From mboxrd@z Thu Jan 1 00:00:00 1970 From: Raymond Yau Subject: Re: wrong decibel data? Date: Thu, 8 Apr 2010 07:38:25 +0800 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-pz0-f178.google.com (mail-pz0-f178.google.com [209.85.222.178]) by alsa0.perex.cz (Postfix) with ESMTP id 073D11038CF for ; Thu, 8 Apr 2010 01:38:26 +0200 (CEST) Received: by pzk8 with SMTP id 8so888681pzk.16 for ; Wed, 07 Apr 2010 16:38:26 -0700 (PDT) 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 Development Mailing List List-Id: alsa-devel@alsa-project.org 2010/4/7 Nicolo' Chieffo > This is what I'm doing: > - got a jack-jack audio cable > - connected the headphone to the mic > - open alsamixer and put everything to 0 dB > - verified that the pass-throw works by using the sound recorder > > ./dbmeasure plughw:0 dbmeasure_hw.log > > exits with this error: > Have you ask the author of "dbmeasure" ? > > Iteration 1, level is 0 (-inf dB). > Volume level measured (0) was too high or too low. > Please adjust mixer so that initial level is between 0.8 and 0.97. > Test run canceled. > > > I've also tried to put the mic level at 100% (22.50 dB) but the output > is the same. > your card seem to support 16/20/24bits if you right shift your 16/24 bits digital audio by 16/24 bits , the digital data are always zero so any software atten on a 16/24bits sound card is still a finite negative number dB instead of -inf dB that 's why the professional user prefer 32bits sound card