From mboxrd@z Thu Jan 1 00:00:00 1970 From: Clemens Ladisch Subject: Re: Verifying mixer dB data/Invalid dB data from USB cards, especially Aureon 5.1 MkII Date: Tue, 16 Feb 2010 09:08:08 +0100 Message-ID: <4B7A5268.5050704@ladisch.de> References: <20100215192451.GA17938@tango.0pointer.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from out2.smtp.messagingengine.com (out2.smtp.messagingengine.com [66.111.4.26]) by alsa0.perex.cz (Postfix) with ESMTP id A3E98243A7 for ; Tue, 16 Feb 2010 09:08:10 +0100 (CET) Received: from compute1.internal (compute1.internal [10.202.2.41]) by gateway1.messagingengine.com (Postfix) with ESMTP id 2BE2BE1457 for ; Tue, 16 Feb 2010 03:08:10 -0500 (EST) Received: from [10.1.2.38] (srv004.schk01.int.dmc-one.com [85.232.8.141]) by mail.messagingengine.com (Postfix) with ESMTPSA id 8E8DAA97B for ; Tue, 16 Feb 2010 03:08:09 -0500 (EST) In-Reply-To: <20100215192451.GA17938@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 Development Mailing List List-Id: alsa-devel@alsa-project.org Lennart Poettering wrote: > Getting back to the invalid dB data from the USB cards: the question > is whether the USB descriptor data is badly parsed, and the dB > mismatch hence systematic for USB cards, USB descriptors use units of 1/256th dB, while ALSA uses 1/100th dB. When the level is computed from the minimum plus a multiple of the step size, rounding errors add up considerately. ALSA 1.0.21 (kernel 2.6.32) added a different TLV type that reports the range with the min/max values to minimize those rounding errors. Regards, Clemens