From mboxrd@z Thu Jan 1 00:00:00 1970 From: Raymond Yau Subject: Re: Verifying mixer dB data/Invalid dB data from USB cards, especially Aureon 5.1 MkII Date: Sat, 20 Feb 2010 15:24:42 +0800 Message-ID: <4f3252891002192324m5a744079h1c17b5a20a419928@mail.gmail.com> References: <20100215192451.GA17938@tango.0pointer.de> <4B7A5268.5050704@ladisch.de> <20100216143200.GB25489@tango.0pointer.de> <20100216144047.GB10586@sirena.org.uk> <20100216154015.GA612@tango.0pointer.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-pv0-f51.google.com (mail-pv0-f179.google.com [74.125.83.179]) by alsa0.perex.cz (Postfix) with ESMTP id 823661037F1 for ; Sat, 20 Feb 2010 08:24:44 +0100 (CET) Received: by pvc22 with SMTP id 22so66179pvc.38 for ; Fri, 19 Feb 2010 23:24:43 -0800 (PST) In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: alsa-devel-bounces@alsa-project.org Errors-To: alsa-devel-bounces@alsa-project.org To: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org 2010/2/17 Jaroslav Kysela > On Tue, 16 Feb 2010, Lennart Poettering wrote: > > > On Tue, 16.02.10 14:40, Mark Brown (broonie@opensource.wolfsonmicro.com) > wrote: > > > >> > >> On Tue, Feb 16, 2010 at 03:32:01PM +0100, Lennart Poettering wrote: > >>> On Tue, 16.02.10 09:24, Jaroslav Kysela (perex@perex.cz) wrote: > >> > >>>> Line: 0dB..47.81dB # seems correct -47.81dB..0dB > >>>> Line Capture: -0.18dB..23.81dB # seems correct > >>>> -17.81dB..6.18dB > >> > >>> Hmm, how did you choose where to put 0dB? > >> > >> The Line one looks like someone got attenuation and gain confused, which > >> is a fairly common mistake for people to make when copying information > >> from one place to another. Possibly a similar thing going on with the > >> Line Capture control, plus a fixed 6dB gain (which may well be a > >> separate amp...). > > > > I remember that a while back we had a discussion on alsa-devel > > regarding the fact that ALSA does not define relative to what the dB > > values reported by the mixer elements actually are measured. Some > > mixer controls export dB values relative to max amplification (e.g. my > > integrated USB speakers here), others relative to the output of some > > other mixer element, and others relative to different standard or > > not-so-standard output voltages. And there is no API to figure out > > what the base is. > > > > Now, what Jaroslav listed above suggests that he chose carefully where > > he put 0dB. I was just wondering about that. Jaroslav, how did you > > choose where to put 0dB? > > Basically, if I remember correctly the discussion, 0dB on all elements > should main unchanged volume, <0dB attenuation and >0dB gain. We cannot > measure precisely other components on path like analog volume wheels > (like SB MP3+ has to change line-out volume), analog amplifiers and other > analog signal modificators. > > So, if you use one headphones and speakers with defined and fixed volume > settings, you can measure differences for the card with broken dB volume > ranges. I just used another HDA card in notebook with 0dB settings on all > playback controls on path, captured stream from this card on my USB card > and played this stream back on my USB card watching and relating the > volume levels according dB values. It's not 100% correct, but at least > it's something to start with. > > Jaroslav > > > Yes, 0dB for 10 bands graphic equalizer of au8830 should be no gain and no attenuation how can I calibrate the au8830 10 bands equalizer control as there are 10 bands peak values ?