===================================================================== > >>>> > >>>> So my question to PA devs. Do pulse audio need to know about noise level > >>>> of microphone? Will it help to make correct decisions? Especial for VoIP > >>>> and automatic gain control. > >>> > >>> We don't currently have any idea of the noise level, so we don't have > >>> code for adjusting our decisions based on that information either. So, > >>> I'd say that pulseaudio doesn't *need* to know about the noise level. Of > >>> course, if someone someday complains that pulseaudio does bad decisions > >>> because it doesn't take the noise level into account, then we would need > >>> that information. > >>> > >> > >> Thank you for your response. > >> I have more questions: > >> Skype continuously trying to adjust record level. > > > > I've never used Skype, but I think I've heard that it allows you to > > disable the automatic gain control. I'd expect that to help with your > > problem. > > Well, it is workaround but not fix. To make conference call we need > automatic gain control. Disabling it will work only for single person > call. The question is how to fix it? > I tested 7 different notebooks, and 4 of them had this issue. It is > nearly impossible for alsa to know about all of them. I don't have a solution. Perhaps it would be better if Skype did AGC in software instead of modifying the hw amplifier levels? We have module-echo-cancel in PulseAudio, which includes AGC too, and AFAIK it does it in software. I know very little about that, though (I don't know how good it is, and I don't have instructions for setting it up for Skype). -- Tanu
