From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lennart Poettering Subject: Re: Verifying mixer dB data/Invalid dB data from USB cards, especially Aureon 5.1 MkII Date: Tue, 16 Feb 2010 15:26:34 +0100 Message-ID: <20100216142633.GA25489@tango.0pointer.de> References: <20100215192451.GA17938@tango.0pointer.de> <4B7A5268.5050704@ladisch.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from tango.0pointer.de (tango.0pointer.de [85.214.72.216]) by alsa0.perex.cz (Postfix) with ESMTP id AB24E243C2 for ; Tue, 16 Feb 2010 15:27:01 +0100 (CET) Content-Disposition: inline In-Reply-To: <4B7A5268.5050704@ladisch.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 On Tue, 16.02.10 09:08, Clemens Ladisch (clemens@ladisch.de) wrote: > > 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. I am really sure that the discrepancy I measure with the Aureon is way beyond rounding errors. Lennart -- Lennart Poettering Red Hat, Inc. lennart [at] poettering [dot] net http://0pointer.net/lennart/ GnuPG 0x1A015CC4