From mboxrd@z Thu Jan  1 00:00:00 1970
From: Rene Herman <rene.herman@keyaccess.nl>
Subject: Re: What does 0dB refer to? (Logitech USB Speakers)
Date: Mon, 21 Apr 2008 19:10:51 +0200
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To: Takashi Iwai <tiwai@suse.de>
Cc: alsa-devel@alsa-project.org, Lennart Poettering <mznyfn@0pointer.de>
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On 21-04-08 15:32, Takashi Iwai wrote:

> At Sun, 20 Apr 2008 02:00:51 +0200,
> Lennart Poettering wrote:

>> My understanding is that the dB values of this USB device are relative          
>> to its maximum gain, and as such consistent in itself. Does the USB
>> spec define the reference level for the dB values?       
> 
> Not clearly.  IIRC, it's against the line level...

The 1.0 spec calls 0 dB line level indeed and (at least in the context of 
the dynamic range compressor, section 3.5.6.6) suggests that it's "usually 
15-20 dB below the maximum level".

Rene.