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: Thu, 18 Feb 2010 09:48:09 +0800 Message-ID: <4f3252891002171748tdcaa87n4d11d9880c0043e3@mail.gmail.com> References: <4B7A5268.5050704@ladisch.de> <20100216143200.GB25489@tango.0pointer.de> <20100216144047.GB10586@sirena.org.uk> <20100216154015.GA612@tango.0pointer.de> <20100216210703.GA18109@tango.0pointer.de> <20100216223938.GA23623@sirena.org.uk> <20100216224212.GA1486@tango.0pointer.de> <20100216233825.GB23623@sirena.org.uk> <20100216235658.GA6766@tango.0pointer.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-pz0-f198.google.com (mail-pz0-f198.google.com [209.85.222.198]) by alsa0.perex.cz (Postfix) with ESMTP id EDC3710386A for ; Thu, 18 Feb 2010 02:48:10 +0100 (CET) Received: by pzk36 with SMTP id 36so9089292pzk.23 for ; Wed, 17 Feb 2010 17:48:10 -0800 (PST) In-Reply-To: <20100216235658.GA6766@tango.0pointer.de> 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 Lennart Poettering > On Tue, 16.02.10 23:38, Mark Brown (broonie@opensource.wolfsonmicro.com) > wrote: > > > > > On Tue, Feb 16, 2010 at 11:42:12PM +0100, Lennart Poettering wrote: > > > On Tue, 16.02.10 22:39, Mark Brown ( > broonie@opensource.wolfsonmicro.com) wrote: > > > > > > Typically the DACs and ADCs will have a full scale signal at line > > > > reference level - it should generally be a good approximation with > > > > nothing else to go on. > > > > > "line reference level"? What is that? > > > > As I understand it (and bear in mind that I'm a software rather than > > electrical engineer) it's not 100% fixed, though since the actual result > > depends very much on what it's connected to an absolute answer isn't as > > important as it might be. 1V RMS is very standard in consumer stuff at > > least. > > > > If you could frame exactly the information that you're looking for then > > I should be able to ask a few people who are electrical engineers and > > get a more coherent answer for you. I guess you're looking at trying > > to have PulseAudio set sensible levels by default? > > Nah. I actually don't need this value for PulseAudio. In PulseAudio I > chose to shift all scales so that maximum amplification becomes 0 dB, > so that the UIs are similar to how most hifi racks do it, and which I > think is a nice, easy and understandable logic. That way my volume > scales range from -inf dB to 0 dB in all cases, regardless of the > hardware/drivers in use. Of course, that means that ALSA's own 0dB is > not directly visible on the scale. Because it might be sometimes > useful to know where it is, we export that position as "base volume" > and the UIs show it with a little marker at the side. > > The reason I was asking how Jaroslav chose the 0dB position for his > measurements was purely because I wanted to do my own measurements for > that Aureon card. The dbmeasure tool I wrote for stuff like that puts > 0dB at max amplification, however Jaroslav didn't, so I was wondering > how he chose 0dB then. > > Lennart > > From the viewpoint of user, they only care how easy to find the point which is no software gain or software auttentation since software gain lead to clipping